JP6178389B2 - Method for manufacturing thermal conductive sheet, thermal conductive sheet, and semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a heat conductive sheet disposed between a heat source such as a semiconductor element and a heat radiating member such as a heat sink, a heat conductive sheet, and a semiconductor device including the heat conductive sheet.

  Conventionally, in semiconductor devices mounted on various electric devices such as personal computers and other devices, heat is generated by driving, and when the generated heat is accumulated, driving of the semiconductor devices and peripheral devices are adversely affected. Therefore, various cooling means are used. As a method for cooling electronic components such as semiconductor elements, there are a method in which a fan is attached to the device and the air in the device casing is cooled, and a method in which a heat sink such as a heat radiation fin or a heat sink is attached to the semiconductor device to be cooled Are known.

  When a semiconductor device is cooled by attaching a heat sink, a heat conductive sheet is provided between the semiconductor device and the heat sink in order to efficiently release the heat of the semiconductor device. As the heat conductive sheet, a material in which a filler such as a heat conductive filler [scale-like particles (boron nitride (BN), graphite, etc.), carbon fiber, etc.] is dispersed in silicone resin is widely used (for example, , See Patent Document 1).

  These heat conductive fillers have anisotropy of heat conduction. For example, when carbon fiber is used as the heat conductive filler, a heat of about 600 W / m · K to 1200 W / m · K in the fiber direction. When boron nitride is used, it has a thermal conductivity of about 110 W / m · K in the plane direction and about 2 W / m · K in the direction perpendicular to the plane direction. It is known to have.

  Here, electronic parts such as a CPU of a personal computer tend to increase in heat dissipation year by year as the speed and performance thereof increase. However, on the contrary, the chip size of a processor or the like has become equal to or smaller than the conventional size due to the advancement of fine silicon circuit technology, and the heat flow rate per unit area is high. Therefore, in order to avoid problems caused by the temperature rise, it is required to more efficiently dissipate and cool electronic components such as CPUs.

  In order to improve the heat dissipation characteristics of the heat conductive sheet, it is required to lower the thermal resistance, which is an index indicating difficulty in transferring heat. In order to reduce the thermal resistance, it is effective to improve the adhesion to an electronic component as a heat source and a heat radiating member such as a heat sink.

  However, if a thermally conductive filler such as carbon fiber is exposed on the sheet surface (see, for example, Patent Document 2), the followability and adhesion to the heat source and the heat radiating member are poor, and the thermal resistance cannot be lowered sufficiently. . Moreover, in order to immerse the thermally conductive filler in the sheet, a method of sandwiching the thermally conductive sheet with a high load between the heat source and the heat radiating member has been proposed (see, for example, Patent Document 3). When it is used for a heat source for which heat resistance is required, the heat conductive filler is not immersed and the thermal resistance cannot be lowered.

  In addition, when a thermally conductive filler such as carbon fiber is exposed on the sheet surface, the sheet surface has low adhesiveness (tackiness) and cannot be temporarily fixed to a heat source or a heat radiating member. Therefore, when mounting a heat conductive sheet between a heat source and a heat radiating member, it becomes necessary to temporarily fix it separately using an adhesive sheet or an adhesive. However, when such an adhesive sheet or adhesive is interposed, the mounting process becomes complicated.

JP 2012-23335 A JP 2014-1388 A JP 2006-335958 A

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, the present invention improves the adhesion to a heat source and a heat radiating member, is excellent in thermal conductivity, can be temporarily fixed without using an adhesive, etc., and is manufactured as a heat conductive sheet excellent in mountability. It is an object to provide a method, a heat conductive sheet, and a semiconductor device using the same.

Means for solving the problems are as follows. That is,
<1> A molded body preparation step of obtaining a molded body of the heat conductive resin composition by molding and curing a heat conductive resin composition containing a binder resin and a heat conductive filler into a predetermined shape;
Cutting the molded body into a sheet shape, and a molded body sheet manufacturing step for obtaining a molded body sheet with the thermally conductive filler protruding on the surface;
Pressing the molded body sheet, and covering the surface of the molded body sheet with an exuding component that has exuded from the molded body sheet so as to follow the convex shape of the protruding thermal conductive filler. It is a manufacturing method of the heat conductive sheet characterized by including.
<2> The binder resin contains a liquid silicone gel main ingredient and a curing agent,
It is a manufacturing method of the heat conductive sheet as described in said <1> whose compounding ratio of the said main ingredient and the said hardening | curing agent is main ingredient: hardening agent = 35: 65-65: 35 by mass ratio.
<3> The molded body preparation step is performed by filling the thermally conductive resin composition in a hollow mold and thermosetting the thermally conductive resin composition.
The thermally conductive filler contains carbon fiber and an inorganic filler,
The method for producing a heat conductive sheet according to any one of <1> to <2>, wherein the carbon fibers are randomly oriented in the heat conductive sheet.
<4> The method for producing a heat conductive sheet according to any one of <1> to <3>, wherein the pressing step is performed using a spacer for compressing the molded body sheet to a predetermined thickness.
<5> The pressing step is performed by pressing a plurality of the molded body sheets adjacently and collectively to obtain a heat conductive sheet in which the plurality of molded body sheets are integrated. 4>. The method for producing a heat conductive sheet according to any one of 4>.
<6> A heat conductive sheet having a sheet body formed by curing a heat conductive resin composition containing a binder resin and a heat conductive filler,
The heat conductive sheet is characterized in that the surface of the sheet body is covered with an exuding component that has exuded from the sheet main body so as to follow the protruding shape of the protruding heat conductive filler.
<7> The heat conductive sheet according to <6>, wherein the heat conductive filler contains carbon fiber and an inorganic filler.
<8> The heat conductive sheet according to <7>, wherein the inorganic filler is attached to a surface of the carbon fiber in a protruding shape formed of the protruding heat conductive filler.
<9> A heat conductive sheet produced by the method for producing a heat conductive sheet according to any one of <1> to <5>.
<10> having a heat source, a heat radiating member, and a heat conductive sheet sandwiched between the heat source and the heat radiating member,
The heat conductive sheet is the heat conductive sheet according to any one of <6> to <9>.

  According to the present invention, the conventional problems can be solved, the object can be achieved, adhesion to a heat source and a heat radiating member is improved, heat conductivity is excellent, and an adhesive is not used. A method of manufacturing a heat conductive sheet that can be temporarily fixed and is excellent in mountability, a heat conductive sheet, and a semiconductor device using the same can be provided.

FIG. 1 is a perspective view showing a state in which a molded body sheet is pressed through a spacer. FIG. 2: A is a perspective view which shows the process of obtaining the large-sized heat conductive sheet by adjoining a some molded object sheet | seat and pressing collectively (the 1). FIG. 2B is a perspective view showing a process of obtaining a large heat conductive sheet by pressing a plurality of molded sheets adjacent to each other and collectively (No. 2). FIG. 3 is a schematic cross-sectional view of an example of the semiconductor device of the present invention. 4A is a SEM (scanning electron microscope) photograph of the surface of the heat conductive sheet sample of Example 4. FIG. 4B is a SEM photograph of the surface of the heat conductive sheet sample of Example 4. FIG. 5A is an SEM photograph of the surface of the heat conductive sheet sample of Example 5. FIG. 5B is an SEM photograph of the surface of the heat conductive sheet sample of Example 5. FIG. 6A is an SEM photograph of the surface of the heat conductive sheet sample of Example 6. FIG. 6B is a SEM photograph of the surface of the heat conductive sheet sample of Example 6. FIG. 7A is an SEM photograph of the surface of the heat conductive sheet sample of Example 7. FIG. 7B is an SEM photograph of the surface of the heat conductive sheet sample of Example 7. FIG. 8A is an SEM photograph of the surface of the heat conductive sheet sample of Comparative Example 2. FIG. 8B is a SEM photograph of the surface of the heat conductive sheet sample of Comparative Example 2. FIG.

(The manufacturing method of a heat conductive sheet, and a heat conductive sheet)
The manufacturing method of the heat conductive sheet of this invention contains a molded object preparation process, a molded object sheet preparation process, and a press process at least, and also includes another process as needed.
The heat conductive sheet of the present invention is a heat conductive sheet having a sheet body formed by curing a heat conductive resin composition containing a binder resin and a heat conductive filler, and the surface of the sheet main body protrudes from the above It is covered with an exuding component that has exuded from the sheet body so as to follow the convex shape of the thermally conductive filler.
The said heat conductive sheet of this invention can be suitably manufactured with the manufacturing method of the said heat conductive sheet of this invention.

<Molded body production process>
As the molded body manufacturing step, a process of obtaining a molded body of the thermally conductive resin composition by molding and curing a thermally conductive resin composition containing a binder resin and a thermally conductive filler into a predetermined shape. If it is, there will be no restriction | limiting in particular, According to the objective, it can select suitably.

<< Thermal conductive resin composition >>
The said heat conductive resin composition contains binder resin and a heat conductive filler at least, and also contains another component as needed.
The said heat conductive resin composition can be prepared with a well-known method.

-Binder resin-
There is no restriction | limiting in particular as said binder resin, According to the objective, it can select suitably, For example, a thermosetting polymer etc. are mentioned.

  Examples of the thermosetting polymer include crosslinked rubber, epoxy resin, polyimide resin, bismaleimide resin, benzocyclobutene resin, phenol resin, unsaturated polyester, diallyl phthalate resin, silicone resin, polyurethane, polyimide silicone, thermosetting type. Examples thereof include polyphenylene ether and thermosetting modified polyphenylene ether. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the crosslinked rubber include natural rubber, butadiene rubber, isoprene rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene propylene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, butyl rubber, halogenated butyl rubber, fluorine rubber, Examples thereof include urethane rubber, acrylic rubber, polyisobutylene rubber, and silicone rubber. These may be used individually by 1 type and may use 2 or more types together.

  Among these, it is particularly preferable that the thermosetting polymer is a silicone resin from the viewpoints of excellent moldability and weather resistance, and adhesion and followability to electronic components.

  There is no restriction | limiting in particular as said silicone resin, Although it can select suitably according to the objective, It is preferable to contain the main ingredient of a liquid silicone gel, and a hardening | curing agent. Examples of such a silicone resin include an addition reaction type liquid silicone resin, a heat vulcanization type millable type silicone resin using a peroxide for vulcanization, and the like. Among these, an addition reaction type liquid silicone resin is particularly preferable as a heat radiating member of an electronic device because adhesion between a heat generating surface of an electronic component and a heat sink surface is required.

  The addition reaction type liquid silicone resin is preferably a two-component addition reaction type silicone resin containing a polyorganosiloxane having a vinyl group as a main ingredient and a polyorganosiloxane having a Si-H group as a curing agent.

In the combination of the main agent of the liquid silicone gel and the curing agent, the mixing ratio of the main agent and the curing agent is preferably main agent: curing agent = 35: 65 to 65:35 by mass ratio.
When the blending ratio is within the preferred range, the exuding component that has exuded from the molded body sheet in the pressing step can easily impart moderate fine tackiness to the obtained heat conductive sheet.

  There is no restriction | limiting in particular as content of the said binder resin in the said heat conductive resin composition, Although it can select suitably according to the objective, 10 mass%-50 mass% are preferable, 15 mass%-40 mass % Is more preferable.

-Thermally conductive filler-
The thermally conductive filler is for efficiently conducting heat from a heat source to the heat radiating member.
As the heat conductive filler, carbon fiber and inorganic filler are preferable.

--- Carbon fiber--
There is no restriction | limiting in particular as said carbon fiber, According to the objective, it can select suitably, For example, what pitched, a PAN system, what graphitized PBO fiber, an arc discharge method, a laser evaporation method, CVD method (chemical) A compound synthesized by a vapor deposition method), a CCVD method (catalytic chemical vapor deposition method), or the like can be used. Among these, carbon fibers obtained by graphitizing PBO fibers and pitch-based carbon fibers are particularly preferable from the viewpoint of thermal conductivity.

  If necessary, the carbon fiber can be used by partially or entirely treating the carbon fiber. Examples of the surface treatment include oxidation treatment, nitriding treatment, nitration, sulfonation, or attaching a metal, a metal compound, an organic compound, or the like to the surface of a functional group or carbon fiber introduced to the surface by these treatments. The process etc. which are combined are mentioned. Examples of the functional group include a hydroxyl group, a carboxyl group, a carbonyl group, a nitro group, and an amino group.

  The average fiber length (average major axis length) of the carbon fiber is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 50 μm to 250 μm, more preferably 75 μm to 200 μm, and 90 μm to 170 μm. Is particularly preferred.

  There is no restriction | limiting in particular as an average fiber diameter (average short axis length) of the said carbon fiber, Although it can select suitably according to the objective, 4 micrometers-20 micrometers are preferable, and 5 micrometers-14 micrometers are more preferable.

The aspect ratio (average major axis length / average minor axis length) of the carbon fiber is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 8 or more, and more preferably 9-30. . When the aspect ratio is less than 8, since the fiber length (major axis length) of the carbon fiber is short, the thermal conductivity may be lowered.
Here, the average major axis length and the average minor axis length of the carbon fiber can be measured, for example, with a microscope, a scanning electron microscope (SEM), or the like.

  There is no restriction | limiting in particular as content of the said carbon fiber in the said heat conductive sheet, Although it can select suitably according to the objective, 10 volume%-40 volume% are preferable, and 12 volume%-38 volume% are more. Preferably, 15 volume%-35 volume% are especially preferable. When the content is less than 10% by volume, it may be difficult to obtain a sufficiently low thermal resistance. When the content exceeds 40% by volume, the moldability of the heat conductive sheet and the orientation of the carbon fibers may be obtained. May be affected.

--Inorganic filler--
There is no restriction | limiting in particular about the shape, material, average particle diameter, etc. as said inorganic filler, According to the objective, it can select suitably. There is no restriction | limiting in particular as said shape, According to the objective, it can select suitably, For example, spherical shape, elliptical spherical shape, lump shape, granular form, flat shape, needle shape etc. are mentioned. Among these, spherical and elliptical shapes are preferable from the viewpoint of filling properties, and spherical shapes are particularly preferable.
In the present specification, the inorganic filler is different from the carbon fiber.

  Examples of the inorganic filler include aluminum nitride (aluminum nitride: AlN), silica, alumina (aluminum oxide), boron nitride, titania, glass, zinc oxide, silicon carbide, silicon (silicon), silicon oxide, aluminum oxide, and metal. And particles. These may be used individually by 1 type and may use 2 or more types together. Among these, alumina, boron nitride, aluminum nitride, zinc oxide, and silica are preferable, and alumina and aluminum nitride are particularly preferable from the viewpoint of thermal conductivity.

  The inorganic filler may be subjected to a surface treatment. When the inorganic filler is treated with a coupling agent as the surface treatment, the dispersibility of the inorganic filler is improved and the flexibility of the heat conductive sheet is improved.

There is no restriction | limiting in particular as an average particle diameter of the said inorganic filler, According to the objective, it can select suitably.
When the inorganic filler is alumina, the average particle size is preferably 1 μm to 10 μm, more preferably 1 μm to 5 μm, and particularly preferably 4 μm to 5 μm. When the average particle size is less than 1 μm, the viscosity increases and mixing may become difficult. When the average particle size exceeds 10 μm, the thermal resistance of the heat conductive sheet may increase.
When the inorganic filler is aluminum nitride, the average particle size is preferably 0.3 μm to 6.0 μm, more preferably 0.3 μm to 2.0 μm, and particularly preferably 0.5 μm to 1.5 μm. If the average particle size is less than 0.3 μm, the viscosity may increase and mixing may be difficult, and if it exceeds 6.0 μm, the thermal resistance of the heat conductive sheet may increase.
The average particle diameter of the inorganic filler can be measured by, for example, a particle size distribution meter or a scanning electron microscope (SEM).

  There is no restriction | limiting in particular as content of the said inorganic filler in the said heat conductive sheet, Although it can select suitably according to the objective, 25 volume%-65 volume% are preferable, and 30 volume%-60 volume% are more. preferable. When the content is less than 25% by volume, the thermal resistance of the heat conductive sheet may increase, and when it exceeds 60% by volume, the flexibility of the heat conductive sheet may decrease.

-Other ingredients-
The other components in the thermally conductive resin composition are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include thixotropic agents, dispersants, curing accelerators, retarders, and slight adhesion. Examples include an imparting agent, a plasticizer, a flame retardant, an antioxidant, a stabilizer, and a colorant.

  There is no restriction | limiting in particular as a method of shape | molding the said heat conductive resin composition in a predetermined shape in the said molded object preparation process, According to the objective, it can select suitably, For example, an extrusion molding method, die molding Law.

In the obtained heat conductive sheet, the molded body preparation step is performed by filling the heat conductive resin composition in a hollow mold and thermosetting the heat conductive resin composition. This is preferable in that the thermally conductive filler (for example, carbon fiber) can be randomly oriented.
In the obtained heat conductive sheet, since the carbon fibers are randomly oriented, the entanglement between the carbon fibers increases, so that the carbon fibers are heated more than in the case where they are oriented in a certain direction. Conductivity increases. Moreover, in the case where the thermally conductive filler contains the carbon fiber and the spherical inorganic filler, in addition to the entanglement of the carbon fibers, the carbon fibers are randomly oriented, Since the number of contact points between the carbon fiber and the spherical inorganic filler also increases, the thermal conductivity is further increased as compared with the case where the carbon fiber is oriented in a certain direction.

  The extrusion molding method and the mold molding method are not particularly limited, and the viscosity of the heat conductive resin composition and the obtained heat conduction can be selected from various known extrusion molding methods and mold molding methods. It can be appropriately employed depending on the characteristics required for the sheet.

  When extruding the thermally conductive resin composition from a die in the extrusion molding method, or when pressing the thermally conductive resin composition into a mold in the mold molding method, for example, the binder resin flows. Some carbon fibers are oriented along the flow direction, but many are randomly oriented.

  In addition, when a slit is attached to the tip of the die, the carbon fiber tends to be easily oriented at the center with respect to the width direction of the extruded molded body block. On the other hand, the carbon fiber tends to be randomly oriented in the peripheral portion with respect to the width direction of the molded body block due to the influence of the slit wall.

  The size and shape of the molded body (block-shaped molded body) can be determined according to the required size of the heat conductive sheet. For example, a rectangular parallelepiped having a vertical size of 0.5 cm to 15 cm and a horizontal size of 0.5 cm to 15 cm can be given. The length of the rectangular parallelepiped may be determined as necessary.

  It is preferable that hardening of the said heat conductive resin composition in the said molded object preparation process is thermosetting. There is no restriction | limiting in particular as the curing temperature in the said thermosetting, It can select suitably according to the objective, For example, when the said binder resin contains the main ingredient of a liquid silicone gel, and a hardening | curing agent, 80 degreeC ~ 120 ° C. is preferred. There is no restriction | limiting in particular as hardening time in the said thermosetting, According to the objective, it can select suitably, For example, 1 hour-10 hours etc. are mentioned.

<Molded sheet production process>
The molded body sheet production step is not particularly limited as long as it is a process of cutting the molded body into a sheet shape and obtaining a molded body sheet with the thermally conductive filler protruding on the surface, and is appropriately selected depending on the purpose. For example, it can be performed by a slicing apparatus.

  In the molded body sheet manufacturing step, the molded body is cut into a sheet shape to obtain a molded body sheet. The thermally conductive filler protrudes from the surface of the obtained molded body sheet. This is because when the molded body is cut into a sheet shape by a slicing device or the like, the cured component of the binder resin is cut by a slicing device or the like due to a difference in hardness between the cured component of the binder resin and the thermally conductive filler. This is considered to be because the cured component of the binder resin is removed from the surface of the thermally conductive filler on the surface of the molded body sheet.

  There is no restriction | limiting in particular as said slicing apparatus, According to the objective, it can select suitably, For example, an ultrasonic cutter, a planer (鉋), etc. are mentioned. As the cutting direction of the molded body, when the molding method is an extrusion molding method, 60 ° to 120 ° with respect to the extrusion direction is preferable because some are oriented in the extrusion direction, and 70 ° to 100 ° The degree is more preferable, and 90 degrees (vertical) is particularly preferable.

  There is no restriction | limiting in particular as average thickness of the said molded object sheet, According to the objective, it can select suitably, For example, 1 mm-5 mm etc. are mentioned.

<Pressing process>
In the pressing step, the molded body sheet is pressed, and the surface of the molded body sheet is caused by an exuding component that has exuded from the molded body sheet so as to follow the convex shape of the protruding thermal conductive filler. If it is the process of covering, there will be no restriction | limiting in particular, According to the objective, it can select suitably.
Here, the “exudation component” is a component that is included in the thermally conductive resin composition but does not contribute to curing, such as a non-curable component and a component that is not cured among the binder resin. Means.

  The said press can be performed using a pair of press apparatus which consists of a flat board and a press head with the flat surface, for example. Moreover, you may carry out using a pinch roll.

  The pressure at the time of pressing is not particularly limited and can be appropriately selected according to the purpose. However, if it is too low, the thermal resistance tends to be the same as when not pressing, and if it is too high, the sheet is stretched. Since there exists a tendency, 0.1 MPa-100 MPa are preferable, and 0.5 MPa-95 MPa are more preferable.

  There is no restriction | limiting in particular as time of the said press, According to the component of binder resin, a press pressure, a sheet area, the amount of exudation of an exuding component, etc., it can select suitably.

  The pressing step may be performed while heating using a press head with a built-in heater in order to further promote the effect of exudation of the exuding component and covering of the sheet main body surface. In order to enhance such an effect, the heating temperature is preferably higher than the glass transition temperature of the binder resin. Thereby, press time can be shortened.

  In the pressing step, the extruding component is exuded from the sheet body by pressing the molded sheet, and the surface is covered with the exuding component. The obtained heat conductive sheet exhibits fine tackiness (tackiness) derived from the exudation component on the surface. Therefore, the obtained heat conductive sheet can improve followability and adhesion to the surface of the heat source and the heat radiating member, and can reduce thermal resistance. Moreover, the increase in thermal resistance can be avoided because the coating with the exuding component has a thickness that reflects the shape of the thermally conductive filler on the sheet surface.

  In addition, the surface of the heat conductive sheet is covered with the exuding component, and the adhesive surface is exposed to the main surface of the heat radiating member or temporarily fixed to the upper surface of the heat source. It becomes. Therefore, it is not necessary to use a separate adhesive for the heat conductive sheet, and it is possible to realize labor saving and cost reduction of the manufacturing process.

  Further, even when the surface of the heat conductive sheet loses the slight adhesiveness during handling, when the pressing is performed, the exuding component exudes from the sheet body again, and the surface is covered with the exuding component. Therefore, the heat conductive sheet can be repaired even when the position of adhesion to the heat radiating member or the position of temporary fixing to the heat source is shifted.

  Further, in the heat conductive sheet, the exuding component oozes out from the entire surface of the sheet body, and the side surface as well as the front and back surfaces of the sheet body are covered. Since the exuding component has an insulating property, the heat conductive sheet is provided with an insulating property on the side surface. Therefore, even when the heat conductive sheet is sandwiched between the heat source and the heat radiating member and bulges out to the periphery and comes into contact with the conductive member disposed in the periphery, the heat source and the heat sink and the conductive material are interposed via the heat conductive sheet. It is possible to prevent the member from being short-circuited.

  In addition, a heat conductive sheet is compressed to the thickness direction by pressing, and can increase the frequency of contact between heat conductive fillers. Thereby, it becomes possible to reduce the thermal resistance of a heat conductive sheet.

  The pressing step is preferably performed using a spacer for compressing the molded sheet to a predetermined thickness. That is, as shown in FIG. 1, the heat conductive sheet is arranged at a predetermined surface corresponding to the height of the spacer 10 by placing the spacer 10 on the mounting surface facing the press head and pressing the molded body sheet 11. It can be formed to a sheet thickness.

  Further, as shown in FIG. 2A, a plurality of (for example, four) molded body sheets 11 are adjacent to each other without arranging the spacers 10, and are heat-pressed collectively by a press head, whereby a plurality of molded body sheets 11 are disposed. Can be manufactured as shown in FIG. 2B. In this case, each molded body sheet 11 has a substantially rectangular shape formed with the same dimensions and the same thickness, and it is preferable that one side is aligned with one side of the adjacent molded body sheet 11 at equal intervals. Thereby, the heat conductive sheet 1 of the uniform thickness without a joint line and an unevenness | corrugation can be manufactured. Further, in the large heat conductive sheet 1, a plurality of molded sheets 11 are integrated, and exuded components are exuded by pressing, so that the entire surface of the sheet main body is covered.

<Lightness L * in L * a * b * color system>
The color of an object generally consists of three elements: lightness (brightness), hue (hue), and saturation (brightness). In order to accurately measure and express these, a color system that expresses these numerically objectively is necessary. An example of such a color system is the L * a * b * color system. The L * a * b * color system can be easily measured by a measuring instrument such as a commercially available spectrocolorimeter.

  The L * a * b * color system is a color system described in “JIS Z 8781-4” and “JIS Z 8730”, for example, and is shown by arranging each color in a spherical color space. . In the L * a * b * color system, lightness is indicated by a position in the vertical axis (z-axis) direction, hue is indicated by a position in the outer peripheral direction, and saturation is indicated by a distance from the central axis.

  The position in the vertical axis (z-axis) direction indicating the brightness is indicated by L *. The value of the lightness L * is a positive number. The smaller the number, the lower the lightness and the darker the tendency. Specifically, the value of L * varies from 0 corresponding to black to 100 corresponding to white.

  Further, in a cross-sectional view obtained by horizontally cutting a spherical color space at a position of L * = 50, the positive direction of the x axis is the red direction, the positive direction of the y axis is the yellow direction, the negative direction of the x axis is the green direction, y The negative direction of the axis is the blue direction. The position in the x-axis direction is represented by a * taking a value of −60 to +60. The position in the y-axis direction is represented by b * taking a value of −60 to +60. Thus, a * and b * are positive and negative numbers representing chromaticity, and the closer to 0, the blacker the color becomes. Hue and saturation are represented by these a * and b * values.

  In the L * a * b * color system, the lightness L * becomes whitish and the lightness L * becomes darker. In the L * a * b * color system, when a * is less than −1, the color becomes green, and when a * is −1 or more, the color becomes red. When b * is less than -1, the color becomes bluish, and when b * exceeds +1, the color becomes yellow.

  The heat conductive sheet contains, for example, carbon fiber as a heat conductive filler and a spherical inorganic filler. When the volume percentage of the carbon fiber is increased, the lightness L * of the surface tends to decrease, and the spherical inorganic substance. When the volume percentage of the filler is increased, the lightness L * tends to increase. Specifically, the surface of the heat conductive sheet containing carbon fibers and a spherical inorganic filler, and the spherical inorganic filler is at least one of alumina, aluminum nitride, and aluminum hydroxide containing at least alumina. When the surface area of the carbon fiber is large and the amount of white alumina or aluminum nitride exposed on the surface is small, the lightness L * tends to be small and the area of the carbon fiber is small and exposed on the surface. When there is much white alumina or aluminum nitride, the lightness L * tends to increase.

  In order to obtain a heat conductive sheet having high heat conductivity, a spherical inorganic filler must be added to maintain the shape, rather than simply increasing the content of carbon fiber having high heat conductivity. Moreover, in order to reduce the viscosity of the heat conductive resin composition at the time of extrusion, the blending of carbon fibers and spherical inorganic fillers must be made to an appropriate amount.

  It has been found that a good thermal conductivity can be obtained when the value of the lightness L * is within a predetermined range. That is, the heat conductive sheet according to the present embodiment contains a heat conductive filler, and the L * value in the L * a * b * color system on the surface of the heat conductive sheet is 25 or more and 70 or less. preferable. It is more preferable that the thermally conductive filler contains carbon fiber and a spherical inorganic filler. Thereby, the heat conductivity of the thickness direction of a heat conductive sheet can be made favorable. Even if the surface of the sheet has a mottled pattern or a streak line, it is sufficient that it is within the range of the above L *. When the surface of the sheet has a mottled pattern or a streak line, the carbon fibers are not oriented in a certain direction in the thickness direction but are oriented randomly. The random orientation increases the number of entanglements between the carbon fibers and the contact point of the spherical inorganic filler, and the thermal conductivity is higher than that in the fixed direction. In the step of extruding the thermally conductive resin composition into the hollow mold, the thermally conductive resin compositions that have come out through the slits adhere to each other inside the hollow mold. In the process, color shades are formed on the surface. Moreover, L * value in the L * a * b * color system of the surface of a heat conductive sheet can be adjusted by adjusting mixing time, stirring speed, etc. If the mixing time is increased or the stirring speed is increased, the fibrous filler becomes smaller and the L * value becomes smaller. Further, if the mixing time is shortened or the stirring speed is decreased, the fibrous filler does not become small, so that L * can be increased. Further, when the surface of the sheet is glossy, the L * value tends to increase. The glossiness of the sheet surface can be adjusted by mixing oil or changing the ratio of the main component of the liquid silicone gel and the curing agent.

(Semiconductor device)
The semiconductor device of the present invention includes at least a heat source, a heat radiating member, and a heat conductive sheet, and further includes other members as necessary.
The heat conductive sheet is sandwiched between the heat source and the heat radiating member.

<Heat source>
There is no restriction | limiting in particular as said heat source, According to the objective, it can select suitably, For example, an electronic component etc. are mentioned. Examples of the electronic component include a CPU, MPU, graphic arithmetic element, and the like.

<Heat dissipation member>
The heat radiating member is not particularly limited as long as the heat generated from the heat source is conducted and dissipated to the outside, and can be appropriately selected according to the purpose. For example, a heat radiating device, a cooler, a heat sink , Heat spreader, die pad, printed circuit board, cooling fan, Peltier element, heat pipe, housing, and the like.

<Heat conduction sheet>
The heat conductive sheet is the heat conductive sheet of the present invention.

  An example of the semiconductor device of the present invention will be described with reference to the drawings.

FIG. 3 is a schematic cross-sectional view showing an example of the semiconductor device of the present invention.
The semiconductor device includes a heat conductive sheet 1, a heat spreader 2, an electronic component 3, a heat sink 5, and a wiring substrate 6.

The heat conductive sheet 1 radiates heat generated by the electronic component 3, and is fixed to the main surface 2 a facing the electronic component 3 of the heat spreader 2, as shown in FIG. 1, and the electronic component 3, the heat spreader 2, It is sandwiched between the two. Further, the heat conductive sheet 1 is sandwiched between the heat spreader 2 and the heat sink 5. The heat conductive sheet 1 radiates heat of the electronic component 3 together with the heat spreader 2.
The heat conductive sheet 1 has an exuded component 8 that has exuded from the sheet body 7 and is covered with the exuded component 8.

  The heat spreader 2 is formed in, for example, a rectangular plate shape, and includes a main surface 2a facing the electronic component 3 and a side wall 2b erected along the outer periphery of the main surface 2a. In the heat spreader 2, a heat conductive sheet 1 is provided on a main surface 2a surrounded by a side wall 2b, and a heat sink 5 is provided on the other surface 2c opposite to the main surface 2a via the heat conductive sheet 1. The heat spreader 2 has a higher thermal conductivity, and the thermal resistance is reduced. The heat spreader 2 efficiently absorbs heat from the electronic component 3 such as a semiconductor element. be able to.

  The electronic component 3 is a semiconductor package such as a BGA, for example, and is mounted on the wiring board 6. Further, the heat spreader 2 also has the front end surface of the side wall 2b mounted on the wiring board 6, and thereby surrounds the electronic component 3 at a predetermined distance by the side wall 2b.

  The heat conductive sheet 1 is adhered to the main surface 2 a of the heat spreader 2, thereby absorbing heat generated by the electronic component 3 and dissipating it from the heat sink 5. Adhesion between the heat spreader 2 and the heat conductive sheet 1 can be performed by the adhesive force of the heat conductive sheet 1 itself.

Examples of the present invention will be described below, but the present invention is not limited to these examples. However, Example 4 is replaced with a reference example.

Example 1
In Example 1, alumina particles (thermal conductive particles: manufactured by Denki Kagaku Kogyo Co., Ltd.) having an average particle diameter of 4 μm, which are coupled to a two-component addition reaction type liquid silicone resin with a silane coupling agent, and average fibers Pitch-based carbon fiber with a length of 150 μm and an average fiber diameter of 9 μm (thermal conductive fiber: manufactured by Nippon Graphite Fiber Co., Ltd.) and aluminum nitride with an average particle diameter of 1 μm coupled with a silane coupling agent (thermal conductive particles: stock) (Manufactured by Tokuyama Co., Ltd.) is dispersed in a volume ratio such that the two-component addition reaction type liquid silicone resin: alumina particles: pitch-based carbon fiber: aluminum nitride = 34 vol%: 20 vol%: 22 vol%: 24 vol% Thus, a silicone resin composition (thermally conductive resin composition) was prepared. The two-component addition reaction type liquid silicone resin is a mixture of 35% by mass of silicone A liquid (main agent) and 65% by mass of silicone B liquid (curing agent). The obtained silicone resin composition was extruded into a rectangular parallelepiped mold (50 mm × 50 mm) with a PET film peel-treated on the inner wall to mold a silicone molded body. The obtained silicone molding was cured in an oven at 100 ° C. for 6 hours to obtain a silicone cured product.

  The obtained silicone cured product was heated in an oven at 100 ° C. for 1 hour and then cut with an ultrasonic cutter to obtain a molded body sheet having a thickness of 3.05 mm. The slice speed of the ultrasonic cutter was 50 mm per second. The ultrasonic vibration applied to the ultrasonic cutter had an oscillation frequency of 20.5 kHz and an amplitude of 60 μm.

  After the obtained molded sheet was sandwiched between peeled PET films, a spacer with a thickness of 2.98 mm was inserted and pressed to obtain a heat conductive sheet sample with a thickness of 3.00 mm. The pressing conditions were 3 min at 50 ° C. and 0.5 MPa setting. The filler visible on the surface immediately after slicing is not covered with the binder, but the filler is pressed against the sheet by the press, and the binder component emerges on the surface by immersing in the sheet, so it reflects the filler shape on the sheet surface Covered with a binder. A binder component can be confirmed on the peeled PET surface that was in contact with the sheet after pressing.

(Example 2)
In Example 2, as a two-component addition reaction type liquid silicone resin, except for using a mixture of 40% by mass of a silicone A solution and 60% by mass of a silicone B solution, the same conditions as in Example 1, A heat conductive sheet sample was prepared.

(Example 3)
In Example 3, as a two-component addition reaction type liquid silicone resin, except that a mixture of 45% by mass of silicone A solution and 55% by mass of silicone B solution was used, the same conditions as in Example 1, A heat conductive sheet sample was prepared.

Example 4
In Example 4, as the two-component addition reaction type liquid silicone resin, except that a mixture of 50% by mass of silicone A solution and 50% by mass of silicone B solution was used, the same conditions as in Example 1 A heat conductive sheet sample was prepared.
The SEM photograph of the surface of the obtained heat conductive sheet sample was shown to FIG. 4A and FIG. 4B.

(Example 5)
In Example 5, as the two-component addition reaction type liquid silicone resin, except that a mixture of 55% by mass of silicone A solution and 45% by mass of silicone B solution was used, the same conditions as in Example 1, A heat conductive sheet sample was prepared.
The SEM photograph of the surface of the obtained heat conductive sheet sample was shown to FIG. 5A and 5B.

(Example 6)
In Example 6, as a two-component addition reaction type liquid silicone resin, except that a mixture of 60% by mass of silicone A solution and 40% by mass of silicone B solution was used, the same conditions as in Example 1, A heat conductive sheet sample was prepared.
The SEM photograph of the surface of the obtained heat conductive sheet sample is shown in FIGS. 6A and 6B.

(Example 7)
In Example 7, as a two-component addition reaction type liquid silicone resin, except that a mixture of 65% by mass of silicone A solution and 35% by mass of silicone B solution was used, the same conditions as in Example 1, A heat conductive sheet sample was prepared.
The SEM photograph of the surface of the obtained heat conductive sheet sample is shown in FIGS. 7A and 7B.

(Comparative Example 1)
In Comparative Example 1, as the two-component addition reaction type liquid silicone resin, except that a mixture of 25% by mass of silicone A solution and 75% by mass of silicone B solution was used, the same conditions as in Example 1 A heat conductive sheet sample was prepared.

(Comparative Example 2)
In Comparative Example 2, the two-component addition reaction type liquid silicone resin was the same as in Example 1 except that a mixture of 30% by mass of silicone A solution and 70% by mass of silicone B solution was used. A heat conductive sheet sample was prepared.
The SEM photograph of the surface of the obtained heat conductive sheet sample was shown to FIG. 8A and 8B.

(Comparative Example 3)
In Comparative Example 3, the two-component addition reaction type liquid silicone resin was the same as in Example 1 except that a mixture of 70% by mass of silicone A solution and 30% by mass of silicone B solution was used. A heat conductive sheet sample was prepared.

(Comparative Example 4)
In Comparative Example 4, the two-component addition reaction type liquid silicone resin was the same as in Example 1 except that a mixture of 75% by mass of silicone A solution and 25% by mass of silicone B solution was used. A heat conductive sheet sample was prepared.

<Evaluation of workability>
About each heat conductive sheet sample, the workability | operativity at the time of cutting out to a sheet form and peeling and sticking from a peeling film was evaluated. As an evaluation standard, a molded sheet having a thickness of 2.00 mm can be cut out from a cured silicone with an ultrasonic cutter, and there is no deformation of the sheet main body when the PET is peeled from the heat conductive sheet sample. Good when it can be stuck in a state where it has developed (○), there is no hindrance to the peeling and sticking work of the sheet after cutting, but it is possible when the adhesive is insufficient (△), cutting work And the case where trouble occurred in the peeling / sticking work was judged as defective (x). The results are shown in Table 1-1 and Table 1-2.

<Tensile breaking elongation and tensile breaking strength>
The silicone cured product of each example and each comparative example was cut to a thickness of 2.00 mm to obtain a molded body sheet, then pressed under the same conditions as in Example 1, and further cut to 50 mm × 10 mm. . Thereafter, using a tensile and compression tester (manufactured by A & D Co., Ltd., Tensilon RTG1225), the sample was pulled in the longitudinal direction at a tensile speed of 100 mm / min, and the elongation rate until breaking and the strength at break were measured. The results are shown in Table 1-1 and Table 1-2.

<Slight adhesion>
The evaluation of the slight adhesiveness of each heat conductive sheet sample was carried out by sandwiching a molded body sheet obtained by slicing a cured silicone product with a PET film not subjected to release treatment, and then inserting a spacer having a thickness of 2.98 mm. After pressing for 3 min at 2 ° C. at a setting of 2.45 MPa, a heat conductive sheet sample for evaluating slight adhesion was obtained by cooling to room temperature.
After peeling the end of the PET film of the heat-conducting sheet sample for slightly tacky evaluation by hand and sandwiching the end with a tester, pulling it at a speed of 50 mm / min 90 ° upward, measuring the load, The slight adhesion (tackiness) was evaluated according to the peeling force (load). The peeling force of each sample is measured with a predetermined width.
The evaluation criteria are as follows. The results are shown in Table 1-1 and Table 1-2.
A (optimal): When the peel force fluctuates in the range of 0.05 (N / cm) to 0.25 (N / cm) ○ (Good): The peel force is 0.02 (N / cm) to 0. 05 (N / cm), or 0.20 (N / cm) to 0.30 (N / cm) in the range of △ (normal): peeling force is 0 (N / cm) to 0.04 ( N / cm) In the case of swinging in the range × (defect): In the case where a part of the sheet that does not exhibit slight adhesiveness is observed

<L * value>
The L * value in the L * a * b * color system was measured for the surface of the heat conductive sheet. For the measurement, a color difference meter (manufactured by Konica Minolta, Inc., CR-221) was used. The results are shown in Table 1-1 and Table 1-2.

<Thermal resistance>
The thermal resistance of each thermal conductive sheet was measured using a thermal conductivity measuring device (manufactured by Sony Corporation) in accordance with ASTM D 5470 and applying a load of 1 kgf / cm ² . The results are shown in Table 1-1 and Table 1-2.

  In the heat conductive sheet samples according to Examples 1 to 7, the uncured component (exudation component) of the binder resin oozes out and covers the entire surface of the sheet, reflecting the shape of the filler on the surface. Adhesiveness is expressed. Therefore, the heat conductive sheet samples according to Examples 1 to 7 have improved followability and adhesion to the surface to be pasted, and were able to reduce thermal resistance.

  In addition, the heat conductive sheet samples according to Examples 1 to 7 can be temporarily fixed by coating the surface with an uncured component (exudation component) of the binder resin and imparting slight adhesiveness to the surface. There is no need to use an adhesive, and labor saving and cost reduction of the manufacturing process can be realized.

  On the other hand, in the heat conductive sheet samples according to Comparative Examples 1 and 2, since the composition ratio of the silicone A liquid was low and 30% by mass or less, the uncured component (exudation component) did not remain sufficiently and was pressed. As a result, the entire surface of the sheet was not covered, and no slight tackiness was exhibited. Moreover, since the heat conductive sheet sample which concerns on the comparative examples 1 and 2 lacked a softness | flexibility, and the carbon fiber was exposed to the surface, the followable | trackability and adhesiveness to the adhesion | attachment object were bad, and heat resistance raised.

  Moreover, in the heat conductive sheet sample which concerns on the comparative examples 3 and 4, since the composition ratio of the silicone A liquid was high and it was 70 mass% or more, there was no hardness which can maintain a shape in a sheet | seat main body, and peeled PET film Attempts to maintain the sheet shape are difficult and handling is difficult. Further, in the heat conductive sheet samples according to Comparative Examples 3 and 4, the carbon fibers were tilted in the surface direction by pressing, the surface of the heat conductive sheet became smooth, and the thermal resistance increased. Moreover, the hardness of the silicone cured product was insufficient, and the process of cutting out into a thin sheet was difficult.

  The method for producing a heat conductive sheet of the present invention improves adhesion to a heat source and a heat radiating member, is excellent in heat conductivity, can be temporarily fixed without using an adhesive, etc., and is excellent in mountability. Since a heat conductive sheet can be manufactured, it can be used suitably for manufacture of the heat conductive sheet clamped between a heat source and a heat radiating member.

DESCRIPTION OF SYMBOLS 1 Thermal conductive sheet 2 Heat spreader 2a Main surface 2b Side wall 2c
DESCRIPTION OF SYMBOLS 3 Electronic component 3a Upper surface 5 Heat sink 6 Wiring board 7 Sheet body 8 Exudation component 10 Spacer 11 Molded body sheet

Claims (9)

Molding a heat conductive resin composition containing a binder resin and a heat conductive filler into a predetermined shape and curing the molded body to obtain a molded body of the heat conductive resin composition; and
Cutting the molded body into a sheet shape, and a molded body sheet manufacturing step for obtaining a molded body sheet with the thermally conductive filler protruding on the surface;
Pressing the molded body sheet, and covering the surface of the molded body sheet with an exuding component that has exuded from the molded body sheet so as to follow the convex shape of the protruding thermal conductive filler. Including
The binder resin contains a liquid silicone gel main ingredient and a curing agent,
The mixing ratio between the curing agent and the main agent, the main agent in a weight ratio: curing agent = 60:40 to 65: A 35,
The thermally conductive filler contains carbon fiber and an inorganic filler,
The inorganic filler contains alumina and aluminum nitride;
The manufacturing method of the heat conductive sheet characterized by the above-mentioned. The molded body preparation step is performed by filling the thermally conductive resin composition in a hollow mold and thermally curing the thermally conductive resin composition ,
Prior Kinetsu conducting sheet, wherein the carbon fibers are oriented randomly, the manufacturing method of the heat conducting sheet according to claim 1.   The manufacturing method of the heat conductive sheet in any one of Claim 1 to 2 with which the said press process is performed using the spacer for compressing the said molded object sheet | seat to predetermined thickness.   4. The heat pressing sheet according to claim 1, wherein the pressing step is performed by pressing a plurality of the molded body sheets adjacent to each other, and collectively pressing the plurality of molded body sheets. 5. The manufacturing method of the heat conductive sheet of description. A heat conductive sheet having a sheet body formed by curing a heat conductive resin composition containing a binder resin and a heat conductive filler,
The binder resin contains a liquid silicone gel main ingredient and a curing agent,
The mixing ratio between the curing agent and the main agent, the main agent in a weight ratio: curing agent = 60:40 to 65: A 35,
The thermally conductive filler contains carbon fiber and an inorganic filler,
The inorganic filler contains alumina and aluminum nitride,
The heat conductive sheet, wherein the surface of the sheet main body is covered with an exuding component that has exuded from the sheet main body so as to follow the convex shape of the protruding heat conductive filler. The heat conductive sheet according to claim 5, wherein the inorganic filler is attached to a surface of the carbon fiber in a protruding shape formed by the protruding heat conductive filler. The heat conductive sheet according to any one of claims 5 and 6, wherein the carbon fibers are randomly oriented in the heat conductive sheet. The L * value in the L * a * b * color system of the surface of the said heat conductive sheet is 25 or more and 70 or less, The heat conductive sheet in any one of Claim 5 to 7. A heat source, a heat radiating member, and a heat conductive sheet sandwiched between the heat source and the heat radiating member,
The semiconductor device according to claim 5, wherein the heat conductive sheet is the heat conductive sheet according to claim 5.