US20070151416A1

US20070151416A1 - Thermal interface material and semiconductor device incorporating the same

Info

Publication number: US20070151416A1
Application number: US11/309,463
Authority: US
Inventors: Ching-Tai Cheng; Nien-Tien Cheng
Original assignee: Foxconn Technology Co Ltd
Current assignee: Foxconn Technology Co Ltd
Priority date: 2005-12-16
Filing date: 2006-08-10
Publication date: 2007-07-05
Also published as: TWI285675B; TW200724661A

Abstract

A semiconductor device (10) includes a heat source (12), a heat-dissipating component (13) for dissipating heat generated by the heat source, and thermal interface material (14) filled in spaces formed between the heat source and the heat-dissipating component. The thermal interface material includes 100 parts by weight of alkenyl groups-containing organopolysiloxane, and Si—H groups-containing compound selected from the group consisting of organo-hydrogenpolysiloxane and polyorganohydrogensiloxane, and 800 to 1200 parts by weight of fillers consisting of aluminum powder having a mean particle size of 0.1 to 1 um and zinc oxide powder having a mean particle size of 1 to 5 um in a weight ratio of from 1/1 to 10/1 .

Description

FIELD OF THE INVENTION

The present invention relates to a thermal interface material which is interposable between a heat-generating electronic component and a heat dissipating component, and it also relates to a semiconductor device using the thermal interface material.

DESCRIPTION OF RELATED ART

With the fast development of the electronics industry, advanced electronic components such as CPUs (central processing units) are being made with ever faster operating speeds. During operation of the advanced electronic components, much heat is generated. In order to ensure good performance and reliability of the electronic components, their operational temperature must be kept within a suitable range. Generally, a heat dissipating apparatus such as a heat sink or a heat spreader is attached to a surface of the electronic component, so that the heat is transferred from the electronic component to ambient air via the heat dissipating apparatus. However, the contact surfaces between the heat dissipating apparatus and the electronic component are rough and therefore are separated from each other by a layer of interstitial air no mater how precisely the heat dissipating apparatus and the electronic component are brought into contact. Thus, the contact resistance is relatively high. A thermal interface material may be applied to the contact surfaces to eliminate the air interstices between the heat dissipating apparatus and the electronic component in order to improve heat dissipation.
The thermal interface material includes base oil and fillers filled in the base oil. The base oil is used for filling the air interstices to create an intimate contact between the heat dissipating apparatus and the electronic component, whilst the fillers are used for improving the thermal conductivity of the thermal interface material to thereby increase the heat dissipation efficiency of the heat dissipating apparatus. However, the base oil may bleed from the thermal interface material when exposed to heat for a long period of time. The thermal interface material therefore tends to gradually harden, finally losing flexibility so that it peels off from the contact surfaces between the heat dissipating apparatus and the electronic component. This results in the thermal interface material undesirably increasing its thermal resistance and the heat dissipating apparatus accordingly decreasing its heat dissipation efficiency over time. The operational temperatures of the electronic components are undesirably increased, which leads to deterioration in their performance. Therefore, a thermal interface material, which can prevent the base oil from bleeding, is needed.

SUMMARY OF THE INVENTION

The present invention relates, in one respect, to a thermal interface material for electronic products, and in another respect, to a semiconductor device using the thermal interface material. According to a preferred embodiment of the present invention, the semiconductor device includes a heat source, a heat-dissipating component for dissipating heat generated by the heat source, and a thermal interface material filled in spaces formed between the heat source and the heat-dissipating component. The thermal interface material includes 100 parts by weight of an alkenyl groups-containing organopolysiloxane, and a Si—H groups-containing compound selected from the group consisting of organo-hydrogenpolysiloxane and polyorganohydrogensiloxane, and 800 to 1200 parts by weight of fillers consisting of aluminum powder having a mean particle size of 0.1 to 1 um and zinc oxide powder having a mean particle size of 1 to 5 um in a weight ratio from 1/1 to 10/1.
Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present thermal interface material can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present thermal interface material. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a schematic cross-sectional view of a semiconductor device having a thermal interface material according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, an electronic device 10 includes a heat source 12 disposed on a circuit board 11, a heat-dissipating component 13 for dissipating heat generated by the heat source 12, and a thermal interface material 14 filled in spaces formed between the heat source 12 and the heat-dissipating component 13. The heat source 12 is an electronic component, such as a central processing unit (CPU) of a computer, which needs to be cooled. The heat-dissipating component 13 is a heat sink, which includes a base 131 and a plurality of fins 133 disposed on the base 131. The heat-dissipating component 13 is attached to the circuit board 11 via a resilient fixing member 15, which provides a resilient force for clamping the heat dissipation component 13 and the circuit board 11 together. The base 131 of the heat-dissipating component 13 is sandwiched between the fixing member 15 and the circuit board 11, and is urged downwardly towards the heat source 12 on the circuit board 11 via the resilient force exerted thereon. The thermal interface material 14 is pressed by the heat-dissipating component 13 thus filled in the spaces formed between the heat source 12 and the heat-dissipating component 13.
The thermal interface material 14 is silicone grease composition having high thermal conductivity, and includes a base oil and an amount of fillers filled in the base oil.
The base oil makes up 100 parts by weight of the thermal interface material 14. The base oil is cured silicone oil including three components: component (A), component (B), and component (C).
Component (A) of the base oil is an organo-hydrogenpolysiloxane having a chemical structure formula:
where a and b are positive numbers satisfying 0.01<a/(a+b)<0.4. Component (A) contains at least a Si—H group at side chains thereof.
Component (B) of the base oil is a polyorganohydrogensiloxane having one of the following chemical structure formulas:
where, M_eis a methyl group, and component (B) contains at least three Si-bonded hydrogen atoms therein.
Component (C) of the base oil is an organopolysiloxane having a chemical structure formula:
where M_eis a methyl group, and m is larger than or equal to 2, so that component (C) contains at least two alkenyl groups therein. In addition, m can also be numbered to satisfy a viscosity of component (C) being in a range from 50 to 5000 cps at 25° C.
The amount of components (A), (B), and (C) of the base oil is such that the ratio of the number of the alkenyl groups in component (C) to the number of the Si—H groups in component (A), and to the number of the Si-bonded hydrogens in component (B) is 4:1:3. Components (A), (B), and (C) of the base oil are used in such proportions that component (C), component (B), and component (A) are heat cured and cross linked together to thereby obtain a composition with a satisfactorily networked structure, giving the thermal interface material a sufficient structure to prevent displacement of the base oil. Alternatively, the base oil may include two components, i.e. component (A)/component (B), and component (C). With this composition, the ratio of Si—H groups in component (A)/component (B) to alkenyl groups in component (C) is 1:1, which heat cures and cross links the component (A)/component (B) and component (C) together to thereby obtain compositions with satisfactorily networked structures. The reaction formula for the Si—H groups and the alkenyl groups is:
The fillers are 800 to 1200 parts by weight of the thermal interface material 14. The fillers are a mixture of aluminum powder and zinc oxide powder in a weight ratio of from 1/1 to 10/1. The aluminum powder is substantially spherical-shaped and has an average particle size from 1 to 5 um. The zinc oxide powder is substantially spherical-shaped and has an average particle size from 0.1 to 1 um.
The thermal interface material further includes a catalyst selected from among platinum and platinum compounds, which serves to promote addition reaction between alkenyl groups in component (C) and Si—H groups in component (A), and/or Si-bonded hydrogen in component (B). Exemplary catalysts are elemental platinum, chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, and platinum coordinate compounds. An appropriate amount of the catalyst is 0.1 to 500 parts by weight of per million parts of component (C).
In the present electronic device 10, the thermal interface material 14 is used to fill the spaces formed between the heat source 12 and the heat-dissipating component 13. After being dispersed, components (A), (B), and (C) cure with the heat produced by the heat source and the catalyst blending thereinto. Once cured, the thermal interface material 14 has a sufficient structure to prevent displacement of the base oil and a long-lasting flexibility to prevent its peeling off from the heat source 12 or the heat-dissipating component 13. Therefore, the silicone composition ensures a high level of heat dissipation efficiency, improving the overall reliability of the electronic device 10.
In the present thermal interface material 14, examples of the substituted hydrocarbon group for methyl attached to a silicon atom include alkyl groups such as ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, decyl and dodecyl; aryl groups such as phenyl, tolyl, xylyl and naphthyl; aralkyl groups such as benzyl, phenylethyl and 2-phenylpropyl; alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, 1-butenyl, 1-hexenyl, cyclohexenyl and octenyl; and substituted ones of the foregoing groups in which some or all of the hydrogen atoms are substituted with halogen atoms (e.g. fluorine, bromine and chlorine), cyano groups or the like, such as chloromethyl, chloropropyl, bromoethyl, 3,3,3-trifluoropropyl and cyanoethyl.
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of portions within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A thermal interface material comprising:

100 parts by weight of base oil; and

800 to 1200 parts by weight of fillers in the base oil;

wherein the base oil comprises Si—H groups contained in at least one of organo-hydrogenpolysiloxane and polyorganohydrogensiloxane, and alkenyl groups contained in organopolysiloxane and cured with the Si—H groups.

2. The thermal interface material as described in claim 1, wherein the organopolysiloxane has a viscosity from 50 to 5000 cps at 25° C.

3. The thermal interface material as described in claim 1, wherein a ratio of the number of the alkenyl groups to the number of the Si—H groups is 1:1.

4. The thermal interface material as described in claim 1, wherein a ratio of the number of the alkenyl groups in the organopolysiloxane to the number of the Si—H groups in the organo-hydrogenpolysiloxane, and to the number of the Si—H groups in polyorganohydrogensiloxane is 4:1:3.

5. The thermal interface material as described in claim 1, wherein the organo-hydrogenpolysiloxane has a chemical structure formula as follows:

a and b herein are positive numbers satisfying 0.01<a/(a+b)<0.4.

6. The thermal interface material as described in claim 1, wherein a chemical structure formula of the polyorganohydrogensiloxane is one of:

7. The thermal interface material as described in claim 1, wherein the fillers are a mixture of aluminum powder and zinc oxide powder in a weight ratio from 1/1 to 10/1.

8. The thermal interface material as described in claim 7, wherein the aluminum powder has an average particle size of from 1 to 5 um, whilst the zinc oxide powder has an average particle size of from 0.1 to 1 um.

9. The thermal interface material as described in claim 1, further comprising a catalyst selected from among platinum and platinum compounds, in such an amount as to give 0.1 to 500 parts by weight of per million parts of the organopolysiloxane.

10. The thermal interface material as described in claim 9, wherein the platinum compounds are chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, and platinum coordinate compounds.

11. A semiconductor device comprising:

a heat source;

a heat-dissipating component for dissipating heat generated by the heat source; and

thermal interface material filled in spaces formed between the heat source and the heat-dissipating component, the thermal interface material comprising:

100 parts by weight of alkenyl groups-containing organopolysiloxane, and Si—H groups-containing compound selected from the group consisting of organo-hydrogenpolysiloxane and polyorganohydrogensiloxane;

800 to 1200 parts by weight of fillers consisting of aluminum powder having a mean particle size of 0.1 to 1 um and zinc oxide powder having a mean particle size of 1 to 5 um in a weight ratio from 1/1 to 10/1; and

a catalyst selected from the group consisting of platinum and platinum compounds, in such an amount as to give 0.1 to 500 parts by weight of per million parts of the organopolysiloxane.

12. The thermal interface material as described in claim 11, wherein a ratio of the number of the alkenyl groups in the organopolysiloxane to the number of the Si—H groups in the organo-hydrogenpolysiloxane, and to the number of the Si—H groups in the polyorganohydrogensiloxane is 4:1:3.

13. The thermal interface material as described in claim 11, wherein the organo-hydrogenpolysiloxane has a chemical structure formula:

a and b herein are positive numbers satisfying 0.01<a/(a+b)<0.4.

14. The thermal interface material as described in claim 11, wherein a chemical structure formula of the polyorganohydrogensiloxane is one of:

15. The thermal interface material as described in claim 11, wherein a chemical structure formula of the organopolysiloxane is:

m herein being larger than or equal to 2.