JPH0677665A - Multilayered circuit board and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a small-sized high-density multilayered circuit board for electronic industries including high-frequency applications by forming heat- resistant surface layer portions in the whole of the board surface or in a part thereof on which a film-like passive element is disposed. CONSTITUTION:A multilayered circuit board which has a resistive conductor wiring 16 having a resistivity which does not exceed 5muOMEGA-cm in an inter-layer 22 formed by sequentially depositing insulating materials, and in which surface layer portions 21 and a film-like passive element 12 are disposed. The heat- resistant surface layer portions 21 are formed in the whole of the board surface or at least in a part thereof on which the film-like passive element 12 is disposed. This can prevent damage of the insulator around the board surface and the inner conductor wiring due to the thermal effect of a beam in trimming. Thus, a high-precision trimming is available and a low-resistance wiring including a high-precision film-like passive element can be provided, so that a multilayered circuit board of a smaller size and higher density can be achieved. Further, a high-speed and high-frequency signal can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer circuit board used in the electronics industry such as for consumer use and computers, and more specifically, a film having a low resistance conductor wiring built therein and having highly precise electric characteristics on its surface. High-density multilayer circuit board having passive elements arranged therein, its manufacturing method and use.

[0002]

2. Description of the Related Art In recent years, hybrid ICs have been required to be smaller and have a higher density, by forming electrode patterns on a green sheet by printing, laminating and sintering them, or by repeating screen printing. A ceramic multilayer wiring board having a wiring pattern inside the board by multilayering and sintering has been used. There are two main types of substrates. As one of them, for example, W and Mo are used as wiring conductors as described in Japanese Patent Publication No. 3-78798.
There is a ceramic multilayer substrate that is co-fired at a high temperature of 00 to 1600 ° C. As another one, for example, Japanese Laid-Open Patent Publication No.
Normally disclosed at 1000 ° C., which is disclosed in Japanese Patent Publication No.
There are low-temperature sinterable ceramic substrates that can sinter the insulator at the following relatively low temperatures.

[0003]

However, the above-mentioned substrate fired at a high temperature has a large conductor resistivity and is difficult to apply to a high-frequency circuit, and the circuit density can be increased by fine wiring. There was a drawback that I could not. on the other hand,
Since the low-temperature sinterable substrate has a low firing temperature, a so-called low-resistance conductor material such as Au, Ag, or Cu can be used as the conductor material for built-in wiring that is simultaneously fired. Therefore, the above-mentioned problems regarding the conductor resistivity can be solved. However, when a passive element such as a thick film resistor is arranged on the surface layer portion of this substrate and a trimming process by a laser beam is added, there is a problem that the insulating layer around the element is also melted due to the thermal effect.

That is, when the output of the laser beam is low, the element is not sufficiently cut and high reliability cannot be obtained. On the other hand, if the output is too high, the insulator itself is damaged because it is a low temperature sinterable material, and there is a problem that the insulation characteristics between layers cannot be guaranteed. Therefore, the conditions for laser trimming are limited to an extremely narrow region, which poses a practical problem. As described above, there is a problem in that it is difficult to obtain a highly accurate element in a multilayer circuit board in which a low resistance conductor wiring is built in and a film-like passive element is arranged on the surface layer. The present invention solves these problems, includes a passive element having high-precision electrical characteristics, and has a built-in low-resistance conductor wiring. An object of the present invention is to provide a circuit board, a manufacturing method thereof and an application.

[0005]

In order to achieve the above object, in the present invention, a low resistance conductor wiring having a resistivity of not more than 5 μΩ-cm is provided between layers formed by laminating insulating materials. A heat-resistant surface layer part is formed on the entire surface of the substrate or at least a part of the surface where the filmy passive element is arranged, Is.

Further, according to the present invention, a low resistance conductor wiring having a resistivity of not more than 5 μΩ-cm is provided between layers formed by laminating insulating materials, and a film-like passive element is arranged in the surface layer portion. In the method for producing a multilayer circuit board, a step of forming a laminate of an insulating material of an inner layer including a low resistance conductor wiring, a step of forming a heat resistant surface layer portion on the entire surface or a local portion of the laminate, The step of forming a film-like passive element at a position where at least a part of the heat-resistant surface layer portion is overlapped, and the electrical characteristics of the film-like passive element are adjusted by a trimming step with a laser beam. In the above, it is preferable that the heat-resistant surface layer part is composed mainly of alumina, and the insulating material has a volume fraction of alumina contained in the composition of 40% at maximum in the inner layer part. It should be at least 50% in parts.

As described above, according to the present invention, the low resistance conductor wiring of Au, Ag, Cu or the like is arranged in the inner layer portion of the substrate in which the insulating material is laminated, and the laser beam is irradiated at least in the trimming step. By providing a heat-resistant surface layer portion at a position corresponding to the portion, the trimming process is facilitated, a passive element having high-precision electrical characteristics is included, and a low-resistance conductor wiring is built in. It is a high-density multi-layer circuit board for the electronic industry including high-frequency applications.

The insulating material is usually made of low-temperature sinterable glass having a low softening point and is co-fired with the wiring conductor.
There are roughly two methods for forming the heat resistant surface layer. One is a method of preparing a green sheet molded body whose composition distribution is adjusted in advance so that a material having high heat resistance such as alumina is unevenly distributed in the surface layer portion, and simultaneously firing the inner layer conductor wiring. The other one is a method of forming a predetermined laminated circuit incorporating a low-resistance conductor wiring and then forming the heat-resistant surface layer portion in another step by another film forming means such as a sol-gel method. Is.

On the surface of the laminated circuit board according to the present invention,
By forming a thick film resistor as a passive element, the subsequent trimming process using a laser beam is facilitated, and a multilayer circuit board including a highly accurate element and including a low resistance conductor wiring is obtained. Further, even when a capacitive element is formed as a passive element, the capacitance of the element can be easily adjusted by laser trimming the electrode portion of the capacitive element. For example, by using lead borosilicate-based glass as the insulating material for the inner layer of the multilayer circuit board according to the present invention, it becomes possible to sinter even at a temperature of about 850 ° C., the strength of the board is secured, and Au, Ag, Cu
Low resistance conductor materials such as can be co-sintered.

In forming the heat-resistant surface layer portion according to the present invention, a so-called graded composition structure is provided in which a proper concentration gradient is provided by a mixed layer of both compositions in the boundary region with the inner layer insulator portion having a different composition. As a result, an unstable phenomenon such as stress generation due to a difference in thermal expansion coefficient when the temperature changes can be suppressed, and a highly reliable circuit board can be provided. Since the multilayer circuit board obtained by the present invention includes the film-like passive element with high precision and has the low resistance conductor wiring, the portable camera-integrated video device and the communication for speeding up the signal are carried out. It can be effectively used as an electronic circuit board that constitutes electronic equipment, computers, etc.

[0011]

The present invention has a structure in which a low-resistance conductor wiring is built in, a heat-resistant surface layer portion is formed on the surface thereof, and a film-like passive element is arranged. Therefore, at the time of trimming with the laser beam, it is possible to suppress damage to the insulator around the surface layer of the substrate and the conductor wiring in the inner layer due to the thermal effect of the beam.
Therefore, highly accurate trimming can be easily performed, and a multilayer circuit board including a highly accurate film-like passive element and having low resistance wiring is realized. On the other hand, the inner layer portion of the substrate has low heat resistance, but the strength of the substrate can be secured by using an insulating material having good low-temperature sinterability.

As the conductor material for the multilayer circuit board, A
By applying at least one of u, Ag, Cu, Pt, and Pd, the conductivity of the circuit can be significantly increased as compared with a high temperature sinterable conductor such as W or Mo. It is possible to make fine wiring patterns. Therefore, in combination with higher reliability of the passive element, smaller size,
A high-density multilayer circuit board can be realized. Furthermore, 5μΩ-
By applying a conductor material having a low resistance of 10 cm or less, it is possible to increase the speed or frequency of signals processed by a circuit.

[0013]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto. . Embodiment 1 FIG. 1 shows an embodiment of the present invention. FIG. 1 is a partial sectional view including a thick film resistor of a multilayer circuit board according to the present invention. First, an organic solvent such as polyvinyl butyral is added to lead borosilicate glass powder and alumina powder as a heat-resistant frit, and the mixture is stirred to form a sludge. A plurality of unfired inductive green sheets are formed from this slurry by a casting film forming method using a doctor blade. At the stage of forming this green sheet, the amount of alumina powder contained is set to three levels. Three types of green sheets A, B, and C are prepared in the order of the alumina powder.
The amount of alumina powder added is about 60%, 40%, and 20%, respectively, based on the volume ratio in the ceramic after firing.
Adjust so that

Next, the outer shape and a plurality of holes (via holes) are formed by punching at the same time with a metal mold made of stainless steel or the like. On this green sheet, usually 3μΩ-cm
A conductor paste containing silver as a main component, which has a lower resistivity, is applied by a screen printing method to form the electrode pattern 11 or the inner layer conductor wiring 16 and fill the via hole 14. It stacks up sequentially using a plurality of similarly prepared green sheets. At this time, by using the green sheet C previously prepared, the inner layer conductor wiring portion 2 having a predetermined number of layers is formed.
No. 2 is formed, and one green sheet is successively laminated in the order of B and A so that the green sheet A is on the surface. Next, using a hot press machine or the like, thermocompression bonding is performed from the upper and lower surfaces under the conditions of a temperature of 120 ° C. and a pressure of 200 kg / cm ² to obtain a green sheet laminate.

This molded body was degreased in air at a temperature of 350 ° C. for about 1 hour and then in air again at 800-1000 ° C.
By firing for about 10 minutes, the alumina composition part 17 is formed on the surface layer part.
A multi-layer circuit board having a heat resistant surface layer portion 21 containing a large amount and containing a low resistance inner layer conductor wiring portion 27 in a low temperature sinterable glass ceramic composition portion 18 is obtained. Further, a resistor 12 mainly composed of RuO ₂ is formed on this substrate by screen printing, and then dried and fired to form a thick film resistor. Usually, a glass paste is further printed-dried on this resistor and fired at a low temperature of 600 ° C. or lower,
The protective film 15 is formed to complete the multilayer circuit board. When the resistance value of the resistor 12 is measured in this state, there is a large variation, and the resistance value is normally dispersed within about ± 15% of the target value.

Then, the trimming portion 13 is formed by the laser beam so as to correspond to the target individual resistance value, and the resistance value is adjusted. By this step, the error of the resistance value of the resistor 12 with respect to the target value can be easily set within ± 1%. Also due to the thermal influence of the laser beam irradiation in this step, since a layer having excellent heat resistance is formed on the surface of the seed substrate, it is possible to minimize damage to the internal insulator and conductor wiring. After trimming without forming a protective film made of glass paste, the resistor 1
2 Protective coating 1 made of resin on the surface at a temperature of 200 ° C or less
By forming 5, the stability of the resistance value can be similarly improved.

In the present embodiment, an example in which an alumina filler is used as the heat resistant material is shown, but other materials such as Al can be used.
Other materials such as N, ZrO ₂ , SiO ₂ , TiO ₂ may be used. In addition, in the present embodiment, an example of a thick film resistor is shown as a film passive element, but this is also applicable to other passive elements formed by a thick film or thin film process such as an inductor and a capacitive element. Similarly, trimming is easily possible. In addition, as the conductor material of the inner layer, Ag
The example using is described in detail, but Au, Pt,
Pd and these alloys can be used as well. Cu can also be applied by firing in an inert gas.

Example 2 By the same procedure as in Example 1, a plurality of green sheets were obtained in which the via holes 14 were filled with a conductor paste and the surface layer electrode patterns 11 and the inner layer conductor wirings 16 were formed. At this time, the content of the alumina filler in the green sheet A shown in Example 1 was adjusted so that the volume percentage in the fired ceramic was about 80, 70, 60, 5 respectively.
It was prepared so as to be 0, 40, 30, 20, 10%.
The thickness of the green sheet was approximately 100 μm. Among these, a plurality of green sheets having the same content of the alumina filler are combined and stacked, and thereafter, a fired multilayer body containing conductor wiring is manufactured in the same manner as in Example 1.

FIG. 2 is a sectional view showing the structure of a sample according to this embodiment. The baking temperature of this substrate is 850 ° C., and the thickness after baking is about 0.7 mm. The following evaluation was performed on these samples. One is the 4-point bending strength, and the other is the insulation resistance value between layers. The former was evaluated in the state where there was no inner layer conductor wiring, that is, the ceramic alone.
For the latter evaluation, the position of the trimming portion 13 shown in FIG. 2 is irradiated with a laser beam for trimming,
The insulation resistance value between the surface layer electrode 11 and the inner layer conductor 16 was measured. Trimming conditions are laser pulse transmission frequency 3
The output is 2.4 W and the beam velocity is 25 mm / sec.

The results of these measurements are shown in FIG. If the volume fraction of alumina exceeds 40%, the transverse rupture strength is significantly reduced. This is because the amount of the glass composition in the layer is insufficient and sufficient firing cannot be performed. On the other hand, the insulation resistance value between layers is usually required to be 10 ⁹ Ω or more. However, if the alumina content is less than 50%, the heat resistance is low and the insulator in the surface layer portion is largely damaged, so that sufficient interlayer insulation resistance cannot be obtained. From the above experimental results, it is understood that it is difficult to realize both of these characteristics, that is, low temperature sinterability and heat resistance with a substrate having the same composition. Therefore, the maximum alumina content in the insulating material is 40% in the inner layer and at least 5 in the surface layer.
It should be 0%.

Example 3 A green sheet laminate is obtained by using the same materials and procedures as in Example 1. Here, only the green sheet C shown in Example 1 having the smallest alumina content is used. This green sheet laminate is fired under the same conditions as in Example 1. Further, an alumina film having a thickness of about 3 μm is formed as the above-mentioned heat resistant surface layer portion by the sol-gel method on the surface of the substrate where the thick film resistor is to be formed in the next step. A thick film resistor is formed on this film as in the first embodiment. Next, a glass paste is applied to this resistor and baked at a temperature of 600 ° C. or less to form a protective film 15, and the protective film 15 is trimmed with a laser beam to finely adjust the resistance value. By,
As in Example 1, a high-density multilayer circuit board including a highly accurate and stable thick film resistor element is obtained.

In this embodiment, an example of forming the heat resistant surface layer portion of alumina by the sol-gel method has been shown, but other materials such as SiO ₂ , CoO, MnO and TiO ₂ are mainly used. May be. Further, the film forming method may be another method such as sputtering or thermal spraying. Although all of the above examples show examples of ceramic multilayer circuit boards, the present invention can be applied to, for example, a printed wiring board using glass epoxy as an insulating material.

Example 4 By the same procedure as in Example 1, a multilayer circuit board having 6 layers of conductor layers and a thick film resistance element arranged on the surface thereof is prepared. Electronic components centering on active elements such as LSI and transistors are joined to this multilayer substrate by soldering by so-called surface mounting technology. Further, the lead frames for input and output to the outside of the circuit are soldered at a narrow pitch of 1.27 mm, and the video signal processing circuit module according to the present invention is completed. The substrate dimensions are 35 mm x 27.5 mm. Circuit patterns of the first layer and the second layer are shown in FIGS. 4 and 5. According to the present invention, a large number of high-precision and fine thick-film resistance elements can be formed at a high density, and an element having a relatively large area such as an LSI can be stacked and mounted thereon, and 30 elements / cm ² or more. It has become possible to implement high-density mounting. By applying this module to a video device with a built-in camera or a portable electronic device, it is effective for further miniaturization and high performance of the device.

Example 5 By the same procedure as in Example 1, a multilayer circuit board in which a thick film resistance element such as a terminating resistor is arranged on the conductor layer 15 layer and the surface is prepared. Electronic components are surface-mounted on this substrate in the same manner as in Example 4, a high frequency system circuit that can be used up to a frequency band of GHz is manufactured, and applied to communication electronic devices. According to the present invention, since the LSI can be arranged on the thick film resistance element, the size of the substrate can be reduced. As a result LSI
The signal access wiring distance between them can be shortened, which is effective in increasing the frequency and speed of communication lines.

[0025]

According to the present invention, since it is possible to provide a multi-layer circuit board having a built-in low-resistance conductor wiring and including a high-precision film-like passive element, it is possible to make the conductor pattern fine wiring. It can contribute to downsizing or high density ratio of electronic circuits, and can be effectively used especially for high speed or high frequency circuits.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a multilayer circuit board according to an embodiment of the present invention.

FIG. 2 is a sectional configuration diagram of a test sample according to Example 2 of the present invention.

FIG. 3 is a graph showing a characteristic evaluation result of a multilayer circuit board according to a second embodiment of the present invention.

FIG. 4 is a first layer circuit pattern diagram of a multilayer substrate according to Example 4 of the present invention.

FIG. 5 is a second layer circuit pattern diagram of the multilayer substrate according to the fourth embodiment of the present invention.

[Explanation of symbols]

11: surface electrode, 12: resistor, 13: trimming part,
14: via, 15: protective film, 16: inner layer conductor, 17:
Alumina composition part, 18: Glass-ceramic composition part, 2
1: heat resistant surface layer part, 22: inner layer conductor wiring part.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H01L 23/12 23/15 27/01 311 8418-4M H05K 1/16 C 6921-4E 3/28 A 7511-4E (72) Inventor Shuji Kato 4026, Kuji-machi, Hitachi City, Hitachi, Ibaraki Prefecture, Hitachi Research Laboratory, Inc. (72) Inventor, Mitsuru Hasegawa 4026, Kuji-machi, Hitachi City, Ibaraki Institute, Hitachi Research Institute, Ltd.

Claims (10)

[Claims] 1. A multi-layer circuit board having low-resistance conductor wiring having a resistivity of not more than 5 μΩ-cm between layers formed by laminating insulating materials, and having a film-like passive element arranged in a surface layer portion. 2. A multilayer circuit board, wherein a heat resistant surface layer portion is formed on the entire surface of the substrate or at least a portion where the filmy passive element is arranged. 2. The multilayer circuit board according to claim 1, wherein the film-shaped passive element is a film-shaped resistor. 3. The multilayer circuit board according to claim 1, wherein the heat-resistant surface layer portion is composed mainly of alumina. 4. The volume fraction of alumina contained in the composition of the insulating material is 40% at maximum in the inner layer portion.
The multilayer circuit board according to claim 1, wherein the surface layer portion is at least 50%. 5. The low resistance conductor wiring is made of Au, Ag,
The multilayer circuit board according to claim 1, which is formed of at least one of Cu, Pt, and Pd. 6. A composition concentration gradient layer, which is a mixture of the constituents of both layers, is provided in a boundary region between the heat resistant surface layer portion and the insulating material constituting the multilayer circuit of the inner layer portion. Item 1. The multilayer circuit board according to item 1. 7. The multilayer circuit board according to claim 1, wherein the film-shaped passive element includes at least one capacitive element. 8. A multi-layer circuit board having a low resistance conductor wiring having a resistivity of not more than 5 μΩ-cm between the layers formed by laminating insulating materials, and having a film-like passive element arranged in the surface layer portion. In the manufacturing method of, a step of forming a laminated body of an insulating material of an inner layer including a low resistance conductor wiring, a step of forming a heat resistant surface layer portion on the entire surface or a local portion of the laminated body, and the formed heat resistant surface layer A method of manufacturing a multilayer circuit board, comprising: forming a film-like passive element at a position where at least a part of each part overlaps with each other; and adjusting electrical characteristics of the film-like passive element by a trimming step using a laser beam. 9. A video device integrated with a camera, comprising the multilayer circuit board according to claim 1 as a constituent member. 10. A communication electronic device comprising the multilayer circuit board according to claim 1 as a constituent member.