Wiring board

Abstract

To provide a wiring board that has a sufficient heat dissipation property and is resistant to peeling at the interface between an insulating resin layer and a copper pattern.SOLUTION: A wiring board 10 has a base material 1, a copper pattern 2 formed on the base material 1, an inter-copper pattern insulating resin layer 3 arranged between copper wirings 2a and 2b forming the copper pattern 2, an insulating resin layer 4 formed on the copper pattern 2 and the inter-copper pattern insulating resin layer 3, and a copper pattern bonding layer 5 that is formed between the insulating resin layer 4 and the copper pattern 2 so as to extend from the inter-copper pattern insulating resin layer 3. The inter-copper pattern insulating resin layer 3 contains 30% by volume or more of an element derived from an inorganic filler, and the copper pattern bonding layer 5 contains 90% by volume or more of an element derived from a resin and may contain 10% by volume or less of an element derived from an inorganic filler, and is formed with a width of 0.1 mm to 0.8 mm from the boundary 5a between the copper pattern 2 and the inter-copper pattern insulating resin layer 3 in the width direction of the copper pattern 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wiring board.

Background Art

[0002] Conventionally, printed wiring boards have been widely used in multilayer boards for power supplies and the like. As a printed wiring board, there is one having a base material, a copper pattern formed on the base material, a copper pattern insulating resin layer disposed between copper wirings forming the copper pattern, and an insulating resin layer formed on the copper pattern and on the copper pattern insulating resin layer.

[0003] Patent Document 1 describes a wiring board having a metal plate, a first insulating layer made of an organic resin provided on the metal plate, a first wiring conductor layer formed on the first insulating layer and formed in a wiring pattern, a second insulating layer made of an organic resin, and a second wiring conductor layer laminated on the first wiring conductor layer via the second insulating layer and formed in a wiring pattern, wherein the second insulating layer is also provided at a portion between the wiring patterns of the first wiring conductor layer.

[0004] As an application of a printed wiring board, there is a printed wiring board through which a large current flows. In such a printed wiring board, when a large current flows, the copper wiring forming the copper pattern generates heat and becomes high temperature. Therefore, conventionally, an inorganic filler is contained in the insulating resin layer and the copper pattern insulating resin layer to improve the thermal conductivity of the insulating resin layer and the copper pattern insulating resin layer, and to enhance the heat dissipation of the printed wiring board.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the conventional wiring board, the adhesion between the copper pattern formed on the base material and the insulating resin layer formed on the copper pattern was insufficient. For this reason, in the conventional wiring board, when thermal stress is applied to the interface between the insulating resin layer and the copper pattern by performing a heat cycle test, a reflow test, etc., the insulating resin layer may peel off from the copper pattern. In particular, in a wiring board provided with an insulating resin layer containing an inorganic filler in order to enhance heat dissipation, the insulating resin layer and the copper pattern are likely to peel off, which has been a problem.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a wiring board having sufficient heat dissipation and in which the interface between the insulating resin layer and the copper pattern is difficult to peel off.

Means for Solving the Problems

[0008] A wiring board according to an aspect of the present invention includes a base material, a copper pattern formed on the base material, an inter-copper-pattern insulating resin layer disposed between copper wirings forming the copper pattern, an insulating resin layer formed on the copper pattern and on the inter-copper-pattern insulating resin layer, and a copper pattern bonding layer formed to extend from the inter-copper-pattern insulating resin layer between the insulating resin layer and the copper pattern. The inter-copper-pattern insulating resin layer contains 30% by volume or more of an element derived from an inorganic filler. The copper pattern bonding layer may contain 90% by volume or more of an element derived from a resin and 10% by volume or less of an element derived from an inorganic filler, and is formed with a width of 0.1 mm to 0.8 mm in the width direction of the copper pattern from the boundary between the copper pattern and the inter-copper-pattern insulating resin layer.

Effects of the Invention

[0009] The wiring board of the present invention includes a base material, a copper pattern formed on the base material, an inter-copper-pattern insulating resin layer disposed between copper wirings forming the copper pattern, an insulating resin layer formed on the copper pattern and on the inter-copper-pattern insulating resin layer, and a copper-pattern bonding layer formed by extending from the inter-copper-pattern insulating resin layer between the insulating resin layer and the copper pattern. And the inter-copper-pattern insulating resin layer contains 30% by volume or more of elements derived from an inorganic filler, and the copper-pattern bonding layer may contain 90% by volume or more of elements derived from a resin and 10% by volume or less of elements derived from an inorganic filler, and is formed with a width of 0.1 mm to 0.8 mm in the width direction of the copper pattern from the boundary between the copper pattern and the inter-copper-pattern insulating resin layer. For this reason, the wiring board of the present invention has sufficient heat dissipation performance, and the interface between the insulating resin layer and the copper pattern is difficult to peel off.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0011] In order to solve the above problems, the inventors have conducted intensive studies as follows. As a method for making the interface between the insulating resin layer and the copper pattern on the wiring board difficult to peel, it is conceivable to form an insulating resin layer with a high resin content to a sufficient thickness on the copper pattern and on the insulating resin layer between the copper patterns. However, an insulating resin layer with a high resin content has a low thermal conductivity. For this reason, a wiring board provided with an insulating resin layer having a high resin content and a sufficient thickness has poor heat dissipation performance, which is not preferable.

[0012] Therefore, the inventors focused on the manufacturing method and conducted repeated studies to make it difficult to peel the interface between the insulating resin layer and the copper pattern in a wiring board with good heat dissipation performance in which the insulating resin layer between the copper patterns contains 30% by volume or more of elements derived from the inorganic filler. Generally, a wiring board having a base material, a copper pattern formed on the base material, an insulating resin layer between the copper patterns disposed between the copper wirings forming the copper pattern, and an insulating resin layer formed on the copper pattern and on the insulating resin layer between the copper patterns is manufactured by the method shown below.

[0013] First, a copper pattern is formed on the base material. Next, a copper pattern insulating resin material that will become the insulating resin layer between the copper patterns is printed between the copper wirings forming the copper pattern and dried to a semi-cured state (B-stage state). Then, a prepreg that will become the insulating resin layer is placed on the copper pattern formed on the base material and on the semi-cured insulating resin layer between the copper patterns, and hot press processing is performed. As a result, the semi-cured insulating resin layer between the copper patterns and the prepreg that will become the insulating resin layer are cured, and the copper pattern, the insulating resin layer between the copper patterns, and the insulating resin layer are integrated to form a wiring board.

[0014] In the method for manufacturing the wiring board described above, the inventors have found that by changing the content of the inorganic filler and thermosetting resin contained in the insulating resin material between copper patterns, the thickness of the insulating resin layer between copper patterns with respect to the thickness of the copper pattern, and the thermocompression bonding conditions, a copper pattern bonding layer is formed that extends from the insulating resin layer between copper patterns between the insulating resin layer and the copper pattern, contains 90% by volume or more of elements derived from the resin and 10% by volume or less of elements derived from the inorganic filler, and is formed with a width of 0.1 mm to 0.8 mm in the width direction of the copper pattern from the boundary between the copper pattern and the insulating resin layer between copper patterns of the copper pattern.

[0015] Such a copper pattern bonding layer is presumed to be formed as follows by performing thermocompression bonding. That is, by starting the thermocompression bonding, a part of the insulating resin material between copper patterns in a semi-cured state tries to overflow from the region sandwiched between the copper wirings forming the copper pattern. At this time, the inorganic filler contained in the insulating resin material between copper patterns is less likely to flow compared to the thermosetting resin contained in the insulating resin material between copper patterns. For this reason, the thermosetting resin flows out from the insulating resin material between copper patterns prior to the inorganic filler.

[0016] The insulating resin material between copper patterns containing a large amount of thermosetting resin flowing out from the semi-cured insulating resin layer between copper patterns enters between the copper pattern and the prepreg that becomes the insulating resin layer, which is a region where the thermosetting resin easily infiltrates, from the boundary between the insulating resin layer between copper patterns and the copper pattern. The insulating resin material between copper patterns containing a large amount of thermosetting resin that has entered between the copper pattern and the prepreg that becomes the insulating resin layer infiltrates along the surface on the prepreg side of the insulating resin layer of the copper pattern, and cures together with the semi-cured insulating resin layer between copper patterns and the prepreg that becomes the insulating resin layer to form a copper pattern bonding layer.

[0017] The copper pattern bonding layer formed in this way may contain 90% by volume or more of elements derived from the resin and 10% by volume or less of elements derived from the inorganic filler. Since it is formed with a width of 0.1 mm or more in the width direction of the copper pattern from the boundary between the copper pattern and the inter-copper-pattern insulating resin layer, the adhesion between the insulating resin layer and the copper pattern can be effectively improved. Further, since the copper pattern bonding layer is formed with a width of 0.8 mm or less in the width direction of the copper pattern from the boundary between the copper pattern and the inter-copper-pattern insulating resin layer, the decrease in heat dissipation due to the presence of the copper pattern bonding layer can be suppressed.

[0018] Furthermore, the inventors have confirmed that in a wiring board in which the inter-copper-pattern insulating resin layer contains 30% by volume or more of elements derived from the inorganic filler, when the contents of the elements derived from the inorganic filler and the resin are within the above ranges, and the copper pattern bonding layer is formed with the above width in the width direction of the copper pattern from the boundary between the copper pattern and the inter-copper-pattern insulating resin layer, a wiring board having sufficient heat dissipation and in which the interface between the insulating resin layer and the copper pattern is difficult to peel off can be obtained, and thus the present invention has been conceived.

[0019] The present invention includes the following aspects. [1] A base material, A copper pattern formed on the base material, An inter-copper-pattern insulating resin layer disposed between the copper wirings forming the copper pattern, An insulating resin layer formed on the copper pattern and on the inter-copper-pattern insulating resin layer, And a copper pattern bonding layer formed to extend from the inter-copper-pattern insulating resin layer between the insulating resin layer and the copper pattern, The inter-copper-pattern insulating resin layer contains 30% by volume or more of elements derived from the inorganic filler, The copper pattern bonding layer may contain 90% by volume or more of elements derived from the resin and 10% by volume or less of elements derived from the inorganic filler, and is formed with a width of 0.1 mm to 0.8 mm in the width direction of the copper pattern from the boundary between the copper pattern and the inter-copper-pattern insulating resin layer. A wiring board.

[0020] [2] The wiring board according to [1], wherein the thickness of the copper pattern bonding layer is 50 μm or less. [3] The wiring board according to [1], wherein the insulating resin layer between the copper patterns contains 45 to 60% by volume of elements derived from an inorganic filler. [4] The wiring board according to [1], wherein the thermal conductivity of the insulating resin layer between the copper patterns is 1.5 W / mK or more.

[0021] Hereinafter, the wiring board of the present embodiment will be described in detail with appropriate reference to the drawings. The drawings used in the following description may show, for the sake of clarity, the characteristic parts enlarged for the sake of convenience. Therefore, the dimensional ratios of the respective components may be different from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and can be appropriately modified and implemented without changing the gist thereof.

[0022] [First Embodiment] [Wiring Board] FIG. 1 is a diagram for explaining a wiring board according to a first embodiment of the present invention, and is a schematic cross-sectional view along the width direction of a copper pattern. The wiring board 10 of the present embodiment can be suitably used for a power supply multilayer board or the like through which a large current flows. The wiring board 10 shown in FIG. 1 includes a base material 1, a copper pattern 2, an insulating resin layer 3 between the copper patterns, an insulating resin layer 4, and a copper pattern bonding layer 5.

[0023] (Base Material) As the base material 1, for example, a conventionally known base material such as one containing a fibrous base material, a thermosetting resin described later, and an inorganic filler described later can be used. As the fibrous base material, a known one can be used. For example, as the fibrous base material, a woven fabric in which warp and weft made of glass fiber, carbon fiber, etc. are woven, a non-woven fabric made of sheet-shaped glass fiber or carbon fiber, etc. can be used. The thickness, shape, and material of the fibers forming the fibrous base material can be appropriately determined according to the use of the wiring board 10.

[0024] (Copper pattern) The copper pattern 2 is formed on the base material 1. The shapes and arrangements of the copper wirings 2a and 2b forming the copper pattern 2 are not particularly limited and can be appropriately determined according to the use of the wiring board 10.

[0025] The thicknesses of the copper wirings 2a and 2b forming the copper pattern 2 can be, for example, 35 μm to 240 μm and can be appropriately determined according to the use of the wiring board 10. For example, when the wiring board 10 of the present embodiment is used for a multi-layer board for power supply through which a large current flows, etc., the thicknesses of the copper wirings 2a and 2b are more preferably 105 μm or more. Further, when the thicknesses of the copper wirings 2a and 2b are 35 μm or more, the insulating resin layer 3 between the copper patterns disposed between the copper wirings 2a and 2b has a sufficient thickness. In this case, in the hot press process performed during manufacturing, the amount of the insulating resin material between the copper patterns that overflows from the insulating resin layer 3 between the copper patterns tends to be appropriate, and the copper pattern bonding layer 5 can be easily formed.

[0026] The widths of the copper wirings 2a and 2b forming the copper pattern 2 can be, for example, 0.1 mm or more and can be appropriately determined according to the use of the wiring board 10. When the widths of the copper wirings 2a and 2b are 0.1 mm or more, the effect of improving the adhesion between the insulating resin layer 4 and the copper pattern 2 by the copper pattern bonding layer 5 becomes remarkable.

[0027] The distance (pitch) between adjacent copper wirings 2a and 2b forming the copper pattern 2 can be, for example, 0.1 mm or more and can be appropriately determined according to the use of the wiring board 10. When the distance between the copper wirings 2a and 2b is 0.1 mm or more, the width of the insulating resin layer 3 between the copper patterns becomes sufficiently wide. In this case, in the hot press process performed during manufacturing, the amount of the insulating resin material between the copper patterns that overflows from the insulating resin layer 3 between the copper patterns tends to be appropriate, and the copper pattern bonding layer 5 can be easily formed.

[0028] (Insulating resin layer between copper patterns) As shown in FIG. 1, the inter - copper - pattern insulating resin layer 3 is disposed between the copper wirings 2a and 2b on which the copper patterns 2 are formed. The inter - copper - pattern insulating resin layer 3 insulates between the copper wirings 2a and 2b. As shown in FIG. 1, the thickness of the inter - copper - pattern insulating resin layer 3 has a dimension that is the sum of the thicknesses of the copper wirings 2a and 2b and the thickness of the copper - pattern bonding layer 5. As the inter - copper - pattern insulating resin layer 3, for example, one containing a thermosetting resin described later and an inorganic filler described later can be used.

[0029] The inter - copper - pattern insulating resin layer 3 contains 30% by volume or more of elements derived from the inorganic filler. Since the content of elements derived from the inorganic filler in the inter - copper - pattern insulating resin layer 3 is 30% by volume or more, the wiring board 10 has good heat dissipation. Preferably, the inter - copper - pattern insulating resin layer 3 contains 45% by volume or more of elements derived from the inorganic filler.

[0030] Preferably, the inter - copper - pattern insulating resin layer 3 contains 60% by volume or less of elements derived from the inorganic filler. When the content of elements derived from the inorganic filler in the inter - copper - pattern insulating resin layer 3 is 60% by volume or less, when forming the inter - copper - pattern insulating resin layer 3, the inorganic filler contained in the inter - copper - pattern insulating resin material that becomes the inter - copper - pattern insulating resin layer 3 can be prevented from reducing the fluidity of the inter - copper - pattern insulating resin material. As a result, it is possible to prevent hindering the filling property of the inter - copper - pattern insulating resin layer 3 disposed between the copper patterns 2. Also, in the hot - press process performed when manufacturing the wiring board 10, a sufficient amount of thermosetting resin flows out from the inter - copper - pattern insulating resin material and enters between the copper pattern 2 and the prepreg that becomes the insulating resin layer 4, so that the copper - pattern bonding layer 5 can be easily formed.

[0031] Preferably, the inter - copper - pattern insulating resin layer 3 has a thermal conductivity of 1.5 W / mK or more, and more preferably 2.0 W / mK or more. When the thermal conductivity of the inter - copper - pattern insulating resin layer 3 is 1.5 W / mK or more, the wiring board 10 has better heat dissipation.

[0032] The inorganic filler contained in the insulating resin layer 3 between copper patterns preferably has an average particle size of 1 μm to 50 μm, more preferably 5 μm to 30 μm. In the wiring board 10 where the average particle size of the inorganic filler contained in the insulating resin layer 3 between copper patterns is 1 μm or more, in the hot press process performed during manufacturing, the thermosetting resin easily flows out from the insulating resin material between copper patterns, and the inorganic filler is less likely to flow out excessively. For this reason, the balance of the content of the thermosetting resin and the inorganic filler contained in the copper pattern bonding layer 5 is likely to be favorable. Also, when the average particle size of the inorganic filler is 50 μm or less, it is possible to prevent the inorganic filler contained in the insulating resin material between copper patterns from hindering the filling property of the insulating resin layer 3 between copper patterns when forming the insulating resin layer 3 between copper patterns.

[0033] (Insulating resin layer) As shown in FIG. 1, the insulating resin layer 4 is formed on the copper pattern 2 and on the insulating resin layer 3 between copper patterns. As the insulating resin layer 4, for example, a conventionally known insulating resin including a fibrous base material, a thermosetting resin described later, and an inorganic filler described later can be used. As the fibrous base material, the same fibrous base material that can be used for the base material 1 can be used.

[0034] When both the insulating resin layer 4 and the base material 1 contain a fibrous base material, the fibrous base material contained in the insulating resin layer 4 and the fibrous base material contained in the base material 1 may be the same or different.

[0035] It is preferable that the insulating resin layer 4 contains 20% by volume or more of elements derived from the inorganic filler with respect to the total volume of elements derived from the thermosetting resin and elements derived from the inorganic filler. When the content of elements derived from the inorganic filler in the insulating resin layer 4 is 20% by volume or more with respect to the total volume, a wiring board 10 with good heat dissipation properties can be obtained. It is more preferable that the insulating resin layer 4 contains 45% by volume or more of elements derived from the inorganic filler with respect to the total volume. It is preferable that the insulating resin layer 4 contains 80% by volume or less of elements derived from the inorganic filler with respect to the total volume, and more preferably 60% by volume or less. When the content of elements derived from the inorganic filler in the insulating resin layer 4 is 80% by volume or less with respect to the total volume, the influence on the moldability of the insulating resin layer 4 due to an excessive content of the inorganic filler can be suppressed.

[0036] (Copper pattern bonding layer) As shown in FIG. 1, the copper pattern bonding layer 5 is formed by extending from the inter - copper - pattern insulating resin layer 3 between the insulating resin layer 4 and the copper pattern 2. The copper pattern bonding layer 5 improves the adhesion between the insulating resin layer 4 and the copper pattern 2 and prevents peeling at the interface between the insulating resin layer 4 and the copper pattern 2.

[0037] The copper pattern bonding layer 5 is formed with a width of 0.1 mm to 0.8 mm in the width direction of the copper pattern 2 from the boundary 5a between the inter - copper - pattern insulating resin layer 3 of the copper pattern 2. Since the width of the copper pattern bonding layer 5 is 0.1 mm or more, the adhesion between the insulating resin layer 4 and the copper pattern 2 can be effectively improved by the copper pattern bonding layer 5. The width of the copper pattern bonding layer 5 is preferably 0.3 mm or more. Also, since the width of the copper pattern bonding layer 5 is 0.8 mm or less, a decrease in the heat dissipation property of the wiring board 10 due to the presence of the copper pattern bonding layer 5 can be suppressed. The width of the copper pattern bonding layer 5 is preferably 0.6 mm or less.

[0038] The thickness of the copper pattern bonding layer 5 is preferably 55 μm or less, more preferably 50 μm or less. When the thickness of the copper pattern bonding layer 5 is 55 μm or less, the decrease in the heat dissipation performance of the wiring board 10 due to the presence of the copper pattern bonding layer 5 can be more effectively suppressed. Further, the thickness of the copper pattern bonding layer 5 is preferably 5 μm or more, more preferably 10 μm or more. When the thickness of the copper pattern bonding layer 5 is 5 μm or more, the adhesion between the insulating resin layer 4 and the copper pattern 2 can be more effectively improved by the copper pattern bonding layer 5.

[0039] The copper pattern bonding layer 5 in the present embodiment contains a thermosetting resin described later and may contain an inorganic filler described later. It preferably contains 90% by volume or more of elements derived from the resin and 10% by volume or less of elements derived from the inorganic filler. Since the copper pattern bonding layer 5 contains 90% by volume or more of elements derived from the resin, the adhesion between the insulating resin layer 4 and the copper pattern 2 can be effectively improved by the copper pattern bonding layer 5. The copper pattern bonding layer 5 preferably contains 95% by volume or more of elements derived from the resin.

[0040] Further, the copper pattern bonding layer 5 preferably contains 98% by volume or less of elements derived from the resin. When the copper pattern bonding layer 5 contains 98% by volume or less of elements derived from the resin, the copper pattern bonding layer 5 can contain components other than the thermosetting resin such as an inorganic filler. Therefore, the copper pattern bonding layer 5 can be easily formed by curing the components that have flowed out from the copper pattern interlayer insulating resin material by hot press processing.

[0041] The copper pattern bonding layer 5 may contain elements derived from the inorganic filler in a range of 10% by volume or less. Since the content of the elements derived from the inorganic filler that may be contained in the copper pattern bonding layer 5 is 10% by volume or less, the copper pattern bonding layer 5 can sufficiently contain the thermosetting resin. Further, the copper pattern bonding layer 5 may not contain an inorganic filler, but if the copper pattern bonding layer 5 contains 3% by volume or more of the elements derived from the inorganic filler, it is preferable because the copper pattern bonding layer 5 can be easily formed by curing the components that have flowed out from the copper pattern interlayer insulating resin material by hot press processing.

[0042] <Thermosetting resin> In the wiring board 10 of the present embodiment, as the thermosetting resin contained in the copper pattern interlayer insulating resin layer 3, the insulating resin layer 4, and the copper pattern bonding layer 5, and which may also be contained in the base material 1, for example, the following can be used respectively.

[0043] As the thermosetting resin, known thermosetting resins can be used. Examples of the thermosetting resin include epoxy resins, polyimide resins, polyamideimide resins, triazine resins, phenolic resins, melamine resins, polyester resins, cyanate ester resins, and modified resins of these resins. These thermosetting resins may be used alone as only one type, or two or more types may be used in combination.

[0044] As the thermosetting resin, since it has good heat resistance, it is preferably included at least one selected from epoxy resins, phenolic resins, and triazine resins. Among these, in particular, since it has excellent adhesion to the copper pattern 2, it is preferable to use an epoxy resin as the thermosetting resin. The epoxy resin may be used alone as only one type, or two or more types may be used in combination.

[0045] The epoxy resin preferably contains a mesogenic skeleton. The reason is that an epoxy resin containing a mesogenic skeleton is likely to be arranged in a state where benzene rings derived from the mesogenic skeleton overlap between adjacent molecules, and the distance between adjacent benzene rings becomes small. This is because the lattice vibration of molecules in the cured product is less likely to be scattered, resulting in a high thermal conductivity.

[0046] The "mesogenic skeleton" is a general term for atomic groups containing two or more benzene rings and having rigidity and orientation. Specifically, the mesogenic skeleton is, for example, a skeleton containing two or more benzene rings, in which the benzene rings are bonded to each other via either a single bond or a non-single bond. The mesogenic skeleton may contain only single bonds, only non-single bonds, or both single bonds and non-single bonds as the types of bonds between benzene rings. The type of non-single bond may be only one type or two or more types. When three or more benzene rings are bonded to the mesogenic skeleton, the direction of the bond is not particularly limited. That is, three or more benzene rings may be bonded linearly, may be bent in the middle, or may be branched in two or more directions.

[0047] The "non-single bond" is a general term for divalent groups containing one or two or more constituent elements and one or two or more multiple bonds. Specifically, the non-single bond contains, for example, any one or two or more of the constituent elements such as carbon (C), nitrogen (N), oxygen (O), and hydrogen (H). Also, the non-single bond contains, as multiple bonds, one or both of a double bond and a triple bond.

[0048] Specific examples of the mesogenic skeleton include biphenyl and terphenyl. The terphenyl may be o-terphenyl, m-terphenyl, or p-terphenyl.

[0049] As the epoxy resin, for example, a main agent (epoxy resin) which is a prepolymer containing an epoxy group (-C3H5O) in the molecule and a curing agent that reacts with the epoxy group of the main agent can be used, which react by heating to thermoset. In the epoxy resin containing a mesogen skeleton, the mesogen skeleton of the epoxy resin may be derived from the main agent of the epoxy resin or may be derived from the curing agent.

[0050] "Main agent" The epoxy resin as the main agent is a compound containing one or more epoxy groups (-C3H5O) in the molecule. The type of the epoxy resin as the main agent is not particularly limited, and examples thereof include glycidyl ether type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, novolac type epoxy resins, cycloaliphatic type epoxy resins, and long-chain aliphatic type epoxy resins. The epoxy resin as the main agent may be, for example, a flame-retardant epoxy resin, a hydantoin-based epoxy resin, and an isocyanurate-based epoxy resin.

[0051] Examples of the glycidyl ether type epoxy resin include bisphenol A type epoxy resin and bisphenol F type epoxy resin. Examples of the novolac type epoxy resin include cresol novolac type epoxy resin and phenol novolac type epoxy resin. Among these, the epoxy resin as the main agent is preferably a compound having a mesogen skeleton in the molecule. This is because a cured product containing a mesogen skeleton can be obtained.

[0052] "Curing agent" As the curing agent, one or more compounds having a group that reacts with the epoxy group of the main agent can be used. Specifically, as the curing agent, for example, polyaddition type curing agents such as acid anhydride-based curing agents, amine-based curing agents, phenol-based curing agents, and mercaptan-based curing agents, and catalyst type curing agents such as imidazole can be used. Among these curing agents, from the viewpoint of obtaining a cured product with good heat resistance, it is preferable to use at least one selected from amine-based curing agents and phenol-based curing agents, and from the viewpoint of storage stability, it is more preferable to use a phenol-based curing agent. As the curing agent, a compound having a mesogenic skeleton in the molecule may be used.

[0053] As the acid anhydride-based curing agent, those commonly used can be used without particular limitation, and commercially available ones may also be used. Examples of the acid anhydride-based curing agent include 3-methyl-1,2,3,6-tetrahydrophthalic anhydride and 4-methyl-1,2,3,6-tetrahydrophthalic anhydride.

[0054] As the amine-based curing agent, those commonly used can be used without particular limitation, and commercially available ones may also be used. From the viewpoint of curability, it is preferable to use a polyfunctional curing agent having two or more functional groups, and from the viewpoint of obtaining a cured product with good thermal conductivity, it is more preferable to use a polyfunctional curing agent having a rigid skeleton.

[0055] Examples of the bifunctional amine curing agent include 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-diamino-3,3'-dimethoxybiphenyl, 4,4'-diaminophenyl benzoate, 1,5-diaminonaphthalene, 1,3-diaminonaphthalene, 1,4-diaminonaphthalene, 1,8-diaminonaphthalene, and the like. Among these, from the viewpoint of obtaining a cured product with good thermal conductivity, it is preferable to use at least one selected from 4,4'-diaminodiphenylmethane and 1,5-diaminonaphthalene as the bifunctional amine curing agent, and it is more preferable to use 1,5-diaminonaphthalene.

[0056] As the phenolic curing agent, those commonly used can be used without particular limitation, and commercially available ones can also be used. As the phenolic curing agent, a low-molecular-weight phenolic compound may be used, or a phenolic resin obtained by novolakizing a low-molecular-weight phenolic compound may be used.

[0057] Examples of the low-molecular-weight phenolic compound include monofunctional ones such as phenol, o-cresol, m-cresol, p-cresol, etc., bifunctional ones such as catechol, resorcinol, hydroquinone, etc., and trifunctional ones such as 1,2,3-trihydroxybenzene, 1,2,4-trihydroxybenzene, 1,3,5-trihydroxybenzene, 1,3,5-tris(4-hydroxyphenyl)benzene, etc. Further, a phenol novolak resin obtained by linking these low-molecular-weight phenolic compounds with a methylene chain or the like and novolakizing it may be used as the curing agent.

[0058] As the phenolic curing agent, since a cured product with good thermal conductivity and heat resistance can be obtained, it is preferable to use 1,3,5-tris(4-hydroxyphenyl)benzene or a phenolic resin containing a biphenylene skeleton.

[0059] The content of the curing agent relative to the total mass of the main agent and the curing agent can be appropriately determined according to the types of the main agent and the curing agent, etc., and is not particularly limited. For example, when an amine-based curing agent is included as the curing agent, the ratio (amine equivalent / epoxy equivalent) of the equivalent weight of the active hydrogen of the amine-based curing agent (amine equivalent) to the epoxy equivalent of the epoxy resin as the main agent is preferably 0.5 to 2, and more preferably 0.8 to 1.2.

[0060] Also, for example, when a phenolic curing agent is included as the curing agent, the ratio (phenolic hydroxyl group equivalent / epoxy equivalent) of the equivalent weight of the active hydrogen of the phenolic hydroxyl group (phenolic hydroxyl group equivalent) to the epoxy equivalent of the epoxy resin as the main agent is preferably 0.5 to 2, and more preferably 0.8 to 1.2.

[0061] "Curing accelerator" When a phenolic curing agent is included as the curing agent, a curing accelerator may be included together with the curing agent as necessary. The type of the curing accelerator is not particularly limited, and an appropriate one can be appropriately selected from the viewpoints of the rate and reaction temperature of the curing reaction, the storage stability of the epoxy resin before the curing reaction, etc. In addition, in the present embodiment, when the thermosetting resin is an epoxy resin, the volume of the thermosetting resin includes only the volumes of the main agent and the curing agent, and does not include the volume of the curing accelerator used as necessary.

[0062] Specific examples of the curing accelerator include imidazole-based compounds, organic phosphorus-based compounds, tertiary amines, and quaternary ammonium salts. The curing accelerator may be used alone or in combination of two or more.

[0063] When the epoxy resin contains a curing accelerator, the content of the curing accelerator relative to the total mass of the main agent and the curing agent can be appropriately determined according to the type of the curing accelerator and the like, and is not particularly limited. From the viewpoint of moldability, the content of the curing accelerator relative to the total mass of the main agent and the curing agent is preferably, for example, 0.5% by mass to 1.5% by mass of the total mass of the main agent and the curing agent, more preferably 0.5% by mass to 1% by mass, and even more preferably 0.75% by mass to 1% by mass.

[0064] In the present embodiment, the thermosetting resin contained in the insulating resin layer 3 between copper patterns is the same as the thermosetting resin contained in the copper pattern bonding layer 5. The thermosetting resins contained in the insulating resin layer 3 between copper patterns and the insulating resin layer 4 and which may be contained in the base material 1 may be different from each other, or may be partially or entirely the same. It is preferable that the thermosetting resin contained in the insulating resin layer 3 between copper patterns is the same as the thermosetting resin contained in the insulating resin layer 4. The reason is that the adhesion between the insulating resin layer 4 and the insulating resin layer 3 between copper patterns and the copper pattern bonding layer 5 becomes better.

[0065] <Inorganic filler> In the wiring board 10 of the present embodiment, as the inorganic filler contained in the insulating resin layer 3 between copper patterns, the insulating resin layer 4, and the copper pattern bonding layer 5 and which may be contained in the base material 1, for example, the following can be used respectively.

[0066] As the inorganic filler, calcium carbonate, magnesium oxide, zinc oxide, boron nitride, aluminum oxide, silica, aluminum nitride, etc. can be used, and it is preferable that it is at least one or more selected from calcium carbonate, magnesium oxide, zinc oxide, and boron nitride. Calcium carbonate, magnesium oxide, zinc oxide, and boron nitride all have a high thermal conductivity. Therefore, when the inorganic filler is one or more of the above, the wiring board 10 has better heat dissipation properties. Also, boron nitride is a compound with particularly high thermal conductivity. Therefore, when boron nitride is included as the inorganic filler, the wiring board 10 has particularly good heat dissipation properties.

[0067] In this embodiment, the inorganic filler contained in the insulating resin layer 3 between copper patterns is the same as the inorganic filler contained in the copper pattern bonding layer 5. The inorganic fillers contained in the insulating resin layer 3 between copper patterns, the insulating resin layer 4, and the base material 1 may be different from each other, or some or all of them may be the same.

[0068] In this embodiment, the thermosetting resin contained in the insulating resin layer 3 between copper patterns is the same as the thermosetting resin contained in the copper pattern bonding layer 5, and the inorganic filler contained in the insulating resin layer 3 between copper patterns is the same as the inorganic filler contained in the copper pattern bonding layer 5. Therefore, the copper pattern bonding layer 5 can be easily formed by curing the components flowing out from the insulating resin material between copper patterns by hot press processing.

[0069] In this embodiment, the case where the thermosetting resin contained in the insulating resin layer 3 between copper patterns is the same as the thermosetting resin contained in the copper pattern bonding layer 5, and the inorganic filler contained in the insulating resin layer 3 between copper patterns is the same as the inorganic filler contained in the copper pattern bonding layer 5 has been described as an example. However, the thermosetting resin and / or the inorganic filler may be different between the insulating resin layer 3 between copper patterns and the copper pattern bonding layer 5.

[0070] <Other components> In the wiring board 10 of this embodiment, the base material 1, the insulating resin layer 3 between copper patterns, the insulating resin layer 4, and the copper pattern bonding layer 5 may each contain other components as necessary in addition to the thermosetting resin and the inorganic filler. Examples of other components include silane coupling agents and elastomers.

[0071] The silane coupling agent plays a role (equivalent to a binder) of forming a covalent bond between the surface of the inorganic filler and the thermosetting resin surrounding it, and efficiently transfers heat in the cured product. The silane coupling agent is not particularly limited, and commercially available ones may be used. The silane coupling agent may be used alone or in combination of two or more.

[0072] Specifically, as the silane coupling agent, it is preferable to use one having an amino group, a mercapto group, a ureido group, or a hydroxyl group at the terminal. The reason is that these silane coupling agents have good compatibility with the thermosetting resin and can reduce the heat conduction loss at the interface between the thermosetting resin and the inorganic filler. In addition, when the silane coupling agent also functions as a curing agent, it is included in the curing agent in the present embodiment.

[0073] As the elastomer, for example, an acrylic resin can be used. Specifically, as the elastomer, a homopolymer or copolymer derived from (meth)acrylic acid or (meth)acrylic acid ester can be used.

[0074] [Method for manufacturing a wiring board] Next, an example of the method for manufacturing the wiring board 10 shown in FIG. 1 will be described. First, the base material 1 is manufactured by the method shown below. First, the above-mentioned thermosetting resin, the above-mentioned inorganic filler, and the above-mentioned other components contained as necessary are mixed at a predetermined ratio using a known method with an organic solvent to prepare a resin paint. Then, the obtained resin paint is impregnated into the fibrous base material and preferably cured until the resin paint becomes in a semi-cured state (B-stage state) to obtain a prepreg. Next, the obtained prepregs are laminated in a plurality as necessary and hot-pressed. By performing the above steps, the semi-cured base material 1 is manufactured.

[0075] Next, a copper foil layer is formed on one surface of the base material 1 by a known method. Then, the copper pattern 2 is formed on the base material 1 by patterning the copper foil layer into a predetermined shape by a known method. Next, between the copper wirings 2a and 2b forming the copper pattern 2 formed on one surface of the base material 1, a copper pattern insulating resin material that becomes the copper pattern insulating resin layer 3 is printed using a screen printing machine and dried to a semi-cured state (B-stage state).

[0076] The copper pattern insulating resin material used when forming the copper pattern insulating resin layer 3 is a resin paint prepared by mixing the above-described thermosetting resin, the above-described inorganic filler, the above-described other components contained as necessary, and an organic solvent in a predetermined ratio using a known method. As the resin paint (copper pattern insulating resin material) used when forming the copper pattern insulating resin layer 3, a resin paint in which the content of the inorganic filler in the solid content contained in the resin paint is 30% by volume or more is used.

[0077] The copper pattern insulating resin material may have the same composition as the resin paint prepared when manufacturing the base material 1, or one or more components or the content among the components contained in the copper pattern insulating resin material may be different from the resin paint prepared when manufacturing the base material 1. Examples of the organic solvent that may be contained in the resin paint prepared when manufacturing the base material 1 and the copper pattern insulating resin material include dioxolane, butyl carbitol acetate (BCA), methyl ethyl ketone, methyl cellosolve, methyl isobutyl ketone, dimethylformamide, propylene glycol monomethyl ether, toluene, xylene, acetone, and the like. These organic solvents may be used alone or in combination of two or more.

[0078] Next, a prepreg that becomes the insulating resin layer 4 is laminated on the copper pattern 2 and the semi-cured copper pattern insulating resin layer 3 formed on one surface of the base material 1, and hot pressing is performed. The prepreg that becomes the insulating resin layer 4 can be manufactured in the same manner as the prepreg used when manufacturing the base material 1.

[0079] The prepreg that becomes the insulating resin layer 4 may be the same as the prepreg used when manufacturing the base material 1, or one or more of the materials or the content used in manufacturing the prepreg that becomes the insulating resin layer 4 may be different from the prepreg used when manufacturing the base material 1.

[0080] In the present embodiment, by performing the above heat pressing process, the semi-cured base material 1, the inter-copper-pattern insulating resin layer 3, and the prepreg that becomes the insulating resin layer 4 are cured, and the base material 1, the copper pattern 2, the inter-copper-pattern insulating resin layer 3, and the insulating resin layer 4 are integrated. At this time, in the present embodiment, a part of the inter-copper-pattern insulating resin material overflows from the inter-copper-pattern insulating resin layer 3 in the semi-cured state from the region sandwiched between the copper wirings 2a and 2b forming the copper pattern 2, and cures while infiltrating along the surface on the prepreg side that becomes the insulating resin layer 4 of the copper pattern 2. As a result, a copper pattern bonding layer 5 extending from the inter-copper-pattern insulating resin layer 3 is formed between the insulating resin layer 4 and the copper pattern 2.

[0081] In the present embodiment, for example, when the inter-copper-pattern insulating resin material contains a thermosetting resin that is an epoxy resin and one or more inorganic fillers selected from aluminum oxide, magnesium oxide, and boron nitride, and the content of the thermosetting resin in the solid content is 40% to 70% by volume and the content of the inorganic filler is 30% to 60% by volume, the shape of the copper pattern bonding layer 5 can be changed by controlling any one or more of the following conditions (1) to (4).

[0082] (1) When the thickness of the inter-copper-pattern insulating resin layer 3 is increased, the amount of the inter-copper-pattern insulating resin material that flows during the heat pressing process tends to increase. Therefore, when the thickness of the copper pattern bonding layer 5 is increased, the width of the copper pattern bonding layer 5 tends to become wider. On the other hand, when the thickness of the inter-copper-pattern insulating resin layer 3 is decreased, the amount of the inter-copper-pattern insulating resin material that flows during the heat pressing process tends to decrease. Therefore, when the thickness of the copper pattern bonding layer 5 is decreased, the width of the copper pattern bonding layer 5 tends to become narrower.

[0083] (2) When the heating rate in the hot press process is increased, the insulating resin material between the copper patterns becomes more likely to flow, and the width of the copper pattern bonding layer 5 becomes wider. When the heating rate in the hot press process is decreased, the insulating resin material between the copper patterns becomes less likely to flow, and the width of the copper pattern bonding layer 5 becomes narrower. (3) When the pressure in the hot press process is increased, the insulating resin material between the copper patterns becomes more likely to flow, and the width of the copper pattern bonding layer 5 becomes wider. When the pressure in the hot press process is decreased and the heating rate is decreased, the insulating resin material between the copper patterns becomes less likely to flow, and the width of the copper pattern bonding layer 5 becomes narrower.

[0084] (4) When drying the insulating resin material between the copper patterns printed between the copper wirings 2a and 2b, by appropriately selecting drying conditions such as the heating temperature and / or heating time for heating the substrate 1, if the amount of solvent remaining in the printed insulating resin material between the copper patterns is increased, the viscosity of the insulating resin material between the copper patterns in the hot press process becomes lower. As a result, the insulating resin material between the copper patterns becomes more likely to flow, and the width of the copper pattern bonding layer 5 becomes wider. Also, by appropriately selecting the above drying conditions, if the amount of solvent remaining in the printed insulating resin material between the copper patterns is decreased, the insulating resin material between the copper patterns becomes less likely to flow, and the width of the copper pattern bonding layer 5 becomes narrower.

[0085] By controlling the above conditions, between the insulating resin layer 4 and the copper pattern 2, it may be formed by extending from the insulating resin layer 3 between the copper patterns, containing 90% by volume or more of elements derived from the resin and 10% by volume or less of elements derived from the inorganic filler, and a copper pattern bonding layer 5 is formed with a width of 0.1 mm to 0.8 mm in the width direction of the copper pattern 2 from the boundary 5a between the insulating resin layer 3 between the copper patterns of the copper pattern 2. Through the above steps, the wiring board 10 of the present embodiment shown in FIG. 1 is obtained.

[0086] In the wiring board 10 of the present embodiment, the insulating resin layer 3 between copper patterns contains 30% by volume or more of elements derived from the inorganic filler, and the copper pattern bonding layer 5 may contain 90% by volume or more of elements derived from the resin and 10% by volume or less of elements derived from the inorganic filler. It is formed with a width of 0.1 mm to 0.8 mm in the width direction of the copper pattern 2 from the boundary 5a between the insulating resin layer 3 between the copper patterns of the copper pattern 2. Therefore, the wiring board 10 of the present embodiment has sufficient heat dissipation properties, and the interface between the insulating resin layer 4 and the copper pattern 2 is difficult to peel off.

[0087] [Second Embodiment] [Wiring Board] FIG. 2 is a diagram for explaining a wiring board according to a second embodiment of the present invention, and is a schematic cross-sectional view along the width direction of a copper pattern. In the wiring board 20 of the second embodiment shown in FIG. 2, the same members as those of the wiring board 10 of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0088] The wiring board 20 of the second embodiment shown in FIG. 2 has a base material 1, a copper pattern 2, an insulating resin layer 3 between copper patterns, an insulating resin layer 4, and a copper pattern bonding layer 5, similarly to the wiring board 10 of the first embodiment shown in FIG. 1. The wiring board 20 shown in FIG. 2 is formed by laminating and integrating two wiring boards 10 shown in FIG. 1 with their surfaces on the base material 1 side facing each other.

[0089] [Manufacturing Method of Wiring Board] Next, an example of a manufacturing method of the wiring board 20 shown in FIG. 2 will be described. First, two semi-cured base materials 1 manufactured in the same manner as in the first embodiment shown in FIG. 1 are prepared. Then, a copper pattern 2 and a semi-cured insulating resin layer 3 between copper patterns are formed on one surface of each of the two semi-cured base materials 1 in the same manner as in the first embodiment.

[0090] Next, prepregs that will become the insulating resin layer 4 are laminated on the copper pattern 2 and the semi-cured insulating resin layer 3 between copper patterns formed on one surface of each of the two semi-cured base materials 1, the base materials 1 are laminated with their surfaces facing each other, and hot pressing is performed in the same manner as in the first embodiment.

[0091] In this embodiment, by performing the above thermal press working, the prepregs that become the semi-cured base material 1, the inter-copper-pattern insulating resin layer 3, and the insulating resin layer 4 are cured, and the two base materials 1, the copper pattern 2, the inter-copper-pattern insulating resin layer 3, and the insulating resin layer 4 are integrated. At this time, in this embodiment, as in the first embodiment, a part of the inter-copper-pattern insulating resin material overflows from the semi-cured inter-copper-pattern insulating resin layer 3 from the region sandwiched between the copper wirings 2a and 2b forming the copper pattern 2, and cures while infiltrating along the surface of the prepreg side that becomes the insulating resin layer 4 of the copper pattern 2. As a result, a copper pattern bonding layer 5 extending from the inter-copper-pattern insulating resin layer 3 is formed between the insulating resin layer 4 and the copper pattern 2. Through the above steps, the wiring board 20 of this embodiment shown in FIG. 2 is obtained.

[0092] In the wiring board 20 of this embodiment, similar to the wiring board 10 of the first embodiment, the inter-copper-pattern insulating resin layer 3 contains 30% by volume or more of elements derived from the inorganic filler, and the copper pattern bonding layer 5 may contain 90% by volume or more of elements derived from the resin and 10% by volume or less of elements derived from the inorganic filler, and is formed with a width of 0.1 mm to 0.8 mm in the width direction of the copper pattern 2 from the boundary 5a between the copper pattern 2 and the inter-copper-pattern insulating resin layer 3. For this reason, the wiring board 20 of this embodiment has sufficient heat dissipation properties, and the interface between the insulating resin layer 4 and the copper pattern 2 is difficult to peel off.

[0093] [Third Embodiment] [Wiring Board] FIG. 3 is a diagram for explaining the wiring board of the third embodiment of the present invention, and is a schematic cross-sectional view along the width direction of the copper pattern. In the wiring board 30 of the third embodiment shown in FIG. 3, the same members as those in the wiring board 10 of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0094] The wiring board 30 of the third embodiment shown in FIG. 3 includes a core material 6 composed of a base material 1, a copper pattern 2 formed on one surface of the base material 1 (the upper surface of the base material 1 in FIG. 3), and a copper pattern interlayer insulating resin layer 3 disposed between the copper wirings forming the copper pattern 2.

[0095] The base material 1 forming the core material 6 is made of an insulating resin containing 30% by volume or more of elements derived from an inorganic filler. In the wiring board 30, since the content of the elements derived from the inorganic filler in the base material 1 of the core material 6 is 30% by volume or more, the wiring board 30 has good heat dissipation. It is preferable that the base material 1 of the core material 6 contains 45% by volume or more of elements derived from an inorganic filler. It is preferable that the base material 1 of the core material 6 contains 60% by volume or less of elements derived from an inorganic filler. When the content of the elements derived from the inorganic filler in the base material 1 of the core material 6 is 60% by volume or less, the influence on the moldability of the base material 1 due to too much content of the inorganic filler can be suppressed.

[0096] In the wiring board 30 of the present embodiment shown in FIG. 3, the case where two layers of the core material 6 are laminated will be described as an example, but it is sufficient that a plurality of core materials 6 are laminated, and the number of laminated core materials 6 may be 3 or more. As shown in FIG. 3, the plurality of core materials 6 are laminated with the base material 1 of one core material 6 (the core material disposed on the upper side in the wiring board 30 shown in FIG. 3) facing the copper pattern 2 of another core material 6 (the core material disposed on the lower side in the wiring board 30 shown in FIG. 3).

[0097] As shown in FIG. 3, on the copper pattern 2 and the copper pattern interlayer insulating resin layer 3 of the core material 6 having a copper pattern 2 that does not face the base material 1 among the plurality of core materials 6 (the core material 6 disposed on the upper side in FIG. 3), an insulating resin layer 4 is formed. And between the insulating resin layer 4 and the copper pattern 2, a copper pattern bonding layer 5 formed by extending from the copper pattern interlayer insulating resin layer 3 is formed in the same manner as the wiring board 10 of the first embodiment and the wiring board 20 of the second embodiment.

[0098] Further, in the wiring board 30 of the present embodiment, between adjacent core materials 6 (between the base material 1 of the core material 6 disposed on the upper side shown in FIG. 3 and the copper pattern 2 of the core material 6 disposed on the lower side), as shown in FIG. 3, there is a core material inter-bonding layer 51 formed by extending from the copper pattern inter-insulating resin layer 3. Similar to the copper pattern bonding layer 5, the core material inter-bonding layer 51 may contain 90% by volume or more of elements derived from the resin and 10% by volume or less of elements derived from the inorganic filler, and is formed with a width of 0.1 mm to 0.8 mm in the width direction of the copper pattern 2 from the boundary 5a between the copper pattern 2 and the copper pattern inter-insulating resin layer 3.

[0099] [Method for manufacturing a wiring board] Next, an example of a method for manufacturing the wiring board 30 shown in FIG. 3 will be described. First, two base materials 1 manufactured in the same manner as in the first embodiment shown in FIG. 1 are prepared. Then, a copper pattern 2 and a semi-cured copper pattern inter-insulating resin layer 3 are formed on one surface of each of the two base materials 1 in the same manner as in the first embodiment, and a core material 6 in a semi-cured state (B-stage state) is obtained.

[0100] Next, the two semi-cured core materials 6 are laminated with the base material 1 of one core material 6 and the copper pattern 2 of another core material 6 facing each other, and a prepreg that becomes the insulating resin layer 4 is laminated on the copper pattern 2 and the semi-cured copper pattern inter-insulating resin layer 3 of one core material 6, and hot press processing is performed in the same manner as in the first embodiment.

[0101] In the present embodiment, by performing the above hot press processing, the base material 1 and the copper pattern inter-insulating resin layer 3 of the two semi-cured core materials 6 and the prepreg that becomes the insulating resin layer 4 are cured, and the base material 1, the copper pattern 2, the copper pattern inter-insulating resin layer 3, and the insulating resin layer 4 of the two semi-cured core materials 6 are integrated.

[0102] At this time, in the present embodiment, a part of the inter-pattern insulating resin material overflows from between the semi-cured copper patterns of the inter-pattern insulating resin layer 3 of the core material 6 having the copper pattern 2 facing the prepreg that becomes the insulating resin layer 4 (the core material 6 arranged on the upper side in FIG. 3), and infiltrates and cures along the surface on the prepreg side of the copper pattern 2 that becomes the insulating resin layer 4. As a result, a copper pattern bonding layer 5 extending from the inter-pattern insulating resin layer 3 is formed between the insulating resin layer 4 and the copper pattern 2.

[0103] At the same time, in the present embodiment, a part of the inter-pattern insulating resin material overflows from between the semi-cured copper patterns of the inter-pattern insulating resin layer 3 of the core material 6 having the copper pattern 2 facing the base material 1 of the core material 6 (the core material 6 arranged on the lower side in FIG. 3), and infiltrates and cures along the surface on the base material 1 side of the semi-cured copper pattern 2. As a result, a core material bonding layer 51 extending from the inter-pattern insulating resin layer 3 is formed between adjacent core materials 6. Through the above steps, the wiring board 30 of the present embodiment shown in FIG. 3 is obtained.

[0104] In the wiring board 30 of the present embodiment, a plurality of core materials 6 are laminated, and there is a copper pattern bonding layer 5 extending from the inter-pattern insulating resin layer 3 between the insulating resin layer 4 and the copper pattern 2, and there is a core material bonding layer 51 extending from the inter-pattern insulating resin layer 3 between adjacent core materials 6. The copper pattern bonding layer 5 and the core material bonding layer 51 may contain 90% by volume or more of elements derived from the resin and 10% by volume or less of elements derived from the inorganic filler, and are formed with a width of 0.1 mm to 0.8 mm in the width direction of the copper pattern 2 from the boundary between the copper pattern 2 and the inter-pattern insulating resin layer. For this reason, the wiring board 30 of the present embodiment has sufficient heat dissipation, and the interfaces between the base material 1 and the copper pattern 2 and between the insulating resin layer 4 and the copper pattern 2 are difficult to peel off.

[0105] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. It goes without saying that the present invention can be variously modified without departing from the gist of the present invention, and such modifications are also included within the scope of the present invention.

Example

[0106] (Example 1) The wiring board 20 shown in FIG. 2 was manufactured by the method shown below. First, a resin paint for Example 1 was prepared by mixing the following thermosetting resin, the following inorganic filler, and the following other components in the following proportions using dioxolane as an organic solvent and a ball mill.

[0107] "Thermosetting resin" As the thermosetting resin, an epoxy resin composition composed of the following main agent, curing agent, and curing accelerator was used. The ratios of the main agent and the curing agent to the total volume of the thermosetting resin and the inorganic filler after curing the resin paint are shown below. Also, the ratio of the curing accelerator to the total mass of the main agent and the curing agent is shown below.

[0108] <Main agent> A mixture containing 50% by mass each of tetramethylbiphenyl type epoxy resin and 4,4'-biphenyl type epoxy resin (epoxy equivalent 175 g / eq, YL-6121H manufactured by Mitsubishi Chemical Corporation); 27.4% by volume Brominated phenol novolac type epoxy resin (BREN105 manufactured by Nippon Kayaku Co., Ltd.); 8.7% by volume <Curing agent> 1,3,5-Tris(4-hydroxyphenyl)benzene; 19.0% by volume <Curing accelerator> 2-Ethyl-4-methylimidazole (manufactured by Shikoku Kasei Co., Ltd., 2E4MZ); 0.3% by mass

[0109] "Inorganic filler" The ratios of each inorganic filler to the total volume of the thermosetting resin and the inorganic filler after curing the main resin coating are shown below. Magnesium oxide (MgO) (average particle size (D50) 20 μm; manufactured by Ube Materials Co., Ltd.) 21.0% by volume in the solid content of the resin coating Aluminum oxide (Al2O3) (average particle size (D50) 3 μm; manufactured by Showa Denko K.K.) 14.0% by volume in the solid content of the resin coating Boron nitride (BN) (average particle size (D50) 8 μm; manufactured by Showa Denko K.K.) 10% by volume in the solid content of the resin coating

[0110] "Other components" The ratios of the coupling agent to the total mass of the main agent and the curing agent of the thermosetting resin are shown below. Silane coupling agent (dispersion agent) (Shin-Etsu Chemical Co., Ltd.; KBM403) as the coupling agent; 0.3% by mass

[0111] The resin coating of Example 1 was impregnated by applying it to a fibrous substrate made of glass fiber (product name; glass cloth; manufactured by Unitika Ltd.) using a die coater, and dried in a drying oven until the resin coating reached the B-stage (semi-cured) state. Thus, the prepreg of Example 1 was obtained. Next, two sheets of the prepreg of Example 1 were laminated and hot-pressed to obtain the semi-cured substrate 1 of Example 1 with a thickness of 0.3 mm.

[0112] Next, two sheets of the semi-cured substrate 1 of Example 1 were prepared, and a copper foil layer was formed and patterned on one surface of each of the two semi-cured substrates 1 to form a copper pattern 2 with a thickness of 105 μm, a minimum width dimension of 0.3 mm, and a minimum pitch dimension of 0.3 mm.

[0113] Next, a copper pattern insulating resin material of Example 1 was prepared by mixing the following thermosetting resin, the following inorganic filler, and the following other components in the following ratios using butyl carbitol acetate (BCA) as an organic solvent and using a planetary mixer in the following ratios.

[0114] "Thermosetting resin" As the thermosetting resin, an epoxy resin composition composed of the following main agent, curing agent, and curing accelerator was used. The ratio of the main agent and the curing agent to the total volume of the thermosetting resin and the inorganic filler after curing the resin paint is shown below. Also, the ratio of the curing accelerator to the total mass of the main agent and the curing agent is shown below.

[0115] <Main agent> A mixture containing 50% by mass each of tetramethylbiphenyl type epoxy resin and 4,4'-biphenyl type epoxy resin (epoxy equivalent 175 g / eq, YL-6121H manufactured by Mitsubishi Chemical Corporation); 32.8% by volume <Curing agent> 1,3,5-tris(4-hydroxyphenyl)benzene; 18.4% by volume <Curing accelerator> 2-ethyl-4-methylimidazole (manufactured by Shikoku Kasei Co., Ltd., 2E4MZ); 0.3% by mass

[0116] "Inorganic filler" Magnesium oxide (MgO) (average particle size (D50) 20 μm; manufactured by Ube Materials Co., Ltd.) 25% by volume in the solid content of the resin paint Aluminum oxide (Al2O3) (average particle size (D50) 3 μm; manufactured by Showa Denko K.K.) 16.2% by volume in the solid content of the resin paint Boron nitride (BN) (average particle size (D50) 8 μm; manufactured by Showa Denko K.K.) 7.9% by volume in the solid content of the resin paint

[0117] "Other components" The ratio of the coupling agent to the total mass of the main agent and the curing agent of the thermosetting resin is shown below. Silane coupling agent (Shin-Etsu Chemical Co., Ltd.; KBM403) as a coupling agent (dispersant); 0.3% by mass

[0118] Next, the copper pattern insulating resin material of Example 1 was printed between the copper patterns formed on one surface of each of the two semi-cured base materials 1 using a screen printing machine, and the base material 1 was heated at 125 °C for 45 minutes to be dried and brought into a semi-cured state (B-stage state). Next, the prepreg of Example 1 was laminated on the copper patterns 2 and on the semi-cured copper pattern insulating resin layer 3 formed on one surface of each of the two semi-cured base materials 1, the base materials 1 were laminated facing each other, and after heating from room temperature to 180 °C at a heating rate of 2.5 °C / min, hot pressing was performed at a temperature of 180 °C for 60 minutes and a pressure of 4.5 MPa. By performing the above steps, the wiring board of Example 1 was manufactured.

[0119] Regarding the wiring board of Example 1 thus obtained, a sample for cross-sectional observation was prepared, and cross-sectional observation was performed using a scanning electron microscope (SEM) (product name: SU5000, manufactured by Hitachi High-Tech Corporation). The sample for cross-sectional observation was prepared by collecting a test piece from the wiring board of Example 1 and performing potting using an embedding resin.

[0120] Figure 4 is an SEM image of the cross-section of the wiring board of Example 1. Figure 4(a) is an SEM image of the cross-section of the copper pattern portion of the wiring board. Figure 4(b) is an SEM image of the cross-section of the copper pattern insulating resin layer portion of the wiring board. Figures 4(c) and 4(d) are enlarged SEM images of a part of the SEM image of Figure 4(a). Figure 4(c) is an SEM image of the cross-section of the upper copper pattern portion of Figure 4(a). Figure 4(d) is an SEM image of the cross-section of the lower copper pattern portion of Figure 4(a).

[0121] In the SEM images shown in FIGS. 4(a) to 4(d), the light gray particles are inorganic fillers, the dark gray portions existing around the inorganic fillers are thermosetting resins, and the light gray plate-like objects are copper wirings 2a and 2b forming the copper pattern 2. In FIGS. 4(a) and 4(b), the portion where light gray and dark gray are mixed and adjacent in the width direction to the copper wirings 2a and 2b forming the copper pattern 2 is the inter-copper-pattern insulating resin layer 3. In FIG. 4(b), the black straight line described on the SEM image is an auxiliary line showing the height of the copper wiring. In FIGS. 4(a) to 4(d), the portions where light gray and dark gray are mixed on the upper (outer) side of the upper copper pattern 2 and on the lower (outer) side of the lower copper pattern 2 are the insulating resin layers 4.

[0122] As shown in FIGS. 4(a), 4(c) and 4(d), in the wiring board of Example 1, on the outer side of the upper copper pattern 2 and also on the outer side of the lower copper pattern 2, a dark gray portion (a region where there is more thermosetting resin and less inorganic filler than the periphery) is formed in a band shape along the interface of the copper pattern 2. From this, it was confirmed that there is a copper pattern bonding layer 5 between the insulating resin layer 4 and the copper pattern 2 in the wiring board of Example 1.

[0123] Also, for the wiring board of Example 1, the element content derived from the inorganic filler, the element content derived from the resin, the width, the thickness of the copper pattern bonding layer 5, the element content derived from the inorganic filler, and the thermal conductivity of the inter-copper-pattern insulating resin layer 3 were measured by the following methods. The results are shown in Table 1.

[0124] (Measurement of the element content derived from the inorganic filler of the copper pattern bonding layer 5 and the inter-copper-pattern insulating resin layer 3, measurement of the element content derived from the resin of the copper pattern bonding layer 5) Regarding the wiring board of Example 1, a sample for cross-sectional observation was prepared as described above, and elemental mapping was performed using an electron probe microanalyzer (EPMA) (trade name: JXA-8500, manufactured by JEOL Ltd.). Then, from the results of the elemental mapping, for the copper pattern bonding layer 5 and the insulating resin layer 3 between the copper patterns, the area ratio of the elements derived from the inorganic filler was calculated and used as the elemental content derived from the inorganic filler. Also, from the results of the elemental mapping, the area ratio of the elements derived from the resin in the copper pattern bonding layer 5 was calculated and used as the elemental content derived from the resin.

[0125] (Measurement of the width and thickness of the copper pattern bonding layer 5) Five samples for cross-sectional observation were prepared from the wiring board of Example 1, each having an observation surface containing the insulating resin layer 3 between the copper patterns and including a copper pattern 2 with a width (length of the cross-section) of 1 mm or more formed in contact with the insulating resin layer 3 between the copper patterns. For the five samples for cross-sectional observation, scanning electron microscope (SEM) (trade name: SU5000, manufactured by Hitachi High-Tech Corporation) observations were performed respectively. From the boundary 5a between the copper pattern 2 of the copper pattern bonding layer 5 and the insulating resin layer 3 between the copper patterns in the obtained SEM images, the width in the width direction of the copper pattern 2 was measured, and the average value was taken as the width of the copper pattern bonding layer 5, and the average value of the measured maximum thickness was taken as the thickness of the copper pattern bonding layer 5.

[0126] (Measurement of the thermal conductivity (thermal resistance) of the insulating resin layer 3 between the copper patterns) Using a table coater, the copper pattern insulating resin material of Example 1 used when manufacturing the wiring board of Example 1 was formed into a sheet to obtain a resin sheet. A plurality of the obtained resin sheets were laminated and cured by vacuum pressing to produce a cured product with a thickness of 0.9 mm. A disk-shaped sample for measurement with a diameter of 10 mm was taken from the obtained cured product.

[0127] Thereafter, for the obtained sample for measurement, using a thermal conductivity measuring device (trade name: TC-7000, manufactured by Ulvac-Riko Inc.), the thermal diffusivity α [m 2 / s] was measured. Also, for the measurement sample, using sapphire as the standard sample, the specific heat Cp [J / (kg·K)] was measured by differential scanning calorimetry (DSC). Also, for the measurement sample, the density r (kg / m 3 ) was measured. Using these measurement results, the thermal conductivity (thermal resistance) of the measurement sample was calculated and taken as the thermal conductivity of the insulating resin layer 3 between the copper patterns.

[0128] "Example 2", "Example 3", "Comparative Example 1" When drying the insulating resin material between the copper patterns printed between the copper wirings, the heating temperature and heating time of the base material 1 were set to 120°C for 35 minutes in Example 2, 120°C for 25 minutes in Example 3, and 120°C for 65 minutes in Comparative Example 1. Otherwise, in the same manner as in Example 1, a wiring board was manufactured.

[0129] "Example 4", "Example 5", "Example 6" A wiring board was manufactured in the same manner as in Example 1, except that the thickness of the insulating resin layer 3 between the copper patterns was changed by varying the amount of the insulating resin material between the copper patterns used.

[0130] "Example 7", "Example 8", "Example 9", "Example 10", "Comparative Example 3" A wiring board was manufactured in the same manner as in Example 1, except that the contents of the thermosetting resin and the inorganic filler contained in the insulating resin material between the copper patterns were changed. Specifically, the content of the elements derived from the inorganic filler in the insulating resin layer between the copper patterns was set to 45% by volume in Example 7, 60% by volume in Example 8, 44% by volume in Example 9, 61% by volume in Example 10, and 29% by volume in Comparative Example 3.

[0131] "Example 11", "Example 12", "Comparative Example 4", "Comparative Example 5" A wiring board was manufactured in the same manner as in Example 1, except that the heating rate in the hot press process was set to 2.0°C / min in Example 11, 3.0°C / min in Example 12, 1.5°C / min in Comparative Example 4, and 3.5°C / min in Comparative Example 5 to form the wiring board.

[0132] "Comparative Example 2" When drying the copper pattern interlayer insulating resin material printed between the copper wirings, the heating temperature and heating time of the base material 1 were set to 120 °C for 75 minutes, and after heating from room temperature to 180 °C at a heating rate of 1.5 °C / min, hot pressing was performed at a temperature of 180 °C for 60 minutes and a pressure of 4.5 MPa. A wiring board was manufactured in the same manner as in Example 1 except for this.

[0133] Regarding the wiring boards of Example 2 to Example 12 and Comparative Example 1 to Comparative Example 5 thus obtained, cross-sectional observation was performed using a scanning electron microscope (SEM) in the same manner as in Example 1, and it was examined whether a copper pattern bonding layer was present. As a result, it was confirmed that a copper pattern bonding layer 5 was present between the insulating resin layer 4 and the copper pattern 2 in the wiring boards of Example 1 to Example 12, Comparative Example 1, and Comparative Example 3 to Comparative Example 5. However, it was not confirmed that the copper pattern bonding layer 5 was present in the wiring board of Comparative Example 2.

[0134] Also, regarding the wiring boards of Example 2 to Example 12 and Comparative Example 1 to Comparative Example 5, the element content derived from the inorganic filler, the element content derived from the resin, the width, the thickness of the copper pattern bonding layer 5, the element content derived from the inorganic filler, and the thermal conductivity of the copper pattern interlayer insulating resin layer 3 were measured in the same manner as in Example 1. The results are shown in Table 1.

[0135] [Table 1]

[0136] Also, regarding the wiring boards of Example 1 to Example 12 and Comparative Example 1 to Comparative Example 5, the thermal resistance and the adhesion strength of the interface between the insulating resin layer 4 and the copper pattern 3 were examined by the methods shown below. The results are shown in Table 2.

[0137] (Evaluation of Thermal Resistance) Regarding the wiring boards of Example 1 to Example 12 and Comparative Example 1 to Comparative Example 5, a heating element was mounted on one surface, the temperature change on the other surface was measured using a thermocouple, and the thermal resistance was calculated. The thermal resistance of the wiring board is preferably 3.0 °C / W or less, more preferably 2.8 °C / W or less, and even more preferably 2.6 °C / W or less.

[0138] (Measurement of the adhesion strength at the interface between the insulating resin layer 4 and the copper pattern 3) Two substrates 1 of each of Examples 1 to 12 and Comparative Examples 1 to 5 in a semi-cured state were prepared. Then, the prepregs of Examples 1 to 12 and Comparative Examples 1 to 5 were laminated on the copper pattern 2 and on the copper pattern intermediate insulating resin layer 3 in a semi-cured state formed on one surface of each of the two substrates 1, and the substrates 1 were laminated facing each other to form a laminate. The obtained laminate was placed between two copper foils with a thickness of 70 μm, heated from room temperature to 180 °C at a heating rate of 2.5 °C / min, and then thermally pressed at a temperature of 180 °C for 60 minutes under a pressure of 4.5 MPa. By performing the above steps, wiring boards, which are test specimens for measuring the adhesion strength of Examples 1 to 12 and Comparative Examples 1 to 5, were manufactured. For each of the test specimens for measuring the adhesion strength thus obtained, using an autograph AGS-G (manufactured by Shimadzu Corporation), the adhesion strength at the interface between the insulating resin layer 4 and the copper pattern 3 was measured according to JIS-C6481.

[0139]

Table 2

[0140] As shown in Table 2, the wiring boards of Examples 1 to 12 all had a thermal resistance of 3.0 °C / W or less and had sufficient heat dissipation properties. Also, the wiring boards of Examples 1 to 12 all had an adhesion strength at the interface between the insulating resin layer 4 and the copper pattern 3 of 0.5 kN / m or more, and the interface between the insulating resin layer 4 and the copper pattern 2 was difficult to peel off.

[0141] On the other hand, as shown in Table 2, in Comparative Example 1 where the element content derived from the inorganic filler in the copper pattern bonding layer 5 is large, Comparative Example 2 without the copper pattern bonding layer 5, and Comparative Example 4 where the width of the copper pattern bonding layer 5 is insufficient, the adhesion strength at the interface between the insulating resin layer 4 and the copper pattern 2 was insufficient. Also, in Comparative Example 3 where the element content derived from the inorganic filler in the inter-copper-pattern insulating resin layer 3 is small, and Comparative Example 5 where the width of the copper pattern bonding layer 5 is too wide, the thermal resistance exceeded 3.0 °C / W and the heat dissipation performance was insufficient.

Explanation of reference numerals

[0142] 1 Substrate, 2 Copper pattern, 2a, 2b Copper wiring, 3 Inter-copper-pattern insulating resin layer, 4 Insulating resin layer, 5 Copper pattern bonding layer, 5a Boundary, 6 Core material, 10, 20, 30 Wiring board, 51 Inter-core-material bonding layer.

Claims

1. A base material, a copper pattern formed on the base material, a copper pattern insulating resin layer disposed between copper wirings forming the copper pattern, an insulating resin layer formed on the copper pattern and on the copper pattern insulating resin layer, and a copper pattern bonding layer formed by extending from the copper pattern insulating resin layer between the insulating resin layer and the copper pattern, wherein the copper pattern insulating resin layer contains 30% by volume or more of an element derived from an inorganic filler, the copper pattern bonding layer may contain 90% by volume or more of an element derived from a resin and 10% by volume or less of an element derived from an inorganic filler, and is formed with a width of 0.1 mm to 0.8 mm in the width direction of the copper pattern from the boundary between the copper pattern and the copper pattern insulating resin layer. A wiring board.

2. The wiring board according to claim 1, wherein the thickness of the copper pattern bonding layer is 50 μm or less.

3. The wiring board according to claim 1, wherein the copper pattern insulating resin layer contains 45% by volume to 60% by volume of an element derived from an inorganic filler.

4. The wiring board according to claim 1, wherein the thermal conductivity of the copper pattern insulating resin layer is 1.5 W / mK or more.

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