JP5047505B2 - Electronic device excellent in heat dissipation and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electronic device excellent in heat dissipation utilizing a thermally conductive silicone composition excellent in thermal conductivity and a method for manufacturing the same.

  Since electronic components such as CPUs mounted on a printed circuit board may deteriorate or be damaged due to temperature rise due to heat generation during use, there is a conventional thermal conductivity between the electronic component and the heat radiation fin. Good heat dissipation sheet and heat dissipation grease are used. The heat-dissipating sheet has the advantage that it can be attached easily, but the surface of the CPU, heat-dissipating fins, etc. may appear smooth, but there are irregularities when viewed microscopically. There is an inconvenience that the heat radiation effect cannot be exhibited as expected as a result of the air layer remaining. In order to solve the problem, an adhesive layer or the like provided on the surface of the heat radiation sheet to improve the adhesion has been proposed, but sufficient results have not been obtained. Thermal grease follows the adherend surface well without being affected by unevenness on the surface of the CPU, radiating fins, etc., and brings about adhesion, but if other parts are soiled or used for a long time, problems such as oil spillage will occur. It tends to happen. Therefore, a method of using a liquid silicone rubber composition as a potting agent or an adhesive has been proposed (Patent Document 1, Patent Document 2).

  By the way, in general, electronic parts such as CPU are sealed between the silicon chip and the organic substrate with an epoxy resin-based underfill agent, etc., but the silicon chip, the organic substrate, and the underfill agent are each thermally expanded. The rate is different. For this reason, the silicon chip and the substrate warp due to the difference in thermal expansion coefficient of each component and member due to temperature change. The center part of the silicon chip may be warped by several tens of microns in the peripheral part. However, the heat spreader or heat sink arranged on the silicon chip does not warp because the structure is large and has high strength. Therefore, if the heat dissipating material sandwiched between the silicon chip and the heat spreader or the heat sink cannot follow the warp of the silicon chip, it will peel off, resulting in an increase in thermal resistance and the desired heat dissipating performance cannot be obtained. Therefore, the heat dissipation material used needs to be flexible enough to follow the warp of the silicon chip. However, the compositions described in Patent Documents 1 and 2 may be peeled off from a substrate or the like without being able to follow the warpage of the silicon chip that occurs during CPU operation because the cured product after curing is very hard. Then, since the desired heat dissipation performance cannot be obtained, there is a problem that the thermal resistance increases with time.

Japanese Unexamined Patent Publication No. 61-157569 JP-A-8-208993

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a highly reliable electronic device having excellent heat dissipation and overcoming the above drawbacks and a method for manufacturing the same.

  As a result of intensive studies to achieve the above object, the present inventors have determined that the shear modulus of the thermally conductive silicone cured product interposed between the heat spreader or the heat sink and the heat generating electronic component is within a specific range. The present invention has been completed by the suppression.

That is, the present invention
Exothermic electronic components,
Heat spreader or heat sink, and
A thermally conductive silicone cured material disposed between the heat spreader or heat sink and the heat-generating electronic component, having a shear modulus at 25 ° C. of 200,000 Pa or less and a thermal conductivity of at least 2 W / mK; An electronic device is provided.

Further, the present invention provides a method for manufacturing the electronic device as described above.
A thermally conductive silicone composition layer having a thermal conductivity of at least 2 W / mK is interposed between the exothermic electronic component and the heat spreader or heat sink;
Manufacturing of an electronic device characterized in that the silicone composition layer is heated and converted into a thermally conductive silicone cured product having a shear elastic modulus at 25 ° C. of 200,000 Pa or less and a thermal conductivity of at least 2 W / mK. A method is provided.

  According to the electronic device of the present invention, the silicon cured product interposed between the heat-generating electronic component and the heat sink or heat spreader not only has good thermal conductivity, but also has flexibility and low elastic modulus, so that the warpage of the silicon chip is reduced. Therefore, the heat dissipation performance is maintained. Since this flexibility and followability are stable and not lost over time, the cured silicone layer does not peel from the electronic component, and the durability of the heat dissipation effect is high.

  In addition, according to the method for manufacturing an electronic device of the present invention, the thermally conductive silicone composition interposed between an electronic component such as a CPU and a heat radiator such as a heat spreader or a heat sink is pasty and extensible. When the heat radiator is pressed and fixed from above, even if there are irregularities on the surface of the electronic component and the heat radiator, the gap can be filled with the heat conductive silicone composition without any gap by pressing. Furthermore, when the composition is cured by a heating process at the time of assembly or heat generation by an electronic component such as a CPU, the above-described electronic device having excellent heat dissipation characteristics can be obtained.

  This will be described in detail below. In this specification, the shear modulus and thermal conductivity are measured values at 25 ° C.

  The thermally conductive silicone cured product used in the present invention has a shear modulus at 25 ° C. of 200,000 Pa or less, preferably 100,000 Pa or less Pa, more preferably in the range of 10,000 to 50,000 Pa. If this shear modulus is larger than 200,000 Pa, it is impossible to follow the warp generated during the operation of a heat-generating component such as a CPU, and desired heat dissipation characteristics cannot be obtained. Generally, the change in shear modulus of silicone rubber is low in temperature dependence, but naturally the shear modulus tends to decrease as the temperature increases. Accordingly, if the shear modulus at 25 ° C. can be suppressed to 200,000 Pa, the temperature will naturally be 200,000 Pa or lower in the temperature range of 25 ° C. or higher at which the electronic component actually operates. For the sake of convenience, the present invention defines only a shear elasticity of 25 ° C., but it is necessary to be 200,000 Pa or less in the temperature range in which the electronic component actually operates.

  Moreover, the heat conductivity of this heat conductive silicone hardened | cured material is 2 W / mK or more, Preferably it is 2.5 W / mK or more, Usually, it is the range of 2.5-6 W / mK. If it is too small, the desired heat dissipation characteristics cannot be obtained.

The thermally conductive silicone cured product is, for example,
(A) an alkenyl group-containing organopolysiloxane;
(B) an organohydrogenpolysiloxane;
(C) a thermally conductive filler;
(D) a platinum-based catalyst;
(E) It is obtained by curing a thermally conductive silicone composition containing a reaction control agent. The thermal conductivity of the composition is substantially the same as the thermal conductivity of the resulting cured product. Hereinafter, this composition will be described.

(A) Alkenyl group-containing organopolysiloxane:
The organopolysiloxane has at least one, preferably 1 to 5, alkenyl group directly bonded to a silicon atom, and the molecular structure is not limited. For example, the organopolysiloxane may be linear or branched. Further, the alkenyl group which may be a mixture of two or more different structures or may be a mixture of two or more different viscosities is exemplified by vinyl group, allyl group, 1-butenyl group, 1-hexenyl group and the like. However, a vinyl group is preferable from the viewpoint of ease of synthesis and cost. Examples of the remaining organic group bonded to the silicon atom include methyl groups, ethyl groups, propyl groups, butyl groups, hexyl groups, alkyl groups such as dodecyl groups, aryl groups such as phenyl groups, 2-phenylethyl groups, 2-phenylpropoxy groups. An aralkyl group such as a sulfur group is exemplified, and a substituted hydrocarbon group such as a chloromethyl group and a 3,3,3, -trifluoropropyl group is also exemplified. Of these, a methyl group of 90% or more is preferable from the viewpoint of ease of synthesis and cost. The alkenyl group bonded to the silicon atom may be present at either the terminal or the middle of the molecular chain of the organopolysiloxane, but in terms of flexibility, it is preferably present only at both terminals. The viscosity at 25 ° C. is usually preferably in the range of 10 to 100,000 mm ² / s, preferably 100 to 50, in view of both the storage stability of the resulting composition and the progress of the composition becoming desirable. , 000 mm ² / s.

(B) Organohydrogenpolysiloxane:
Organohydrogenpolysiloxane has at least one Si-H group in which one hydrogen atom is directly bonded to a Si atom, preferably 1 to 10, and may be linear or branched, and have different structures. Two or more kinds of mixtures may be used, or two or more kinds of mixtures having different viscosities may be used. Groups other than Si-H groups include methyl groups, ethyl groups, purpyl groups, butyl groups, hexyl groups, alkyl groups such as dodecyl groups, aryl groups such as phenyl groups, 2-phenylethyl groups, 2-phenylpropyl groups, etc. And substituted hydrocarbon groups such as chloromethyl group and 3,3,3-trifluoropropyl group. Of these, a methyl group of 90% or more is preferable from the viewpoint of ease of synthesis and cost. The Si—H group bonded to the silicon atom may be present at either the terminal or the middle of the molecular chain of the organopolysiloxane.

(C) Thermally conductive filler:
The thermally conductive filler is for imparting thermal conductivity to the silicone cured product. For example, it is selected from aluminum, silver, copper, nickel, zinc oxide, alumina, magnesium oxide, aluminum nitride, boron nitride, silicon nitride, diamond, graphite or combinations thereof. These heat conductive fillers usually have an average particle size in the range of 0.1 to 50 μm, preferably 1 to 20 μm. If it is too small, the viscosity of the composition will be too high and the progress will be poor, and the resulting composition will be non-uniform. Moreover, the shape of these heat conductive fillers may be either spherical or indefinite.

(D) Platinum-based catalyst:
The platinum-based catalyst is selected from platinum and a platinum compound. This catalyst promotes an addition reaction (hydrosilylation reaction) between an alkenyl group directly bonded to a Si atom and a Si—H group directly bonded to a Si atom. As this component, conventionally known components can be used, and examples thereof include platinum alone, chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, and platinum coordination compounds.

(E) Reaction control agent:
The reaction control agent suppresses the progress of the hydrosilylation reaction at room temperature and extends shelf life and pot life. Known reaction control agents can be used, and acetylene compounds, various nitrogen compounds, organic phosphorus compounds, oxime compounds, organic chloro compounds, and the like can be used. These can be used after being diluted with an organic solvent such as toluene, xylene or isopropyl alcohol in order to improve dispersibility in the silicone resin.

Other ingredients:
In addition to the above essential components, other components can be added to the composition as necessary.

For example, in order to improve the wettability of the thermally conductive filler and the silicone component, the general formula (1):
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is an alkyl group having 6 to 15 carbon atoms, R ² is a saturated or unsaturated monovalent hydrocarbon group having 1 to 8 carbon atoms, and R ³ is 1 carbon atom. Is an alkyl group of -6, a is an integer of 1, 2 or 3, b is an integer of 0-2, and a + b = 1-3. ]
May be used as needed. Specific examples of the alkyl group having 6 to 15 carbon atoms represented by R ¹ in the general formula (1) include hexyl group, octyl group, nonyl group, decyl group, dodecyl group, tetradecyl group and the like. . If the number of carbon atoms is too small, the wettability with the filler is not sufficient, and if it is too large, the organosilane is solidified at room temperature, which is inconvenient to handle and the low temperature characteristics of the resulting composition deteriorate. Further, a is 1, 2 or 3, but is particularly preferably 1. R ² in the above formula is a saturated or unsaturated monovalent hydrocarbon group having 1 to 8 carbon atoms, and examples thereof include an alkyl group, a cycloalkyl group, and an alkenyl group. Are alkyl groups such as methyl, ethyl, propyl, hexyl and octyl, cycloalkyl such as cyclopentyl and cyclohexyl, alkenyl such as vinyl and allyl, aryl such as phenyl and tolyl Groups, aralkyl groups such as 2-phenylethyl group, 2-methyl-2-phenylethyl group, 3,3,3, -trifluoropropyl group, 2- (nanofluorobutyl) ethyl group, 2- (heptadecafluoro Examples thereof include halogenated hydrocarbon groups such as octyl) ethyl group and p-chlorophenyl group, and methyl group and ethyl group are particularly preferable. R ³ is one or more alkyl groups having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group, and a methyl group and an ethyl group are particularly preferable.

[式中、Ｒ^４はＲ^３と同じ意味を有し、Ｒ^５は炭素原子数１〜４のアルコキシ基、ｃは５〜１００の整数である。]
等が挙げられる。 Specific examples of the organosilane represented by the general formula (1) include the following.
C ₆ H ₁₃ Si (OCH ₃ ) _3, C ₁₀ H ₂₁ Si (OCH ₃ ) ₃ , C ₁₂ H ₂₅ Si (OCH ₃ ) ₃ , C ₁₂ H ₂₅ Si (OC ₂ H ₅ ) ₃ ,
C ₁₀ H ₂₁ Si (CH ₃ ) (OCH ₃ ) ₂ , C ₁₀ H ₂₁ Si (C ₆ H ₅ ) (OCH ₃ ) ₂ , C ₁₀ H ₂₁ Si (CH ₃ ) (OC ₂ H ₅ ) ₂ ,
C ₁₀ H ₂₁ Si (CH = CH ₂ ) (OCH ₃ ) ₂ , C ₁₀ H ₂₁ Si (CH ₂ CH ₂ CF ₃ ) (OCH ₃ ) ₂
Other components that can be optionally blended include, for example,

[Wherein, R ⁴ has the same meaning as R ³ , R ⁵ is an alkoxy group having 1 to 4 carbon atoms, and c is an integer of 5 to 100. ]
Etc.

  The above heat conductive silicone composition can be stored for a long time at a low temperature as a one-component addition-curing type by mixing required components.

  In the implementation of the heat dissipation method of the present invention or the manufacture of an electronic device, the composition is packed in, for example, a commercially available syringe and applied onto a heat-generating electronic component such as a CPU, and the obtained coating layer is applied to a heat spreader or heat sink. And paste together. For this reason, if the viscosity of the composition is too low, dripping occurs at the time of coating, and if it is too high, the coating efficiency is deteriorated. Therefore, the range of 10 to 1000 Pa · s is usually preferable, and more preferably 50 to 400 Pa. -S.

  After the exothermic electronic component is bonded to the surface of the heat spreader or heat sink through the composition layer, the electronic component and the heat spreader or heat sink are fixed by bonding or fastening with a clamp or the like. Press. If the thickness of the thermally conductive silicone composition layer sandwiched at that time is less than 5 μm, there is a risk that a gap will be generated between the electronic component and the heat sink due to slight displacement of the pressure, and if the thickness is greater than 100 μm, The thickness is in the range of 5 to 100 μm, preferably 10 to 50 μm, because the thermal resistance increases due to the thickness and the heat dissipation effect deteriorates.

  After the composition is applied on the electronic component, it may be positively heated and cured, or may be cured by heat generation during operation of the electronic component. Cured product generated by curing has a low elastic modulus, so even if the electronic component warps, it can follow it, so it will not peel off from the electronic component and will continue to maintain excellent heat dissipation characteristics over time. .

  Hereinafter, the present invention will be described in more detail by examples.

Each measurement shown by an Example and a comparative example was performed as follows.
-Viscosity: Measured with a spiral rotational viscometer (Malcom Co., Ltd., type PC-1TL used) (25 ° C, 10 rpm)
-Thermal conductivity: A model made by Kyoto Electronics Industry Co., Ltd., poured into a 3 cm deep mold of a thermally conductive silicone composition before being heated and cured in accordance with the provisions of JIS R2616, and covered with a polyethylene wrap for kitchen. Measured with QTM-500.

  -Shear elastic modulus: In accordance with the provisions of ISO6721-10, a viscoelasticity measuring device (Rheometric Scientific, using type RDAIII) was used, and two parallel plates with a diameter of 2.5 cm were used ( The thickness of the thermally conductive silicone composition is set to 2 mm). In the measurement, first, the temperature was raised from room temperature to 125 ° C. at 5 ° C./min, and after reaching 125 ° C., the temperature was maintained for 2 hours to completely cure the thermally conductive silicone composition. Then, it cooled to 25 degreeC and measured the shear elastic modulus of the heat conductive silicone composition after hardening (frequency: set to 1.0 Rad / sec, strain (displacement): 10%).

-Thermal resistance measurement:
<Creation of specimen>
The thermally conductive silicone composition was sandwiched between a 10 mm square silicon plate and a nickel plate, and was cured by heating in an oven at 125 ° C. for 90 minutes while applying a pressure of 140 kPa.

<Thermal resistance measurement method>
The thermal resistance value of the test piece produced as described above was measured by a laser flash method, and the measured value was used as an initial value. After that, place the test piece in a thermal shock tester that repeats the temperature cycle of -40 ° C for 30 minutes and + 125 ° C for 30 minutes, and the thermal resistance of the test piece after 500 cycles and 1000 cycles is the same as the initial value And measured.

Example 1-4
Components (A) to (E) shown below and organosilane which is a wettability improver were mixed as follows to obtain silicone compositions used in Examples 1 to 4 and Comparative Examples 1 to 3.

  That is, components (A) and (C) are charged into a 5 liter gate mixer (trade name: 5 liter planetary mixer, manufactured by Inoue Seisakusho Co., Ltd.), organosilane is added as necessary, and mixed at 70 ° C. for 1 hour. did. The resulting mixture is cooled to room temperature, and then components (B), (D), and (E) are added to the mixture in the amounts shown in Table 1 (Example) or Table 2 (Comparative Example). Mixed to be uniform.

Ingredient (A):
A-1: Dimethylpolysiloxane having both ends blocked with dimethylvinylsilyl groups and a viscosity at 25 ° C. of 600 mm ² / s

-Component (B) Organohydrogenpolysiloxane represented by the following formula
B-1

B-2

B-2

B-3

B-3

B-4

B-4

Ingredient (C):
C-1: Aluminum powder with an average particle size of 4.9μm
C-2: Aluminum powder with an average particle size of 15.0μm
C-3: Zinc oxide powder with an average particle size of 1.0μm
C-4: Aluminum powder with an average particle size of 70μm
C-5: Aluminum powder with an average particle size of 1.2μm

-Component (D):
D-1: A-1 solution of platinum-divinyltetramethyldisiloxane complex, containing 1% as platinum atoms

Ingredient (E):
E-1: 50% toluene solution of 1-ethynyl-1-cyclohexanol

・ Organosilane:
Organosilane 1: C ₆ H ₁₃ Si (OCH ₃ ) ₃
Organosilane 2: C ₁₀ H ₂₁ Si (OCH ₃ ) ₃

Example 5
FIG. 1 is a longitudinal sectional view of a semiconductor device showing an example of an electronic device of the present invention. As shown in FIG. 1, this semiconductor device includes a CPU 2 mounted on a substrate 1, a radiator 3 provided on the CPU 2, and thermal conductivity provided between the CPU 2 and the radiator 3. And a layer 4 of the silicone composition. The radiator 3 is made of aluminum, and has a finned structure in order to increase the surface area and improve the heat radiation action. Further, the radiator 3 and the substrate 1 are clamped and fixed by a clamp 5, and the silicone composition layer 4 is pressed between the CPU 2 and the radiator 3.

  The upper surface of the CPU 2 is a 2 cm × 2 cm flat surface, on which 0.2 g of the heat conductive silicone composition of Example 1 was applied and pressed with the radiator 3 as described above. The thickness of the composition layer thus sandwiched between the CPU 2 and the radiator 3 was 30 μm.

  When the semiconductor device having such a configuration was placed at about 100 ° C., which is a heat generation temperature when a host computer, a personal computer, a word processor, or the like was used, the composition was cured in the usage environment, but stable heat dissipation was achieved. Sustained heat diffusion and prevented CPU performance degradation and damage due to heat accumulation.

Example 6
FIG. 2 is a longitudinal sectional view of a semiconductor device showing another example of the electronic device of the present invention. The CPU 7 is mounted on the substrate 6, and the heat dissipating body 9 is provided on the CPU 7 via the heat conductive silicone composition layer 8. Here, the radiator 9 is made of copper and has a nickel coating on the surface.

  The upper surface of the CPU 7 is a 1 cm × 1 cm flat surface, on which 0.1 g of the heat conductive silicone composition of Example 2 was applied, and the heat radiating body 9 was placed thereon and pressed. Thus, the thickness of the composition layer sandwiched between the CPU 7 and the radiator 9 was 25 μm.

  When the semiconductor device having the above configuration was placed at about 100 ° C., which is an exothermic temperature when used in a host computer, personal computer, word processor, etc., the composition cured in the environment of use, but stable heat dissipation. Sustained heat diffusion and prevented CPU performance degradation and damage due to heat accumulation.

Longitudinal section of semiconductor device Vertical section of another semiconductor device

Explanation of symbols

1. Substrate 2. CPU
3. Radiator (heat sink)
4). 4. Thermally conductive silicone composition layer Clamp 6. Substrate 7. CPU
8). 8. Thermally conductive silicone composition layer Radiator

Claims (2)

Exothermic electronic components,
Heat spreader or heat sink, and
Located between the heat spreader or heat sink and the heat-generating electronic component, the shear modulus after curing at 25 ° C. is 200,000 Pa or less, and the thermal conductivity is at least 2 W / mK in the following composition before curing. An electronic device comprising a thermally conductive silicone cured product having:
The thermally conductive silicone cured product is
(A) an alkenyl group-containing organopolysiloxane;
(B) an organohydrogenpolysiloxane;
(C) a thermally conductive filler;
(D) a platinum-based catalyst;
(E) An electronic device comprising a reaction control agent, wherein the thermally conductive filler of component (C) is a cured product of a thermally conductive silicone composition that is a filler made of only aluminum, zinc oxide, or a combination thereof. . A thermally conductive silicone composition layer having a thermal conductivity of at least 2 W / mK is interposed between the exothermic electronic component and the heat spreader or heat sink;
A method for producing an electronic device, wherein the silicone composition layer is heated and converted to a thermally conductive silicone cured product having a shear modulus at 25 ° C. of 200,000 Pa or less,
The thermally conductive silicone composition is
(A) an alkenyl group-containing organopolysiloxane;
(B) an organohydrogenpolysiloxane;
(C) a thermally conductive filler;
(D) a platinum-based catalyst;
(E) Thermal conductivity containing a reaction control agent and having a thermal conductivity of at least 2 W / mK, provided that the thermal conductive filler of component (C) is a filler consisting of aluminum, zinc oxide or a combination thereof only . The method for manufacturing an electronic device according to claim 1, wherein the method is a silicone composition.

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