JP2000260915A - Ceramic package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance bonding strength of an electronic part by preventing a brazing material from creeping upon the electronic part mounting surface. SOLUTION: A metal plate 20 for heat dissipation comprises an eaves 21 having an upper surface 22 for mounting a semiconductor element 50 fixedly, and a shaft 25 having bottom 26 being bonded to a kovar plate 10 through a brazing material 15. A space of sufficient volume is ensured between the inner wall of an opening 31, and the side wall of the shaft 25 and a brazing material reservoir 16 is formed between them. Since excess brazing material 15 is stored in the brazing material reservoir 16 at the time of brazing, it is prevented from creeping upon the semiconductor element mounting surface 22. Consequently, incomplete bonding of the semiconductor element 50 is prevented and the semiconductor element 50 can be secured rigidly to the metal plate 20 for heat dissipation. According to the structure, the semiconductor element 50 can be operated normally and stably for a long term.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ceramic package provided with a heat radiating member having an electronic component mounting surface for mounting electronic components.

[0002]

2. Description of the Related Art In semiconductor devices, Si chips and Ga
2. Description of the Related Art Electronic components such as a semiconductor element such as an As chip and a chip capacitor are mounted on an electronic component mounting surface provided in an electronic component mounting package and put to practical use. Ceramics such as alumina have excellent heat resistance, durability, and thermal conductivity, so they are suitable as a material for the body of this electronic component mounting package, and ceramic electronic component mounting packages are currently in active use. .

[0003] In order to reduce the package size, increase the mounting density on a mounting board, and improve the electrical characteristics, this ceramic electronic component mounting package is generally formed by stacking and firing a plurality of green sheets. A ceramic package body is manufactured.

Further, for example, a ceramic package for optical communication is provided with a heat radiating member made of metal or the like having excellent heat conductivity in order to quickly dissipate heat generated during operation of the semiconductor element into the atmosphere. Some semiconductor devices are directly mounted on the upper surface of the semiconductor device.

[0005]

As a technique for forming a heat dissipating member used in the above-described ceramic package for optical communication, for example, the thermal expansion coefficient is close to the thermal expansion coefficient of the ceramic package body and the thermal conductivity is about 200 W / There is known a composite material having a material of about mK and comprising a porous sintered body of tungsten or molybdenum impregnated with molten copper.

However, as shown in FIGS. 5A and 5B, for example, the heat radiation member 1 is brazed to one surface of a ceramic package body 2 having an opening 4 using a brazing material 3 such as silver brazing. When joined, the brazing material 3 spreads between the inner wall of the opening 4 and the outer wall of the heat radiating member 1,
There is a problem that it climbs up to the semiconductor element mounting surface 5. Hereinafter, the reason why the above problem occurs will be described.

The required amount of the brazing material 3 is determined by the clearance between the heat dissipating member 1 and the ceramic package body 2. If the clearance becomes smaller than a certain level due to manufacturing variations, extra parts other than those involved in joining are used. The brazing material 3 flows out to a portion other than the joint of the heat radiation member 1. The excess brazing material 3 that has flowed out is formed on the inner wall of the opening 4 and the heat dissipating member 1.
And spreads out to the outer wall and crawls up to the semiconductor element mounting surface 5.

When the brazing material 3 climbs up on the semiconductor element mounting surface 5, irregularities are formed on the semiconductor element mounting surface 5, so that a gap is formed below the semiconductor element when the semiconductor element is mounted, and Poor bonding may occur.
Therefore, there is a problem that the semiconductor element cannot be firmly fixed to the heat radiation member 1.

The present invention has been made to solve such a problem, and provides a ceramic package which prevents a brazing material from creeping up on a mounting surface of an electronic component and improves the joining strength of the electronic component. The purpose is to:

[0010]

According to the ceramic package of the present invention, the first heat radiating member is joined to one surface of the ceramic package body by a brazing material, and the second heat radiating member is formed by the first heat radiating member. A brazing material joined to the first heat radiating member through an opening of the ceramic package main body, and having an electronic component mounting surface on the other surface side of the ceramic package main body; It is formed between the inner wall of the opening and the outer wall of the second heat radiating member. Therefore, at the time of brazing, excess brazing material is stored in the brazing material storage portion, and it is possible to prevent the brazing material from climbing up on the electronic component mounting surface. Thereby, it is possible to prevent the occurrence of a bonding failure of the electronic component and to firmly fix the electronic component to the second heat radiating member. Therefore, the electronic component can be normally and stably operated for a long time.

According to the ceramic package of the second aspect of the present invention, the second heat radiation member has an eaves portion and a shaft portion, the eaves portion has an electronic component mounting surface on an upper surface, and the shaft portion has a shaft portion. The bottom surface is joined to the first heat dissipating member, and the brazing material pool is formed between the inner wall of the opening and the side wall of the shaft. Therefore, during brazing, excess brazing material is reliably stored in the brazing material storage portion. Therefore, by reliably preventing the brazing material from creeping up on the electronic component mounting surface, it is possible to reliably prevent the bonding failure of the electronic component and to surely improve the bonding strength of the electronic component.

According to the ceramic package of the third aspect of the present invention, the first heat radiation member is made of a material having a coefficient of thermal expansion close to that of the material of the ceramic package body. When the ceramic package body is brazed using a brazing material such as silver brazing, for example, the deformation of the first heat dissipation member is small, and the first heat dissipation member and the ceramic package body can be firmly joined. Therefore, the semiconductor element can be firmly fixed to the ceramic package.

As a material of the first heat radiation member, for example, an iron-nickel-cobalt alloy (29
% Nickel, 17% cobalt) or the like. By using Kovar as the material of the first heat radiating member, the thermal expansion coefficient of the first heat radiating member can be approximated to that of the ceramic package body.

According to the ceramic package of the fourth aspect of the present invention, the second heat radiating member has a metal plate made of any metal material selected from molybdenum, copper-molybdenum, and copper-tungsten. Therefore, a heat radiating member having an appropriate coefficient of thermal expansion and a high thermal conductivity can be obtained.

Further, a plating film of, for example, nickel or the like is formed on the outer peripheral surface of the above-mentioned metal plate, and is processed into a desired shape, so that the brazing material can be easily accumulated between the inner wall of the opening and the outer wall of the metal plate. A part can be formed.

Further, by exposing the portion of the metal plate corresponding to the brazing material reservoir, excess brazing material wets between the inner wall of the opening of the ceramic package body and the outer wall of the metal plate during brazing. Spreading can be prevented, and crawling on the electronic component mounting surface can be prevented.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. One embodiment in which the present invention is applied to a ceramic package for optical communication will be described with reference to FIGS.

As shown in FIGS. 1 and 2, the ceramic package 100 includes a Kovar plate 10 as a first heat radiating member, a metal plate 20 for heat radiating as a second heat radiating member, and an alumina material as a ceramic package body. It is composed of a package body 30, a lead frame 40 and the like.

The Kovar plate 10 is joined to one surface of the package body 30 by a brazing material 15, and the heat dissipation metal plate 20 is joined to the Kovar plate 10 by the brazing material 15 through an opening 31 of the package body 30 described later. Have been. As the brazing material 15, silver brazing is preferable.
A silver-copper eutectic alloy containing about 85% by weight and containing 15 to 28% by weight of copper is more preferable.

The heat-dissipating metal plate 20 includes a package body 30.
The eaves portion 21 having a semiconductor element mounting surface 22 as an electronic component mounting surface on which the semiconductor element 50 is mounted and fixed on the other surface side, that is, the upper surface, and the bottom surface 26 are joined to the Kovar plate 10 by the brazing material 15. And a shaft 25. The semiconductor element 50 is mounted and fixed on the semiconductor element mounting surface 22 using an adhesive such as glass, resin, or brazing material. The semiconductor element 50 is electrically connected to the lead frame 40 via a bonding wire 45. The semiconductor element 50 is hermetically sealed by joining a lid or the like (not shown) to the upper surface of the package body 30 with a sealing material such as solder, low-melting glass, resin, or brazing material. In FIG. 2, the semiconductor element and the bonding wires are omitted.

As shown in FIGS. 3A and 3B, the heat-dissipating metal plate 20 is a copper-tungsten plate 60 as a metal plate made of a metal material in which a porous sintered body of tungsten is impregnated with molten copper. Is formed by forming a nickel plating film 61 on the outer peripheral surface, cutting the side wall of a portion to be the shaft member 25, and processing it into a desired shape. In FIG. 3B, the eaves 2
1, the semiconductor element mounting surface 22 and the side wall surface 23;
5, a nickel plating film 61 is formed on the bottom surface 26, and the copper-tungsten plate is exposed on the lower surface 24 of the eaves portion 21 and the side wall surface 27 of the shaft portion 25. Here, the dimensions of the copper-tungsten plate 60 are length × width × height = 4 mm × 4 m
m × 1 mm, where w is the cutting width and t is the height of the shaft portion 25, w = 0.1 mm and t = 0.7 mm.

The package body 30 having an opening 31 and formed in a frame shape is joined to the Kovar plate 10 using the brazing material 15 so as to surround the entire circumference of the heat-dissipating metal plate 20.
One surface of the package body 30, that is, the Kovar plate 10
A not-shown joining pattern made of tungsten, molybdenum, or the like joined to the Kovar plate 10 via the brazing material 15 is provided on the end face on the side. The surface of this bonding pattern is plated with nickel, gold, or the like.

A plurality of wiring patterns such as tungsten and molybdenum are formed from one surface of the package body 30 to the other surface. The wiring pattern is via 3
2. It is composed of an inner layer wiring 33 and a wiring pad 34, and the surface of the wiring pad 34 is plated with nickel, gold or the like. One end of the wiring pattern is electrically connected to a lead frame 40 connected to an external electric circuit such as a printed circuit board. The wiring pad 34 at the other end of the wiring pattern is connected to a bonding wire of the semiconductor element 50 by a bonding wire. 45, it is electrically connected.

A space having a predetermined volume is formed by the inner wall of the opening 31 of the package body 30, the side wall of the shaft portion 25 of the heat radiation metal plate 20, the lower wall of the eaves 21, and the outer wall of the Kovar plate 10. . Then, between the inner wall of the opening 31 and the side wall of the shaft portion 25, that is, the inner wall of the opening 31 and the heat dissipating metal plate 20.
The brazing material 15 accumulates between the outer wall of the brazing material and the brazing material accumulating portion 16.

Next, a method for manufacturing the metal plate 20 for heat radiation will be described. (1) As shown in FIG.
Is sintered at 800 ° C. in a nitrogen-hydrogen mixed gas atmosphere. Then, a nickel plating film 61 is formed on the outer peripheral surface of the copper-tungsten plate 60 by an electrolytic plating method using a plating solution containing nickel sulfate, nickel chloride or the like as a main component.

(2) As shown in FIG. 3B, the shaft member 2 of the copper-tungsten plate on which the nickel plating film 61 is formed
Then, the side wall of the portion that becomes 5 is cut, the copper-tungsten plate is exposed, and the copper-tungsten plate is processed into a desired shape to obtain the metal plate 20 for heat radiation.

Next, a method of manufacturing the package body 30 will be described. (3) Magnesia, silica, calcined talc,
Powder to which a small amount of a sintering aid such as calcium carbonate and a coloring agent such as titanium oxide, chromium oxide, and molybdenum oxide are added,
A plasticizer such as dioxyl phthalate, a binder such as an acrylic resin or a butyral resin, and a solvent such as toluene, xylene and alcohol are added, and the mixture is sufficiently kneaded to obtain a viscosity of 200.
A slurry of 0 to 40000 cps is produced, and a plurality of 0.3 mm-thick alumina green sheets, for example, are formed by a doctor blade method.

(4) Each green sheet is processed into a desired shape using a punching die, a punching machine, or the like, and further, a plurality of via holes are punched to form a conductor using tungsten powder, molybdenum powder, or the like in each via hole. The vias are filled to form vias. An inner layer pattern is formed on the green sheet corresponding to the inner layer of the package body using the same conductive paste as the via. A conductor pattern is screen-printed on the green sheet corresponding to the front and back layers of the package body using the same conductor paste as the via.

(5) A green sheet corresponding to an inner layer having a via and an inner layer pattern formed thereon and a green sheet corresponding to a surface layer on which a conductor pattern is screen-printed,
This green sheet laminate is heated to, for example,
It is integrated by thermocompression bonding under the condition of 0 to 250 kg / cm ² .

(6) The integrated green sheet laminate is fired at 1500 to 1600 ° C. in a nitrogen-hydrogen mixed gas atmosphere. Thereby, the resin component in the conductive paste is decomposed and eliminated, and a wiring pattern and a bonding pattern are formed on the package body made of alumina. (7) The pad portion and the bonding pattern of the formed wiring pattern are plated with nickel, gold, or the like to obtain the package body 30 shown in FIG.

Next, as shown in FIGS. 4A and 4B, the package body 3 manufactured in the above steps (3) to (7) is manufactured.
The Kovar plate 10 prepared in advance on one surface of the Kovar plate 10 is joined to the Kovar plate 10 through the opening 31 of the package body 30 by using a brazing material 15 such as silver brazing.
The heat-dissipating metal plate 20 produced in the steps (1) and (2) is joined using a brazing material 15 such as silver brazing. At this time, a space is formed by the inner wall of the opening 31, the side wall of the shaft portion 25, the lower wall of the eaves portion 21, and the outer wall of the Kovar plate 10. The tungsten plate is exposed. Therefore, it is possible to prevent the excess brazing material 15 from spreading between the inner wall of the opening 31 and the side wall of the shaft portion 25. Then, the brazing material pool 16 is formed between the inner wall of the opening 31 and the side wall of the shaft 25. Therefore, the surplus brazing material 15 is stored in the brazing material storage portion 16, and it is possible to prevent the brazing material 15 from climbing up on the semiconductor element mounting surface 22.

The thermal expansion coefficient of alumina as the material of the package body 30 is 7.8 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of Kovar as the material of the Kovar plate 10 is 9.
Since the thermal expansion coefficients of the two are approximately 1 × 10 ⁻⁶ / ° C., the thermal expansion coefficients of the two are close to each other, and when the Kovar plate 10 is joined to the package body 30 using a brazing material 15 such as silver brazing, the Kovar plate 10
Of the package body 30 and the Kovar plate 10
And can be firmly joined. Therefore, the semiconductor element 50 can be firmly fixed to the ceramic package 100.

(8) As shown in FIG. 1, the lead frame 40 is electrically connected to the electrode portion of the wiring pattern, and the semiconductor element 50 is mounted on the semiconductor element mounting surface 22 of the ceramic package 100. Are electrically connected to the wiring pattern pads 34 by wire bonding. Then, the semiconductor element mounting surface 2
2 is hermetically sealed.

Next, Table 1 shows the results of a test of the rate at which the brazing material 15 creeps up on the semiconductor element mounting surface 22 of the present embodiment. 3B, the cutting width w of the heat-dissipating metal plate 20 is fixed at w = 0.1 mm, and the height t of the shaft portion 25 is changed. Table 1 shows the results of the test for the rate of occurrence of crawling. The number of tests n is all n = 50. The reason why w is fixed at 0.1 mm is to increase the contact area between the bottom surface 26 of the shaft portion 25 and the Kovar plate 10 to secure heat radiation. That is, when the cutting width w becomes larger than a certain value, the heat radiation property decreases.

[0035]

[Table 1]

As shown in Table 1, in Comparative Example 1,
t = 0.5 mm, and the crawling occurrence rate is 34%. Further, in Comparative Example 2, t = 0.3 mm,
The rate of crawling is 100%. Further, in Comparative Example 3, t = 0.0 mm, that is, not cut,
The rate of crawling is 100%. For this reason, in Comparative Example 1, Comparative Example 2, and Comparative Example 3, unevenness is formed on the surface on which the semiconductor element is mounted, and there is a possibility that defective bonding of the semiconductor element occurs. Therefore, the semiconductor element cannot be firmly fixed to the metal plate for heat radiation.

On the other hand, in this embodiment, t = 0.7 m
m, and the crawling rate is 0%. That is,
A sufficient volume of space is secured between the inner wall of the opening 31 and the side wall of the shaft portion 25, and the brazing material accumulation portion 16 is formed between the inner wall of the opening 31 and the side wall of the shaft portion 25. It is possible to prevent the brazing material 15 from creeping up on the semiconductor element mounting surface 22. Thereby, it is possible to prevent the occurrence of a bonding failure of the semiconductor element 50 and to firmly fix the semiconductor element 50 to the metal plate 20 for heat radiation. Therefore, the semiconductor element 50 can be normally and stably operated for a long time.

Further, in this embodiment, since the thermal expansion coefficients of the package body 30 and the Kovar plate 10 are similar, the Kovar plate 10 is joined to the package body 30 using a brazing material 15 such as silver brazing. When the Kovar plate 10
Of the package body 30 and the Kovar plate 10
And can be firmly joined. Therefore, the semiconductor element 50 can be firmly fixed to the ceramic package 100.

Furthermore, in this embodiment, since the heat-dissipating metal plate 20 has a copper-tungsten plate, a heat-dissipating metal plate having an appropriate coefficient of thermal expansion and a high thermal conductivity can be obtained. it can. Further, by forming a nickel plating film 61 on the outer peripheral surface of the copper-tungsten plate 60 and cutting the side wall of the portion to be the shaft portion 25, the inner wall of the opening 31 and the side wall of the shaft portion 25 can be easily formed. The brazing material pool 16 can be formed. Further, since the copper-tungsten plate is exposed on the side wall of the shaft portion 25, the excess brazing material 15 is prevented from spreading between the inner wall of the opening portion 31 and the side wall of the shaft portion 25 during brazing. In addition, it is possible to reliably prevent crawling on the semiconductor element mounting surface 22.

In one embodiment of the present invention described above, copper-
Nickel plating film 61 on the outer peripheral surface of tungsten plate 60
Was formed, and the metal plate for heat dissipation was manufactured by cutting the side wall of the portion to be the shaft portion 25. In the present invention, the metal plate for heat dissipation was manufactured by removing the side wall of the portion to be the shaft portion by etching. Alternatively, the heat dissipation metal plate may be manufactured by separately manufacturing the eaves portion and the shaft portion and joining them.

In this embodiment, the copper-tungsten plate 6
In the present invention, a nickel plating film may be formed on the outer peripheral surface of a metal plate made of molybdenum or copper-molybdenum.

In the present embodiment, the present invention is applied to a surface-mount type optical communication ceramic package.
The present invention may be applied to an insertion type such as GA (Pin Grid Array) or other types of ceramic packages.

The present invention is applicable not only to electronic component packages made of alumina but also to any ceramic package made of aluminum nitride, mullite, glass ceramics fired at a low temperature, and the like.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment in which the present invention is applied to a ceramic package for optical communication.

FIG. 2 is a perspective view showing an embodiment in which the present invention is applied to a ceramic package for optical communication.

3A and 3B show a heat-dissipating metal plate according to an embodiment of the present invention, wherein FIG. 3A is a cross-sectional view before cutting, and FIG. 3B is a cross-sectional view after cutting.

4A and 4B are views for explaining a method of manufacturing a ceramic package according to an embodiment of the present invention, wherein FIG. 4A is a cross-sectional view before bonding and FIG. 4B is a cross-sectional view after bonding.

5A and 5B are views for explaining a conventional method for manufacturing a ceramic package, in which FIG. 5A is a cross-sectional view before bonding, and FIG. 5B is a cross-sectional view after bonding.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 Kovar plate (first heat dissipating member) 15 brazing material 16 brazing material accumulating portion 20 heat dissipating metal plate (second heat dissipating member) 21 eaves portion 22 semiconductor element mounting surface (electronic component mounting surface) 25 shaft portion 30 package body (Ceramic package body) 31 Opening 60 Copper-tungsten plate (metal plate) 61 Nickel plating film 50 Semiconductor element (electronic component) 100 Ceramic package

Claims (4)

[Claims] 1. A ceramic package having a heat dissipating member having an electronic component mounting surface for mounting an electronic component, wherein the ceramic package has an opening, and is joined to one surface of the ceramic package main body by a brazing material. A first heat dissipating member, a second heat dissipating member joined to the first heat dissipating member by a brazing material through the opening, and having the electronic component mounting surface on the other surface side of the ceramic package body; And a brazing material reservoir formed between the inner wall of the opening and the outer wall of the second heat radiating member, for storing the brazing material. 2. The second heat radiation member has an eave portion and a shaft portion, the eave portion has the electronic component mounting surface on an upper surface, and the shaft portion has a bottom surface on the first heat radiation member. 2. The ceramic package according to claim 1, wherein the brazing material pool is joined between the inner wall of the opening and the side wall of the shaft. 3. 3. The ceramic package according to claim 1, wherein the first heat radiating member is made of a material having a thermal expansion coefficient close to a thermal expansion coefficient of a material of the ceramic package body. 4. The device according to claim 1, wherein the second heat radiating member includes a metal plate made of any metal material selected from molybdenum, copper-molybdenum, and copper-tungsten. 3. The ceramic package according to 3.