JP2010126584A - Prepreg sheet and method for producing prepreg sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg sheet having excellent handleability in such an application that is used for heat transfer from a heat-generating member to a heat-releasing member. <P>SOLUTION: The prepreg sheet 1 is obtained by supporting a semi-cured state thermosetting resin composition on a substrate sheet 2 so that thermal bonding to an adherend is possible, and has a form of a piece of sheet so as to be used by being interposed between the heat-generating member and the heat-releasing member for releasing heat generated from the heat-generating member, wherein an inorganic filler is contained in the thermosetting resin composition so as to be used for heat transfer from the heat-generating member to the heat-releasing member. The prepreg sheet 1 is formed by solidifying resin varnish 30, which is obtained by liquefying the thermosetting resin composition, after the substrate sheet, which is obtained by profile processing a fiber sheet 20 to the form of a piece of sheet, is impregnated with the resin varnish 30. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, a semi-cured thermosetting resin composition is supported on a base sheet so as to be thermally bonded to an adherend, and a heat generating member and heat generated from the heat generating member are dissipated. In particular, the present invention relates to a prepreg sheet having a sheet piece shape to be used between the heat radiating member and the manufacturing method thereof, and more specifically, can be used for heat transfer from the heat generating member to the heat radiating member. Thus, the present invention relates to a prepreg sheet in which an inorganic filler is contained in the thermosetting resin composition and a method for producing the same.

Conventionally, an electronic component called a power module or the like is used as a switching power supply element such as an inverter. As the power module, a control element and the like are mounted on a circuit board together with a power transistor for switching the power supply. What is sealed with a mold is widely used.
Since this power module generates a large amount of heat from the power transistor, a circuit board with high heat dissipation is used as the circuit board. A metal base circuit board in which a circuit layer and a metal plate layer are laminated via an insulating layer is used. It is used.
Then, the metal plate layer of the metal base circuit board is exposed on the module surface, and heat is transferred from the surface of the metal plate layer to a heat radiating member such as a heat radiating fin to dissipate the heat, thereby preventing a temperature rise inside the power module Things have been done.

When heat is released from a heat generating member such as a power module using a heat radiating member, for example, by simply bringing the heat generating member and the heat radiating member into contact with each other, an air layer is formed between them and sufficient heat is generated. Conduction may not be performed.
For this reason, a heat conductive sheet formed into a sheet shape by an adhesive polymer composition highly filled with an inorganic filler is interposed between the heat generating member and the heat radiating member, and the heat conductive sheet generates heat. Adhesion between the member and the heat radiating member prevents the formation of an air layer and ensures heat dissipation.

For example, in Patent Document 1, an insulating sheet excellent in thermal conductivity in which a thermosetting resin composition containing an inorganic filler and an epoxy resin is supported on one side of a copper foil sheet in a semi-cured state is heated on a heat sink. It is described that it is used for heat radiation outside the module by bonding.
When the inorganic filler is highly filled in this way, the thermosetting resin composition becomes brittle. For example, when it is formed into a thin sheet, there is a possibility that cracking may occur with a small force (for example, Patent Document 1). Paragraph [0042]).

By the way, conventionally, a prepreg sheet called “Garaepo” in which an epoxy resin composition is impregnated in a glass fiber woven sheet is widely used for electronic parts.
In recent years, the use of a prepreg sheet supported in a state in which this glass fiber woven sheet is impregnated with an epoxy resin composition containing an inorganic filler has been studied (for example, Patent Document 2 below).
Forming a single epoxy resin composition into a sheet by supporting an epoxy resin composition containing an inorganic filler on a base sheet such as the copper foil sheet in Patent Document 1 or the glass cloth in Patent Document 2 Compared with the case where it is made to be able to prevent a crack, handling property becomes favorable.

  However, when the prepreg sheet is used in a state of being interposed between the heat generating member and the heat radiating member, for example, after the prepreg sheet having a sheet shape having a larger area than the heat generating member is heated and bonded to the heat generating member, Cutting and removing the portion that protrudes from the member is not only labor-intensive, but also has a large material loss. Therefore, it is usually used in a state in which the outer shape is processed in advance in a predetermined shape.

At this time, a sheet in which the thermosetting resin composition is supported on a base sheet larger than the adhesion area to the adherend is used as a raw material sheet, and the raw material sheet is punched out to cut out a prepreg sheet having a predetermined shape. In some cases, peeling may occur between the base sheet and the epoxy resin composition carried at the cut end, and dust may be generated.
This dust may adhere to the adhesive surface when heat-adhering the prepreg sheet to the adherend and damage the adhesion between the prepreg sheet and the adherend, so care must be taken during the bonding operation. May occur and the operation may become complicated.

  That is, the prepreg sheet in which the thermosetting resin composition containing the inorganic filler is supported on the base sheet is less likely to be cracked and easier to handle than the thermosetting resin composition sheet. It is hard to say that workability has been improved sufficiently, leaving room for improvement.

JP 2004-165281 A JP 2008-274046 A

  An object of the present invention is to provide a prepreg sheet that is excellent in handleability in applications such as those used for heat transfer from a heat generating member to a heat radiating member. Yes.

  The present invention relating to a prepreg sheet for solving the above-mentioned problem is that a thermosetting resin composition in a semi-cured state is supported on a base sheet so that it can be thermally bonded to an adherend, and a heating member, It has a sheet piece shape to be interposed between and used with a heat radiating member for radiating heat generated from the heat generating member, and can be used for heat transfer from the heat generating member to the heat radiating member. A prepreg sheet in which an inorganic filler is contained in the thermosetting resin composition, and a fiber varnish of the resin varnish obtained by liquefying the thermosetting resin composition is processed into the sheet piece shape. It is characterized by being formed by impregnating a base sheet and then solidifying.

  Further, the present invention relating to the prepreg sheet manufacturing method comprises a base sheet that carries a semi-cured thermosetting resin composition so that it can be thermally bonded to an adherend. It has a sheet piece shape to be interposed between and used with a heat radiating member for radiating generated heat, and the thermosetting so that it can be used for heat transfer from the heat radiating member to the heat radiating member. A prepreg sheet manufacturing method for manufacturing a prepreg sheet in which an inorganic filler is contained in a conductive resin composition, wherein a base sheet is manufactured by externally processing a fiber sheet so as to have the sheet piece shape Performing a process and a varnish preparation process for preparing a resin varnish in which the thermosetting resin composition is liquefied, impregnating the base sheet with the resin varnish, and impregnating the base sheet The resin varnish was conducted and varnishes solidification step of solidifying is characterized by preparing a prepreg sheet.

In the prepreg sheet of the present invention, the fiber sheet is impregnated and solidified with a thermosetting resin composition in a base sheet formed in advance into a sheet piece shape used as a prepreg sheet. The generation of dust can be suppressed as compared with the conventional prepreg sheet formed by cutting the outer shape after impregnation and solidification.
Therefore, it is possible to reduce the labor for dust while improving the thermal conductivity by the inorganic filler, and the handling property of the prepreg sheet can be improved as compared with the conventional one.
Moreover, according to the prepreg sheet manufacturing method of the present invention, it is possible to produce a prepreg sheet in which generation of dust is suppressed, and it is possible to provide a prepreg sheet excellent in handleability.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing a prepreg sheet of this embodiment.
FIG. 2 is a schematic process explanatory view showing the prepreg sheet manufacturing method of the present embodiment.

As shown in FIG. 1, a prepreg sheet 1 according to this embodiment is carried in a state in which a thermosetting resin composition 3 is impregnated on a base sheet 2 and has a sheet piece shape. Yes.
More specifically, the prepreg sheet 1 is usually formed in a predetermined sheet piece shape suitable for a heat generating member or a heat radiating member. For example, an adherend to which the prepreg sheet 1 is thermally bonded is attached to a heat sink on the module surface. In the case of a power module in which the metal plate is exposed, it is usually a sheet piece shape having a contour shape adapted to the exposed region of the metal plate.
Note that FIG. 2 illustrates a case where the outer shape is processed into a rectangle with a corner cut away.

The base sheet 2 used in the prepreg sheet 1 has a sheet piece shape that is substantially the same shape as the prepreg sheet 1 and will be described in detail later. Usually, the shape of the base sheet 2 remains as it is. This is reflected in the prepreg sheet 1.
This base material sheet 2 is formed by cutting out the base material sheet 2 from a fiber sheet 20 having a size capable of collecting a plurality of pieces.

The fiber sheet 20 that is the material of the base sheet 2 is not particularly limited in its type. For example, natural fibers such as cotton, wool, and silk, polyethylene resin fibers, polypropylene resin fibers, polyester resin fibers, and polyamide resins. Mention may be made of fibers, synthetic resin fibers such as polyimide resin fibers and fluorine resin fibers, and inorganic fibers such as carbon fibers, glass fibers, rock wool and metal fibers, which are used singly or in combination.
The fiber sheet 20 is a woven fabric woven using yarns formed from these fibers, a non-woven fabric in which fibers are randomly bonded with a binder, or the like. It is possible to use a felt-like material that is entangled with each other in a state of being deposited to a thickness of about 5 mm and is retained in a sheet shape.

  Since the fiber sheet 20 is usually reflected in the base sheet 2 in a state of formation such as fiber density, it is possible to employ a fiber sheet that is suitable for impregnation with a thermosetting resin composition. Preferably, the thickness of the fiber is usually 4 to 8 μm, and the proportion of voids (porosity) in the volume can be usually 50 to 65%.

The thermosetting resin composition 3 to be carried on the base sheet 2 cut out from the fiber sheet 20 is carried in a semi-cured state so as to enable thermal adhesion to the adherend.
As the thermosetting resin composition 3, for example, an epoxy resin composition in which an epoxy resin is used as a base resin is suitable.
Whether or not the epoxy resin composition is in a semi-cured state can be determined by using a differential scanning calorimeter (DSC) based on whether or not a thermal change due to the curing reaction of the epoxy resin is observed. Moreover, when other thermosetting resin compositions are used, it can confirm that it is a semi-hardened state by having the reactivity of hardening reaction similarly.

Examples of the epoxy resin used in the epoxy resin composition include a bisphenol type and a novolac type. Examples of the bisphenol type include a bisphenol A type epoxy resin and a bisphenol F type epoxy resin, and Examples thereof include those obtained by modifying these with CTBN, and those having an epoxy equivalent of 180 to 2500 g / eq. In addition, this epoxy equivalent can be calculated | required based on JISK7236.
Of these, a bisphenol A type epoxy resin having an epoxy equivalent of any one of 900 to 2500 g / eq, which is not modified such as CTBN modification, is preferable.
Moreover, as a novolak type thing, a cresol novolak type epoxy resin and a phenol novolak type epoxy resin are mentioned, for example, o-cresol novolak type epoxy resin which has any softening point of 70-90 degreeC may be illustrated. it can. The softening point can be measured by the ring and ball method of JIS K 7234.
These epoxy resins can be contained in the epoxy resin composition alone or in a mixed state.

As the inorganic filler, from the viewpoint of imparting excellent thermal conductivity to the prepreg sheet 1, it is preferable to contain a larger amount of high thermal conductivity.
Examples of such inorganic fillers include boron nitride particles, aluminum nitride particles, silicon nitride particles, gallium nitride particles, aluminum oxide particles, silicon carbide particles, silicon dioxide particles, diamond particles having a particle diameter of several nanometers to several tens of micrometers. Is mentioned.
Among these, boron nitride particles are suitable in that they have a high thermal conductivity while being relatively inexpensive.
Although the blending ratio of such an inorganic filler is appropriately determined according to the use of the prepreg sheet 1, it is almost difficult to suppress the generation of dust from the cut end face in a general prepreg sheet. It is preferable to mix | blend in the ratio used as 40 volume% or more with the solid content of a thermosetting resin composition at the point which the effect of this invention may become more remarkable.

In addition, the epoxy resin composition may contain a so-called curing agent or accelerator for curing the epoxy resin.
The curing agent is not particularly limited, and examples thereof include amine curing agents such as diaminodiphenyl sulfone, dicyandiamide, diaminodiphenylmethane, and triethylenetetramine, phenol novolac resins, aralkyl type phenol resins, and dicyclopentadiene modified phenols. Resin, phenolic curing agents such as naphthalene type phenolic resin and bisphenolic phenolic resin, acid anhydrides and the like can be used.
In particular, when the prepreg sheet is strongly required to have electrical insulation, phenol novolac resin, diaminodiphenyl sulfone, and the like are preferable in that it is easy to ensure reliability in electrical characteristics.
The curing accelerator is not particularly limited, but an amine-based curing accelerator such as imidazoles, triphenyl phosphate (TPP), or boron trifluoride monoethylamine is a curing reaction during storage of the prepreg sheet. It is suitable at the point which can suppress progress of this.

  In addition to the above epoxy resin, inorganic filler, curing agent, accelerator, dispersant, tackifier, anti-aging agent, antioxidant, processing aid, stabilizer, antifoaming agent, flame retardant, Rubbers such as thickeners and pigments, and those generally used as plastic compounding chemicals can be appropriately contained in the epoxy resin composition.

  Next, the prepreg sheet manufacturing method using such a base sheet 2 and an epoxy resin composition will be described.

In the prepreg sheet manufacturing method in the present embodiment, a base sheet preparation step of manufacturing a base sheet by externally processing a fiber sheet so as to have the sheet piece shape, and liquefying the thermosetting resin composition After performing the varnish preparation step for preparing the resin varnish, the impregnation step for impregnating the base sheet with the resin varnish, and the varnish solidification step for solidifying the resin varnish impregnated in the base sheet in the impregnation step And carry out.
Below, each process is demonstrated, referring FIG.

(Base sheet production process)
In this base material sheet manufacturing step, a prepreg sheet 1 that is manufactured using a fiber sheet 20 having a sheet shape much larger than the base material sheet 2 as a material so that a plurality of base material sheets 2 can be collected. The base sheet 2 is produced by externally processing the fiber sheet 20 so as to have a sheet piece shape that is substantially the same shape as the above.
Specific means for this outer shape processing are not particularly limited, and punching processing using a Thomson blade or the like, outer shape cutting processing using a laser processing machine, or the like can be employed.

(Varnish production process)
This varnish production process is a process of adjusting a liquid thermosetting resin composition for impregnating the base material sheet 2 produced in the base material sheet production process. For example, when using the above-described epoxy resin, etc. In this method, a liquid epoxy resin composition can be prepared using an organic solvent soluble in the epoxy resin.
For example, an epoxy resin, an inorganic filler, a curing agent, an accelerator, and other compounding agents are dispersed in an organic solvent such as methyl ethyl ketone to prepare a liquid epoxy resin composition, which is impregnated into the base sheet 2 as an epoxy resin varnish. Can be made.
The resin varnish to be adjusted at this time depends on the base material sheet 2 to be used, but it is usually preferable to adjust the viscosity so that the viscosity is 500 to 10,000 (mPa · s).
In particular, when using a felt-like base sheet formed of fibers having a thickness of 4 to 8 μm and a porosity of 50 to 65%, the viscosity of the base sheet is set to such a viscosity. It becomes an epoxy resin varnish excellent in impregnation.
In addition, about this viscosity, it can measure by the method based on JISC2103.
Specifically, it can be measured by JIS K 7117-1, B-type viscometer measurement method, conditions: 23 ° C., No. 4 spindle, 20 rpm.

However, even when the resin varnish is adjusted so as to have the above viscosity, when the prepreg sheet 1 is produced if the content of the organic solvent is increased too much, a cavity due to volatilization of the organic solvent is formed inside the prepreg sheet. If this is done, the thermal conductivity may be reduced.
Therefore, it is preferable to adjust the amount of the organic solvent so that the volatile content in the resin varnish is 10 to 50% by mass.
Further, the formation of the cavities is also related to the state of the base sheet 2. For example, when the thickness of the base sheet 2 is too thick, the removal of the organic solvent is deteriorated, causing internal foaming to form the cavities. It may be formed.
From such a viewpoint, from the viewpoint of the impregnating property of the resin varnish to the base material sheet 2, when using the felt-like base material sheet 2, the thickness thereof is preferably set to any one of 1 to 5 mm. is there.

(Impregnation process)
The impregnation step is a step of impregnating the base sheet 2 prepared in the base sheet preparation step with the resin varnish prepared in the varnish preparation step, and the impregnation method of the resin varnish is particularly limited. Instead, a method of simply immersing the base sheet 2 in the tank 40 in which the resin varnish 30 is stored may be employed.
Further, for example, the impregnation may be performed by spraying the resin varnish onto the base sheet with a spray coater or the like.

(Solidification process)
This solidification step is a step of solidifying the impregnated resin varnish by drying the base sheet 2 impregnated with the resin varnish in the impregnation step.
The resin varnish can be solidified by a general varnish drying and solidifying method such as heat drying, vacuum drying, or vacuum heat drying.
In addition, when heating the base material sheet 2 impregnated with the resin varnish for the solidification step, it is preferable to set the conditions with care so that the curing reaction does not proceed excessively due to the heating.

The prepreg sheet obtained through such a process is, for example, interposed between a metal plate exposed surface of a power module and a member mounting surface provided for mounting a heat generating member on a heat radiation fin. Pressurize in the direction to bring the module and the radiation fin close to each other and heat to the curing reaction temperature of the epoxy resin composition to thermally bond one side to the power module and to thermally bond the other side to the radiation fin. .
In addition, although the cavity inside the prepreg sheet was described in the varnish preparation process, by adjusting the flow amount of the epoxy resin composition at the time of this thermal bonding, there is no residual bubble inside after thermal bonding, and the thermal conductivity It is possible to achieve an excellent adhesion state.

Since the prepreg sheet produced by the prepreg sheet manufacturing method of the present embodiment has been processed into the form at the time of use from the production stage of the base sheet, the heat generating member is left as it is without performing cutting or the like It is possible to be thermally bonded by interposing between the heat sink and the heat radiating member.
In that case, since a cut surface is not formed unlike the conventional prepreg sheet, generation | occurrence | production of the dust from an edge part is also suppressed and an adhesion | attachment process can be implemented easily.
Moreover, the thermosetting resin composition in a semi-cured state containing an inorganic filler is usually very brittle and requires careful handling. However, the prepreg sheet produced by the prepreg sheet manufacturing method of this embodiment is a thermosetting resin composition. Since the conductive resin composition is supported in a state of being impregnated in the base material sheet, it is easy to handle.
Thus, according to the prepreg sheet manufacturing method according to the present embodiment, for example, it is excellent in handleability even in applications where high filling of inorganic filler is required, such as used for heat transfer from a heat generating member to a heat radiating member. A prepreg sheet can be provided.

  In the present embodiment, it is widely used among thermosetting resins, has a good balance of properties usually required for prepreg sheets such as heat resistance and electrical insulation, and contains a large amount of inorganic filler. The epoxy resin composition is exemplified as the thermosetting resin composition in that it is likely to be brittle in the B-stage state at the time of being used, and the effects of the present invention can be exhibited more remarkably, but other thermosetting resins The use of the composition is also within the intended scope of the present invention.

  Further, in the present embodiment, the resin varnish is used with an organic solvent in that it is possible to easily produce a resin varnish while suppressing the progress of the curing reaction, and in that it is easy to adjust the viscosity of the varnish. Although the varnish preparation process which produces a varnish is illustrated, for example, when liquefaction of a resin composition is possible only by heating, a resin varnish in a hot melt state is prepared without using an organic solvent. Also good.

  Further, although not described in detail here, conventionally known technical matters in the prepreg sheet and the manufacturing method thereof can be adopted in the present invention.

Sectional drawing of the prepreg sheet | seat in one Embodiment. The schematic process drawing which shows the prepreg sheet manufacturing method of one Embodiment.

Explanation of symbols

  1: prepreg sheet, 2: base sheet, 3: thermosetting resin composition, 20: fiber sheet, 30: resin varnish, 40: tank

Claims (8)

A semi-cured thermosetting resin composition is carried on a base sheet so that it can be thermally bonded to an adherend, a heat generating member, and a heat radiating member for radiating heat generated from the heat generating member, The thermosetting resin composition contains an inorganic filler so that it can be used for heat transfer from the heat generating member to the heat radiating member. A prepreg sheet,
A prepreg formed by solidifying after impregnating a base sheet formed by externally processing a fiber sheet into a sheet piece shape with a resin varnish obtained by liquefying the thermosetting resin composition Sheet.   The prepreg sheet according to claim 1, wherein a ratio of the inorganic filler to a solid content of the thermosetting resin composition is 40% by volume or more.   A prepreg sheet in which a base sheet in which a felt-like fiber sheet having a thickness of 1 to 5 mm is externally processed into the sheet piece shape is used.   The prepreg sheet according to any one of claims 1 to 3, wherein the thermosetting resin composition is an epoxy resin composition having an epoxy resin as a base resin. A semi-cured thermosetting resin composition is carried on a base sheet so that it can be thermally bonded to an adherend, a heat generating member, and a heat radiating member for radiating heat generated from the heat generating member, The thermosetting resin composition contains an inorganic filler so that it can be used for heat transfer from the heat generating member to the heat radiating member. A prepreg sheet manufacturing method for manufacturing a prepreg sheet,
A base sheet preparation step for manufacturing a base sheet by externally processing a fiber sheet into the sheet piece shape, and a varnish preparation step for preparing a resin varnish in which the thermosetting resin composition is liquefied. A prepreg sheet is manufactured by performing an impregnation step of impregnating the base sheet with the resin varnish and a varnish solidification step of solidifying the resin varnish impregnated in the base sheet. Sheet manufacturing method.   The method for producing a prepreg sheet according to claim 5, wherein a ratio of the inorganic filler to a solid content of the thermosetting resin composition is 40% by volume or more.   The prepreg sheet manufacturing method of Claim 5 or 6 which implements the base material sheet preparation process which shape-processes the felt-like fiber sheet which has any thickness of 1-5 mm in the said sheet piece shape, and produces a base material sheet.   The prepreg sheet manufacturing method according to any one of claims 5 to 7, wherein the thermosetting resin composition is an epoxy resin composition having an epoxy resin as a base resin.

Images