JP3856573B2 - Leadless package manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a leadless package for encapsulating electronic components, and more particularly, to a method for manufacturing a ceramic laminated type leadless package (wiring substrate) for encapsulating electronic components such as a crystal resonator, a SAW filter, a transistor, and an IC. .
[0002]
[Prior art]
FIG. 11 shows an example of this type of leadless package (hereinafter also simply referred to as a package) 1. This is provided with a cavity 3 in the center of the upper surface of the package body 2, and a brazing metal layer 5 that is formed slightly inside the outer peripheral edge of the surface 4 and with a predetermined width along the outer peripheral edge. A plating ring (hereinafter also simply referred to as a ring) 31 is brazed with a silver (Ag) row 9 after Ni plating or the like is applied. The sealing ring 31 is made of Kovar, 42 alloy, or the like, and is configured so as to be sealed with a lid (not shown) after an electronic component is mounted on the cavity 3. The side surface 11 is provided with a suitable number of castellations (recesses) 12 having a semicircular arc shape or a square shape in plan view. In this example, a wiring layer is provided on the castellation 12 on the side surface 11 having a long side in plan view. A formed metal layer (hereinafter also referred to as a side metal layer) 13 is provided (see FIGS. 12 and 13).
[0003]
Further, a metal layer (also referred to as a connecting metal layer) 17 is provided between the brazing metal layer 5 and the side metal layer 13 so as to connect both metal layers, and between the metal layers 5 and 13. The electrical continuity is taken. Further, the main body 2 is provided with a metal layer 16 at appropriate positions along the outer peripheral edge of the back surface 15, and is electrically connected to the side metal layer 13 of the castellation 12. Note that the width W1 of the brazing metal layer 5 is set wider than the width of the sealing ring 31, and a fillet for brazing is formed in a good shape outside the ring 31.
[0004]
The ceramic package 1 provided with such a castellation 12 is usually manufactured as follows in order to manufacture (produce) a large number at once. That is, a green sheet (ceramic green sheet) for making multiple layers is manufactured, through holes for castellation and the like are drilled in this, and high metal such as tungsten or molybdenum is used for the metal layer that forms each wiring layer. A metal (conductor) paste containing a melting point metal as a component is screen-printed or screen-printed while being evacuated. A plurality of predetermined green sheets printed with the metal paste layer are laminated and pressed to form a large unfired (raw) ceramic large substrate (large format).
[0005]
FIG. 14 shows a package unit 1a (one package part) and a package unit 1a part adjacent to the package unit 1a of the green sheet 21 forming the surface of the unfired ceramic large substrate thus formed. In FIG. 14, corresponding to the fact that the brazing metal layer 5 in the finished product (package) is formed slightly inwardly from the outer peripheral edge of the surface 4, each package unit 1 a of the green sheet 21 is partitioned. The metal paste 5a is printed so that a predetermined width (for example, 0.1 mm) is pulled inward from the boundary line (one-dot chain line in the figure) k. This is to prevent the molten solder from spreading into the adjacent package unit 1a when the ring is brazed after the fired ceramic large substrate after lamination is formed into a brazing metal layer.
[0006]
On the other hand, as shown in the enlarged view in FIG. 14, among the green sheets 21 forming the surface, between the metal paste layers 5a forming the both brazing metal layers 5 of the adjacent package unit 1a, there is a castellation. The metal paste layer 17a for the connection metal layer 17 is printed so as to sandwich the hole 12a. As shown in the enlarged view, the metal paste layer 17a is printed with a width W2 wider than the diameter of the through hole 12a in consideration of a shift during printing, and straddles the boundary line k outside the hole 12a. (To cross). Further, as described above, the metal paste layer 5a forming the brazing metal layer 5 is printed with a predetermined amount pulled down from the boundary line, but is printed with a width W1 wider than the width of the ring 31.
[0007]
A large-sized unfired ceramic large substrate obtained by laminating and pressure-bonding such green sheets has, for example, dividing grooves (also referred to as break grooves) for dividing into package units on both sides. Insert the blade vertically and horizontally by pressing the blade along k. And after this grooving (process), it fires and it becomes a baked ceramic large substrate, and simultaneously, each metal paste layer is made into a metal layer. Next, in order to be able to braze to such a metal layer, Ni plating is usually applied, and as shown in FIG. 15, each of the brazing metal layers 5 to which the plating (not shown) is applied is applied. Each of them is also brazed with a silver solder 9. After that, Ni plating and Au (gold) plating are applied to the sealing ring 31 and the like, and finally, cutting (breaking) is performed along the dividing groove 26 provided in the boundary line k to divide into package units. To do. Thus, a number of leadless packages 1 with the sealing ring 31 shown in FIG. 11 are manufactured simultaneously.
[0008]
[Problems to be solved by the invention]
By the way, in the manufacturing method, brazing of the sealing ring 31 is usually performed by mounting various packages having different heat capacities in a brazing furnace in terms of manufacturing efficiency. In such a case, even if temperature control is strict, it is necessary to give a certain range to the temperature in consideration of the solderability of other packages. For this reason, for example, if the brazing temperature is set lower, the following problem may occur. In other words, since the brazing temperature is low, a preferable fillet is formed in the brazed joint cross section, such as a case where the braze does not melt sufficiently, a void is formed in the joining row 9 or a lodge is formed. As a result, the bonding strength of the ring 31 may be reduced, sealing failure may occur, or appearance may be deteriorated.
[0009]
On the other hand, when brazing the sealing ring 31 at a high temperature, the bra is sufficiently melted to fill the joining surface, that is, the brazing metal layer 5, and a preferable fillet is formed. However, since the surface of the metal layer 5 is coated with Ni plating that is easy to wet the row, the molten row spreads wet on the Ni plating surface simultaneously with melting. In this case, as described above, the metal layer is not formed at the position of the boundary line k between the package units 1a, so that the row does not get wet, and therefore, the row does not spread beyond the boundary line. However, the brazing metal layer 5 is connected to the metal layer 13 in the castellation hole 12a via the connection metal layer 17, so that the metal layer 13 in the hole 12a spreads out (flows) into the metal layer 13. was there. In other words, if there is such a flow, the castellation holes covered or filled with brazing material will be cracked from the ceramic when splitting (the metallization of the castellation part of the adjacent product is peeled off) or split into irregular shapes. Or
[0010]
Further, as described above, the metal paste layer 17a for the connecting metal layer 17 is formed in the through hole 12a in order to ensure the conduction between the brazing metal layer 5 and the metal layer (side metal layer) 13 for castration. (See the enlarged view of FIG. 14), in the boundary line k, in the vicinity of the hole 12a, a bridge may be formed over the dividing groove 26. When plating is performed under such a melting-low bridge and divided in a subsequent process, the division is not performed normally. As shown in FIG. 16, the ceramic or metal layer 17 on the side surface 11 forming the divided surface is broken. (Dent) e occurs, and as shown in FIG. 17, a problem occurs such that a protrusion (burr) v is generated on the side surface 11 forming the opposite divided surface.
[0011]
The present invention has been made to solve such problems of leadless packages manufactured by dividing a fired ceramic large substrate after brazing a sealing ring. It is an object of the present invention to provide a manufacturing method capable of manufacturing a package even when a high temperature is applied so as to be brazed in a molten state without causing the molten solder to spread and spread on unnecessary portions such as a metal layer for castration.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a brazing metal layer brazed to a brazing metal layer formed along and along the outer peripheral edge of a surface, and a side metal layer on a side surface. And a ceramic laminated type leadless package comprising a metal layer for electrical connection between the brazing metal layer and the side metal layer,
Both the through-hole for said castellations are perforated, of said metal layer, by laminating the green sheets which have a metal paste layer printed so as to form a metal layer made provided in accordance with the ceramic layer Form a large unfired ceramic substrate for multi-cavity,
A dividing groove for dividing is put into a package unit on at least one main surface of the unfired ceramic large substrate,
After that, the fired ceramic large substrate and simultaneously the metal paste layer as a metal layer,
Then, plating the brazing metal layer ,
Attach each row the sealing ring of the brazing metal layer which is applied with the plating, then applying a plating for finishing the sealing ring,
Thereafter, in a method of simultaneously manufacturing a large number of the leadless packages with sealing rings by dividing along the dividing grooves,
Before the split grooving step,
A metal paste layer for the connection metal layer of each package unit of the green sheet forming the surface of the package, the metal paste layer for the brazing metal layer and the metal for the side metal layer A non-fired raw non-wetting material paste that can be co- fired is printed so as to cross between the paste layers and continuously cover the periphery of the through hole in an annular shape. In the ceramic large substrate, a dividing groove is formed on the boundary line from above the low non-wetting material paste.
[0013]
In such a manufacturing method, when an unsintered ceramic large substrate is fired, the solder is placed on the surface of the connecting metal layer so as to cross between the brazing metal layer and the metal layer of the castellation hole. A non-wetting material layer is formed simultaneously. Therefore, after that, for example, when Ni plating is applied and the sealing ring is brazed, even if the brazing temperature is set high and the brazing is sufficiently melted, the molten non-wetting material layer spreads out. Prevents dams and prevents their spreading. That is, it is possible to prevent the molten row from flowing into the castellation hole and into the dividing groove near the hole. Therefore, even if it is divided after finishing plating, the occurrence of defects such as poor appearance and chipped cut surfaces is prevented.
[0014]
In other words, according to the present invention, even when various products are mixed and brazed, the brazing temperature can be set high so that the bra is sufficiently melted. In the above means, “before the divided grooving step” is used when the low non-wetting material paste is printed after the grooving step, and the vicinity of the hole in the groove is partially covered by the paste. This is because chips and protrusions are generated in the same manner as in the case where melted solder flows into the break cross section during a break, and the problem of the present invention cannot be solved.
[0015]
In the present invention, the low non-wetting material paste may be printed “before the split grooving step”, and thus the low non-wetting material paste may be printed after the green sheets are laminated. It is preferable in terms of production efficiency to print before the sheets are laminated. The low-wetting material paste may be any material that can be fired at the same time and does not wet the raw material after firing, but is preferably the same material as the green sheet. Therefore, when the green sheet has alumina ceramic as a main component, it is preferable to use an alumina paste having the main component as a raw material.
[0016]
A typical plating for brazing applied to a brazing metal layer made of a refractory metal such as tungsten or molybdenum is Ni plating. However, it is sufficient if it is wet with the brazing material. Other types of plating can also be used. For example, one or a plurality of platings such as Au, Ag, Cu, and Co. As a finishing plating, a Ni plating is generally applied to a package which is an object of the present invention, and an Au plating is applied thereon, but the present invention is not limited to this.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a perspective view of a ceramic leadless package 1 according to the present embodiment, in which a main body (substrate) 2 is substantially rectangular in a plan view and is provided with a cavity 3 at the center of the upper surface. Yes. Then, a rectangular frame-shaped sealing ring 31 is placed on the brazing metal layer 5 which is inside the outer peripheral edge of the surface (upper surface) 4 and has a predetermined width W1 along the outer peripheral edge. 9 is brazed. The width W1 of the brazing metal layer 5 is wider than the width of the ring 31 so that a fillet in brazing is formed well outside the ring 31, and the outer edge is outside the outer edge of the ring 31. It is supposed to be located. Further, a metal layer (side metal layer) 13 is formed on the side surface 11 of the main body 2 on a castellation 12 having a semicircular arc shape in a plan view in the thickness direction or a castellation having a square shape (not shown). (See FIG. 2). However, in this example, the metal layer 13 is formed only on the castellation 12 formed on the long side in plan view, and this metal layer 13 is connected to the metal layer 16 formed at a suitable position on the outer peripheral edge of the back surface 15 ( (See FIG. 3).
[0018]
Note that the brazing metal layer 5 and the side metal layer 13 are connected via the connecting metal layer 17 to ensure electrical continuity. However, the connecting metal layer (the brazing metal layer 5 and the side metal layer 5 is secured). An alumina layer (also referred to as a low non-wetting material layer) 18 is formed so as to cover and cross 17) (between the metal layer 13). In the package 1 of this example, although not shown, Ni (nickel) plating and Au (gold) plating are applied as finish plating to the surface of the metal layer including the sealing ring 31. However, Ni plating (not shown) is applied to the brazing metal layer 5 before brazing of the ring 31. The main body 2 in this example has a three-layer structure of alumina ceramic, has a total thickness of about 1 mm, and is about 7 × 5 mm in plan view. The ring 31 has a rectangular frame shape and the cross section of the wire portion is about □ 0.3 mm.
[0019]
Next, a manufacturing method of such a ceramic laminated type leadless package 1 will be described in detail. For example, a composition powder obtained by adding 10% of a sintering aid to 90% alumina is dispersed and mixed with a resin, a plasticizer, and an organic solvent to form a slurry, and this is used for each green sheet ( Large format). Then, in the green sheet (large format), a cavity and a through hole for castellation (for example, a diameter of 0.4 mm) are drilled according to the design of each layer.
[0020]
Next, a metal (conductor) paste mainly composed of tungsten and molybdenum powder is printed on the surface of the sheet on the pattern of each metal layer (wiring layer) by screen printing, and is further drawn by vacuuming in the through hole. . At this time, as shown in FIGS. 4 and 5, the printing surface (printing pattern) of the metal paste 5a for the brazing metal layer 5 among the surfaces of the green sheet 21 forming the surface of the package is the same as the conventional one. A minute gap (for example, 0.2 mm) H is provided between the package units 1a adjacent to each other with the boundary line k interposed therebetween. A one-dot chain line k in the figure indicates a boundary (line) that partitions the package unit 1a.
[0021]
Also, as shown in FIGS. 4 to 6, the green sheets 21 forming the surface of both the adjacent package units 1a are connected so that the brazing metal layer 5 and the side metal layer 13 can be electrically connected. The metal paste layer 17a for the connection metal layer 17 is printed at the same time so as to sandwich the castellation hole 12a between the attachment metal layers (pastes 5a), so as to be continuous with the metal paste layer 13a on the inner surface of the hole 12a. It has become. At this time, if necessary, as shown in FIGS. 4 and 5, the metal paste layer 17a for the connection metal layer has a width larger than the diameter of the through-hole 12a in the same manner as in the past in consideration of a shift during printing. Printing is performed at W2 so as to straddle (cross) the boundary line k outside the hole 12a.
[0022]
Next, as shown in FIG. 7, on the metal paste layer 17 a for the connection metal layer 17 of each package unit 1 a in the green sheet 21 that forms the surface of the package 1, The non-wetting material paste 18a is printed (applied) with a predetermined thickness so as to cover and cross between the metal paste layer 5a for the side metal layer 13a and the metal paste layer 13a for the side metal layer 13. However, in this example, an alumina paste made of the same material as that of the green sheet 21 was printed, and its width W3 was made larger than the width W2 of the metal paste layer 17a for the connecting metal layer 17.
[0023]
The green sheets thus formed are then laminated and thermocompression bonded to produce a large unfired ceramic large substrate. Next, as shown in FIG. 8, in the unfired ceramic large substrate 25 formed by laminating the green sheets 21 to 23, the boundary line k between the adjacent package units 1a, or not shown. A dividing groove 26 having a predetermined depth is inserted by pressing a blade vertically and horizontally so that it can be divided along a boundary line between the package unit and the disposal margin (periphery of the large substrate) near the outer periphery. This dividing groove 26 may be on one side, but in this example, it was put on both sides in order to facilitate cutting.
[0024]
After inserting the dividing grooves 26, the unfired ceramic large substrate 25 is fired at a temperature of about 1500 ° C. in a reducing atmosphere for a predetermined time. Then, the fired ceramic large substrate is obtained by simultaneously firing the metal layers 5, 13, 16, 17 and the low non-wetting material layer 18. Thereafter, for brazing of the sealing ring 31, the metal layers 16 and 17 on both the front and back surfaces including the brazing metal layer 5 and the metal layer 13 of the hole 12 for castellation are formed by electrolytic plating or electroless plating. Ni plating is applied. At this time, since the low non-wetting material layer 18 is made of alumina ceramic, no plating is applied.
[0025]
Next, in such a fired ceramic large substrate 27, as shown in FIGS. 9 and 10, on the brazing metal layer 5 to which Ni plating (not shown) is applied (Ni plating surface). Then, the sealing ring 31 is set (arranged) via the silver row (preform) 9. Then, the row is reflowed and cooled at a temperature (for example, 850 ° C.) at which the silver row 9 is sufficiently melted. By doing so, the sealing ring 31 is brazed to the Ni plating surface of the brazing metal layer 5. At this time, since the melting temperature is high, the row 9 is sufficiently dissolved and spreads on the joint surface. Therefore, there is no occurrence of low accumulation or void, and a well-formed fillet is formed at the edge of the joint surface, and the ring 31 is joined with high sealing performance and joint strength.
[0026]
In this brazing, the solder spreads simultaneously with melting, but the metal layer 5 does not have a width H at the boundary k between adjacent package units 1a. That is, the ceramic has a minute width H across the dividing groove 26. Since it is exposed, it does not get wet and spread as in the conventional case (see FIG. 10). On the other hand, the row spreading wet toward the castellation hole 12a can be prevented from spreading due to the dam action of the row non-wetting material layer 18 to prevent wetting and spreading. For this reason, it is prevented that low adheres to the Ni plating surface in the hole 12a, and does not spread to the boundary line k near the hole 12a. Accordingly, the melting row does not form a bridge beyond the dividing groove 26.
[0027]
Next, in the fired ceramic large substrate 27 to which the sealing ring 31 is brazed in this manner, Ni plating and gold plating are applied as finishing plating, and then cut (folded) along the dividing grooves 26. To do. Thus, a large number of leadless packages 1 shown in FIG. 1 can be obtained at one time. Each package 1 thus obtained does not have a conventional bridge due to the spread of the wetness of the row, so that the occurrence of chips and protrusions on the side surface 11 of the package 1 forming the cut surface is prevented. As described above, in the manufacturing method according to the present invention, even when the brazing temperature of the sealing ring 31 is set high, the brazing material does not spread over the castellation 12, and problems such as chipping at the time of division do not occur. .
[0028]
In the above-described embodiment, the printing width W3 of the alumina paste is made wider by about 0.2 mm than the printing width W2 of the metal paste 17a in consideration of printing deviation and dimensional error of the metal paste (see FIG. 7). However, this may be set appropriately according to the printing accuracy. Also, the solder non-wetting material layer 18 is located between the brazing metal layer 5 and the metal layer 13 of the castellation 12, and the melted brazing when the ring 31 is brazed is the castellation hole 12 a or the dividing groove. It is only necessary to prevent or block the flow into the (boundary line) 26. Therefore, the formation pattern (planar shape) is not limited to the above-described form. Further, the printing thickness of the low non-wetting material paste such as alumina paste may be appropriately set so as to prevent the molten raw material from spreading according to the width of the printing pattern, the thickness of the raw material, and the like.
[0029]
【The invention's effect】
As is clear from the above description, according to the present invention, when brazing the sealing ring, even if the brazing temperature is high so that the brazing is performed in a sufficiently melted state, the molten Since it does not wet and spread over unnecessary parts such as a metal layer for castration, it is possible to prevent appearance defects and cracks during cutting. That is, according to the present invention, the brazing temperature can be set to a high temperature at which the row is sufficiently wet and spread, so that even when various packages having different heat capacities are mixed and brazed, temperature management is facilitated, sealing failure and ring Thus, the quality of the package can be improved without incurring a bonding failure.
[Brief description of the drawings]
FIG. 1 is a partially omitted perspective view of an embodiment of a package manufactured by a manufacturing method according to the present invention as viewed from the front side.
FIG. 2 is an enlarged view of a main part of the package of FIG.
3 is a cross-sectional view taken along line AA in FIG.
FIG. 4 is a partially enlarged plan view of a green sheet forming a surface.
FIG. 5 is an enlarged view of part B in FIG. 4;
6 is a cross-sectional view taken along line CC in FIG.
FIG. 7 is a diagram in which an alumina paste is printed between a hole for castration and a metal layer paste layer for brazing.
FIG. 8 is a partially enlarged cross-sectional view in which a dividing groove is provided in a large unfired ceramic substrate.
FIG. 9 is a cross-sectional view through the center of a hole for casting when a sealing ring is silver-brazed to a brazing metal layer of a fired ceramic large substrate.
10 is a plan view of FIG. 9. FIG.
FIG. 11 is a partially omitted perspective view of a conventional package as viewed from the surface side.
12 is an enlarged view of a main part of the package of FIG.
13 is a cross-sectional view taken along line AA in FIG.
FIG. 14 is a partially enlarged plan view of a green sheet forming a surface and an enlarged view of a main part thereof.
FIG. 15 is a cross-sectional view in which a sealing ring is silver brazed to a brazing metal layer of a conventional fired ceramic large substrate.
FIG. 16 is a partial perspective view for explaining a problem caused by spreading of the melted row when the large substrate of FIG. 15 is divided into package units.
FIG. 17 is a partial perspective view for explaining a problem caused by wet spreading of a molten row when the large substrate of FIG. 15 is divided into package units.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Leadless package 1a Package unit 4 Package surface 5 Brazing metal layer 5a Metal paste layer for brazing metal layer 9 Row 11 Side surface 12 Castation 12a Cast hole through hole 13 Side surface metal layer 13a Side surface metal Metal paste layer 17 for connection Metal layer 17a for connection Metal paste layer 18 for connection metal layer Low non-wetting material layer 18a Low non-wetting material paste (alumina paste)
21, 22, 23 Green sheet 25 Unfired ceramic large substrate 26 Dividing groove 27 Firing ceramic large substrate 31 Sealing ring

Claims (3)

A sealing ring is brazed to a brazing metal layer formed inside and along the outer peripheral edge of the surface, and includes a castellation having a side metal layer on a side surface. A method of manufacturing a ceramic laminate type leadless package comprising a metal layer for connection for electrical conduction between a metal layer and the side metal layer,
Both the through-hole for said castellations are perforated, of said metal layer, by laminating the green sheets which have a metal paste layer printed so as to form a metal layer made provided in accordance with the ceramic layer Form a large unfired ceramic substrate for multi-cavity,
A dividing groove for dividing is put into a package unit on at least one main surface of the unfired ceramic large substrate,
After that, the fired ceramic large substrate and simultaneously the metal paste layer as a metal layer,
Then, plating the brazing metal layer ,
Attach each row the sealing ring of the brazing metal layer which is applied with the plating, then applying a plating for finishing the sealing ring,
Thereafter, in a method of simultaneously manufacturing a large number of the leadless packages with sealing rings by dividing along the dividing grooves,
Before the split grooving step,
A metal paste layer for the connection metal layer of each package unit of the green sheet forming the surface of the package, the metal paste layer for the brazing metal layer and the metal for the side metal layer A non-fired raw non-wetting material paste that can be co- fired is printed so as to cross between the paste layers and continuously cover the periphery of the through hole in an annular shape. A method for manufacturing a leadless package, characterized in that, in a large ceramic substrate, dividing grooves are formed on the boundary line from above the low non-wetting material paste.   2. The method of manufacturing a leadless package according to claim 1, wherein the low non-wetting material paste is printed before the green sheets are laminated.   The method for manufacturing a leadless package according to claim 1 or 2, wherein the low non-wetting material paste is made of the same material as the green sheet.

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