JPH0964229A - Ceramic package with heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate no fatigue failure in the junction portion between a ceramic package board and its lid, even by the temperature cycle tests of the ceramic package with a metallic heat sink, by making the thermal expansion coefficients of both the metallic heat sink and the ceramic package board in a specific temperature range fall within the scope of a specific multiplication. SOLUTION: Thirty Cu/W heat sinks 22 of 45mm×45mm in external shape, 1mm in thickness, 5wt.% in Cu content, 95wt.% in W content and about 5.5×10<-6> / deg.C in thermal expansion coefficient for temperature range of -65 deg.C to 150 deg.C, and thirty Cu/W heat sinks 22 of the same size as the foregoing ones which have different Cu contents from the foregoing ones are manufactured respectively to perform their temperature cycle tests in the temperature range of -65 deg.C to 150 deg.C. As a result, in case of ceramic packages 10 wherein their package boards are all made of alumina and the thermal expansion coefficients of their metallic heat sinks 22 fall within the scope of 4.8×10<-6> / deg.C to 6.2×10<-6> / deg.C in the temperature range of -65 deg.C to 150 deg.C, no fatigue failure of solder layer portions 15 is observed, even in their temperature cycle tests comprising respectively a thousand cycles in the same temperature range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat dissipation plate-equipped ceramic package, and more particularly to a PGA (Pin Grid Array) type heat dissipation plate-equipped ceramic package for mounting a semiconductor element.

[0002]

2. Description of the Related Art In a semiconductor device using a PGA type package, a semiconductor element such as an integrated circuit is housed in a semiconductor element mounting portion provided on a package base,
The semiconductor element mounting portion is airtightly sealed with a lid for practical use. Since ceramics such as alumina are excellent in heat resistance, durability, reliability, etc., they are suitable as materials for the package base and lid, and ceramic IC packages are now actively used.

In this ceramic package, when a ceramic package base is sealed with a ceramic lid, solder is used as a sealing material because it can be sealed at a relatively low temperature and is inexpensive. However, the solder and ceramic cannot be directly joined. Therefore, a base metal layer is formed on the package base and the lid sealing portion. Therefore, the package base and the lid are joined by solder through the base metal layer. Furthermore, for heat dissipation of the semiconductor element,
A metal heat dissipation plate may be silver brazed to the package base.

The structure of a ceramic package (semiconductor device) with a heat dissipation plate on which such a semiconductor element is mounted and a method of manufacturing the semiconductor device will be specifically described. In the following, a portion of the semiconductor device excluding a semiconductor element and a wiring portion such as wire bonding will be referred to as a package.

FIG. 3 is a cross-sectional view schematically showing a ceramic package (semiconductor device) with a heat dissipation plate on which a semiconductor element is mounted.

This ceramic package 30 with a heat sink
Comprises a package base 12 which is a container for mounting the semiconductor element 18, a lid 11 which is a lid for sealing the semiconductor element 18, and a heat dissipation plate 32 which promotes heat dissipation of the semiconductor element 18. There is.

First, the package base 12 will be described. The semiconductor element 18 is provided at the center of the package base 12.
The base metal layer 2 is formed in which the cavity 16 for mounting the substrate is formed and which is used when sealing with the lid 11 around the cavity 16.
0 is formed, and external connection pins 21 for connecting to a board (not shown) are formed around the base metal layer 20 by silver brazing via the base metal layer (not shown) formed on the package base 12. It is fixed. Further, the cavity portion 16 is usually formed in a stepped shape in its peripheral portion, a pad 19 for wire bonding is formed in an intermediate step portion, and a semiconductor element mounting portion 17 is formed in a bottom surface portion.
It has become. Then, the semiconductor element 18 is fixed to the semiconductor element mounting portion 17, and the pad (not shown) formed on the semiconductor element 18 and the pad 19 formed on the cavity portion 16 are bonded by the wire bonding using the wire 23. It is connected.

The cavity 16 is sealed by a lid 11 in order to protect the semiconductor element 18 mounted in the cavity 16. Sealing with the lid 11 is performed by joining using solder, and the cavity portion 16
The cavity portion 16 is sealed via the base metal layer 20 formed around the base metal layer 14 and the base metal layer 14 formed on the substrate 13 forming the lid 11.

Further, the lid 11 of the package base 12
In order to dissipate the heat radiated from the semiconductor element 18 to the surface (outer surface) opposite to the surface to which is bonded, a metal heat dissipation plate 32 is formed on the base metal layer 12 of the package base 12 (not shown). ) Is joined by silver brazing. A metal layer (not shown) for grounding is usually formed also on the semiconductor element mounting portion 17.

A method of manufacturing a semiconductor device using the package substrate 12, the lid 11 and the heat dissipation plate 32 as components is as follows.

First, the package base 12 is formed by stacking and firing green sheets on which conductor patterns and the like are printed.
Then, a metal radiator plate 32 such as a radiator plate made of Cu or a radiator plate made by impregnating molten Cu into a porous body made of W (hereinafter referred to as a radiator plate made of Cu / W) is used as a package base. 12
Braze silver on.

Next, after the semiconductor element 18 is fixed to the semiconductor element mounting portion 17 of the package base 12 by resin bonding or the like, a pad (not shown) on the semiconductor element 18 side and the cavity portion 16 are formed by a wire bonding method. Connected to the pad 19.

Next, with the solder layer 15 formed on the base metal layer 14 of the lid 11 on the lower side, the solder layer 15 is superposed on the base metal layer 20 formed on the upper surface of the package base 12, and a spring and a clip are formed. The lid 11 with a fixing jig such as
And the package base 12 are temporarily fixed. In this state, the package substrate 12 and the lid 11 are loaded into the heating furnace, the solder layer 15 formed on the lid 11 is melted to bond the lid 11 and the package substrate 12, and then the semiconductor element 18 is cooled. The package base 12
It is hermetically sealed inside.

[0014]

The ceramic package 30 with a heat radiating plate manufactured in this manner is required to have durability even under severe temperature conditions. For that purpose, the ceramic package 30 with a heat radiating plate is -65. ℃
A temperature cycle test is performed to repeatedly apply a temperature change of 150 ° C. to 150 ° C. and test the durability of the ceramic package 30 with a heat sink against the temperature change.

However, when the conventionally used ceramic package 30 with a heat sink is subjected to the temperature cycle test, there is a large difference in the coefficient of thermal expansion between the package base 12 and the heat sink 32 in the temperature range of the temperature cycle test. There is a problem in that the package base 12 is deformed, and the solder layer 15 that is a joint portion between the package base 12 and the lid 11 may be fatigue-damaged due to the deformation.

As described above, there is a large difference in the coefficient of thermal expansion between the package base 12 and the heat dissipation plate 32 in the temperature range when the temperature cycle test is performed, and due to the difference in the coefficient of thermal expansion, the solder layer is caused. Fatigue failure of 15 is due to the following reasons. That is, the temperature at which the heat dissipation plate 32 is brazed to the package base 12 by silver brazing varies depending on the composition of the silver brazing solder, but is usually in the range of about 780 to 950 ° C. Conventionally, after this silver brazing, before cooling,
The thermal expansion coefficient of the heat radiating plate 32 is set so that the silver brazing portion between the package base 12 and the heat radiating plate 32 is not cracked or the like in the vicinity of the temperature at which the silver brazing is performed.
It was designed to have a coefficient of thermal expansion of 2 as close as possible.

Therefore, there is no great difference in the coefficient of thermal expansion between the temperature near the silver brazing temperature and the room temperature, and no cracks or the like occur in the silver brazing portion.

For example, as the package substrate 12, Al ₂
Taking a case where a so-called Cu / W plate made of O ₃ is used and porous W is impregnated with molten Cu as a heat dissipation plate 32, a package base made of Al ₂ O ₃ is used. 12 has a thermal expansion coefficient of about 5.
While it is 5 × 10 ⁻⁶ / ° C., it is 7.2 × 10 ⁻⁶ / ° C. near the silver brazing temperature, and the coefficient of thermal expansion has temperature dependence. On the other hand, the heat radiating plate 32 has no temperature dependence, and conventionally, the whole heat radiating plate ceramic package 10 is balanced in accordance with the thermal expansion coefficient of Al ₂ O ₃ near the silver brazing temperature.

However, when a temperature cycle of -65 ° C. to 150 ° C. is applied, the difference in the coefficient of thermal expansion between the package base 12 and the heat dissipation plate 32 becomes large, and FIGS. 4 (a) and 4 (b) show the difference. As shown, in the case of raising the temperature from −65 ° C. to 150 ° C. (FIG. 4A) and in the case of lowering the temperature from 150 ° C. to −65 ° C. (FIG. 4B), the reverse of the package base 12 is performed. Bending occurs in the direction, and this bending repeatedly applies a force to the solder layer 15 to cause plastic deformation, resulting in destruction.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a ceramic package in which a fatigue fracture does not occur at a joint portion between a package base and a lid even by a temperature cycle test.

[0021]

Means for Solving the Problems and Effects Thereof That is, a ceramic package (1) with a heat radiating plate according to the present invention seals the ceramic package base having a cavity for accommodating a semiconductor element. In a ceramic package with a heat dissipation plate, which includes a lid, a solder layer that hermetically seals the package base and the lid, and a metal heat dissipation plate bonded to the outer surface of the package base with a brazing material The thermal expansion coefficient of the metal heat sink in the temperature range of −65 ° C. to 150 ° C. is 0.87 to 1.13 times the thermal expansion coefficient of the package base.

According to the ceramic package with a heat sink described in (1) above, the thermal expansion coefficient of the metal heat sink is 0.87 to 1.13 of the thermal expansion coefficient of the package base in the temperature range of the temperature cycle test. Since it is within the double range, a large change does not occur in the warp degree of the package base even if a temperature cycle test is performed, and as a result, fatigue failure due to plastic deformation is caused in the solder layer between the package base and the lid. Does not happen. Therefore, it is possible to provide a ceramic package with a heat sink having excellent durability.

Further, the ceramic package with a heat sink according to the present invention (2) is the ceramic package with a heat sink according to the above (1), wherein the package base is made of alumina and is made of metal in the temperature range of -65 ° C to 150 ° C. The linear expansion coefficient of the heat sink is 4.8 × 10 ^{-6 /} ° C ~ 6.2
It is characterized by being in the range of × 10 ^-6 / ° C.

According to the ceramic package with a heat radiating plate (2) of the present invention, even if a temperature cycle test is performed, a ceramic package made of alumina and a lid are provided as in the case of the ceramic package with a heat radiating plate described in (1) above. Fatigue failure due to plastic deformation does not occur in the solder layer in between.
Therefore, it is possible to provide a ceramic package with a heat sink made of alumina, which is excellent in durability.

[0025]

2 is a sectional view schematically showing an embodiment of a ceramic package with a heat sink according to the present invention.

The structure of the ceramic package 10 with a heat radiating plate according to the embodiment is the same as the structure of the conventional ceramic package shown in FIG. 3 except that the heat radiating plate 22 has a different coefficient of thermal expansion. The description is omitted.

Next, with respect to the ceramic package with the heat radiating plate according to the embodiment, materials other than its structure will be described. The material for forming the package substrate 12 is not particularly limited, and any ordinary ceramic package substrate material can be used. Package base 12
The materials, such as alumina, oxide ceramic, borosilicate glass mullite, MgO-Al ₂ O ₃
-SiO ₂ -B ₂ O ₃ based glass, CaO-Al ₂ O ₃ -
Examples thereof include glass ceramics such as SiO ₂ —B ₂ O ₃ glass and non-oxide ceramics such as aluminum nitride and silicon carbide. Of these materials, alumina is generally most often used as the package base 12. Base metal layer 2 formed on package base 12
0 is W, M which can be co-fired with the package base 12 normally.
and a Ni-plated layer and an Au-plated layer formed thereon,
With this configuration, the bondability with solder at the time of sealing and the long-term stability as a package are ensured.

The material for forming the lid 11 is -65.degree.
In the temperature range of 150 ° C. to 150 ° C., it is preferable that the package base 12 and the lid 11 expand and contract in the same manner as the package base 12 so that plastic deformation does not occur in the solder layer 15 portion. The same material as is preferable. Examples of the base metal layer 14 of the lid 11 include metals such as Ag-Pt and Ag-Pd.

The package base 12 has a cavity portion (recess) 16 for mounting a semiconductor element in the central portion, and if the cavity portion 16 is of the PGA type sealed by the lid 11, its shape and size Is not limited. The lid 11 is also the cavity portion 1 of the package base 12.
Any material capable of sealing 6 may be used. The solder layer 15 is preferably as high as possible in thermal shock resistance, strength, etc. For example, it is preferable that the solder layer 15 contains five components of Sn—Ag—In—Bi—Pb.

The heat sink 22 made of metal has a temperature of -65 ° C to 150 ° C.
In the temperature range of ° C, it must be 0.87 to 1.13 times the coefficient of thermal expansion of the package substrate 12, and among the materials satisfying these conditions, those having high thermal conductivity are preferable. When the thermal expansion coefficient of the heat dissipation plate 22 is less than 0.87 of the thermal expansion coefficient of the package base 12, or 1.
If it exceeds 13 times, the solder layer 15 that is the joint portion between the package base 12 and the lid 11 is easily fractured by fatigue.

The linear expansion coefficient of the package base 12 is -6.
Alumina is 5.5 in the temperature range of 5 ° C to 150 ° C.
× 10 ^-6 / ℃, aluminum nitride 3.2 × 10 ^-6 / ℃
, Mullite is about 2.7 × 10 ⁻⁶ / ° C. and glass ceramic is about 4.4 × 10 ⁻⁶ / ° C.
It is necessary to select the material of the heat dissipation plate 22 according to the linear expansion coefficient of the material forming the.

The material of the heat sink 22 is Cu, which has good thermal conductivity.
In such a case, the coefficient of linear expansion of Cu is about 17 × 10 ⁻⁶ / ° C., which is often too large compared to the material of the package base 12. Therefore, a material having a small coefficient of linear expansion such as W or Mo is used for Cu. In addition, it is necessary to adjust its linear expansion coefficient.
Further, a metal material having a coefficient of thermal expansion of 0.87 to 1.13 times the thermal expansion coefficient of the material forming the package base 12 may be selected.

When the heat dissipation plate 22 made of Cu / W is used, the amount of molten Cu to be impregnated is adjusted to adjust the thermal expansion coefficient of the heat dissipation plate 22.

When the material constituting the package base 12 is alumina, the linear expansion coefficient of alumina is 5.5 × 10 ⁻⁶ / ° C. in the temperature range of −65 ° C. to 150 ° C. About 0.87 to 1.1 for expansion coefficient
3 times, that is, the coefficient of linear expansion is 4.8 × 10 ^-6
It is preferable to select the heat radiating plate 22 composed of a material having a temperature of / ° C to 6.2 x 10 ^-6 / ° C. As a material having a linear expansion coefficient within the above range, a Cu / W radiator plate having Cu in the range of 2.5 to 9 wt% and W in the range of 97.5 to 91 wt% can be mentioned.

A ceramic package base 12 having the above-mentioned cavity 16; a lid 11 for sealing the cavity 16; a package base 12 and a lid 11;
A solder layer 15 that hermetically seals between the
When the temperature of the ceramic package 10 is changed in the range of −65 ° C. to 150 ° C., the thermal expansion and contraction of the heat radiating plate 22 cause the package base 12 and the lid 11 to change. A simulation was performed in order to investigate in detail the influence on the equivalent strain generated in the joint portion (solder layer 15). In this simulation, the outer shape is 66 mm × 66 mm, the thickness is 3 mm, the outer frame of the cavity 16 is 37 mm × 37 mm, the outer shape is 45 mm × 45 mm, and the thickness is 1 m.
m heat radiating plate 22 was brazed with silver, and then the outer shape was 42 mm
The lid 11 having a thickness of 42 mm and a thickness of 1 mm is Sn, Ag,
It was performed based on the condition that it was sealed with solder composed of In, Bi, and Pb. FIG. 1 is a graph showing the result of the simulation.

As is clear from the graph shown in FIG.
Linear expansion coefficient of 4.8 × 10 ^-6 /℃~6.2×10 ^-6 / ℃
In the range of 1, the maximum equivalent strain value is smaller than the 1000 cycle allowable strain (1.5%) in the temperature cycle test, and the durability is sufficient in the temperature cycle test.

[0037]

EXAMPLES AND COMPARATIVE EXAMPLES Examples and effects of the ceramic package 10 with a radiator plate according to the embodiment shown in FIG. 2 specified by numerical values will be described below. In the ceramic package 10 according to the example, first, as the heat dissipation plate 22, the outer shape is 45 mm × 45 m.
m / thickness 1mm, Cu content 5wt%, W content 95wt%, Cu / W heat dissipation coefficient of about 5.5x10 ^-6 / ° C at -65 ° C to 150 ° C Board 22
(Example 1) The size is the same as in Example 1, the Cu content is 7 wt%, the W content is 93 wt%, and the thermal expansion coefficient is about 5.
7 × 10 ⁻⁶ / ° C. Cu / W radiator plate 22 (Example 2),
The size is the same as in Example 1, the Cu content is 4.5 wt%,
W content is 95.5 wt%, thermal expansion coefficient is about 5.3 × 1
30 Cu / W heat sinks 22 (Example 3) each having a temperature of 0 ^-6 / ° C were manufactured. Then, similar to the case of the simulation, these heat dissipation plates 22 have an outer shape of 66 mm × 66 mm, a thickness of 3 mm, and a cavity portion 16 respectively.
Has an outer frame of 37 mm x 37 mm and a linear expansion coefficient of -65 ° C.
Silver brazing is applied to the alumina package substrate 12 of 5.5 × 10 ⁻⁶ / ° C. at ˜150 ° C., and then the outer shape is 42 m.
An alumina lid 11 having a size of m × 42 mm and a thickness of 1 mm is joined to the package base 12 with a solder composed of Sn, Ag, In, Bi, and Pb to seal the cavity portion 16 of the package base 12 to form a ceramic package. Completed 10.

Using the ceramic package 10 with a heat sink according to Examples 1 to 3 thus manufactured,
A temperature cycle test was performed in the temperature range of 65 ° C to 150 ° C.

The heat radiating plate 32 which has been conventionally used
As shown in FIG. 3, except that the Cu / W radiator plate 22 having a Cu content of 11 wt% and a W content of 89 wt% and a coefficient of thermal expansion of 6.5 × 10 ⁻⁶ / ° C. was used. Ceramic package with heat sink manufactured in the same way as the example 3
For 0 (Comparative Example 1), the temperature cycle test was performed as in the case of the example.

As a result, in the ceramic package 30 with the radiator plate according to Comparative Example 1, 10 out of 10 solder layer 15 were subjected to the temperature cycle test of 1000 cycles.
Fatigue fracture in the part was observed, while Examples 1-3
In the heat dissipation plate-equipped ceramic package 10 of the above, no fatigue fracture was observed in the solder layer 15 portion in the 1000-cycle temperature cycle test.

As described above, in the ceramic package 10 according to the embodiment, the package base 12 is made of alumina, and the thermal expansion coefficient of the metal radiator plate 22 is 4 in the temperature range of -65 ° C to 150 ° C. .8 × 10 ^-6 /
Since it is in the range of ℃ ~ 6.2 × 10 ^-6 / ℃, -65 ℃
Even in the temperature cycle test of 1000 cycles in the temperature range of up to 150 ° C., no fatigue fracture of the solder layer 15 portion was observed, and a ceramic package excellent in durability can be provided.

The same applies when the package base 12 made of a material other than alumina is used.

[Brief description of drawings]

FIG. 1 is a graph showing the results of simulations performed on the relationship between the linear expansion coefficient of a heat sink and the maximum equivalent strain by changing the thermal expansion coefficient of the heat sink of the ceramic package with a heat sink.

FIG. 2 is a cross-sectional view schematically showing a ceramic package with a heat dissipation plate according to an embodiment of the present invention.

FIG. 3 is a sectional view schematically showing a conventional ceramic package with a heat sink.

FIG. 4A is a cross-sectional view schematically showing a package base when the temperature is raised from −65 ° C. to 150 ° C.
(B) is sectional drawing which showed typically the package base | substrate in the case of temperature-falling from 150 degreeC to -65 degreeC.

[Explanation of symbols]

 10 Ceramic Package with Heat Sink 11 Lid 12 Package Base 15 Solder Layer 22 Heat Sink

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Yamamoto 2701-1 Iwakura, East branch, Omine Town, Mine City, Yamaguchi Prefecture Sumitomo Metal Ceramics Co., Ltd.

Claims (2)

[Claims] 1. A ceramic package base having a cavity for accommodating a semiconductor element, a lid for sealing the cavity, and a solder layer for hermetically sealing between the package base and the lid. A ceramic package with a heat sink, which is formed of a metal heat sink joined to the outer surface of the package base with a brazing material,
The thermal expansion coefficient of the metal heat sink in the temperature range of ℃ to 150 ℃ is 0.87 of the thermal expansion coefficient of the package substrate.
A ceramic package with a heat sink characterized by being in the range of up to 1.13 times. 2. The package base is made of alumina, and the thermal expansion coefficient (linear expansion coefficient) of the metal heat sink in the temperature range of −65 ° C. to 150 ° C. is 4.8 × 10 ⁻⁶ / ° C.
The ceramic package with a heat sink according to claim 1, wherein the ceramic package is in the range of 6.2 × 10 ^-6 / ° C.