JP7102793B2 - Resin substrate - Google Patents

Description

The present invention relates to a resin substrate.

In recent years, the number of electronic devices installed in automobiles has been increasing, and the miniaturization of these electronic devices is rapidly progressing. On the other hand, the amount of heat generated from a densified conductor is increasing with the miniaturization, and how to dissipate the heat has become an important issue.
As a technique for improving the heat dissipation of a conventional glass-epoxy resin printed circuit board, a metal base substrate that forms a circuit pattern on one or both sides of a metal substrate via an insulating layer, and a copper plate on a ceramic substrate such as alumina or aluminum nitride. A substrate in which the above is directly bonded has been proposed. It is difficult to achieve both the metal base substrate and the ceramic substrate in terms of performance and cost.
Then, in order to obtain the heat dissipation of the resin substrate, a resin composition in which the resin viscosity is lowered and the inorganic filler is filled in a high concentration, and a resin substrate have been proposed. For example, Patent Document 1 discloses a heat conductive sheet-like material that can be filled with an inorganic filler at a high concentration and has excellent heat dissipation, and a heat conductive substrate using the same, and heat dissipation is required. It is considered to be suitable for substrate applications.

Japanese Patent No. 33127223

However, a resin substrate filled with an inorganic filler at a high concentration as described in Patent Document 1 has a reduced fluidity at the time of melting, and therefore has a reduced embedding property in a complicated circuit pattern when manufacturing a laminated board. There is a problem such as doing.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resin substrate that improves thermal conductivity without lowering moldability.

The present inventors provide the following means for solving the above problems.

[1] A resin substrate formed by heating and pressurizing one or two or more prepregs in which a thermosetting resin composition containing an inorganic filler is held on a fiber base material and is in a semi-cured state.
When the thickness of the resin substrate is t and the area of the cut surface in the thickness direction of vertical t and horizontal 2 t is 100 area%,
A resin substrate characterized in that a portion of 10% or less of an element derived from an inorganic filler excluding oxygen and a fiber base material is present in an area% of 0.5 to 8%.
[2] The cut surface in the thickness direction of the resin substrate is equally divided in the thickness direction by the number of laminated prepregs n, and the areas of vertical t / n and horizontal 2t corresponding to one prepreg are set from A1 to An. When the area of each of A1 to An is 100 area%, the portion of 10% or less of the element derived from the inorganic filler and the fiber base material excluding oxygen is characterized by having 0 to 20 area% of each of A1 to An. The resin substrate according to [1].
[3] The resin substrate of [1] or [2], wherein the prepreg contains a prepreg having voids on one side or both sides.

By partially creating a portion having a small amount of the filler and a portion having a large amount of the filler in the resin substrate of the present invention, the portion having a large amount of the filler becomes a heat conduction path, and the thermal conductivity is increased. Since the total amount of the inorganic filler filled can be reduced, the embedding property in a complicated circuit pattern is also good. It is possible to provide a resin substrate having improved thermal conductivity without lowering moldability.

It is sectional drawing which shows the structure of the resin substrate of 1st Embodiment of this invention. It is sectional drawing which shows the structure of the resin substrate of the 2nd Embodiment of this invention. It is sectional drawing for demonstrating an example of the manufacturing method of the substrate of 1st Embodiment of this invention. It is sectional drawing for demonstrating another example of the manufacturing method of the resin substrate of 1st Embodiment of this invention. It is sectional drawing for demonstrating an example of the manufacturing method of the resin substrate of the 2nd Embodiment of this invention. It is a top view which shows the structure of the substrate for formability evaluation. It is sectional drawing which shows the structure of the substrate for formability evaluation shown in FIG.

Hereinafter, the present embodiment will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may be enlarged for convenience in order to make the features of the present invention easy to understand, and the dimensional ratios of the respective components may differ from the actual ones. be. The materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited thereto, and the present invention can be appropriately modified without changing the gist thereof.

(Resin substrate)
The resin substrate of the present invention is a resin substrate formed by heating and pressurizing two or more prepregs in which a thermosetting resin composition containing an inorganic filler is held on a fiber base material and is in a semi-cured state. The resin substrate of the present invention is derived from an inorganic filler and a fiber base material excluding oxygen when the thickness of the resin substrate is t and the area of the cut surface in the thickness direction of vertical t and horizontal 2 t is 100 area%. It is characterized in that there is 0.5 to 8 area% of a portion containing 10% or less of an element. The portion where the amount of the inorganic filler other than oxygen and the element derived from the fiber base material is 10% or less is a portion where the inorganic filler is small, and hereinafter, it is also referred to as "sparse portion of the inorganic filler". Further, it is preferable that the portion (sparse portion of the inorganic filler) containing 10% or less of the element derived from the inorganic filler excluding oxygen and the fiber base material is 1 to 7 area%, and more preferably 2 to 6 area%. Further, it is preferable that the portion of the inorganic filler excluding oxygen and the element derived from the fiber base material is 5% or less is 0.5 to 6 area%, and more preferably 1 to 5 area%.

If there is such a place where the inorganic filler is small (sparse part of the inorganic filler), there is a part where the inorganic filler is abundant. Since a heat conduction path is easily formed in a portion having a large amount of inorganic filler (also referred to as “dense portion of inorganic filler”), the thermal conductivity of the resin substrate is improved. When the sparse portion of the inorganic filler is less than 0.5 area%, the heat conduction path is small and the heat conductivity does not increase. If the sparse portion of the inorganic filler is more than 8 area%, there are many places where the inorganic filler having low thermal conductivity is small, and the thermal conductivity is lowered.
In the resin substrate of the present invention, the cut surface in the thickness direction of the substrate is equally divided in the thickness direction by the number of laminated prepregs n, and the area of vertical t / n and horizontal 2t corresponding to one prepreg is set from A1 to An. When the area of each of A1 to An is 100 area%, the portion of the inorganic filler excluding oxygen and the element derived from the fiber base material of 10% or less (sparse portion of the inorganic filler) is 0 from A1 to An, respectively. It is preferable to have ~ 20 area%. It is more preferable that the sparse portion of the inorganic filler is 0.3 to 10 area% in each of A1 to An. It is more preferable that A1 to An each have 1.0 to 7.0 area% of a portion having a small amount of the inorganic filler (sparse portion of the inorganic filler).
If each prepreg has a portion of 20 area% or more and a small amount of the inorganic filler (sparse portion of the inorganic filler), heat conduction is inhibited and the thermal conductivity is lowered.

[First Embodiment]
<Structure of resin substrate>
FIG. 1 is a cross-sectional view showing the configuration of the resin substrate 10 according to the first embodiment of the present invention. The resin substrate 10 of the first embodiment of the present invention is a resin substrate formed by heating and pressurizing three prepregs in which a thermosetting resin composition containing an inorganic filler is held on a fiber base material 15 and is in a semi-cured state. be. The resin substrate 10 of this embodiment contains a cured product 12 of a thermosetting resin composition and a fiber base material 15. The cured product 12 of the thermosetting resin composition is obtained by curing the thermosetting resin composition containing the inorganic filler, and is composed of the inorganic filler and the cured product of the thermosetting resin.

<Layer structure of resin substrate>
The resin substrate 10 of the present embodiment has a three-layer structure derived from three prepregs. The first layer has a cured product 12-1 of a thermosetting resin composition derived from the first prepreg (not shown) and a fiber base material 15-1, and the second layer is thermosetting derived from the second prepreg. It has a cured product 12-2 of a sex resin composition and a fiber base material 15-2, and the third layer is a cured product 12-3 of a thermosetting resin composition derived from a third prepreg and a fiber base material 15-. Has 3 and.

In the resin substrate 10 of the present embodiment, a metal foil may be further laminated on the inside (the interface between the prepreg and the prepreg) and on the surface layer to form a metal foil-covered substrate. When the metal foil is laminated on the surface layer, the metal foil may be attached to only one surface or both sides.

The metal foil is not particularly limited, and can be appropriately selected from commonly used metal foils. Specific examples thereof include gold foil, copper foil, and aluminum foil, and copper foil is generally used. The thickness of the metal foil is not particularly limited as long as it is 1 μm to 200 μm, and a suitable thickness can be selected according to the electric power used and the like.

Further, as the metal foil, nickel, nickel-phosphorus, nickel-tin alloy, nickel-iron alloy, lead, lead-tin alloy and the like are used as intermediate layers, and a copper layer of 0.5 μm to 15 μm and a copper layer of 10 μm to 10 μm on both surfaces thereof. It is also possible to use a three-layer structure composite foil provided with a 150 μm copper layer, or a two-layer structure composite foil in which aluminum and copper foil are composited.

The metal plate is preferably made of a metal material having a high thermal conductivity and a large heat capacity. Specifically, copper, aluminum, iron, alloys used for lead frames and the like can be exemplified.

The thickness of the metal plate can be appropriately selected depending on the intended use. For example, the material of the metal plate can be selected according to the purpose, such as aluminum when weight reduction and workability are prioritized, and copper when heat dissipation is prioritized.

In the substrate 10, in order to increase the peel strength of the metal foil (copper foil), there may be a pre-step of surface-treating the metal foil by a conventionally known method.

The conditions for pressing and molding the metal foil and the prepreg are not particularly limited as long as the uncured / semi-cured thermosetting resin of the prepreg can be cured. For example, heating and pressure treatment are preferable. The heating temperature in the heating and pressurizing treatment is not particularly limited. It is usually in the range of 100 ° C. to 250 ° C., preferably in the range of 130 ° C. to 230 ° C. Further, the pressurizing conditions in the heating and pressurizing treatment are not particularly limited. It is usually in the range of 1 MPa to 20 MPa, preferably in the range of 1 MPa to 15 MPa. Further, a vacuum press is preferably used for the heating and pressurizing treatment.
Further, the resin substrate provided with the metal foil may be subjected to any one or more of various treatments such as etching treatment and drilling treatment, if necessary.

<Inorganic filler sparse part>
The resin substrate 10 of the present embodiment is characterized by having a portion (sparse portion of the inorganic filler) 18 in which the amount of the inorganic filler is small. When the thickness of the resin substrate 10 is t and the area of the cut surface in the thickness direction of vertical t and horizontal 2 t is 100 area%, the inorganic filler sparse portion is 0.5 to 8 area%. The portion 18 where the inorganic filler of the present invention is small (sparse portion of the inorganic filler) is a portion where the element derived from the inorganic filler excluding oxygen and the fiber base material is 10% or less.

"Components of sparse parts of inorganic filler"
The component of the sparse portion 18 of the inorganic filler is not particularly limited as long as the effects of thermal conductivity and moldability of the resin substrate of the present invention can be achieved, but from the viewpoint of easy production, the sparse portion 18 of the inorganic filler 18 The cured product of the resin composition preferably contains the same type of thermosetting resin and inorganic filler as the cured product of the surrounding resin composition.

"Arrangement of sparse parts of inorganic filler"
The arrangement (distribution) of the sparse portion 18 of the inorganic filler of the present embodiment is not particularly limited as long as it has the effects of thermal conductivity and moldability of the resin substrate, but from the viewpoint of easily forming a thermal conduction path, thermal conduction It is preferably in a position that does not obstruct the pathway. For example, in the sparse portion 18 of the inorganic filler of the present embodiment, as shown in FIG. 1, the fiber base material 15-1 of the first layer and the fiber base material of the second layer are formed on the cut surface of the resin substrate 10 in the thickness direction. It is formed between 15-2. More specifically, for example, it is preferable that the resin substrate 10 is formed at a portion not directly below the opening of the fiber substrate of the same layer on the cut surface in the thickness direction of the resin substrate 10 shown in FIG. Further, from the viewpoint of easy production, as an example, at the connecting surface between the cured product 12-1 of the resin composition of the first layer and the cured product 12-2 of the resin composition of the second layer, the cured product 12-1 It may be formed on the side of.

"Size of sparse part of inorganic filler"
The size of the sparse portion 18 of the inorganic filler of the present embodiment is not particularly limited as long as it has the effects of thermal conductivity and moldability of the resin substrate, but from the viewpoint of easily forming a thermal conductive path, for example, the present embodiment. As shown in FIG. 1, the width of the sparse portion 18 of the inorganic filler is preferably equal to or less than the opening diameter of the fiber base material on the cut surface of the resin substrate 10 in the thickness direction.

"Shape of sparse part of inorganic filler"
The shape of the sparse portion 18 of the inorganic filler of the present embodiment is not particularly limited as long as it has the effects of thermal conductivity and moldability of the resin substrate, but from the viewpoint of easily forming a thermal conductive path, for example, the present embodiment. As shown in FIG. 1, the inorganic filler sparse portion 18 has a substantially elliptical shape or a flat plate shape in which the width parallel to the substrate surface is larger than the thickness parallel to the substrate thickness on the cut surface of the resin substrate 10 in the thickness direction. It is preferably in the form of a disk).

<Manufacturing method of resin substrate>
The laminated substrate of this embodiment is a cured prepreg.
In one embodiment of the method for manufacturing a resin substrate of the present embodiment, first, as shown in FIGS. 3A to 3B, for example, two second prepregs 33-1 and two second prepregs 33-2 are used. The substrate 37 can be formed by a heating press / molding step.

As shown in FIGS. 3C to 3D, the substrate 37 further uses one first prepreg 31 having a gap, and faces the side surface of the first prepreg 31 having a gap and the substrate 37. The resin substrate 30 of the present embodiment can be formed by the heat pressing / molding step.
When the resin substrate 30 is produced by laminating the first prepreg 31 having voids and the substrate 37, the resin preferentially flows into the voids to fill the voids, so that there is little inorganic filler in the voids. A portion (sparse portion 38 of the inorganic filler) is generated, and a portion having a large amount of the inorganic filler is generated around the portion having the void.
The size of the gap of the first prepreg 31 is smaller than the opening of the fiber base material 35-1, so that the amount of pushing the slit die into the fiber base material 35-1 and the contact angle, and the amount of paint discharged Controlled by. If there are many voids larger than the opening of the fiber base material 35-1, the area of the sparse portion of the inorganic filler per prepreg may become large, and heat conduction may be difficult to transfer.

The conditions for pressing and molding the second prepreg 33 to form the substrate 37 are not particularly limited as long as the uncured / semi-cured thermosetting resin of the second prepreg 33 can be cured. Unlike the above-mentioned method for producing a prepreg, it is preferable that the conditions are such that the curing reaction substantially proceeds. For example, heating and pressure treatment are preferable. The heating temperature in the heating and pressurizing treatment is not particularly limited. It is usually in the range of 100 ° C. to 250 ° C., preferably in the range of 130 ° C. to 230 ° C. Further, the pressurizing conditions in the heating and pressurizing treatment are not particularly limited. It is usually in the range of 1 MPa to 20 MPa, preferably in the range of 1 MPa to 15 MPa. Further, a vacuum press is preferably used for the heating and pressurizing treatment.

The condition for forming the resin substrate 30 by pressing and molding the first prepreg 31 and the substrate 37 is that the uncured / semi-cured thermosetting resin of the first prepreg 31 is cured to form the inorganic filler sparse portion 38. If possible, there is no particular limitation. It is usually in the range of 100 ° C. to 250 ° C., preferably in the range of 130 ° C. to 230 ° C. Further, the pressurizing conditions in the heating and pressurizing treatment are not particularly limited. It is usually in the range of 1 MPa to 20 MPa, preferably in the range of 1 MPa to 15 MPa. Further, a vacuum press is preferably used for the heating and pressurizing treatment.

In the example shown in FIG. 3, the number of the second prepregs 33 used for the substrate 37 is two, but the number is not limited to two, and one or three or more may be used. This number can be appropriately set based on conditions such as the thickness and strength of the second prepreg 33. Further, although the number of the first prepreg 31 used for the resin substrate 30 is one, the number is not limited to one, and two or more may be used.

In another example of the method for producing a resin substrate of the present embodiment, first, as shown in FIGS. 4A to 4B, for example, a first prepreg 41 having a gap and a second prepreg 43 having no gap- The resin substrate 40 is produced by laminating 1 and the second prepreg 43-2 having no voids. Specifically, the resin substrate 40 can be formed by a heat pressing / molding step so as to face the side surface of the first prepreg 41 having a gap and the second prepreg 43-1. Since the resin preferentially flows into the void portion of the second prepreg 41 to fill the void, the inorganic filler sparse portion 48 having less inorganic filler is formed around the void portion in the portion having the void. There are places where there are many inorganic fillers.

The condition for forming the resin substrate 40 by pressing and molding the first prepreg 41, the second prepreg 43-1 and the second prepreg 4-3 is that the uncured / semi-cured thermosetting resin of the prepreg is cured and inorganic. The present invention is not particularly limited as long as the filler sparse portion 48 can be formed. It is usually in the range of 100 ° C. to 250 ° C., preferably in the range of 130 ° C. to 230 ° C. Further, the pressurizing conditions in the heating and pressurizing treatment are not particularly limited. It is usually in the range of 1 MPa to 20 MPa, preferably in the range of 1 MPa to 15 MPa. Further, a vacuum press is preferably used for the heating and pressurizing treatment.

In the example shown in FIG. 4, the number of the first prepreg 41 used for the resin substrate 40 is one, but the number is not limited to one, and two or more may be used. The number of the second prepreg 43 is two, but the number is not limited to two, and one or three or more may be used.

<Method of producing the first prepreg with voids>
The first prepreg having voids used for producing the resin substrate of the first embodiment of the present invention is a resin composition prepared by mixing a thermosetting resin and an inorganic filler from one side of a fiber base material such as a glass cloth. In a coating method in which the resin composition is held by the fiber base material by applying it using a slit die and passing it through the opening of the fiber base material to the coating back surface of the fiber base material, a slit in the fiber base material such as glass cloth is used. By controlling the die pushing amount and contact angle, and the paint ejection amount, it is possible to reduce the amount of paint passing through the opening of the fiber base material such as glass cloth and to produce a first prepreg with voids on the back surface of the coating. can.

Other methods for forming voids in the prepreg include addition of a foaming agent that vaporizes at a semi-curing temperature and processing of a concave putter on the surface of the prepreg (embossing). In that case, it is preferable that the back surface of the gap is not convex or the periphery of the gap is not convex. Further, by adding an organic filler (particles), it is possible to prepare a sparse portion of an inorganic filler. For example, after producing a second prepreg that does not have a gap, which will be described later, a sword-shaped protrusion is pressed against one side to create unevenness, and then a flat plate is pressed against the convex portion to flatten the convex portion. For example, a void can be formed.

Specifically, as the resin composition, for example, when each of the epoxy resin and the curing agent contained in the resin composition is solid, the resin composition is crushed into a powder and mixed to obtain a powder resin composition. The resin composition melted by heating and melting can be used.

Further, as the resin composition, a paint having a resin composition obtained by adding a solvent such as methyl ethyl ketone or cyclohexanone to the resin composition and mixing the resin composition can be used.

The content of the resin composition in the first prepreg is not particularly limited. From the viewpoint of moldability, it is preferably 20 vol% or more, and more preferably 30 vol% or more. Further, from the viewpoint of alignment accuracy and dimensional accuracy of the multilayer substrate, it is preferably 80 vol% or less, more preferably 70 vol% or less, and further preferably 60 vol% or less.

When the paint of the resin composition is used, the drying method is not particularly limited as long as at least a part of the organic solvent contained in the paint can be removed, and is appropriately selected from the commonly used drying methods according to the organic solvent contained in the paint. be able to. Generally, a method of heat treatment at about 60 ° C. to 150 ° C. can be mentioned.
The solidification at this time means that the liquid material having fluidity changes to a solid state in which it can stand on its own. The solidified state can include both a state in which a part of the organic solvent contained in the paint remains and a semi-cured state. For example, it can be solidified at 60 to 150 ° C. for about 1 to 120 minutes, preferably at 70 to 120 ° C. for about 3 to 90 minutes.

When the first prepreg is prepared using the paint of the resin composition, the solvent residual ratio in the prepreg is preferably 2.0% by mass or less, more preferably 1.0% by mass or less, and 0. It is more preferably 8.8% by mass or less.

The solvent residual ratio is obtained from the mass change before and after drying when the prepreg is cut into 40 mm squares and dried in a constant temperature bath preheated to 190 ° C. for 2 hours.

<Method of producing a second prepreg without voids>
The second prepreg having no voids used in the resin substrate of the first embodiment of the present invention comprises a fiber base material and a resin composition.

The second prepreg having no voids used for producing the resin substrate of the first embodiment of the present invention is a resin composition prepared by mixing a thermosetting resin and an inorganic filler on one side of a fiber base material such as a glass cloth. In a coating method in which the resin composition is retained in the fiber base material by applying the resin composition from the fiber base material using a slit die and passing the resin composition through the opening of the fiber base material through the coating back surface of the fiber base material, the resin composition is applied to the fiber base material such as glass cloth. By controlling the pushing amount and contact angle of the slit die and the discharging amount of the paint, a second prepreg having no gap can be produced.

The second prepreg having no voids used for producing the resin substrate of the first embodiment of the present invention can also be obtained by impregnating the above-mentioned fiber base material with, for example, the above-mentioned resin composition. Specifically, the second prepreg is obtained by impregnating the fiber base material with the resin composition and heating and drying the resin composition impregnated with the fiber base material.

The content of the resin composition in the second prepreg is not particularly limited. From the viewpoint of moldability, it is preferably 20 vol% or more, and more preferably 30 vol% or more. Further, from the viewpoint of the alignment accuracy of the multilayer substrate and the dimensional accuracy of the metal leaf adhesion, it is preferably 80 vol% or less, more preferably 70 vol% or less, and further preferably 60 vol% or less.

The method of impregnating the fiber base material with the resin composition is not particularly limited. For example, a method of applying by a coating machine can be mentioned. Details include a vertical coating method in which the fiber base material is passed through the resin composition and pulled up, and a horizontal coating method in which the fiber base material is pressed and impregnated after the resin composition is applied on the support film. Can be done.

Specifically, for example, when the epoxy resin and the curing agent contained in the resin composition are each solid, they are crushed into powder and mixed to heat and melt the powdery resin composition. The second prepreg can be obtained by impregnating the molten resin composition with a fiber base material.

When a solvent such as methyl ethyl ketone or cyclohexanone is added to the resin composition to prepare a coating material for the resin composition, the coating material for the resin composition is impregnated with a fiber base material. Then, the solvent component is removed by drying to solidify the resin composition.

The drying method is not particularly limited as long as at least a part of the organic solvent contained in the paint can be removed, and can be appropriately selected from the commonly used drying methods according to the organic solvent contained in the paint. Generally, a method of heat treatment at about 60 ° C. to 150 ° C. can be mentioned.
The solidification at this time means that the liquid material having fluidity changes to a solid state in which it can stand on its own. The solidified state can include both a state in which a part of the organic solvent contained in the paint remains and a semi-cured state. For example, it can be solidified at 60 to 150 ° C. for about 1 to 120 minutes, preferably at 70 to 120 ° C. for about 3 to 90 minutes.

The surface of the second prepreg may be smoothed in advance by hot pressure treatment with a press, a roll laminator, or the like before laminating or pasting. The method of hot pressure treatment is the same as the method described in the method for producing a semi-cured resin composition sheet. Further, the treatment conditions such as the heating temperature, the degree of depressurization, and the pressing pressure in the hot pressurization treatment of the prepreg are the same as the conditions mentioned in the heating / pressurizing treatment of the semi-cured resin composition.

When the second prepreg is prepared using the paint of the resin composition, the solvent residual ratio in the prepreg is preferably 2.0% by mass or less, more preferably 1.0% by mass or less, and 0. It is more preferably 8.8% by mass or less.

The solvent residual ratio is obtained from the mass change before and after drying when the prepreg is cut into 40 mm squares and dried in a constant temperature bath preheated to 190 ° C. for 2 hours.

<Fiber base material>
The first prepreg and the second prepreg used for the resin substrate of the present embodiment are composed of a resin composition and a fiber base material. The fiber base material used for the resin substrate of the present embodiment is not particularly limited as long as it is usually used when manufacturing a metal foil-clad laminated substrate or a multilayer printed wiring board, and is usually a fiber base such as a woven fabric or a non-woven fabric. The material is used.

The opening of the fiber base material according to the present embodiment is not particularly limited. From the viewpoint of thermal conductivity and insulating property, the opening is preferably twice or more the average particle size (D50) of the filler. Further, the porosity of the fiber base material is preferably 30% or more. The porosity of the fiber base material is the ratio of the area of the opening portion to the area of the fiber base material.

The material of the fiber base material is not particularly limited. Specifically, inorganic fibers such as glass, alumina, boron, silica-alumina glass, silica glass, tyrano, silicon carbide, silicon nitride, and zirconia, aramid, polyether ether ketone, polyetherimide, polyether sulfone, and carbon. , Organic fibers such as cellulose, and mixed abstracts thereof. Of these, a glass fiber woven fabric (glass cloth) is preferably used. As a result, for example, when a substrate is constructed using a prepreg, a flexible substrate that can be bent arbitrarily can be obtained. Further, it is possible to reduce the dimensional change of the multilayer substrate due to the temperature change and moisture absorption in the manufacturing process.

The thickness of the fiber base material according to this embodiment is not particularly limited. From the viewpoint of imparting better flexibility, it is more preferably 75 μm or less, and from the viewpoint of impregnation property, it is preferably 60 μm or less. The lower limit of the thickness of the fiber base material is not particularly limited, but is usually about 10 μm.

<Resin composition>
The first prepreg and the second prepreg used for the resin substrate of the present embodiment are composed of a resin composition and a fiber base material. This resin composition contains an inorganic filler and a thermosetting resin. The first prepreg and the second prepreg used for the resin substrate of the present embodiment may use the same type of thermosetting resin composition or different types of thermosetting resin compositions, and may be produced. From the viewpoint of ease, it is preferable to use the same type of thermosetting resin composition.

"Inorganic filler"

The inorganic filler used for the first prepreg and the second prepreg of the present embodiment is any one or more of the particulate inorganic materials. Specific examples of this inorganic filler are magnesium oxide (MgO), aluminum oxide (Al ₂ O ₃ ) and boron nitride (BN), aluminum nitride (AlN), silica (SiO ₂ ) and the like.
As the inorganic filler, magnesium oxide is preferable because it is inexpensive, has high thermal conductivity (42 to 60 W / (m · K)), and has high volume resistivity (> 10 ¹⁴ Ω · cm).
The average particle size of the inorganic filler is 2 to 80 μm. The measurement is performed using a known particle size measuring device by a laser diffraction / scattering method (for example, "Microtrack MT-3000 type" manufactured by Nikkiso Co., Ltd.). (The laser diffraction / scattering method is a measurement method that utilizes the fact that when the filler particles are irradiated with laser light, the intensity pattern of the scattered light changes depending on the particle size).

The content of the filler contained in the resin composition is not particularly limited. The filler is preferably contained in an amount of 40% to 80% by volume of the total solid content of the resin composition. When the filler is contained in the resin composition in an amount of 40% by volume to 80% by volume in the total volume, the effect of further increasing the thermal conductivity of the resin composition can be obtained.
The content of the filler is more preferably 40% by volume to 70% by volume, further preferably 45% by volume to 60% by volume, from the viewpoint of enhancing thermal conductivity and fluidity.
Here, the total solid content of the resin composition means a residue obtained by removing volatile components from the resin composition.

The content (volume%) of the filler in the present specification is a value calculated by the following formula (1).

Filler content (volume%) = (W1 / D1) / ((W1 / D1) + (W2 / D2) + Σ (Wi / Di)) x 100 ... (1)

Here, each variable is as follows.
W1: Mass composition ratio of filler (mass%)
W2: Mass composition ratio of thermosetting resin (mass%)
Wi: Mass composition ratio (mass%) of each other arbitrary solid component other than the thermosetting resin
D1: Specific density of filler D2: Specific density of thermosetting resin Di: Specific density of each other arbitrary solid component other than thermosetting resin

The filler may be used alone or in combination of two or more. For example, two or more kinds of fillers having different D50s and having an average particle diameter (D50) of 2 μm or more and 80 μm or less can be used in combination, but the combination is not limited to this.

"Thermosetting resin"
Examples of the thermosetting resin according to the present embodiment include epoxy resin, phenol resin and cyanate resin.

The thermosetting resin of the present embodiment is not particularly limited as long as it is a compound having a thermosetting functional group, for example. Specific examples thereof include epoxy resins, polyimide resins, polyamideimide resins, triazine resins, phenol resins, melamine resins, polyester resins, cyanate ester resins, and modified resins of these resins. These resins may be used alone or in combination of two or more.

The thermosetting resin is preferably at least one of the resins selected from the epoxy resin, the phenol resin and the triazine resin from the viewpoint of heat resistance, and more preferably the epoxy resin from the viewpoint of adhesiveness. The epoxy resin may be used alone or in combination of two or more.

The thermosetting resin may be a monomer or a prepolymer in which the monomer is partially reacted with a curing agent or the like. For example, as in the case of the epoxy resin having a mesogen group in the molecule described later, the resin having a mesogen group in the molecule is generally easy to crystallize and has low solubility in a solvent, but it is partially reacted and polymerized. Since crystallization can be suppressed by allowing the mixture to be formed, the moldability may be improved.

It is preferable that the thermosetting resin used for the first prepreg and the second prepreg of the present embodiment contains an epoxy resin.

<< Epoxy resin >>
The epoxy resin is any one or more of the compounds containing one or more epoxy groups (−C _{3H 5} O) in one molecule. Above all, the epoxy resin preferably contains two or more epoxy groups in one molecule. The epoxy resin may be a monomer or a prepolymer in which the monomer is partially reacted with a curing agent or the like.

The type of epoxy resin is not particularly limited, but for example, glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, novolac type epoxy resin, cyclic aliphatic type epoxy resin and long chain aliphatic type epoxy resin. And so on.

The glycidyl ether type epoxy resin is, for example, a bisphenol A type epoxy resin and a bisphenol F type epoxy resin. The novolak type epoxy resin is, for example, a cresol novolac type epoxy resin and a phenol novolac type epoxy resin. In addition, the type of epoxy resin may be, for example, a flame-retardant epoxy resin, a hydantoin-based epoxy resin, an isocyanurate-based epoxy resin, or the like.

The specific example of the glycidyl ether type epoxy resin is not particularly limited as long as it is a compound containing a glycidyl ether type structure (group). As described above, the type is not limited as long as it contains a specific structure, and the same applies to specific examples of other epoxy resins such as glycidyl ester type epoxy resins.

Above all, the epoxy resin preferably contains a mesogen skeleton in one molecule. The reason is as follows.

First, in the epoxy resin molecules, the benzene rings tend to overlap each other, so that the distance between the benzene rings becomes small. As a result, the density of the epoxy resin is improved in the resin composition containing the epoxy resin. Further, in the epoxy resin cured product, high thermal conductivity can be obtained because the lattice vibration of the molecules is less likely to be scattered.

This "mesogen skeleton" is a general term for atomic groups containing two or more aromatic rings and having rigidity and orientation. Specifically, the mesogen skeleton is, for example, a skeleton containing two or more benzene rings and having benzene rings bonded to each other via either a single bond or a non-single bond.

When three or more benzene rings are bonded, the direction of the bond is not particularly limited. That is, three or more benzene rings may be bonded so as to be linear, may be bonded so as to be bent once or more in the middle, or may be bonded so as to branch in two or more directions. You may.

"Non-single bond" is a general term for divalent groups containing one or more constituent elements and one or more multiple bonds. Specifically, the non-single bond contains any one or more of the constituent elements such as carbon (C), nitrogen (N), oxygen (O) and hydrogen (H). .. In addition, the non-single bond includes one or both of a double bond and a triple bond as a multiple bond.

The mesogen skeleton may contain only a single bond, a non-single bond, or both a single bond and a non-single bond as the type of bond between the benzene rings. .. Further, the type of non-single bond may be only one type or two or more types.

Specific examples of the mesogen skeleton are biphenyl and terphenyl. The terphenyl may be o-terphenyl, m-terphenyl, or p-terphenyl.

Specific examples of the thermosetting resin used in the prepreg of the present embodiment include YL-6121H (tetramethyl biphenol type epoxy resin 50%, 4,4'-biphenol type epoxy 50% mixture, epoxy) manufactured by Mitsubishi Chemical Corporation. Equivalent 175 g / eq), BREN105 (brominated polyfunctional epoxy resin, epoxy equivalent 271 g / eq) manufactured by Nippon Kayaku Co., Ltd., YH434L (tetrafunctional polyglycidylamine, epoxy equivalent 122 g / eq) manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd., DIC 830-S manufactured by 830-S Co., Ltd. (bisphenol F type epoxy resin, epoxy equivalent 173 g / eq), FX289Z manufactured by Nippon Steel & Sumikin Chemical Co., Ltd. (phosphor modified epoxy resin, epoxy equivalent 225 g / eq) and the like can be mentioned.

From the viewpoint of moldability, adhesiveness, and thermal conductivity, the thermosetting resin is preferably contained in an amount of 20% to 60% by volume, preferably 30% by volume, based on the total volume of the total solid content of the resin composition. It is more preferably contained in an amount of% to 60% by volume, and further preferably contained in an amount of 40% to 55% by volume.
When the resin composition contains a curing agent and a curing accelerator described later, the content of the thermosetting resin referred to here includes the content of these curing agents and the curing accelerator.

"Hardener"
It is preferable that the resin composition of the present embodiment further contains at least one kind of curing agent. The curing agent is not particularly limited as long as the thermosetting resin can be thermally cured. When the thermosetting resin is an epoxy resin, examples of the curing agent include a heavy addition type curing agent such as an acid anhydride-based curing agent, an amine-based curing agent, a phenol-based curing agent, and a mercaptan-based curing agent, and imidazole. Such as a catalytic curing agent and the like.
Above all, from the viewpoint of heat resistance, it is preferable to use at least one kind selected from an amine-based curing agent and a phenol-based curing agent, and further, from the viewpoint of storage stability, it is preferable to use at least one kind of phenol-based curing agent. More preferred.

As the amine-based curing agent, those usually used can be used without particular limitation, and commercially available ones may be used. Among them, a polyfunctional curing agent having two or more functional groups is preferable from the viewpoint of curability, and a polyfunctional curing agent having a rigid skeleton is more preferable from the viewpoint of thermal conductivity.

Examples of bifunctional amine-based curing agents include 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, and 4,4'-diamino-3,3'-dimethoxybiphenyl. , 4,4'-Diaminophenylbenzoate, 1,5-diaminonaphthalene, 1,3-diaminonaphthalene, 1,4-diaminonaphthalene, 1,8-diaminonaphthalene and the like. Among them, from the viewpoint of thermal conductivity, at least one selected from 4,4'-diaminodiphenylmethane and 1,5-diaminonaphthalene is preferable, and 1,5-diaminonaphthalene is more preferable.

As the phenol-based curing agent, commonly used ones can be used without particular limitation, and commercially available low-molecular-weight phenol compounds and novolakized phenol resins can be used.

Examples of low-molecular-weight phenol compounds include monofunctional ones such as phenol, o-cresol, m-cresol, and p-cresol, bifunctional ones such as catechol, resorcinol, and hydroquinone, and 1,2,3-tritri. Trifunctional substances such as hydroxybenzene, 1,2,4-trihydroxybenzene, 1,3,5-trihydroxybenzene, and 1,3,5-tris (4-hydroxyphenyl) benzene can be used. Further, a phenol novolac resin obtained by connecting these small molecule phenol compounds with a methylene chain or the like to form a novolak can also be used as a curing agent.

As the phenolic curing agent, 1,3,5-tris (4-hydroxyphenyl) benzene, which is a polyfunctional low molecular weight phenol curing agent, is preferable from the viewpoint of thermal conductivity, heat resistance, solvent solubility and the like.

When the resin composition of the present embodiment contains a curing agent, the content of the curing agent in the resin composition is not particularly limited. For example, when the curing agent is an amine-based curing agent, the ratio of the active hydrogen equivalent (amine equivalent) of the amine-based curing agent to the epoxy equivalent of the epoxy resin (amine equivalent / epoxy equivalent) is 0.5 to 2. It is preferably 0.8 to 1.2, and more preferably 0.8 to 1.2. When the curing agent is a phenolic curing agent, the ratio of the equivalent of active hydrogen of the phenolic hydroxyl group (phenolic hydroxyl group equivalent) to the epoxy equivalent of the mesogen-containing epoxy resin (phenolic hydroxyl group equivalent / epoxy equivalent) is 0. It is preferably .5-2, more preferably 0.8-1.2.

"Curing accelerator"
When a phenolic curing agent is used in the resin composition of the present embodiment, a curing accelerator may be used in combination if necessary. By using a curing accelerator in combination, it can be further sufficiently cured. The type and amount of the curing accelerator are not particularly limited, but an appropriate one can be selected from the viewpoints of reaction rate, reaction temperature, storage stability and the like. Specific examples of the curing accelerator include imidazole compounds, organophosphorus compounds, tertiary amines, and quaternary ammonium salts. These may be used alone or in combination of two or more.

When the resin composition contains a curing accelerator, the content of the curing accelerator in the resin composition is not particularly limited. From the viewpoint of moldability, the total mass of the thermosetting resin and the curing agent is preferably 0.5% by mass to 1.5% by mass, more preferably 0.5% by mass to 1% by mass. It is more preferably 0.75% by mass to 1% by mass.

"Silane coupling agent"
The resin composition preferably further contains at least one of the silane coupling agents. As an effect of adding the silane coupling agent, it plays a role of forming a covalent bond (corresponding to a binder agent) between the surface of the filler or the second filler and the thermosetting resin surrounding the surface, and heat is generated. It contributes to the improvement of insulation reliability by efficiently transmitting the heat and preventing the infiltration of water.

The type of the silane coupling agent is not particularly limited, and a commercially available product may be used. Considering the compatibility with a thermosetting resin (preferably an epoxy resin) and a curing agent contained as necessary, and the reduction of heat conduction defects at the interface between the resin and the filler, in the present invention, , It is preferable to use a silane coupling agent having an epoxy group, an amino group, a mercapto group, a ureido group, or a hydroxyl group at the terminal. These silane coupling agents may be used alone or in combination of two or more.

"Other ingredients"
The resin composition in the present invention may contain other components in addition to the above components, if necessary. For example, elastomers, dispersants and the like can be mentioned. Examples of the elastomer include acrylic resins, and more specifically, homopolymers or copolymers derived from (meth) acrylic acid or (meth) acrylic acid esters. Examples of the dispersant include Ajinomoto Fine-Tech Co., Ltd.'s Ajisper series, Kusumoto Kasei Co., Ltd.'s HIPLAAD series, and Kao's Co., Ltd. Homogenol series. Two or more of these dispersants can be used in combination.

<Paint of resin composition>
When a solid thermosetting resin is used as the resin composition, for example, at least one organic solvent may be added to prepare the paint of the resin composition. By including an organic solvent, it can be adapted to various molding processes. As the organic solvent, a commonly used organic solvent can be used. Specific examples thereof include alcohol solvents, ether solvents, ketone solvents, amide solvents, aromatic hydrocarbon solvents, ester solvents, nitrile solvents and the like. For example, methyl isobutyl ketone, dimethylacetamide, dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, γ-butyrolactone, sulfolane, cyclohexanone, methyl ethyl ketone and the like can be used. These may be used alone or as a mixed solvent in which two or more kinds are used in combination.

<Semi-curing resin composition>
The semi-cured resin composition of the present invention (sometimes referred to simply as "resin composition") is derived from the resin composition, and the resin composition is semi-cured. When the semi-cured resin composition is molded into a sheet, for example, the handleability is improved as compared with a resin composition sheet made of a resin composition which has not been semi-cured. From this point of view, it is preferable that the resin composition composed of the prepreg of the present embodiment is a semi-cured resin composition.

Here, the semi-cured resin composition is 100 ° C., whereas the viscosity of the semi-cured resin composition is ¹⁰⁴ Pa · s to ¹⁰⁵ Pa · s at room temperature (25 to 30 ° C.). Has the characteristic that the viscosity is lower than the normal temperature. For example, the semi-cured resin composition can retain its sheet shape at room temperature, but melts at a high temperature of about 100 ° C. Further, the cured resin composition after curing, which will be described later, is not melted by heating. The viscosity is measured by dynamic viscoelasticity measurement (DMA) (for example, Rheo Stress 6000 manufactured by Thermo Scientific Co., Ltd.). The measurement conditions are a frequency of 1 Hz, a load of 40 g, and a heating rate of 3 ° C./min, and the measurement is performed by a shear test.

Examples of the semi-curing treatment include a method of heating the resin composition at a temperature of 60 ° C. to 200 ° C. for 1 minute to 30 minutes.

<Cured product of resin composition>
The cured product of the resin composition is derived from the resin composition, and is obtained by curing the resin composition. The cured product of the resin composition is excellent in thermal conductivity and insulating property. The substrate and the laminated substrate of one embodiment of the present invention are, for example, cured of the prepreg of the present embodiment, and the resin composition obtained by curing the resin composition used for the prepreg of the present embodiment is cured. Including things.

The cured product of the resin composition can be produced by curing the uncured resin composition or the semi-cured resin composition. The curing treatment method can be appropriately selected depending on the composition of the resin composition, the purpose of the cured product, and the like, but is preferably heat / pressure treatment.
For example, the resin composition by heating the uncured resin composition or the semi-cured resin composition at 100 ° C. to 250 ° C. for 1 hour to 10 hours, preferably 130 ° C. to 230 ° C. for 1 hour to 8 hours. A cured product is obtained.

[Second Embodiment]
<Structure of resin substrate>
FIG. 2 is a cross-sectional view showing the configuration of the resin substrate 20 according to the second embodiment of the present invention. The resin substrate 20 of the second embodiment of the present invention is a resin substrate formed by heating and pressurizing three prepregs in which a thermosetting resin composition containing an inorganic filler is held on a fiber base material 25 and is in a semi-cured state. be. The resin substrate 20 of the present embodiment contains a cured product 22 of a thermosetting resin composition and a fiber base material 25. The cured product 22 of the thermosetting resin composition is obtained by curing the thermosetting resin composition containing the inorganic filler, and is composed of the inorganic filler and the cured product of the thermosetting resin.
The types of the thermosetting resin composition and the fiber base material that can be used for the resin substrate 20 are the same as those of the resin substrate 10 of the first embodiment.

Similar to the resin substrate 10 of the second embodiment, the resin substrate 20 of the present embodiment is formed by further laminating a metal foil on the inside (intersection of the prepreg and the prepreg) and on the surface layer thereof to form a metal foil-covered substrate. You may. When the metal foil is laminated on the surface layer, the metal foil may be attached to only one surface or both sides. Further, the resin substrate provided with the metal foil may be subjected to any one or more of various treatments such as etching treatment and drilling treatment, if necessary.

<Layer structure of resin substrate>
The resin substrate 20 of the present embodiment has a three-layer structure derived from three prepregs. The first layer has a cured product 22-1 of a thermosetting resin composition derived from the first prepreg (not shown) and a fiber base material 25-1, and the second layer has a second prepreg (not shown). It has a cured product 22-2 of a thermosetting resin composition derived from it and a fiber base material 25-2, and the third layer is a cured product 22 of a thermosetting resin composition derived from a third prepreg (not shown). It has -3 and a fiber base material 25-3.

<Inorganic filler sparse part>
The resin substrate 20 of the present embodiment is characterized by having a portion (sparse portion of the inorganic filler) 28 having a small amount of the inorganic filler. When the thickness of the resin substrate 20 is t and the area of the cut surface in the thickness direction of vertical t and horizontal 2 t is 100 area%, the inorganic filler sparse portion is 0.5 to 8 area%. The portion 28 of the present invention in which the amount of the inorganic filler is small (the sparse portion of the inorganic filler) is a portion where the element derived from the inorganic filler excluding oxygen and the fiber base material is 10% or less.
Further, in the resin substrate 20 of the present invention, the cut surface in the thickness direction of the substrate 20 is equally divided in the thickness direction by the number of laminated prepregs 3, and the area of vertical t / n and horizontal 2t corresponding to one prepreg is obtained. When A1 to A3 are used and the areas of A1 to A3 are 100 area%, there are 0 to 20 area% of inorganic filler sparse parts in A1 to A3, respectively.
The components, size, and shape of the sparse portion 28 of the inorganic filler of the present embodiment are the same as those of the sparse portion 18 of the inorganic filler of the first embodiment.

<Arrangement of sparse parts of inorganic filler>
The arrangement (distribution) of the sparse portion 28 of the inorganic filler of the present embodiment is not particularly limited as long as it has the effects of thermal conductivity and moldability of the resin substrate, but is dispersed from the viewpoint of easily forming a thermal conduction path. It is preferably in a state. For example, in the sparse portion 28 of the inorganic filler of the present embodiment, as shown in FIG. 2, the fiber base material 25-1 of the first layer and the fiber base material of the second layer are formed on the cut surface of the resin substrate 20 in the thickness direction. It is formed between 25-2, between the second layer fiber base material 25-2 and the second layer fiber base material 25-3, respectively. More specifically, for example, it is preferable that the resin substrate 20 is formed at a portion not directly below the opening of the fiber substrate of the same layer on the cut surface in the thickness direction of the resin substrate 20 shown in FIG. Further, from the viewpoint of easy production, as an example shown in FIG. 2, a connecting surface between the cured product 22-1 of the resin composition of the first layer and the cured product 22-2 of the resin composition of the second layer, the second It may be formed on the side of the cured product 22-3 at the connecting surface between the cured product 22-2 of the resin composition of the layer and the cured product 22-3 of the resin composition of the third layer.

(Manufacturing method of resin substrate)
In the method for manufacturing the laminated substrate of the present embodiment, first, as shown in FIGS. 5A to 5C, for example, one of the first prepregs 51-1 having a gap and one of the second prepregs 53 are used. One of the first prepregs 51-2 having voids is laminated in this order to prepare a resin substrate 50. Specifically, the side surface of the first prepreg 51 as the outer layer having a gap and the second prepreg 53 as the intermediate layer are arranged so as to sandwich the prepreg 2, and the heating press / molding step is performed. Therefore, the resin substrate 50 can be formed. Since the resin preferentially flows into the void portion of the first prepreg 51 to fill the void, the inorganic filler sparse portion 58 having less inorganic filler is formed around the void portion in the portion having the void. There are places where there are many inorganic fillers.

The first prepreg 51 and the second prepreg 53 can be obtained in the same manner as the first prepreg 41 and the second prepreg 43 of the first embodiment, respectively.

The conditions for forming the resin substrate 50 by pressing and molding the first prepreg 51 and the second prepreg 53 are that the uncured / semi-cured thermosetting resin of the first prepreg 51 and the second prepreg 53 is cured, and the inorganic filler is used. As long as the sparse portion 58 can be formed, the present invention is not particularly limited. It is usually in the range of 100 ° C. to 250 ° C., preferably in the range of 130 ° C. to 230 ° C. Further, the pressurizing conditions in the heating and pressurizing treatment are not particularly limited. It is usually in the range of 1 MPa to 20 MPa, preferably in the range of 1 MPa to 15 MPa. Further, a vacuum press is preferably used for the heating and pressurizing treatment.

In the example shown in FIG. 5, the number of the first prepreg 51 used for the resin substrate 50 is two, but the number is not limited to two, and three or more may be used. The number of the second prepreg 53 used for the resin substrate 50 is one, but the number is not limited to one, and two or more may be used. This number can be appropriately set based on conditions such as the thickness and strength of the first prepreg 51 and the second prepreg 53.

Examples of the present invention will be described in detail.

(Example 1)
<Preparation of the first prepreg with voids>
The following materials were prepared as the resin composition.
Epoxy resin as a thermosetting resin (tetramethylbiphenol type epoxy resin 50%, 4,4'-biphenol type epoxy 50% mixture, epoxy equivalent 175 g / eq, Mitsubishi Chemical Corporation YL-6121H) ... 60 parts by mass
Hardener (1,3,5-tris (4-hydroxyphenyl) benzene, active hydrogen equivalent 118 g / eq) ... 40 parts by mass Hardening accelerator (2-ethyl-4-methylimidazole, 2E4MZ manufactured by Shikoku Kasei Co., Ltd.) ... 1 Parts by mass Methylethylketone as an organic solvent ... 50 parts by mass

These materials were put into a medialess disperser (Despamill MD-10 manufactured by Asada Iron Works Co., Ltd.) and stirred to prepare a resin mixture. Next, magnesium oxide powder (average particle size 30 μm, thermal conductivity 45 W / (m · K)) was added to this resin mixed solution as an inorganic filler, and the mixture was well stirred and dispersed to prepare a paint of the first resin composition. did. At this time, the magnesium oxide powder was adjusted to be 60% by volume (hereinafter, filling rate) when the solid content volume obtained by removing methyl ethyl ketone from the coating material of the resin composition was 100% by volume.

Furthermore, glass cloth (IPC standard 1080, non-open fiber glass cloth manufactured by Arisawa Mfg. Co., Ltd., thickness 0.055 mm, mass 47 g / m ² , density 66 x 46 lines / 25 mm, plain weave type) is used as the fiber base material. board. In a coating method in which a paint of the adjusted resin composition is applied from one side of the glass cloth using a slit die and passed through the opening of the glass cloth to the back side of the glass cloth to hold the paint. By controlling the amount of the slit die nozzle pushed into the glass cloth to 4.8 mm, the amount of paint passing through the opening of the glass cloth was reduced, and a first prepreg having voids on the back surface of the coating was produced. As the drying conditions, methyl ethyl ketone was removed by heating and drying at 100 ° C., and the mixture was cut into a length of 150 mm and a width of 150 mm to obtain a first prepreg of this example containing a resin composition layer and a glass cloth. The thickness was 172 μm.

<Resin substrate>
Using two of the obtained first prepregs, the side having the respective voids and the side having the voids were laminated facing each other, heated and pressurized (temperature 170 ° C., 1 MPa for 20 minutes), and further added. The second heating and pressurization (temperature 200 ° C., 4 MPa for 1 hour) was carried out to obtain a resin substrate having an inorganic filler sparse portion with a small amount of the inorganic filler. The thickness was 340 μm.
When the side without the voids of the first prepreg is A and the side with the voids is B, the layer structure of the two first prepregs AB is represented by "AB / BA" in this embodiment. It is shown in Table 1.
Since the resin preferentially flows into the voids of the first prepreg to fill the voids, the voids are filled with inorganic fillers with less inorganic filler, and the voids are surrounded by inorganic particles. There are places where there is a lot of filler.

(Examples 2, 3 and 6)
<Preparation of the first prepreg with voids>
The amount of the slit die nozzle pushed into the glass cloth was different from that shown in Table 1, and each first prepreg having a gap was prepared in the same manner as in Example 1.

<Resin substrate>
The resin substrate of this example was prepared in the same manner as in Example 1 except that the prepared first prepregs were laminated in the layer structure shown in Table 1 using the number of sheets shown in Table 1.
In Example 2, two sheets were first cured in the order of [AB / BA] / BA, and then one sheet was laminated and cured.
In Examples 3 and 6, two sheets of [AB / BA] were first cured to form an inner layer, two sheets BA / AB were laminated on one surface of the outer layer, and two sheets BA / AB were laminated on the other surface and pressed.
The methods A and B for displaying the layered structure of the laminate have the same meaning as in the first embodiment.

(Example 4)
<Preparation of the first prepreg with voids>
The first prepreg of this example having voids was prepared in the same manner as in Example 1 except that the amount of the slit die nozzle pushed into the glass cloth is shown in Table 1.

<Making a second prepreg without voids>
Using the same resin composition paint as the first prepreg of Example 1 as the paint of the resin composition and the same glass cloth as the first prepreg of Example 1 as the fiber base material, this paint was applied to the glass cloth. In the coating method in which the paint is applied from one side using a slit die and the paint is held on the glass cloth by passing it through the opening of the glass cloth through the coating back surface of the glass cloth, the amount of the slit die nozzle pushed into the glass cloth is set to 5 mm. By controlling, the amount of paint passing through the opening of the glass cloth was increased, and a second prepreg having no voids on the back surface of the coating was produced. As the drying conditions, methyl ethyl ketone was removed by heating and drying at 100 ° C., and the mixture was cut into a length of 150 mm and a width of 150 mm to obtain a second prepreg of this example containing a resin composition layer and a glass cloth. The thickness was 172 μm.

<Resin substrate>
Using 4 first prepregs and 2 second prepregs, in the arrangement of "AA / AB / [AB / BA] / BA / AA", 2 of [AB / BA] are cured first. Each resin substrate was obtained in the same manner as in Example 1 except that two AA / AB sheets were laminated on one surface of the outer layer and two BA / AA sheets were laminated on the other surface and pressed as the inner layer.
The second prepreg having no voids is displayed as AA, and the method of displaying the first prepreg having voids and the method of displaying the layer structure are the same as those in the first embodiment.

(Examples 5 and 7)
<Preparation of the first prepreg with voids>
The first prepreg of this example having voids was prepared in the same manner as in Example 1 except that the amount of the slit die nozzle pushed into the glass cloth is shown in Table 1.

<Preparation of a third prepreg with voids>
The third prepreg of this example having voids was prepared in the same manner as in Example 1 except that the amount of the slit die nozzle pushed into the glass cloth is shown in Table 1.

<Resin substrate>
Using 5 first prepregs and 1 third prepreg, in the arrangement of "AA / AC / [AB / BA] / BA / AB", 2 of [AB / BA] are cured first. Each resin substrate was obtained in the same manner as in Example 1 except that two AA / AC sheets were laminated on one surface of the outer layer and two BA / AB sheets were laminated on the other surface and pressed as the inner layer.
The third prepreg is a prepreg having a larger void than the first prepreg, and the side having the void is C, and the display method and the layer structure of the first prepreg having the void are the same as those in the first embodiment. be.

(Comparative Example 1)
<Making a second prepreg without voids>
A second prepreg having no voids was prepared in the same manner as in Example 4.
<Resin substrate>
The resin substrate of this example was formed in the same manner as in Example 1 except that six second prepregs were laminated and pressed in a layered structure of "AA / AA / [AA / AA] / AA / AA". was gotten.

(Comparative Example 2)
<Preparation of the first prepreg with voids>
The first prepreg of this example having voids was prepared in the same manner as in Example 1 except that the amount of the slit die nozzle pushed into the glass cloth is shown in Table 1.
<Making a second prepreg without voids>
A second prepreg having no voids was prepared in the same manner as in Example 4.
<Resin substrate>
Using 5 first prepregs and 1 second prepreg, they were laminated and pressed in the arrangement of "AA / AB / [AB / BA] / BA / AB" in the same manner as in Example 1. The resin substrate of this comparative example was obtained.
(Comparative Example 3)
<Preparation of the first prepreg with voids>
The first prepreg of this example having voids was prepared in the same manner as in Example 1 except that the amount of the slit die nozzle pushed into the glass cloth is shown in Table 1.
<Resin substrate>
The resin substrate of this example was obtained in the same manner as in Example 1 except that six first prepregs prepared in this comparative example were used.

(Evaluation method)
When the characteristics of each of the resin substrates were examined, the results shown in Table 1 were obtained. Here, the area ratio (%) of the sparse portion of the inorganic filler on the thickness cut surface of each resin substrate, the thermal conductivity of the resin substrate, and the moldability were investigated.

<Area ratio of sparse parts of inorganic filler>
After cutting the obtained resin substrate in the thickness direction, the cut surface was polished to obtain a smooth cut surface. While observing the glass cloth and the inorganic filler on the cut surface with an SEM (scanning electron microscope), elemental analysis is performed with the EDX (energy dispersive X-ray analyzer) attached to the SEM to perform elemental analysis on the glass cloth. And the inorganic element contained in the inorganic filler and the element concentration were measured.
In the case of a resin substrate having a substrate thickness of t, element mapping is performed with a glass cloth and an inorganic element containing an inorganic filler in the range of vertical t and horizontal 2 t of the cut surface, and the inorganic element detected from the glass cloth or the inorganic filler is used. A portion having an element concentration of less than 10% (sparse portion of the inorganic filler) was identified, and the area% of the sparse portion of the inorganic filler was calculated when the entire measurement range was 100 area%.
When the outer layer of the substrate has a copper foil, the thickness of the substrate is t excluding the copper foil of the outer layer.
When the copper foil is contained in the inner layer of the substrate, it is included in the thickness of the substrate because it is etched and does not exist uniformly. SEM observation and elemental analysis are performed in the same observation range as above. The portion where the element derived from the glass cloth, the inorganic filler, and the metal foil (copper foil) is 10% or less is defined as the sparse portion of the inorganic filler. The area ratio of the sparse portion of the inorganic filler is determined with the area excluding the metal foil as 100 area%.

<Thermal conductivity of resin substrate>
In order to investigate the thermal conductivity, the thermal conductivity (W / (m · K)) of the resin substrate was measured. Specifically, first, a resin substrate was cut to prepare a circular measurement sample (diameter = 10 mm, thickness = 0.3 to 1.0 mm). Subsequently, the measurement sample was analyzed using a thermal conductivity measuring device (TC series manufactured by Advance Riko Co., Ltd. (formerly ULVAC Riko Co., Ltd.)), and the thermal diffusion coefficient α (m ² / s) was measured. In addition, using sapphire as a standard sample, the specific heat Cp of the measurement sample was measured using differential scanning calorimetry (DSC). Further, the density r of the measurement sample was measured using the Archimedes method. Finally, the thermal conductivity λ (W / (m · K)) was calculated based on the following mathematical formula (2).

λ = α × Cp × r ・ ・ ・ ・ ・ (2)
(Λ is the thermal conductivity (W / (m · K)), α is the thermal diffusivity (m ² / s), Cp is the specific heat (J / kg · K), and r is the density (kg / m ³ ). .)

<Formability of resin substrate>
First, the formability evaluation substrate 100 shown in FIGS. 6 and 7 was manufactured. Copper foil layers 104 and 105 having a thickness of 105 μm were arranged on the surface of the substrate, and the copper foil layers 104 were partially etched to form a mesh-like groove 106 (width = 0.5 mm, depth = 105 μm). .. In this case, the distance between the groove 106 closest to the outer edge (four sides) of the metal layer 104 and the outer edge of the copper foil layer 104 was set to 9.5 mm, and the distance between the grooves 106 was set to 9.5 mm.
When evaluating the moldability, two first prepregs are used on the moldability evaluation substrate 100 in Examples 1 to 4, 6 and Comparative Examples 2 and 3, and a copper foil / prepreg (AB / BA) is used. ) Formability evaluation The substrates 100 were stacked in this order to form a laminated body. In Examples 5 and 7, one second prepreg and one third prepreg were used, and the copper foil / prepreg (BA / AC) / moldability evaluation substrate 100 was laminated in this order to form a laminated body. In Comparative Example 1, two second prepregs were used, and the copper foil / prepreg (AA / AA) / moldability evaluation substrate 100 were stacked in this order to form a laminated body. As this copper foil, a 70 μm copper foil was used. Subsequently, using a flat plate press, the laminate was heated (temperature = 180 ° C.) and pressurized (pressure = 4 MPa) in the lamination direction. As a result, a part of the prepreg entered the groove 106 of the evaluation substrate 100, so that a multilayer substrate was obtained. The cross section of the multilayer substrate was observed using a metallurgical microscope.

Regarding the observation results of the microscope, the case where the groove 106 was filled with the resin composition was evaluated as “◯”, and the case where the inside of the groove 6 was not filled with the resin composition was evaluated as “x”.

<Porosity>
The voids in the prepreg were evaluated as porosity.
The porosity was determined by observing the back surface of the prepreg (the side having voids) with a size of 5 mm × 5 mm and determining the area of the prepreg with respect to the area of the prepreg.
For example, if the prepreg is 5 mm × 5 mm and the pores are 0.4 mm ² , the porosity is 1.6%.
The larger the porosity, the larger the sparse part of the filler.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the configurations and combinations thereof in the respective embodiments are examples, and the configurations are added or omitted within a range not deviating from the gist of the present invention. , Replacement, and other changes are possible.

12, 22, 32, 42, 52, ... A cured product of the resin composition,
15, 25, 35, 45, 55 ... Fiber base material (glass cloth),
18, 28, 38, 48, 58 ... Inorganic filler sparse part,
10, 20, 30, 40, 50 ... Resin substrates 31, 41, 51 ... First prepreg,
33, 43, 53 ... Second prepreg.
102 ... Fiber substrate,
103 ... Resin cured product layer,
104, 105 ... Copper foil layer 106 ... Groove

Claims (3)

A resin substrate formed by heating and pressurizing one or two or more prepregs in which a thermosetting resin composition containing an inorganic filler is held on a fiber base material and is in a semi-cured state.
When the thickness of the resin substrate is t and the area of the cut surface in the thickness direction of vertical t and horizontal 2 t is 100 area%,
There is 0.5 to 8 area% of the element derived from the inorganic filler and fiber base material excluding oxygen, which is 10% or less .
In the direction parallel to the surface of the resin substrate, the portion where the element derived from the inorganic filler and the fiber base material excluding oxygen is 10% or less and the element derived from the inorganic filler and the fiber base material excluding oxygen are 10%. It is lined up alternately with the part beyond
A resin substrate characterized by this. A resin substrate formed by heating and pressurizing one or two or more prepregs in which a thermosetting resin composition containing an inorganic filler is held on a fiber base material and is in a semi-cured state.
When the thickness of the resin substrate is t and the area of the cut surface in the thickness direction of vertical t and horizontal 2 t is 100 area%,
There is 0.5 to 8 area% of the element derived from the inorganic filler and fiber base material excluding oxygen, which is 10% or less.
On the cut surface in the thickness direction of the resin substrate, a portion of the inorganic filler excluding oxygen and an element derived from the fiber base material of 10% or less is formed at a portion not directly below the opening of the fiber base material. And the width is equal to or less than the opening diameter of the fiber base material.
A resin substrate characterized by this. The cut surface in the thickness direction of the resin substrate is equally divided in the thickness direction by the number of laminated prepregs n, and the areas of vertical t / n and horizontal 2t corresponding to one prepreg are set from A1 to An. A claim is characterized in that each of A1 to An has a portion of 10% or less of an element derived from an inorganic filler excluding oxygen and a fiber base material, respectively, when the area of each of the above is 100 area%. 1 or the resin substrate according to claim 2 .

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