JPH08274467A - Via-hole forming method for multilayer ceramic board - Google Patents

Abstract

PURPOSE: To obtain a multilayer ceramic board having neither protrudent parts of series via-hole parts nor irregularities on the surface wherein these via-holes pierce a pluralities of layers at the same positions. CONSTITUTION: Conical or square conical via-holes are formed at the same positions of green sheets 1a-1d and charged with a conductor from smaller apertures thereof to form via-holes with leaving spaces not charged with the conductor at the larger apertures. The conductor is charged in only a part of the via-hole. A via-hole part land pattern is formed on only the periphery of the via-hole. By using green sheets having via-holes only, one layer is formed with a pair of the sheets to expand the volume of the via-hole. The size of the via-hole is made larger than a required size. The green sheets worked by these methods are laminated, pressure-welded and backed to form superimposed series via-holes on a straight line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming vias in a multilayer ceramic substrate used as a substrate for mounting electronic components to form an electronic circuit.

[0002]

2. Description of the Related Art Multilayer ceramic substrates can be made as high as several tens of layers, have high thermal conductivity, and have a small number of thermal expansion coefficients, so silicon chips can be directly mounted, and high density mounting is highly effective. It is often used for computer mounting boards, multi-chip modules, and hybrid IC boards because it is advantageous for the shortest connection, contributing to miniaturization, weight reduction, and high functionality of electronic devices.

As is well known, ceramic substrates, organic solvents, binders, plasticizers, wetting agents, etc. are kneaded into clay called slurry by the doctor blade method, etc. Is formed into a flat sheet having a predetermined thickness by the above method, dried, and then baked at a high temperature. Here, what is kept until drying is called a green sheet, and what is obtained by stacking and sintering the green sheets is a multilayer ceramic substrate. Although the expression "ceramic" is a generic name and its material is wide-ranging, when viewed as a ceramic plate, there is no big difference in the manufacturing method, and all of them have gone through the green sheet forming process.

In the case of a circuit board composed of a single-plate ceramic plate, the manufacturing process thereof is one green sheet or a plurality of green sheets which are laminated by thermocompression and sintered to form one ceramic single plate. After that, a conductor pattern such as a circuit pattern and a component land pattern, a resistance pattern, and the like are formed on the surface of the ceramic single plate by a thick film method, and sintered to obtain a circuit board. In the case of a circuit board composed of a single plate ceramic plate as described above, the ceramic single plate manufacturing process and the pattern manufacturing process are separated. Further, by mounting components on the component land pattern of the circuit board, a module having one function is obtained. The thick film method uses a mesh screen from which a desired circuit pattern shape has been removed, a paste-like conductor material, a resistance material, etc., and transfers the above-mentioned mesh screen pattern shape to the surface of a ceramic single plate with a paste material. This is a method of forming a circuit pattern by firing at a temperature of up to 1000 ° C. to sinter the ceramic and the paste material.

In the case of a circuit board composed of a multilayer ceramic plate, a plurality of green sheets having a thickness of about 100 to 200 μm are used and they are stacked to form a multilayer circuit.
Since the circuit has a three-dimensional structure, it is necessary to form what connects the layers that are the three-dimensional portions. This inter-layer connection is called a via or via hole. A hole having a diameter of 100 to 200 μm is made at a predetermined position for each layer, and the same conductor paste as that used in the thick film method is filled in the hole. To form. Here, the hole for this via or the via hole is called a hole for via,
A state in which the conductor paste is filled is called a via. The holes for vias are formed by punching, and punching is performed for each green sheet at a time, or N holes are punched.
It is carried out either by drilling one hole by a C punching device. After completing the drilling of the via holes, fill the conductors in the via holes with a metal mask with through holes that are punched out in a position that matches the via hole positions on the green sheet. The conductor paste is used to print and fill, and then dried to remove the solvent component that is mixed with the conductor paste for easy printing. Although there is a difference between the mesh screen and the metal mask, the printing method is the same as the thick film method.

Next, a desired pattern is formed on the surface of the green sheet, and the pattern forming method is exactly the same as the thick film method described above. The difference is that in the thick film method, baking is performed after pattern formation, but in the case of a multilayer ceramic substrate, a circuit pattern is printed on a green sheet that is kept in a dry state, and this circuit pattern also contains solvent components mixed in the paste. It is necessary to dry it in order to remove it and to keep it until it is dry. Such punching, filling, and circuit pattern printing for vias are performed for each green sheet, and for each green sheet forming each layer of the multilayer substrate.
After forming desired vias and circuit patterns on the green sheets for each layer, the plurality of green sheets are stacked in a predetermined order by aligning the positions of the vias of each layer, thermocompression-bonded, and fired to make contact with each other. Only when the circuit pattern and the green sheet are sintered can it be called a single multilayer ceramic. Here, the sintering of the green sheet and the sintering of the circuit pattern and the green sheet
It is called simultaneous firing because it is performed simultaneously in two firing steps.

The firing of the circuit pattern located in the inner layer of the multilayer ceramic substrate can be performed only by this simultaneous firing, but the pattern formation on the outermost surface of the multilayer ceramic substrate is performed by the simultaneous firing and the simultaneous firing. There is a case where a pattern is printed on the surface using a thick film method like the single-plate ceramic substrate and then fired to form the pattern. This second firing step is referred to as secondary firing for convenience of distinction from the simultaneous firing step. Whether the outermost layer pattern is formed by simultaneous firing,
Whether or not the paste is formed by secondary firing depends on the case, but it is almost determined by the material system of the paste used. In the case of a multi-layer ceramic substrate, a thick film resistance pattern can be formed in the same way as in the case of a single plate ceramic, and it is possible to form it in the inner layer part, but it is not often used because the resistance value accuracy can only be made low. Not not. The resistance pattern in the outermost surface layer is formed by a thick film method, and the resistance value can be adjusted by trimming after firing, so that it is very commonly used.

There are many types of multilayer ceramic substrates depending on the composition of the ceramics, but they can be roughly classified into two types depending on the difference in sintering temperature, and those with a sintering temperature of around 1500 ° C. are fired at high temperature. A multilayer ceramic substrate having a sintering temperature of about 800 to 1000 ° C. is called a low temperature firing multilayer ceramic substrate. When forming a resistance pattern on these multilayer ceramic substrates,
Since a material similar to a thick film resistor is used as the material system of the resistance pattern, the firing temperature is 800 to 1000 ° C. as in the case of the thick film method, which is considerably different from the firing temperature of the high temperature fired multilayer ceramic substrate. Therefore, the resistance pattern cannot be simultaneously fired on the high temperature fired multilayer ceramic substrate, and is limited to the second firing. Further, in the low temperature fired multilayer ceramic substrate, since the firing temperature of the low temperature fired multilayer ceramic substrate is almost the same as that of the thick film resistor, simultaneous firing is possible and secondary firing can be performed.

As described above, the green sheet formed by molding in a dry state is the base of the ceramic, and when the green sheet is fired, crystal grain growth of the ceramic occurs and at the same time, the crystals are bonded to each other. In the process, the phenomenon that the volume shrinks occurs. This is called firing shrinkage,
This phenomenon occurs in both single-plate ceramic plates and multi-layer ceramic substrates, and is a phenomenon that cannot be avoided as long as a ceramic material is used. However, this firing shrinkage occurs when a dry green sheet is fired, and even if the fired / sintered ceramic substrate has been fired again by secondary firing or the like, it will further shrink. However, when a conductor pattern or resistance pattern formed by the thick film method is fired on the surface of a single plate ceramic plate or a sintered multilayer ceramic substrate, the conductor pattern and resistance pattern are sintered with the substrate surface. When it does, it causes firing shrinkage independently.

Since the multilayer ceramic substrate aims to reduce the size of electronic equipment, it is necessary to minimize the area occupied by the circuit pattern and vias. For this reason, the circuit pattern is made finer and the diameter of the via is made smaller. On the other hand, the vias are arranged in series continuously in a straight line in the thickness direction of the multilayer ceramic substrate to reduce the projected occupation area of the vias and to expand the circuit pattern forming region. A large circuit pattern formation area means more freedom in wiring,
This means that optimum wiring will be easier. This series via refers to a multilayer ceramic substrate formed by stacking a plurality of green sheets, having vias at exactly the same positions on each green sheet, and from one outermost surface layer to the other outermost surface layer of the multilayer ceramic substrate. There is a case of penetrating up to one, a case of penetrating from one outermost surface layer to any of the inner layers, and a case of penetrating only the inner layer.

The series vias described so far are for electrically connecting the circuit patterns formed on the respective layers of the multilayer ceramic substrate, but the series vias are also used as heat dissipation vias called thermal vias. . The thermal via is a heat conduction path for facilitating transfer of heat generated from the components attached to one surface of the multilayer ceramic board to the other surface side through the multilayer ceramic board, and must be provided with the shortest distance. , Serial vias are most suitable. Since ceramic is originally a material with high thermal conductivity, thermal vias are often not necessary when the number of stacked layers in the multilayer ceramic substrate is small or when the amount of heat generated by components is small, but the number of wiring lines required for high integration is high. As the number of green sheets increases, the number of green sheet layers increases, and the power consumption of parts increases, the effectiveness of thermal vias is increasing.

FIG. 21 is a perspective view showing the structure of a conventional multilayer ceramic substrate, and FIG. 22 is a perspective view showing the layer structure of the one shown in FIG. 21. The green sheets 1a, 1b, 1c, 1d.
Is an example in which a multi-layer ceramic substrate 2 having a four-layer structure is configured by four sheets of
Alternatively, either low temperature fired ceramic may be used. If the multilayer ceramic substrate 2 has been fired, the four green sheets 1a to 1d are integrated and the boundary between layers is not exposed, so the expression "green sheet" is not appropriate, but it is convenient for explaining the configuration. Above, it is called a green sheet regardless of before and after firing. The green sheet 1a, which is the outermost surface layer, is provided with a via 3a penetrating the green sheet 1a at a desired position.
A land 4a covering the via 3a, a component land 5, a circuit pattern 6a connecting the land 4a and the component land 5, and a resistance pattern 7 are formed on the surface of a. Land 4a,
Since the component land 5 and the circuit pattern 6a are actually formed simultaneously, they cannot be considered as being strictly separated, but they are separated for convenience of explanation. Reference numeral 8 denotes an electric component attached to the component land 5, which may be a heat generating component.

The green sheet 1a, which is the component mounting surface of the multilayer ceramic substrate 2, has such a structure.
Green sheet 1b which is the inner layer of the multilayer ceramic substrate 2
1d has the same structure except that the component land 5 is not provided. The green sheet 1b is provided with a via 3b penetrating the green sheet 1b, a land 4b covering the via 3b, and a circuit pattern 6b connecting between the lands 4b. Has been.
The correlation between the green sheets 1a and 1b is that the green sheet 1b has a land 4b at the same position as the via 3a of the green sheet 1a, and when the green sheets 1a to 1d are stacked, the green sheet 1a and the green sheet 1a are stacked. 1b is connected. The case where the via 3b is provided in the land 4b and the case where the via 3b is provided
May not be provided, but when the via 3b is provided, it is a portion to be connected to the green sheet 1c which is the next layer, and when the via 3b is not provided, the land 4b Layer green sheet 1c
Is the part that is not connected to. Similarly, the green sheet 1c includes vias 3c, lands 4c, and circuit patterns 6c.
And the green sheet 1d is provided with vias 3d, lands 4d, and circuit patterns 6d. The grid pattern of the circuit pattern 6d is an example of a common circuit such as a power supply or a ground.

The via 3d penetrates the green sheet 1d and is connected to the surface of the multilayer ceramic substrate 2 opposite to the component mounting surface. Green sheets 1a-1
vias 3 in exactly the same position in each of d
In the portion where a to 3d are provided, the green sheet 1a
When 1d to 1d are stacked, a four-layer serial via 9 penetrating the green sheets 1a to 1d is formed.
Further, in the portions where the vias 3a to 3c are respectively provided at exactly the same positions in each of the green sheets 1a to 1c, the three-layer serial via 10 is connected to the green sheets 1a to 1c.
In the portion where the vias 3a to 3b are provided at exactly the same position in each of the 1b, the two-layer serial via 1 is provided.
1 is formed. Here, the land 4a of the green sheet 1a, the circuit pattern 6a, the component land 5
The dashed line indicates that the land or pattern of the outermost surface of the multilayer ceramic substrate 2 is formed in the green sheet state and simultaneously fired, and the green sheets 1a to 1d are laminated and fired. This is because it may be formed by secondary firing later, and either method may be used.

23 to 26 are cross-sectional views showing the processing steps for one green sheet. FIG. 23 shows the holes 12 for vias in each of the green sheets 1a to 1d.
It shows the method of providing. 13 is a green sheet 1a
It is a collective punching tool for providing a via hole 12 to 1d. A plurality of needles 14 are attached to a desired position on the collective punching tool 13, and when the green sheet 1a is taken as an example, the holes 14 are formed in the green sheet 1a by the needles 14. Although the shape of the via hole 12 is determined by the shape of the needle 14, a needle having a circular or square cross section is generally used.

Further, the three-dimensional shape of the via hole 12 is formed by penetrating the needle 14 into the green sheet 1a, so that when the needle 14 is penetrated, the green sheet is dragged and the needle 14 is pierced. The diameter of the via hole 12 is different between the protruding side and the protruding side, and it is large on the side where the needle 14 is stuck and small on the protruding side. If the cross-sectional shape of the needle 14 is circular, the via hole 12 is conical. If the needle 14 has a rectangular cross section, the via hole 12 has a pyramidal shape. Here, batch punching is taken as an example, but an NC device capable of punching at an arbitrary position with one needle may be used. The method for forming the via hole 12 is exactly the same for the green sheets 1b to 1d.

FIG. 24 shows the step of filling the via holes 12 provided in the green sheets 1a to 1d with the conductive paste 15. Taking the green sheet 1a as an example, FIG.
The green sheet 1a is printed by using a metal mask 17 having through holes 16 provided at positions corresponding to the positions of the via holes 12 provided in the green sheet 1a.
Conductor paste 15 with a squeegee 18 in the via hole 12 of
Push in to fill. The diameter of the through hole 16 is the needle 14
The same diameter or a slightly larger size is provided in consideration of the printing position shift. The via holes 12 are filled with the conductive paste 15 to form the vias 3a in the green sheet 1a. However, since the vias 3a are not actually provided without sintering, the vias are not formed at this point. Although it is not proper to call it, for convenience of description, it is called a via regardless of before and after sintering, and the conductor paste 15 is also called a conductor paste before and after firing.

In filling the via hole 12, the conductor paste 15 has a high viscosity, but is in a liquid state, so that it is very difficult to control its amount. Further, since the diameter of the through hole 16 is adapted to the larger diameter of the conical shape or the pyramidal shape, the filling amount of the via becomes large. Due to these two factors, the conductor paste 15 is often projected on the surface of the via 3a opposite to the printed surface to form the via projection 19. Also in this filling step, the green sheets 1b to 1d are the same as the case of the green sheet 1a.

FIG. 25 shows the green sheet 1 after filling vias.
7A shows the state of “a”, and when the metal mask 17 is separated from the green sheet 1a, the conductor mask 15 remains on the printing surface side of the vias 3a to 3d because the metal mask 17 has a thickness, and the via protrusion 20 is formed. . Therefore, via projections 19 are formed on both sides of the green sheet 1a,
20 will be formed.

FIG. 26 shows the step of forming the land 4a, the component land 5, and the circuit pattern 6a when one green sheet is the green sheet 1a, and the green sheet 1b.
In the case of 1d to 1d, the steps of forming the lands 4b to 4d and the circuit patterns 6b to 6d are shown, and the method is a thick film printing method using the mesh screen 21 and the conductor paste 15. In the green sheet 1a, the lands 4a, the component lands 5, the circuit patterns 6a, etc. are described separately, but when they are formed with the same kind of the conductor paste 15, it is possible to print simultaneously with one mesh screen 21. And is simply printed as a conductor pattern on the surface of one green sheet 1a. The same applies to the green sheets 1b to 1d.

Taking the green sheet 1a as an example, the mesh screen 21 is provided with through holes 22 having the same shape as the land 4a, the component land 5, and the circuit pattern 6a. When printed on 1a, the shape of the through holes 22 is transferred by the conductor paste 15 to form conductor patterns such as the lands 4a, the component lands 5, and the circuit patterns 6a. Here, the conductor pattern is printed even on the green sheet 1a which is the outermost layer when laminated, so that it is an example of the case of simultaneous firing, but in the case of secondary firing, the conductor is attached to the green sheet 1a at this point. Patterns are rarely formed, and the green sheets 1b, 1 that become inner layers when laminated
Lands 4b to 4d and circuit patterns 6b to only c and 1d
6d is formed.

In the green sheets 1a to 1d, the lands 4a to 4d are printed by covering the lands 4a to 4d on the vias 3a to 3d in order to connect with the vias 3a to 3d. In order to do so, a considerable amount of pressure is applied to the mesh screen 21 by the squeegee 18, and this pressure causes the via protrusion 2 in FIG.
0 is compressed, and the lands 4b to 4d are printed and formed in a flat state on the surface of the green sheet. In addition, the via protrusion 19 part in FIG. 25 is the opposite surface of the printing using the mesh screen 21, and since this surface is in contact with the flat and hard jig and tool surface, it is also crushed by the pressure during printing, and the via protrusion 19 Are compressed and pushed into the vias 3a-3d. Therefore, after printing a pattern such as a land, no protrusion of vias is seen on both sides of the green sheet.

FIG. 27 is a cross-sectional view showing a conventional multilayer ceramic substrate, which has been drilled as described above.
It shows a multilayer ceramic substrate 2 in which green sheets 1a to 1d on which vias are filled and patterns are respectively formed are laminated and sintered, and the four-layer serial vias 9 and three layers described with reference to FIG. 22 are shown. The configurations of the serial via 10 and the two-layer serial via 11 are shown. In the green sheet laminating step, the green sheets 1a to 1d are stacked in a predetermined order with the positions of the vias 3a to 3d of the respective green sheets aligned, and the green sheets 1a to 1d are evenly distributed over the entire surface at a temperature in the range of room temperature to 100 ° C.
Green sheet 1 with a pressure of about 00 kg / cm ²
In a to 1d, the abutting boundary surfaces are crimped and then fired. When fired, the multilayer ceramic substrate 2 fused and integrated is completed by the chemical reaction on the boundary surface and the growth of crystal grains.

Here, as described with reference to FIGS. 24 to 26, when the green sheets 1a to 1d are independent, the via protrusions 1 are formed on both sides of the vias 3a to 3d.
Although there were 9 and 20, they were compressed and flattened in the next pattern printing process. Green sheet 1a ~
When 1d is stacked, in the four-layer serial via 9 where a plurality of vias are stacked, the conductor paste in which the via protrusions 19 and 20 are compressed is also overlapped by four layers.
Although it seems that the volume is proper because it is compressed, the amount of paste used actually exceeds the total amount of the conductor paste 15 that is proper to form the four-layer serial via 9. Three-layer serial via 10 and two-layer serial via 11 in which the number of layers of via protrusions 19 and 20 are overlapped
However, it is the same that the total amount of the appropriate conductive paste 15 is exceeded.

Next, when pressure bonding and firing are carried out, the green sheets 1a to 1d undergo firing shrinkage of 10 to 20% in all of the longitudinal, lateral and thickness directions, and the diameter and thickness of the via hole 12 are also reduced. To be done. Further, since the green sheets 1a to 1d and the conductor paste 15 are not the same composition, the firing shrinkage rate is not the same, and the conductor paste 15 has a lower firing shrinkage rate than the green sheets 1a to 1d. Therefore, when the multilayer ceramic substrate 2 is fired, the volume of the vias 3a to 3d shrinks as the green sheets 1a to 1d shrink, but the vias 3a to 3d shrink.
Since the contraction rate of the conductive paste 15 filled inside the a to 3d is smaller than the contraction rate of the green sheets 1a to 1d, the volume after firing exceeds the volume of the via hole 12 and is outside the vias 3a to 3d. Sintered in the extruded state,
A serial via protrusion 23 occurs.

Both the green sheet and the conductor paste are contracted, and the difference in contraction rate means that the difference in contraction rate appears as expansion. Therefore, in the four-layer serial via 9 portion that completely penetrates the multilayer ceramic substrate 2, the serial via protrusions 23 are formed on both surfaces of the multilayer ceramic substrate 2, and the three-layer serial via portion 10 and 2 are formed.
In the portion 11 of the layered serial via, the serial via protrusion 23 is formed only on the surface of the multilayer ceramic substrate 2. The protrusion height of the serial via protrusion 23 increases in proportion to the number of vias stacked in series.

FIG. 28 is a sectional view showing the surface pattern printing step of the multilayer ceramic substrate 2, and FIG. 29 is a sectional view showing the surface pattern finish of the multilayer ceramic substrate 2. Figure 2
Reference numeral 8 shows a process of forming the resistance pattern 7 on the surface of the multilayer ceramic substrate 2 using the resistance paste 24 and the mesh screen 21 by the thick film method. Serial vias 9, 1
In the 0th and 11th parts, a plurality of vias are overlapped with each other, so that a via protrusion 23 is generated. The mesh screen 21 hits the via protrusion 23 and floats up.
Surface of multilayer ceramic substrate 2 and mesh screen 21
It is difficult to control the film thickness, such as the gap between and cannot be kept constant, or the adhesion becomes non-uniform, and it is not possible to form a uniform printed film thickness. For example, when a 10-layer substrate is composed of 10 green sheets, the height of the serial via protrusion 23 is 50 to 50.
In some cases, the print setting film thickness of the resistor is 40 to 60 μm, and the height of the serial via protrusion 23 exceeds this film thickness. Thicker than thick. The height of this serial via protrusion 23 is the number of green sheets to be stacked,
That is, it goes without saying that the higher the number of stacked vias becomes, the higher the resistance pattern 7 formed in such a state becomes. As a matter of course, the desired resistance value cannot be obtained.

In addition to the resistance pattern 7, a conductive pattern such as a land 4a, a component land 5 and a circuit pattern 6a may be formed on the surface of the multilayer ceramic substrate 2 by secondary firing. The resistance pattern 7 makes it difficult to control the thickness of the conductor pattern due to the influence.
It is similar to that it is difficult to control the film thickness. in this way,
When the resistance pattern 7 or the secondary firing conductor pattern is formed on the surface of the multilayer ceramic substrate 2 in a state where the film thickness control is difficult, the state that the film thickness is too thick or the thickness is non-uniform after the secondary firing It will not be resolved and will affect the next process such as component mounting.

FIG. 30 is a sectional view showing the mounting of components. When the electrical component 8 is mounted at a position overlapping the serial via protrusion 23 of the multilayer ceramic substrate 2, the electrical component 8 is tilted as shown in FIG. A gap is created between the electric component 8 and the multilayer ceramic substrate 2. Although the inclination of the electric component 8 is out of the question, it looks normal when there is a gap between the electric component 8 and the multilayer ceramic substrate 2 while keeping the horizontal position, but from the aspect of characteristics such as electrical / thermal connection, It may cause a malfunction event. Also, when the multilayer ceramic substrate 2 is attached to the case 25 or the like, there is a problem that a gap is created between the case 25 and the multilayer ceramic substrate 2 as in the case of attaching the electric component 8.

[0030]

In each green sheet, the via protrusions 19 and 20 generated on both sides when the via hole 12 is filled with the conductive paste 15 are also compressed and pushed into the via hole 12. Because I'm out, Bahia 1
The conductor paste 15 per piece is excessive in terms of the amount used even though the volume is contracted. Further, in the portion where a plurality of vias are overlapped in a straight line in series like the serial vias 9, 10, 11, This excessive amount is also piled up, and the amount of the conductor paste 15 used is considerably larger than the amount suitable for the entire volume of the via hole 12.

From the above two points, what looked normal up to lamination and pressure bonding, but after firing, the volume of the via hole 12 was reduced due to the shrinkage of the green sheet, and the shrinkage ratio between the green sheet and the conductor paste. Due to the difference, the conductor paste 15 expands and is pushed out of the vias 3a to 3d, a series via protrusion 23 is generated on the surface of the multilayer ceramic substrate 2, and the surface of the multilayer ceramic substrate 2 becomes uneven. The protruding height of the serial via becomes higher as the number of vias forming the serial via increases.

Since the lands 4a to 4d are formed by printing on the vias 3a to 3d, the vias 3a to 3d are formed.
In the 3d portion, the conductor paste 15 is additionally piled up by the film thickness of this land, and there is a problem that the film thickness of this land promotes the protruding height of the series via 23.

Further, because of the serial via protrusion 23, when the circuit pattern 6a and the resistance pattern 7 are formed by printing on the surface of the multilayer ceramic substrate 2 by the secondary firing, the control of the printed film thickness is hindered and the printed film is printed. There is a problem that the thickness of the film becomes uneven. As the number of stacked green sheet layers increases, the number of overlapping vias also increases. Therefore, as the number of green sheet layers increases, the height of the serial via protrusion 23 increases, and it becomes more difficult to print a pattern on the surface. There is a problem.

When the electric component 8 is attached to the surface of the multilayer ceramic substrate 2, the component is inclined due to the via protrusion 23, a gap is formed, attachment is impossible, or even if attachment is possible, heat conduction is possible. Sex decreases. Also, when mounting the multilayer ceramic substrate 2 on the case 25,
Due to the presence of the via protrusion 23, the multilayer ceramic substrate 2
A gap is created between the case 25 and the case 25, and the multilayer ceramic substrate 2
There is a mounting problem such as a decrease in thermal conductivity between the case and the case 25.

It is an object of the present invention to obtain a multilayer ceramic substrate having a smooth surface which does not hinder the printing of the circuit pattern or the resistance pattern on the outermost surface and the mounting of components even when a serial via is formed.

[0036]

In Embodiment 1 of the present invention, attention is paid to the fact that the holes for vias formed by punching in the green sheets are conical or pyramidal, and when a plurality of green sheets are stacked. The holes for vias are punched out at positions where they become serial vias, and the amount of the conductor paste filled is suppressed by filling the conductor paste from the side where the opening diameter of the vias is small. A series of vias are formed by stacking, press-bonding and sintering a plurality of green sheets with the shapes of via holes aligned in the same direction.

In the second embodiment of the present invention, an elliptical or rectangular via hole is formed at a position where a serial via is formed when laminated, and the elliptical or rectangular center portion or one end of the via hole is formed. The conductive paste is filled in the same standard amount, and a plurality of green sheets are stacked, pressed and sintered to form a series via.

In the third embodiment of the present invention, a via hole is provided at a position which becomes a serial via when stacked, a via is formed by filling a conductive paste, and the via is surrounded so as not to overlap with the via. Form a land pattern on the
A series via is formed by pressure bonding and sintering.

The fourth embodiment of the present invention is a green sheet which becomes an odd-numbered layer when laminated, among a plurality of green sheets in which holes for vias are provided at positions which become serial vias when laminated. Or only for the green sheets that are even-numbered layers, that is, only for the alternating layers, holes for vias are filled with a conductive paste, and laminated, pressure-bonded and sintered to form a series via.

In the fifth embodiment of the present invention, holes for vias are provided at positions which become serial vias when laminated, but when laminated, the green sheet becomes an odd numbered layer or an even numbered layer. That is, the diameter of the via holes is changed in alternate layers, and only the via holes of the green sheet belonging to the layer with the smaller hole diameter are filled with the conductor paste, and laminated, pressure-bonded and sintered to form a serial via. It was done.

In Example 6 of the present invention, two kinds of green sheets having different thicknesses are used, one of the green sheets is used as an odd-numbered layer or an even-numbered layer, and the green sheets having different thicknesses are alternated. Stack on. Each green sheet is provided with a via hole at a position that becomes a serial via when laminated, and only the via hole of the green sheet belonging to the layer in which the thicker green sheet is used is filled with the conductor paste. , Laminated, pressure bonded, and sintered to form a serial via.

[0042]

In the first embodiment of the present invention, the filling amount of the conductive paste in the via of each green sheet forming the multilayer ceramic substrate can be suppressed in units of one via.

In the second embodiment of the present invention, the filling amount of the conductive paste in the via of each green sheet forming the multilayer ceramic substrate can be easily changed in units of one via. Further, even if the filling amount varies, there is a volume margin to absorb the variation.

In the third embodiment of the present invention, it is possible to suppress the total amount of the conductor paste with respect to the total volume of the holes for a plurality of vias forming the series vias of the multilayer ceramic substrate.

In the fourth embodiment of the present invention, the total amount of the conductor paste can be suppressed with respect to the total volume of the holes for a plurality of vias forming the series via of the multilayer ceramic substrate. Further, even if the filling amount varies, there is a volume margin to absorb the variation.

In the fifth embodiment of the present invention, it is possible to suppress the total amount of the conductor paste with respect to the total volume of the holes for a plurality of vias forming the series vias of the multilayer ceramic substrate. Further, even if the filling amount varies, there is a volume margin to absorb the variation. In addition, there is a volume margin to absorb the volume change due to the reduction of the via hole due to the contraction of the green sheet.

In the sixth embodiment of the present invention, the total amount of the conductor paste can be suppressed with respect to the total volume of the holes for a plurality of vias forming the series via of the multilayer ceramic substrate. Further, even if the filling amount varies, there is a volume margin to absorb the variation. In addition, there is a volume margin to absorb the volume change due to the reduction of the via hole due to the contraction of the green sheet. Also, the total volume of the via holes in the serial via portion with respect to the number of laminated layers can be adjusted.

[0048]

【Example】

Embodiment 1 FIG. 1 is a sectional view showing an embodiment of the present invention, taking a case of four layers as an example. FIG. 2 is a cross-sectional view showing a method for filling vias using the green sheet 1a as an example, and FIG. 3 is a green sheet 1
FIG. 4 is a sectional view showing the printing of the conductor pattern in a, and FIG. 4 is a sectional view showing the laminated structure. Green sheets 1a-1
d, lands 4a to 4d, circuit patterns 6a to 6d, resistance patterns 7, electric components 8, four-layer series vias 9, three-layer series vias 10, two-layer series vias 11, holes 12 for vias,
Batch punching tool 13, needle 14, conductor paste 15, through hole 16, metal mask 17, printing squeegee 1
8, via protrusion 20, mesh screen 21,
Through hole 22 of mesh screen 21, resistance paste 2
4, the case 25 is similar to the case of the conventional example,
The overall structure of the multilayer ceramic substrate 30 is no different from that of the conventional example.

The punching of the via holes 12 of the green sheets 1a to 1d is performed in exactly the same way as in the conventional example shown in FIG. 23, but conventionally, the conductor paste 15 is printed and filled from the direction in which the punching needle 14 is inserted. Whereas it did, printing and filling from the opposite side, via 31a
To form 31d. That is, the holes 12 for conical or pyramidal vias are filled from the smaller opening diameter. printing·
Although the filling method is the thick film method using the metal mask 17 as in the conventional case, the diameter of the through hole 16 provided in the metal mask 17 is adjusted to the smaller opening diameter of the via hole 12. Form.

Since the conductor paste 15 is pushed into the via hole 12 from the smaller opening diameter to the larger opening diameter, the conductor paste 15 does not sufficiently enter. Some parts are not filled. Therefore, the metal mask 17 is used for the smaller aperture.
The conductive paste 15 is protruded by a thickness equal to or less than the above, and the via protruding portion 20 is formed, which is the same as in the conventional case, but the protrusion is to the side where the opening diameter of the via hole 12 is smaller. The amount of the conductor paste 15 is small. Further, the conductor paste does not stick out to the surface having the larger opening diameter.

As described above, since the amount of the conductive paste 15 filled in the via holes 12 at the time of forming the via in one green sheet is suppressed, the green sheet 1
Taking a as an example, when the land 4a and the circuit pattern 6a are formed by printing on the via 31a portion as shown in FIG. 3, from the surface side of the green sheet 1a having the larger opening diameter of the via hole 12 Since there is no protrusion on the surface when printing is performed, the protruding conductor paste 15 is not compressed and pushed into the via 31a as in the case of the conventional example, but the hole 12 for the via is formed by the conductor paste. Since there is a portion which is not completely filled with 15, the central portion of the land 4a will fall into the via hole 12 and the central portion will have a concave shape. At this time, at the same time, the via protrusion 20 on the surface opposite to the printing surface is crushed by the printing pressure as described in the conventional example.
Since there is a space in which the conductor paste 15 is not yet filled, it is not compressed and pressed by pressure, but is pressed in a non-compressed state and the space in the via hole 12 is filled. , Bia protruding 20
Disappears and becomes flat.

As described above, in the via 31a, the filled paste 15 and the conductive paste 15 having the thickness of the land 4a are formed.
The volume of the green sheet 1 is slightly smaller than the volume of the via hole 12 even when combined with
When four sheets of a to 1d are laminated, two series, three series, four series and vias 31a to 31d are formed as in the series vias 9 to 11.
Even if they are stacked, the total amount of the conductive paste 15 does not exceed an appropriate amount with respect to the total volume of the holes 12 for a plurality of vias forming the serial via, and the outermost surface portion of the serial vias 9, 10, 11 after lamination / press bonding. Then, some depression occurs.

Next, when firing is performed, the green sheets 1a ...
1d shrinks in all directions, and the surface depressions in the serial vias 9, 10 and 11 disappear almost due to the shrinking of the periphery, and as shown in FIG. 1, a multilayer ceramic substrate 30 having no protrusions on the surface is obtained. . Therefore, the multilayer ceramic substrate 3
When the resistance pattern 7 and the like are formed by secondary firing after sintering of 0, the method is exactly the same as the conventional example, but since there is nothing protruding on the surface of the multilayer ceramic substrate 30, the printed film thickness is Can be formed as set.

Embodiment 2 FIG. 5 is a plan view showing an embodiment of the present invention, showing a via shape in a green sheet. FIG. 6 is a sectional view showing filling of vias in the green sheet, and FIG. 7 is a sectional view showing a layer structure. In the figure, green sheet 1a-
1d, lands 4a to 4d, conductor paste 15, through hole 1
6, the metal mask 17, the print squeegee 18, and the via protrusion 19 are the same as in the conventional example.

Taking the green sheet 1a as an example, a needle having an elliptical cross section is used for punching in the same manner as in the conventional case, and an elliptical via hole 32 is formed.
The conductor paste 15 is filled only in the central portion of the hole 32 for the elliptical via, and the elliptical via 33a is formed. Although the method of filling the conductor paste 15 is the same as the conventional method, the size of the through hole 16 of the metal mask 17 is a circle having the same diameter as the minor diameter of the hole 32 for the elliptical via. It is smaller than the major axis of the hole 32 for use.

Therefore, when the conductor paste 15 is printed, the conductor paste 15 is formed only in the central portion of the elliptical via hole 32.
Is pushed in, and spaces 34 are formed at both ends of the elliptical via hole 32 in the major axis direction. The pressed conductor paste 15 is in contact with only the short side wall of the elliptical via hole 32. However, the adhesiveness and surface tension of the conductor paste and the size of the elliptical via hole 32 are different. Has a long diameter of about 0.5 mm, so it will not fall out, but as in the case of the conventional example, it protrudes to the opposite side and the via protrusion 1
9 can occur. Further, via projections corresponding to the thickness of the metal mask 17 occur on the printing surface side at the moment of printing, but do not immediately flow into the space portions 34 on both sides and remain as projections.

Next, when the land 4a and the circuit pattern 6a are formed by printing using the mesh screen 21 in the same manner as in the conventional example, the land 4a has a slightly elliptical hole for the via as shown in FIG. Although it falls into the space portions 34 on both sides of the space 32, since the plane area of the space portion 34 is very small, it does not fall to the extent that a depression appears on the land surface. This printing pressure causes the via protrusion 19 to be pressed into the elliptical via hole 32 without being compressed, and the via protrusion 19 disappears, resulting in a flat surface. Space 3 in this way
Although a large portion of No. 4 is filled with the conductor paste 15, the size of the hole 32 for the elliptical via is set in consideration of this amount, so that some space still remains.

When the green sheets 1a to 1d in which the elliptical vias 33a to 33d are thus formed are stacked and pressure-bonded and then fired, the total volume of the holes 32 for the elliptical vias forming the serial vias is calculated. Since the amount of the conductor paste is suppressed, the volume reduction of the elliptical via hole 32 due to the contraction of the green sheets 1a to 1d is absorbed,
From the surface of the multilayer ceramic substrate 30 to the serial vias 9,1
It is possible to obtain the multilayer ceramic substrate 30 in which the 0 and 11 parts do not project and the surface has no irregularities.

In this example, the holes for vias have an elliptical shape, but a rectangular shape can have the same function. Further, although the conductor paste is filled only in the central portion of the elliptical via hole, the same function can be obtained by filling the conductor paste close to any one end in the major axis direction. The pattern formation by the secondary firing on the surface of the multilayer ceramic substrate 30 is the same as that of the first embodiment, and there is no obstacle in printing.

Embodiment 3 FIG. 8 shows an embodiment of the present invention, and is a plan view showing a part of a green sheet, and FIG. 9 shows a portion of a mesh screen used for forming the one shown in FIG. The plan view shown in FIG. 10 is a cross-sectional view of what is shown in FIG. The green sheets 1a to 1d, lands 4a to 4d, circuit patterns 6a to 6d, and conductor paste 15 are the same as those in the conventional example. Taking the green sheet 1b as an example, the via holes 12 are formed in the same manner as in the conventional example.
After that, the conductor paste 15 is filled to form the via 3b.

Next, the circuit pattern 6b and the hollow land 35 are formed.
Is printed using the mesh screen 36, but the circuit pattern 6b is the same as in the conventional example. The hollow land 35 has the same diameter as the via hole 12.
The pattern has the same shape with the center removed, and is formed along the periphery of the via hole 12. To form the hollow land 35, the mesh screen 36 may be filled in a position corresponding to the via hole 12. The mesh screen 36 shown in FIG. 9 is entirely composed of a net, and the opening of the net is closed by covering the whole portion other than the printing pattern portion with resin. The shaded portion in FIG. 9 is the net portion covered with the resin, and the non-hatched portion is open only by the net, and serves as the through hole 37. Since the through hole 37 is formed in the same shape and size as the desired pattern shape, the conductor paste 15 passes through the through hole 37 and the shape of the through hole 37 is transferred to the surface of the green sheet 1b.

In this way, the hollow land 35 is the via 3b.
Therefore, the total amount of the conductor paste 15 in the via 3b can be suppressed to be small. FIG. 10 is a cross section of the green sheet 1b after the hollow land 35 and the circuit pattern 6b are formed, but the via 3 is formed in the same manner as in the conventional example.
Since the via protrusions 19 and 20 generated on both sides of the via 3b when the conductive paste 15 is filled in b are pressed into the via 3b by the printing pressure using the mesh screen 36 as in the case of the conventional example. , Hollow land 3
Only 5 and the circuit pattern 6b are projected to the surface of the green sheet 1b.

When the hollowing lands 35 are provided on the green sheets 1a, 1c and 1d in the same manner as the green sheet 1b, and then the stacking and pressure bonding are performed, the hollowing lands 35 are projected and the vias 3a are formed. Since ~ 3d is retracted, a slight gap may be generated in this recessed portion, but when firing is performed, the green sheets 1a to 1d contract in all directions, so that this gap is not compressed, and the green sheet 1a to 1d is compressed.
A multilayer ceramic substrate equivalent to the multilayer ceramic substrate 30 shown in FIG.

Embodiment 4 FIG. 11 is a cross-sectional view showing an embodiment of the present invention, showing a layer structure of a green sheet. 12 is a sectional view showing the state shown in FIG. 11 after pressure bonding, and FIG. 13 is a sectional view showing the state shown in FIG. 12 after firing. The green sheets 1a to 1d are similar to the conventional example, and the vias 3a to 3d and the circuit patterns 6a to 6d are also formed in the same manner as in the conventional example. Green sheets 38a-3
8d has only holes 12 for vias formed at exactly the same positions as the green sheets 1a to 1d. For example, green sheet 38a has holes 12 for vias formed at exactly the same positions as green sheet 1a. The green sheets 1b and 38b, 1c and 38c, 1d and 38d are provided with via holes 12 at exactly the same positions. In other words, one set of two green sheets is equivalent to one conventional sheet.

In this example, the first, third, fifth and seventh green sheets 1a to 1d counted from the green sheet 1a.
The odd-numbered layer formed by forming the vias 3a to 3d and the circuit patterns 6a to 6d using the conductor paste 15 and the second, fourth, sixth, and eighth green sheets 38a to 38.
The even-numbered layer constituted by d is provided with only the via holes 12. Since the vias 3a to 3d are formed in exactly the same manner as in the conventional example, the amount of the conductor paste 15 in the vias 3a to 3d is large.

These green sheets 1a-1d, 38
When a to 38d are alternately stacked, the eight-layer series via 39, the six-layer series via 40, and the four-layer series via 41 have holes 12 for vias alternately and are arranged in series, but are not connected at all. When pressure bonding is performed after stacking, the conductor paste 15 of the vias 3a to 3d above and below the via hole 12 which is a cavity is pressed. However, since the amount of the conductor paste 15 is insufficient to completely fill it, some cavities also remain. When fired after pressure bonding, green sheets 1a-1
Since d, 38a to 38d contract in all directions, the volume of the via hole 12 also decreases, and the cavity is filled with the conductive paste 15 to form the series vias 39, 40, 41.
A multilayer ceramic substrate 42 having the same surface as the multilayer ceramic substrate 30 shown in FIG.

Embodiment 5 FIG. 14 is an embodiment of the present invention, and is a sectional view showing the layer structure of the serial via portion, FIG. 15 is a sectional view showing what is shown in FIG. 14 after pressure bonding, and FIG. 16 is shown in FIG. It is sectional drawing which shows what was shown after baking. The green sheets 1a to 1d are the same as the conventional example, and the vias 3a to 3d and the circuit patterns 6a to 6d are also formed in the same manner as the conventional example.
The green sheets 43a to 43d are the green sheets 1a.
Only the large-diameter holes 44 for vias are formed at exactly the same positions as .about.1d and are about three times as large as the holes 12 for vias.

In this example, the first, third, fifth and seventh green sheets 1a to 1d counted from the green sheet 1a.
Vias 3a-3d are provided in the second, fourth, sixth, eighth
The second green sheets 43a to 43d are provided with only large-diameter holes 44 for vias. Vias 3a-3d
Is formed in exactly the same way as in the conventional example, so the amount of the conductor paste 15 in the vias 3a to 3d is large. When these green sheets 1a to 1d and green sheets 43a to 43d are alternately stacked, an 8-layer serial via 45 is formed.
Since there are large-diameter holes 44 for vias alternately in the portion where they are arranged, they are arranged in series and are not connected at all. When pressure bonding is performed after stacking, as shown in FIG. 15, the via holes 3a to 3d above and below the hollow large-diameter hole 44 for vias fall, but the vias above and below contact each other for vias. The large-diameter hole 44 does not fall to such an extent that it is filled, and a small cavity remains.

When fired after pressure bonding, the green sheet 1a
1d and 43a to 43d contract in all directions, and the holes 12 for the vias of the green sheets 1a to 1d and the green sheet 4 are formed.
Since the volume of the large-diameter holes 44 for the vias 3a to 43d is also reduced, the conductor paste 15 is extruded from the vias 3a to 3d and the cavities left in the large-diameter holes 44 for the vias of the green sheets 43a to 43d are filled. , 8-layer serial via 4
5, the connection is completed in the vertical direction, and a multilayer ceramic substrate 46 having a series via similar to the four-layer serial via 9 of the multilayer ceramic substrate 30 shown in FIG.

Embodiment 6 FIGS. 17 to 20 are sectional views showing an embodiment of the present invention. FIGS. 17 and 19 show partial cross-sections of serial vias of laminated and pressure-bonded green sheets, and FIGS. Shows the state after firing of those shown in FIGS. 17 and 19, respectively. 17 and 18, the green sheets 47a to 47d have the same thickness as the green sheets 1a to 1d and 3 respectively.
Except that it is thinner than 8a to 38d, it has substantially the same configuration as the example of the fourth embodiment, and the green sheet 38 of the fourth embodiment is used.
a to 38d are replaced with green sheets 47a to 47d. As described in the fourth embodiment, the hole 1 for the via of the green sheets 47a to 47d is also used here.
2 is filled with the conductor paste 15 of the vias 3a to 3d above and below.

The reason why the green sheets 47a to 47d are thinner than the green sheets 38a to 38d is that the 8-layer serial via 3 is used when the diameter of the vias 3a to 3d is particularly small.
When the total amount of the conductor paste 15 constituting the serial via portion such as 9, becomes small, a cavity remains in the via hole 12 even after lamination, pressure bonding, and firing, and the vias above and below the via hole 12 cannot be connected to each other. This is because there are cases. The total volume of the holes forming the serial via is adjusted by changing the thickness of the green sheet in consideration of the total amount of conductive paste 15 forming the serial via, the number of layers, the via diameter, and the shrinkage rate of the green sheet. It is possible to obtain the multilayer ceramic substrate 48 having the same surface as the ceramic substrate 30 and having no irregularities.

19 and 20, the thickness of the green sheets 47a to 47d is the green sheet 1a.
.About.1d and 43a to 43d, except that the green sheets 43a to 43d of the fifth embodiment are the same as the example of the fifth embodiment.
Is replaced with. As described in the fifth embodiment, the large-diameter holes 44 for the vias of the green sheets 47a to 47d are filled with the conductive paste 15 of the vias 3a to 3d above and below the green sheets 47a to 47d.

The green sheets 47a to 47d are made thinner than the green sheets 43a to 43d because the vias 3a to 3d have a small diameter, but the conductor paste forming the serial via portion is formed in the case of a high multilayer structure. This is highly effective when the total amount of 15 is large and it is necessary to reduce the thickness of the multilayer ceramic substrate 49 as much as possible in order to maximize the thermal conductivity even in a high multilayer structure. The total amount of conductor paste 15 constituting the serial vias, the number of layers, the via diameter, the thickness of the multilayer ceramic substrate 49,
The total volume of the holes forming the serial vias is adjusted by changing the thickness of the green sheet in consideration of the shrinkage rate of the green sheet, and the multilayer ceramic substrate 49 having the same surface as the multilayer ceramic substrate 30 with no unevenness is formed. Obtainable.

[0074]

According to the present invention, since the filling amount of the conductor paste in the via is suppressed in units of one via, in the serial via portion where a plurality of vias are stacked, the conductor used for the total volume of the via holes is used. This has the effect of suppressing the total amount of paste, and suppressing the phenomenon in which the serial via part projects to the surface after pressure bonding and firing.

According to the present invention, the via hole is formed into an ellipse or a rectangle, and only a part of the hole is filled with the conductive paste. Therefore, the filling amount of the conductive paste in the via is suppressed in units of one via, and the filling of the conductive paste is suppressed. Even if there is variation in quantity, there is a volume margin to absorb that variation,
Furthermore, the diameter of the via hole can be adjusted to optimize the relationship between the total volume of the via hole and the total amount of conductive paste and the shrinkage ratio. The total amount of the conductive paste used with respect to the total volume of is suppressed, and there is an effect that the phenomenon in which the series via part projects to the surface after pressure bonding and firing is suppressed.

According to the present invention, since the land in the via is not overlapped and the total amount of the conductive paste in the via portion is suppressed in units of one via, the total volume of the via holes is reduced in the serial via portion where a plurality of vias are stacked. Therefore, the total amount of the conductive paste used can be suppressed, and the phenomenon in which the serial via part protrudes on the surface after lamination, pressure bonding, and firing is suppressed.

According to the present invention, since the conductor paste is alternately filled in the series via portion where a plurality of vias are stacked, even if the filling amount of the conductor paste varies, there is a volume margin to absorb the variation, and the plurality of vias are provided. In the serial via portion in which the layers are stacked, the total amount of the conductive paste used with respect to the total volume of the via holes is suppressed, and it is possible to suppress the phenomenon in which the serial via portion is projected to the surface after lamination, pressure bonding, and firing.

According to the present invention, since the conductor paste is alternately filled in the series via portion where a plurality of vias are stacked and the via holes are alternately different, even if the filling amount of the conductor paste varies, the variation is absorbed. In the serial via part where multiple vias are stacked, the diameter of the via hole can be adjusted to optimize the relationship between the total volume of the via hole, the total amount of conductive paste, and the shrinkage ratio. This has the effect of suppressing the phenomenon in which the serial via portion projects to the surface after lamination, pressure bonding, and firing.

According to the present invention, the green sheets have different thicknesses alternately, and by selecting the thickness of the green sheets, it is possible to adjust the total volume of the via holes in the serial via portion where a plurality of vias are stacked. Also, the diameter of the holes for vias can be adjusted, and the relationship between the total volume of the holes for vias and the total amount of conductive paste and the shrinkage ratio can be optimized, so that the serial via part is the surface after lamination, pressure bonding and firing. This has the effect of suppressing the phenomenon of protrusion.

[Brief description of drawings]

FIG. 1 is a sectional view of a multilayer ceramic substrate showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a via filling process according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a process of printing a circuit pattern according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing a layer structure of a multilayer ceramic substrate according to Example 1 of the present invention.

FIG. 5 is a plan view showing the shape of a via according to the second embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a via filling step according to Example 2 of the present invention.

FIG. 7 is a sectional view showing a layer structure of a multilayer ceramic substrate according to Example 2 of the present invention.

FIG. 8 is a partial plan view showing a hollowed land according to a third embodiment of the present invention.

FIG. 9 is a plan view showing a mesh screen according to Embodiment 3 of the present invention.

FIG. 10 is a sectional view showing a hollow land according to a third embodiment of the present invention.

FIG. 11 is a sectional view showing a layer structure according to a fourth embodiment of the present invention.

FIG. 12 is a cross-sectional view showing a crimped state according to Example 4 of the present invention.

FIG. 13 is a sectional view showing a multilayer ceramic substrate according to a fourth embodiment of the present invention.

FIG. 14 is a sectional view showing a layer structure according to a fifth embodiment of the present invention.

FIG. 15 is a sectional view showing a crimped state according to Example 5 of the present invention.

FIG. 16 is a sectional view showing a multilayer ceramic substrate according to a fifth embodiment of the present invention.

FIG. 17 is a sectional view showing a crimped state according to Example 6 of the present invention.

FIG. 18 is a sectional view showing a multilayer ceramic substrate according to a sixth embodiment of the present invention.

FIG. 19 is a sectional view showing a crimped state according to Example 6 of the present invention.

FIG. 20 is a sectional view showing a multilayer ceramic substrate according to a sixth embodiment of the present invention.

FIG. 21 is a perspective view showing a conventional multilayer ceramic substrate.

FIG. 22 is a perspective view showing a layer structure of a conventional multilayer ceramic substrate.

FIG. 23 is a cross-sectional view showing a method for forming via holes in a conventional example.

FIG. 24 is a cross-sectional view showing a method for filling vias in a conventional example.

FIG. 25 is a cross-sectional view showing a state of vias in a conventional example.

FIG. 26 is a cross-sectional view showing a pattern printing method in a conventional example.

FIG. 27 is a sectional view showing a conventional multilayer ceramic substrate.

FIG. 28 is a cross-sectional view showing a pattern printing method on the surface of a multilayer ceramic substrate in a conventional example.

FIG. 29 is a sectional view showing a conventional multilayer ceramic substrate.

FIG. 30 is a sectional view showing a mounting structure in a conventional multilayer ceramic substrate.

[Explanation of Codes] 1a to 1d, 38a to 38d, 43a to 43d, 47a
-47d Green sheet 2, 30, 42, 46, 48, 49 Multilayer ceramic substrate 3a-3d, 31a-31d Via 4a-4d Land 5 Component land 6a-6d Circuit pattern 7 Resistance pattern 8 Electrical component 9 4 layer series via 10 Three-layer serial via 11 Two-layer serial via 12 Hole for via 13 Batch punching tool 14 Needle 15 Conductor paste 16, 22, 37 Through hole 17 Metal mask 18 Squeegee 19, 20 Via protrusion 21, 36 Mesh screen 23 Serial via protrusion 24 Resistance paste 25 Case 32 Hole for elliptical via 33a to 33d Elliptical via 34 Space portion 35 Hollow land 39, 45 8 layer serial via 40 6 layer serial via 41 4 layer serial via 44 Large diameter hole for via

Claims (6)

[Claims] 1. A plurality of green sheets are used, and a conical or pyramidal via hole whose diameter is reduced from one surface side to the other surface side at the same position on each of the plurality of green sheets. To form a via by filling the hole for this via with the conductive paste from the other surface side toward the one surface side, and the plurality of green sheets on which the via is formed are A method for forming a via in a multilayer ceramic substrate, characterized in that serial vias are formed so that they all face in the same direction, are stacked, pressure-bonded, and fired in a predetermined order to continuously overlap in a straight line. 2. A plurality of green sheets are used, and an elliptical or rectangular hole for a via is formed at the same position on each of the plurality of green sheets, and the center of the elliptical or rectangular hole of each green sheet. The conductor paste is uniformly filled in only one part or on one side to form a via, and a plurality of green sheets on which this via is formed are stacked, pressure-bonded, and fired in a predetermined order to form a straight line. A method for forming a via in a multi-layer ceramic substrate, characterized in that serial vias that are continuously overlapped are formed. 3. A plurality of green sheets are used, a via hole is formed at the same position on each of the green sheets, and then a conductor paste is filled to form vias. The green sheets having the vias are formed. Form a land pattern surrounding the above-mentioned via part in the shape of the same size as the above-mentioned via and hollowing out, and stack and press-bond all of the multiple green sheets with this via and land pattern in a predetermined order. A method for forming a via in a multilayer ceramic substrate, characterized in that firing is performed to form serial vias that are continuously overlapped in a straight line. 4. A plurality of green sheets are used, holes for vias are formed at the same positions for each of the plurality of green sheets, and only the green sheets which become an odd number layer when laminated are formed, or an even number layer. Only for the green sheets that will be used, fill the above holes for vias with a conductive paste to form vias, and stack, press-bond and fire all of the multiple green sheets with the vias in a predetermined order to form a straight line. A method for forming a via in a multilayer ceramic substrate, characterized in that a series via is continuously formed on the substrate. 5. A plurality of green sheets are used, and when laminated, the via holes having different hole diameters are formed at the same positions in the green sheet which becomes the odd-numbered layer and the green sheet which becomes the even-numbered layer. Open, only each green sheet belonging to the layer with the smaller hole diameter Fill the holes for vias with conductive paste to form vias, and stack, press-bond and fire all green sheets in the specified order to form a straight line. The method for forming vias in a multilayer ceramic substrate according to claim 4, wherein serial vias that are continuously overlapped are formed. 6. An odd number obtained when two kinds of green sheets having different thicknesses are used, and holes for vias are formed at the same positions for all of these two kinds of green sheets to stack the two kinds of green sheets. Characterized in that the vias are formed by filling the holes for vias with the conductive paste only in each green sheet belonging to the layer in which the thicker green sheet is used The method for forming a via in a multilayer ceramic substrate according to claim 5.