JPH08306849A - Heat dissipation member and semiconductor device provided with the heat dissipation member - Google Patents

Abstract

(57) [Abstract] [Purpose] With respect to the temperature change due to the amount of heat generated during the operation of the semiconductor chip, and with respect to the temperature change immediately after resin molding, between the semiconductor chip and the sealing resin. Provided is a heat dissipation member in which peeling is less likely to occur [Configuration] The heat sink 14 is sealed by exposing the surface 20 opposite to the surface on which the semiconductor chip 12 is mounted from the sealing material 26. The heat sink 14 is composed of a plurality of structural bodies, is exposed from the sealing material 26, and the thermal expansion coefficient of the structural body of the central portion B on which the semiconductor chip 12 is mounted is the peripheral portion C.
It is closer to the thermal expansion coefficient of the semiconductor chip 12 than the thermal expansion coefficient of the above structure. Therefore, the difference between the expansion / contraction amount of the semiconductor chip 12 and the expansion / contraction amount of the heat sink 14 due to the temperature change is reduced, and peeling or cracking between them is less likely to occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat dissipation member on which a resin-sealed semiconductor chip is mounted, and a semiconductor device having the heat dissipation member.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor device such as a plastic package, the amount of heat generated from the chip has tended to increase as the frequency (speed) of the semiconductor chip increases, and the existing lead frame has a sufficient heat dissipation property. Can't get Therefore, by attaching a heat sink as a heat dissipation member to the die pad on which the chip is mounted, or directly attaching the chip to the heat sink, a part of the heat sink is exposed to the outside of the package to improve its heat dissipation. I am trying. In addition, the heat sink is made of one type of constituent material, and considering its heat dissipation,
Oxygen-free copper and aluminum are used.

[0003]

However, in the above-mentioned conventional semiconductor device, the heat dissipation due to the heat sink cannot keep up with the amount of heat generated due to the higher frequency (higher speed) of the semiconductor chip. The temperature difference between the temperature of the heat sink, the semiconductor chip, and the sealing resin in and the temperature of the heat sink, the semiconductor chip, and the sealing resin when the semiconductor chip is not operating becomes large. In addition, the temperature difference between the temperature of the heat sink, the semiconductor chip, and the sealing resin during the resin molding process of the heat sink and the semiconductor chip and the temperature of the heat sink, the semiconductor chip, and the sealing resin immediately after the resin molding is large. This temperature difference may act on the heat sink, the semiconductor chip, and the sealing resin, which have different coefficients of thermal expansion, and may cause peeling or cracks between the members. In particular, peeling that occurs between the heat sink and the semiconductor chip and between the heat sink and the sealing resin causes deterioration of the semiconductor chip due to deterioration of heat dissipation, deterioration of the semiconductor chip due to deterioration of sealability inside the semiconductor device, and the like. There is a problem that it becomes a factor that hinders the reliability of the semiconductor device.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to realize a semiconductor chip with respect to a temperature change due to the amount of heat generated during the operation of the semiconductor chip and a temperature change immediately after resin molding. It is an object of the present invention to provide a heat dissipating member that is less likely to peel off between the heat dissipating member and the sealing resin, and a highly reliable semiconductor device including the heat dissipating member.

[0005]

In order to solve the above problems, the present invention has the following constitution. That is, in the heat dissipation member in which the surface opposite to the surface on which the semiconductor chip is mounted is exposed and sealed from the encapsulating material, the heat dissipating member is composed of a plurality of components and is exposed from the encapsulating material. The thermal expansion coefficient of the structure of the portion on which the chip is mounted is closer to the thermal expansion coefficient of the semiconductor chip than the thermal expansion coefficient of the structure of the other portion. If this configuration is adopted, the difference between the expansion / contraction amount of the portion of the heat dissipation member on which the semiconductor chip is mounted and the expansion / contraction amount of the semiconductor chip with respect to the temperature change is reduced, so that the heat dissipation member and the semiconductor chip are Peeling and cracks are less likely to occur between the two.

Further, if the coefficient of thermal expansion of the constituent of the other portion is closer to the coefficient of thermal expansion of the encapsulant than the coefficient of thermal expansion of the constituent of the portion on which the semiconductor chip is mounted, the temperature changes further. On the other hand, peeling between the heat dissipation member and the sealing material can be made less likely to occur.

Specifically, the constituent body of the portion on which the semiconductor chip is mounted may be made of copper / tungsten alloy or copper / molybdenum alloy.

The constituent body of the other portion may be formed of copper or a copper alloy.

Further, using the above-mentioned heat dissipation member, the semiconductor chip mounted on the heat dissipation member, and the lead frame electrically connected to the semiconductor chip, the structure of the portion on which the semiconductor chip is mounted, If the semiconductor device is configured by exposing the surface opposite to the semiconductor chip mounting surface and sealing it with the sealing material, between the heat dissipation member and the semiconductor chip, and /
Alternatively, it is possible to prevent peeling or cracking between the heat dissipation member and the sealing resin.

[0010]

The thermal expansion coefficient of the component of the portion where the heat dissipation member is composed of a plurality of components and exposed from the encapsulant and the semiconductor chip is mounted is higher than that of the components of the other parts. Since the coefficient of thermal expansion is close to that of the semiconductor chip, the difference between the amount of expansion and contraction of the semiconductor chip and the amount of expansion and contraction of the heat dissipation member due to temperature change is small, and peeling and cracking between the two hardly occur.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a heat dissipation member and a semiconductor device according to the present invention will be described in detail below with reference to the accompanying drawings.
The semiconductor device according to the present embodiment is a semiconductor device using a lead frame with an exposed heat sink.

First, the configuration of the semiconductor device 10 will be described with reference to FIG. Reference numeral 12 is a semiconductor chip, which is formed using silicon. Reference numeral 14 is a heat sink as a heat dissipation member, and the lower surface of the heat sink 14 in FIG. 1 is a mounting surface 18 of the semiconductor chip 12 to which the semiconductor chip 12 is bonded with an adhesive 15 such as silver epoxy. The upper surface of the heat sink 14 in FIG.
The exposed surface 20 serves to dissipate the heat inside. The exposed surface 20 is a surface located on the opposite side of the mounting surface 18. Reference numeral 22 is a lead frame, which is electrically connected to the semiconductor chip 12 by using a gold bonding wire 24 as an example. In order to dissipate the heat inside the semiconductor device 10 to the outside, the lead frame 22 is often made of, for example, a copper-based alloy having a high thermal conductivity. One end side of the lead frame 22 inside the semiconductor device 10 is the heat sink 14. Are thermally coupled to each other via a heat resistant insulating tape 16. 26 is a sealing material, and a synthetic resin material such as epoxy is used. The sealing material 26 is the lead frame 2
2, the heat sink 14 and the semiconductor chip 12 are sealed (resin-sealed) except the other end side of the lead frame 22 and the exposed surface 20 of the heat sink 14 to form a package 28 of the semiconductor device 10.

Further, the heat sink 14 will be described in detail with reference to FIGS. As shown in FIG. 2 and FIG. 3 as an example, the heat sink 14 has a columnar shape in which the exposed surface 20 is circular, and the resin-sealed peripheral surface has a quadrangular shape with gently chamfered corners. Collar part 30
Are formed. The heat sink 14 is formed in a cylindrical shape so that the concentration of thermal stress generated in the package 28 is relaxed to prevent cracks from being generated in the sealing material 26 around the semiconductor chip 12, and the resin is applied from both upper and lower sides of the lead frame 22. This is to maintain the balance of the amount of resin in the case of sealing and prevent mold flash of the sealing resin during press working.

A collar portion 30 is provided on the peripheral surface of the heat sink 14.
By providing, the surface area can be increased and the heat dissipation property can be improved. Further, even if the interface between the heat sink 14 and the heat-resistant insulating tape 16 peels off and a crack occurs, the progress of the crack can be prevented by the step due to the flange portion 30 and the crack can be prevented from reaching the outside of the package 28.

Further, the internal structure of the heat sink 14 is different from that of the conventional heat sink 14, as shown in FIGS. 1 and 3, in a portion close to the semiconductor chip 12 which generates heat (as an example, the semiconductor chip 12 is mounted in close contact with the semiconductor chip 12). A structure in which different types of structures are used for the central portion B of the heat sink 14 including the area A) and the other portion (peripheral portion of the heat sink 14) C, and both components are integrally formed. Has become. The structure used for the central portion B is made of a material having a coefficient of thermal expansion closer to that of the constituent material of the semiconductor chip 12 than the structure used for the peripheral portion C. The central portion B is formed continuously from the mounting surface 18 of the heat sink 14 to reach the exposed surface 20.

As an example, a copper material (copper or a copper alloy) such as oxygen-free copper is used as the material of the structure of the peripheral portion C, so that the material of the structure of the central portion B is used. Is oxygen-free copper (coefficient of thermal expansion 17.2-18.8, the unit is [× 10 ^-6
/ ° C]. The same applies to the following), copper / tungsten alloy (coefficient of thermal expansion 6.8 to 8.5) or copper / molybdenum alloy (thermal) having a coefficient of thermal expansion close to that of silicon (coefficient of thermal expansion of about 4.2), which is a constituent material of the semiconductor chip 12. Coefficient of expansion
7.2-8.4) are used. The above-mentioned thermal expansion coefficient is just an example, and may slightly increase or decrease depending on the temperature or the composition ratio.

In this way, the heat sink 14 is attached to the central portion B of the heat sink 14 to which the semiconductor chip 12 is closely attached.
If a structure having a coefficient of thermal expansion closer to that of the semiconductor chip 12 than that of the peripheral portion C is used, even if the temperature changes due to the amount of heat generated during operation of the semiconductor chip 12,
Further, the expansion / contraction amount of the heat sink 14 and the semiconductor chip 1 are also affected by the temperature change immediately after the resin molding, which will be described later.
The difference between the amount of expansion and contraction of No. 2 is smaller than that in the case of using only oxygen-free copper for the heat sink 14 as in the conventional example, and cracks are less likely to occur between the heat sink 14 and the semiconductor chip 12. can do.

Further, in the structure of the peripheral portion C of the heat sink 14 which has a large area of close contact with the sealing material 26, the thermal expansion coefficient of the sealing material 26 ( Since it is possible to use constituent materials with a coefficient of thermal expansion closer to 15 ~ 21),
It is possible to prevent the occurrence of cracks between the adhesive 4 and the sealing material 26. Oxygen-free copper described above has good thermal conductivity, and its thermal expansion coefficient is also close to that of epoxy resin, so that it is suitable as a material for the structural body of the peripheral portion of the heat sink 14. The coefficient of thermal expansion of the structure of the peripheral portion C may be set to be closer to the coefficient of thermal expansion of the sealing material 26 than the coefficient of thermal expansion of the semiconductor chip 12 and the structure of the central portion B. Specifically, using the thermal expansion coefficient of each of the above-mentioned constituents, it is sufficient if the constituent has a thermal expansion coefficient of about 9 or more.

When assembling the semiconductor device 10 configured as described above, first, the mounting surface 1 of the heat sink 14 is mounted.
A heat-resistant insulating tape 16 is attached to the peripheral portion of 8. Next, one end of the lead frame 22 and the heat sink 14
Are joined with the heat-resistant insulating tape 16 attached to the peripheral portion of the mounting surface 18. After that, the heat sink 14
On the central portion B of the mounting surface 18 of the semiconductor chip 12 with an adhesive.
Glue. Then, the lead frame 22 and the semiconductor chip 12 are electrically connected by the bonding wire 24, and the lead frame 22 and the semiconductor chip 12 are inserted into a molding die (not shown) for resin molding. The resin is sealed except for the exposed surface 20. After that, deburring, exterior treatment, trim and form process and the like are performed.

When the semiconductor chip 12 becomes large,
Since a large amount of heat is generated and it is assumed that the heat sink 14 is insufficient in heat dissipation, it is necessary to previously form a mounting screw hole for mounting another radiation fin on the exposed surface 20 of the heat sink 14. You can leave it.

[0021]

By using the heat dissipation member according to the present invention,
Since the difference between the expansion / contraction amount of the semiconductor chip mounting part of the heat dissipation member and the expansion / contraction amount of the semiconductor chip with respect to the temperature change is small, peeling or cracks may occur between the heat dissipation member and the semiconductor chip. It will be difficult. In addition, the thermal expansion coefficient of the structure of the other part is set to be closer to the thermal expansion coefficient of the encapsulant than the thermal expansion coefficient of the semiconductor chip and the structure of the part where the semiconductor chip is mounted. Since the difference between the amount of expansion / contraction of the other part of the heat dissipation member and the amount of expansion / contraction of the encapsulant is small with respect to the change, peeling is less likely to occur between the heat dissipation member and the encapsulant. Further, using the above-mentioned heat dissipation member, the semiconductor chip mounted on the heat dissipation member, and the lead frame electrically connected to the semiconductor chip, the semiconductor chip mounting surface of the structure of the portion on which the semiconductor chip is mounted If the semiconductor device is configured by exposing the surface on the side opposite to the above and sealing with a sealing material, peeling or cracks between the heat dissipation member and the semiconductor chip and / or between the heat dissipation member and the sealing resin. Can be made less likely to occur and the reliability of the semiconductor device can be improved, and the like.

[Brief description of drawings]

FIG. 1 is a perspective sectional view showing a structure of a semiconductor device provided with a heat dissipation member according to the present invention.

FIG. 2 is a plan view of the heat dissipation member of FIG.

FIG. 3 is a sectional view taken along the line DD of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Semiconductor device 12 Semiconductor chip 14 Heat sink 20 Exposed surface 26 Sealing material B Central part (proximity part) C Peripheral part (other part)

Claims (5)

[Claims] 1. A heat dissipation member in which a surface opposite to a surface on which a semiconductor chip is mounted is exposed and sealed from a sealing material, wherein the heat dissipation member is composed of a plurality of constituents and is exposed from the sealing material. The heat dissipation member, wherein the thermal expansion coefficient of the constituent body of the portion on which the semiconductor chip is mounted is closer to the thermal expansion coefficient of the semiconductor chip than the thermal expansion coefficient of the constituent body of the other portion. 2. The coefficient of thermal expansion of the structure of the other portion is
From the coefficient of thermal expansion of the portion where the semiconductor chip is mounted,
The heat dissipation member according to claim 1, wherein the heat dissipation member has a coefficient of thermal expansion close to that of the sealing material. 3. The heat dissipating member according to claim 1, wherein the constituent body of the portion on which the semiconductor chip is mounted is made of a copper / tungsten alloy or a copper / molybdenum alloy. 4. The heat dissipating member according to claim 1, 2 or 3, wherein the constituent body of the other portion is made of copper or a copper alloy. 5. A heat dissipating member according to claim 1, which mounts a semiconductor chip, a semiconductor chip mounted on the heat dissipating member, and electrically connected to the semiconductor chip. And a lead frame, and a surface of the structure on which the semiconductor chip is mounted opposite to the semiconductor chip mounting surface is exposed and sealed with a sealing material.