WO2018225687A1 - Laminate for circuit boards, metal base circuit board and power module - Google Patents

Abstract

Provided is a laminate for circuit boards, which comprises a metal substrate, an insulating layer that is provided on at least one surface of the metal substrate, and a metal foil that is provided on the insulating layer. The insulating layer contains a resin component and an inorganic filler; and the resin component has a phase separation structure that comprises a discontinuous phase containing a thermosetting resin and a continuous phase containing a rubber.

Description

Circuit board laminate, metal base circuit board and power module

The present invention relates to a circuit board laminate, a metal base circuit board manufactured from the circuit board laminate, and a power module including the metal base circuit board.

The recent development of electronics technology is remarkable, and the performance and miniaturization of electrical and electronic equipment are rapidly progressing. In connection with this, the metal base circuit board corresponding to high-density mounting used for these is further miniaturized and densified more than before. Accordingly, various performance improvements are also demanded for metal base circuit boards, and a wide range of efforts are being made to meet these demands.

Up to now, resin compositions using epoxy resins have been widely used as resin compositions used for the insulating layer constituting the metal base circuit board. For example, Japanese Patent Application Laid-Open No. 2007-254709 discloses an epoxy resin-containing composition as a resin composition that can provide an insulating layer having high interface adhesion strength with a conductor layer even if the surface roughness of the insulating layer is small. A resin composition containing a phenolic curing agent, a phenoxy resin, and rubber particles is disclosed. In addition, International Publication No. 2009/119598 discloses a resin composition in which a specific phenoxy resin and a cyanate resin are added to an epoxy resin-containing composition in order to improve heat resistance and moisture resistance reliability in addition to plating adhesion. Is disclosed.

With the rapid progress in performance and miniaturization of the electric and electronic devices described above, the amount of heat generated by the components mounted with the electric elements and / or electronic elements is increasing. For this reason, a metal base circuit board compatible with high-density mounting is required to further improve workability and water absorption resistance and oxidation deterioration resistance under high temperature moisture absorption conditions.

The present invention provides a circuit board laminate having excellent processability and water absorption and oxidation degradation resistance under high temperature moisture absorption conditions, a metal base circuit board produced from the circuit board laminate, and An object of the present invention is to provide a power module including the metal base circuit board.

According to one aspect of the present invention, there is provided a circuit board laminate comprising a metal substrate, an insulating layer provided on at least one surface of the metal substrate, and a metal foil provided on the insulating layer. The insulating layer contains a resin component and an inorganic filler, and the resin component has a phase separation structure including a discontinuous phase containing a thermosetting resin and a continuous phase containing rubber. A laminated board is provided.

According to another aspect of the present invention, the circuit board laminate includes at least a rubber having a weight average molecular weight of 1.5 million or less as the rubber.

According to yet another aspect, the circuit board laminate includes at least a rubber having a saturated main chain structure as the rubber.

According to yet another aspect, the circuit board laminate includes at least acrylic rubber as the rubber.

According to still another aspect, in the circuit board laminate, the blending ratio of the rubber in the insulating layer is 1 to 40% by mass with respect to the total mass of the resin component.

According to still another aspect, the circuit board laminate includes at least a cyanate resin as the thermosetting resin.

According to still another aspect, the circuit board laminate includes a bisphenol-type cyanate resin and a novolac-type cyanate resin as the thermosetting resin.

According to still another aspect, in the circuit board laminate, the compounding ratio of the epoxy resin as the thermosetting resin is 0 to 10% by mass with respect to the total mass of the thermosetting resin.

Further, according to another aspect of the present invention, there is provided a metal base circuit board obtained by patterning the metal foil included in any one of the circuit board laminates.

According to another aspect of the present invention, a power module including the metal base circuit board is provided.

According to the present invention, a circuit board laminate having excellent processability and water resistance and oxidation deterioration resistance under high temperature moisture absorption conditions, a metal base circuit board produced from the circuit board laminate, and It has become possible to provide a power module comprising this metal base circuit board.

FIG. 1A is an SEM photograph showing an example of a phase separation structure made of a continuous phase rubber and a discontinuous phase thermosetting resin. FIG. 1B is an optical micrograph showing an example of a structure in which an inorganic filler is dispersed in a phase separation structure composed of a continuous phase rubber and a discontinuous phase thermosetting resin. FIG. 1C is an optical micrograph showing an example of a structure in which an inorganic filler is dispersed in a continuous phase thermosetting resin. FIG. 1D is an SEM photograph showing an example of a phase separation structure composed of a continuous phase thermosetting resin and discontinuous phase rubber particles. FIG. 1E is an SEM photograph showing an example of a structure in which an inorganic filler is dispersed in a phase separation structure composed of a continuous phase thermosetting resin and discontinuous phase rubber particles. FIG. 2 is a perspective view schematically showing a circuit board laminate according to an embodiment of the present invention. 3 is a cross-sectional view taken along the line II-II of the circuit board laminate shown in FIG. FIG. 4 is a cross-sectional view schematically showing an example of a metal base circuit board obtained from the circuit board laminate shown in FIGS. 2 and 3. FIG. 5 is a cross-sectional view schematically showing a power module according to the embodiment of the present invention. FIG. 6 is a cross-sectional view schematically showing a conventional power module. FIG. 7A is a graph showing the behavior of tan δ obtained by DMA measurement for the insulating layer included in the circuit board laminate of Example 3. FIG. 7B is a graph showing the behavior of tan δ obtained by DMA measurement for the insulating layer included in the circuit board laminate of Comparative Example 3.

Hereinafter, embodiments of the present invention will be described in detail.
A circuit board laminate according to an embodiment of the present invention includes a metal substrate, an insulating layer provided on at least one surface of the metal substrate, and a metal foil provided on the insulating layer. 2 and 3 has a three-layer structure in which an insulating layer 3 is formed on one side of a metal substrate 2 and a metal foil 4 is formed on the insulating layer 3. In another embodiment of the present invention, the circuit board laminate has a five-layer structure in which the insulating layer 3 is formed on both surfaces of the metal plate 2 and the metal foil 4 is further formed on each insulating layer 3. May be. 2 and 3, the X and Y directions are parallel to the main surface of the metal substrate 2 and perpendicular to each other, and the Z direction is a thickness direction perpendicular to the X and Y directions. FIG. 2 shows a rectangular circuit board laminate 1 as an example, but the circuit board laminate 1 may have other shapes.

The insulating layer included in the circuit board laminate according to the embodiment is a cured product of a coating film formed using a resin composition containing at least a resin component and an inorganic filler. The insulating layer contains at least a thermosetting resin and rubber as a resin component.

The resin component forms a phase separation structure in the insulating layer. This phase separation structure is a sea-island structure in which a discontinuous phase is dispersed in a continuous phase (matrix), the discontinuous phase contains a thermosetting resin, and the continuous phase contains rubber. Thus, in the embodiment, in the insulating layer, the rubber is not dispersed as a discontinuous phase in the matrix, but the rubber forms a continuous phase (matrix), and the thermosetting resin is contained in the continuous phase. One of the characteristics is that it has a phase separation structure dispersed as a discontinuous phase (dispersed phase). Hereinafter, the phase separation structure having a continuous phase containing rubber and a discontinuous phase containing a thermosetting resin, which is included in the insulating layer, is referred to as a phase separation structure of the present invention.

Rubber has low water absorption, but even if rubber is dispersed as a discontinuous phase (dispersed phase) in the matrix constituting the insulating layer, the low water absorption desired for the metal base circuit board cannot be obtained. When the rubber constitutes a continuous phase (matrix) in the insulating layer, the water absorption suppressing effect in the insulating layer is exhibited, contributing to the improvement in low water absorption in the metal base circuit board. In addition, since rubber has low oxygen permeability, the rubber constituting a continuous phase also contributes to improvement of oxidation resistance in the metal base circuit board.

¡Flexible rubber is compatible with thermosetting resin to improve processability, and a phase separation structure is formed with curing, improving the mechanical strength and stress relaxation of the insulating layer.

The presence or absence of the phase separation structure of the present invention in the insulating layer can be confirmed by, for example, microscopic observation and / or scattering measurement. In the case of microscopic observation, the phase separation structure can be confirmed by a scanning electron microscope (SEM), an atomic force microscope, an optical microscope, a transmission electron microscope, or the like. In the case of scattering measurement, the presence or absence of a phase-separated structure may be confirmed by small-angle incident small-angle X-ray scattering measurement, elemental analysis, energy dispersive X-ray analysis, electron probe microanalyzer, X-ray photoelectron spectroscopy, etc. it can.

The presence or absence of the phase separation structure of the present invention in the insulating layer can also be confirmed by DMA measurement (dynamic viscoelasticity measurement). The means for confirming the phase separation structure of the present invention by this DMA measurement is particularly effective when the compounding ratio of the rubber in the resin component is not high. For example, it is a particularly effective means when the blending ratio of the rubber is usually less than 50% by mass, preferably 40% by mass or less, based on the total mass of the resin component.
That is, in the case of the phase separation structure of the present invention in which rubber forms a continuous phase, a peak derived from rubber can be clearly observed by DMA measurement even if the blending ratio of rubber is small. On the other hand, in the case of a reverse phase separation structure in which rubber forms a discontinuous phase, such as rubber particles, a rubber-derived peak is not detected by DMA measurement unless the rubber compounding ratio is high. This is presumed that in the case of a reverse phase separation structure in which the rubber forms a discontinuous phase, the behavior of the resin is dominant when the rubber compounding ratio is small, and it is difficult to observe the rubber-derived peak by DMA measurement. Is done.

The phase separation structure of the present invention will be described below using the photographs shown in FIGS. 1A to 1E. Here, all of the photographs shown in FIGS. 1A to 1E are photographs in which the insulating layer is cut and its cross section is mechanically polished.
FIG. 1A is a scanning electron microscope (SEM) photograph showing an example of the phase separation structure of the present invention. In order to easily explain the phase separation structure of the present invention, the phase separation structure shown in FIG. 1A does not contain an inorganic filler. In the phase separation structure shown in FIG. 1A, a discontinuous phase (dispersed phase) thermosetting resin 102 is dispersed in a continuous phase rubber 101. Thus, rubber | gum comprises a continuous phase, and as above-mentioned, low water absorption and oxidation degradation resistance improve.

On the other hand, the SEM photograph in FIG. 1D shows a phase separation structure opposite to the phase separation structure of the present invention (hereinafter referred to as “reverse phase separation structure”). In the reverse phase separation structure shown in FIG. 1D, discontinuous phase (dispersed phase) rubber particles 112 are dispersed in the continuous phase thermosetting resin 111. In such a reverse phase separation structure, the above effect cannot be obtained even if a rubber component is contained.

FIG. 1B is an optical micrograph showing an example of a structure in which an inorganic filler is dispersed in the phase separation structure of the present invention. Here, two types of inorganic fillers 103a and 103b are used as the inorganic filler. The inorganic filler 103a is aluminum nitride, and the streaky inorganic filler 103b surrounded by a solid line is boron nitride. From this photograph, the phase separation structure of the present invention can be confirmed from the gaps or voids between the inorganic fillers 103a and 103b. For example, in the broken line frame A, it is confirmed that the discontinuous phase (dispersed phase) thermosetting resin 102 is dispersed in the continuous phase rubber 101 in the voids of the inorganic filler (aluminum nitride) 103a. Is done.
In contrast to the phase separation structure shown in FIG. 1B, FIG. 1C is an optical micrograph of a system containing no rubber. In the structure shown in FIG. 1C, the inorganic filler (aluminum nitride) 123a and the streaky inorganic filler (boron nitride) 123b surrounded by the solid line are dispersed in the thermosetting resin 121 in the continuous phase. Yes. Looking inside the broken line frame A ′, it can be seen that the voids of the inorganic filler (aluminum nitride) 123 a are filled with only the thermosetting resin 121.

FIG. 1E is an SEM photograph showing an example of a structure in which an inorganic filler is dispersed with respect to FIG. 1D showing a reverse phase separation structure. Here, in the continuous phase thermosetting resin 111, two kinds of inorganic fillers, that is, an inorganic filler (alumina) 113a and a streaky inorganic filler (boron nitride) 113b surrounded by a broken line, The rubber particles 112 are dispersed. It can be seen that the rubber particles 112 are not uniformly dispersed in the gap between the two kinds of inorganic fillers (alumina) 113a and the inorganic filler (boron nitride) 113b.
The rubber that can be used in the present invention may be a polymer material having rubber elasticity at room temperature. For example, the rubber may have a modulus of elasticity of 100 MPa or less at room temperature (for example, 25 ° C.).

In the insulating layer, in order to form the phase separation structure of the present invention, in the insulating layer resin composition before curing, the rubber and the thermosetting resin are dissolved in a solvent and are in a compatible state in which they are uniformly dispersed. Is preferred. When the thermosetting resin is cured by heating from this state, the molecular weight of the thermosetting resin partially increases to increase the viscosity, and finally the viscosity becomes higher (harder) than the rubber. Considering from the viewpoint of viscosity, a component having a lower viscosity forms a continuous phase, so that the phase separation structure of the present invention having a continuous phase containing rubber and a discontinuous phase containing a thermosetting resin is formed.

For this reason, the weight average molecular weight of rubber is preferably 1.5 million or less, more preferably 1.3 million or less, and still more preferably 900,000 or less, from the viewpoint of solubility in a solvent. The lower limit of the weight average molecular weight of the rubber is not particularly limited, but is preferably 50,000 or more, for example.
Here, the important average molecular weight represents a polystyrene equivalent value measured by a GPC (gel permeation chromatography) method.

Examples of rubber that can be suitably used in the embodiment include the following. That is, diene rubbers such as styrene butadiene rubber, isoprene rubber, butadiene rubber, chloroprene rubber, or acrylonitrile butadiene rubber; butyl rubber, ethylene propylene rubber, ethylene propylene diene rubber, urethane rubber, silicone rubber, fluorine rubber, chlorosulfonated polyethylene Non-diene rubbers such as rubber, chlorinated polyethylene, acrylic rubber, polysulfide rubber, or epichlorohydrin rubber; styrene, olefin, ester, urethane, amide, polyvinyl chloride (PVC), or Examples include fluorine-based thermoplastic elastomers; or natural rubber.

In the embodiment of the present invention, it is preferable that the main chain of the rubber has a saturated structure. Here, the main chain having a saturated structure means a structure in which the polymer main chain does not have a double bond or a triple bond unsaturated bond in a bond between carbon atoms.

Examples of the rubber having a saturated main chain structure include, for example, butyl rubber, ethylene propylene rubber, ethylene propylene diene rubber, urethane rubber, silicone rubber, fluorine rubber, chlorosulfonated polyethylene rubber, chlorinated polyethylene, acrylic rubber, polysulfide rubber, or Non-diene rubbers such as epichlorohydrin rubber, or thermoplastic elastomers such as styrene, olefin, ester, urethane, amide, PVC, or fluorine are listed. In one embodiment, acrylic rubber is particularly preferred.
The insulating layer may contain 1 type independently as rubber | gum, and may contain 2 or more types.

Examples of the thermosetting resin constituting the discontinuous phase include cyanate resin, epoxy resin, phenol resin, urea resin, melamine resin, acrylic resin, urethane resin, maleimide resin, benzoxazine resin, polyimide resin, polyamideimide resin, Examples include unsaturated polyester resins, silicone resins, diallyl phthalate resins, alkyd resins, and the like. One type may be used alone as the thermosetting resin, or two or more types may be used in combination.

In the embodiment of the present invention, a cyanate resin is particularly preferable as the thermosetting resin. Examples of the cyanate resin include bisphenol type cyanate resin and novolak type cyanate resin.
Examples of the bisphenol type cyanate resin include bisphenol A type cyanate resin, bisphenol E type phenol resin, and tetramethylbisphenol F type cyanate resin. The weight average molecular weight of the bisphenol cyanate resin is not particularly limited, and may be an oligomer or a monomer. For example, from the viewpoint of heat resistance, tetramethylbisphenol F type cyanate resin, bisphenol A type cyanate resin, and bisphenol E type cyanate resin are excellent in this order, and from the viewpoint of reactivity, bisphenol A type cyanate resin is excellent.

In one embodiment of the present invention, it is preferable to use a mixed system of a bisphenol type cyanate resin and a novolac type cyanate resin as the thermosetting resin. As the ratio, for example, the mass ratio represented by bisphenol type cyanate resin: novolac type cyanate resin is preferably 11: 1 to 1: 1, and more preferably 9: 1 to 2: 1. .

Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, triazine type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol S type epoxy. Resin, phenol novolac type epoxy resin, o-cresol novolac type epoxy resin, biphenyl novolac type epoxy resin, triphenylmethane type epoxy resin, dicyclopentadiene type epoxy resin, alicyclic epoxy resin, brominated epoxy resin, etc. Examples thereof include an epoxy resin having two or more epoxy groups.

However, in the embodiment of the present invention, when the epoxy resin is not contained or the epoxy resin is contained, the content is preferably a predetermined amount or less with respect to the total mass of the thermosetting resin. There is. For example, the content of the epoxy resin is preferably 0 to 10% by mass, more preferably 0 to 7% by mass, and still more preferably 0 to 5% by mass based on the total mass of the thermosetting resin.

As described above, the resin component of the insulating layer has a phase separation structure composed of a discontinuous phase containing a thermosetting resin and a continuous phase containing rubber. The blending ratio of the continuous phase containing is preferably lower than the blending ratio of the non-continuous phase containing the thermosetting resin. In one embodiment, the compounding ratio of the rubber is preferably in the range of 1 to 40% by mass, more preferably 5 to 30% by mass, with respect to the total mass of the resin component, and 5 to 20% by mass. More preferably it is.

In the embodiment, the insulating layer contains an inorganic filler together with a resin component. Examples of the inorganic filler include alumina, aluminum nitride, boron nitride, silicon nitride, magnesium oxide, and silicon oxide. It is preferable to use one or more selected from these. The inorganic filler is present in the resin component without distinction between the discontinuous phase and the continuous phase. That is, the inorganic filler may be present in the discontinuous phase, may be present in the continuous phase, or may be present in both. In addition, the inorganic filler may be present across the discontinuous phase and the continuous phase.

In a system containing an inorganic filler, the exothermic reaction accompanying curing tends to be suppressed by the presence of the inorganic filler. Specifically, the reaction heat is absorbed by the inorganic filler, so that the curing reaction is delayed, and depending on the surface functional groups of the inorganic filler, problems such as inhibiting the curing reaction of the thermosetting resin are conceivable. For this reason, a surface-treated inorganic filler may be used, and it is preferable to use an inorganic filler in an appropriate combination with an effect accelerator described later. As the surface treatment of the inorganic filler, for example, the surface of the inorganic filler may be modified with a functional group that can chemically bond with the thermosetting resin, or a functional group highly compatible with the thermosetting resin. May be modified with a group (for example, cyanate group, epoxy group, amino group, hydroxyl group, carboxyl group, vinyl group, styryl group, methacryl group, acrylic group, ureido group, mercapto group, sulfide group, isocyanate group, etc.) For example, silane coupling treatment or plasma treatment is used.

In the embodiment, the proportion of the inorganic filler contained in the insulating layer is preferably 50 to 90% by volume based on the total volume of the resin components. The content of the inorganic filler is more preferably 60 to 80% by volume. If the filling rate is too low, the desired thermal conductivity cannot be obtained and the inorganic filler tends to precipitate. On the other hand, if the filling rate is too high, the viscosity becomes too high, a uniform coating film cannot be obtained, and pore defects may increase.

The insulating layer may contain a curing accelerator. The curing accelerator is not particularly limited, and examples thereof include benzoxazine compounds, borate complexes, zinc naphthenate, cobalt naphthenate, tin octylate, cobalt octylate, bisacetylacetonate cobalt (II), and triacetyl. Examples thereof include organic metal salts such as acetonate cobalt (III), phenol compounds such as phenol, bisphenol A, and nonylphenol.

The benzoxazine compound only needs to have at least one benzoxazine ring in the molecule. As the benzoxazine compound, a monomer may be used, or a compound in which several molecules are polymerized into an oligomer state may be used. In one embodiment, the benzoxazine compound is preferably a monomer having two or more benzoxazine rings in the molecule. A plurality of types of benzoxazine compounds having different structures may be used simultaneously.

Examples of the benzoxazine compound include Pd-type benzoxazine, bisphenol F-type benzoxazine, and Fa-type benzoxazine, among which Pd-type benzoxazine is preferable. Since the Pd type benzoxazine has a rigid skeleton such as a diphenylmethylene skeleton, the compound derived from the Pd type benzoxazine forms a cross-linked structure having better thermal characteristics as compared with, for example, a compound derived from a Ba type benzoxazine. Can do.

The borate complex may be a phosphorus borate complex or a non-phosphorus borate complex.
Examples of phosphoric borate complexes include tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra-p-tolylborate, tri-tert-butylphosphonium tetraphenylborate, di-tert-butylmethylphosphonium tetraphenylborate, p-tolyltri Examples thereof include phenylphosphonium tetra-p-tolylborate, tetraphenylphosphonium tetrafluoroborate, and triphenylphosphine triphenylborate.

Examples of non-phosphorous borate complexes include sodium tetraphenyl borate, pyridine triphenyl borate, 2-ethyl-4-methylimidazolium tetraphenyl borate, 1,5-diazobicyclo [4.3.0] nonene-5 Examples thereof include tetraphenyl borate and lithium triphenyl (n-butyl) borate.

In the embodiment, when a curing accelerator is added to the insulating layer, the content can be appropriately set. For example, when a benzoxazine compound is used as a curing accelerator, the content is preferably 1 to 20% by mass, more preferably 5 to 15% by mass based on the total mass of the thermosetting resin. preferable.

In the embodiment, the insulating layer may further contain other components. Other components that the insulating layer may contain include, for example, coupling agents such as silane coupling agents and titanium coupling agents, ion adsorbents, anti-settling agents, hydrolysis inhibitors, leveling agents, and antioxidants. Agents and the like.

The insulating layer is a cured product of a coating film formed from a resin composition containing at least the resin component and the inorganic filler described above. As described above, this resin composition is preferably in a compatible state in which the rubber and the thermosetting resin are uniformly dispersed to enable the formation of the phase separation structure of the present invention. And a solvent capable of dissolving the resin. Examples of such a solvent include amide solvents such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), 1-methoxy-2-propano- And ether solvents such as ethylene glycol monomethyl ether, ketone solvents such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclohexanone and cyclopentanone, and aromatic solvents such as toluene and xylene. . As the usage form, one type of solvent may be used alone, or two or more types may be mixed and used.

The coating film (for example, dry film) before the phase separation structure of the present invention is formed is preferably in a compatible state in which the rubber and the thermosetting resin are uniformly dispersed with each other. Excellent. For this reason, the insulating layer having the phase separation structure of the present invention formed through a compatible state of such rubber and thermosetting resin is excellent in processability.

In the laminated board for a circuit board according to the embodiment, the metal substrate is made of, for example, a single metal or an alloy. As a material of the metal substrate, for example, aluminum, iron, copper, aluminum alloy, or stainless steel can be used. The metal substrate may further contain a nonmetal such as carbon. For example, the metal substrate 2 may contain aluminum combined with carbon. The metal substrate may have a single layer structure or a multilayer structure.

The metal substrate has a high thermal conductivity. Typically, the metal substrate 2 has a thermal conductivity of 60 W · m ⁻¹ · K ⁻¹ or more.
The metal substrate may have flexibility or may not have flexibility. The thickness of the metal substrate is, for example, in the range of 0.2-5 mm.

The metal foil is provided on the insulating layer. The metal foil faces the metal substrate with an insulating layer interposed therebetween.
The metal foil is made of, for example, a single metal or an alloy. As a material of the metal foil, for example, copper or aluminum can be used. The thickness of the metal foil is, for example, in the range of 10 to 500 μm.

The laminated board for circuit boards which concerns on embodiment can be manufactured with the following method, for example.
First, the above-described resin composition is applied to at least one of a metal substrate and a metal foil. For application of the resin composition, for example, a roll coating method, a bar coating method, or a screen printing method can be used. You may carry out by a continuous type and may carry out by a single plate type.

After drying the coating film as necessary, the metal substrate and the metal foil are stacked so that they face each other with the coating film in between. Furthermore, they are hot pressed. A circuit board laminate is obtained as described above.

In this method, the resin composition is applied to at least one of a metal plate and a metal foil to form a coating film. In another embodiment, the dispersion is applied to a substrate such as a PET film and dried in advance. A coating film may be formed and thermally transferred to one of the metal substrate and the metal foil.

Next, the metal base circuit board obtained from the laminated board for circuit boards described above will be described.
FIG. 4 shows an embodiment of a metal base circuit board. A metal base circuit board 1 ′ shown in FIG. 4 is obtained from the circuit board laminate 1 shown in FIGS. 2 and 3, and includes a metal board 2, an insulating layer 3, and a circuit pattern 4 ′. It is out. The circuit pattern 4 ′ is obtained by patterning the metal foil 4 of the circuit board laminate described with reference to FIGS. 2 and 3. This patterning can be obtained, for example, by forming a mask pattern on the metal foil 4 and removing the exposed portion of the metal foil 4 by etching. The metal base circuit board 1 ′ can be obtained, for example, by performing the above-described patterning on the metal foil 4 of the circuit board laminate 1 and performing processing such as cutting and drilling as necessary. it can.

Since the metal base circuit board according to the embodiment is obtained from the above-described laminated board for circuit boards, it is excellent in low water absorption, workability, and oxidation deterioration resistance.

FIG. 5 shows a power module according to an embodiment. Since the power module 100 includes the metal base circuit board 13 according to an embodiment of the present invention including the metal substrate 13c, the insulating layer 13b, and the circuit pattern 13a, the power module 100 has low water absorption, workability, and oxidation deterioration resistance. Excellent. In the present situation where the heat generation temperature tends to increase as the performance of power devices increases, the module of the present invention can be suitably used even in a temperature region that cannot be handled by conventional power modules.

Furthermore, the power module 100 according to the embodiment has fewer constituent members (layers) by providing the metal base circuit board 13 as compared with the conventional power module 200 shown as an example in FIG. Since it becomes thinner, a compact design with lower thermal resistance becomes possible. In addition, there is a merit that assembly is easy because processing such as drilling and cutting is easy.

Examples of the present invention will be described below. The present invention is not limited to these.
<Preparation of composition>
Synthesis Examples 1 to 6: Preparation of Resin Compositions 1 to 6 Bisphenol-type cyanate resin (hereinafter also referred to as “B-type cyanate resin”) (trade name “BA200”; manufactured by Lonza Japan Co., Ltd.) and novolak-type cyanate resin (Hereinafter also referred to as “N-type cyanate resin”) (trade name “PT30”; manufactured by Lonza Japan Co., Ltd.) was mixed such that B-type cyanate resin: N-type cyanate resin = 9: 1 by mass ratio. . 10 parts by mass of a Pd-type benzoxazine compound represented by the following formula (trade name “Pd-type benzoxazine”; manufactured by Shikoku Kasei Kogyo Co., Ltd.) as a curing accelerator for 100 parts by mass of the resulting cyanate resin mixture. The mixture was added, stirred at 100 ° C. until the mixture became homogeneous, and was made into a solution with the solvent methyl ethyl ketone (MEK).

Into the obtained resin solution, rubber (acrylic ester copolymer whose polymer main chain is a saturated bond) is added to 1, 5, 10, 20, and 100 parts by mass of the entire resin component (including the rubber), respectively. 30 to 40 parts by mass and a 1: 1 (mass ratio) mixture of aluminum nitride (AlN) and boron nitride (BN) as a filler (inorganic filler) to a total volume of 65% by volume with respect to the entire resin component Resin compositions 1 to 6 were prepared by dispersing as described above.

Synthesis Example 7: Preparation of Resin Composition 1R Mass ratio of B-type cyanate resin (trade name “BA200”; manufactured by Lonza Japan Co., Ltd.) and N-type cyanate resin (trade name “PT30”; manufactured by Lonza Japan Co., Ltd.) Were mixed so that B type cyanate resin: N type cyanate resin = 9: 1. 10 parts by mass of a Pd-type benzoxazine compound represented by the above formula (trade name “Pd-type benzoxazine”; manufactured by Shikoku Kasei Kogyo Co., Ltd.) as a curing accelerator with respect to 100 parts by mass of the resulting mixture of cyanate resin. The mixture was added, stirred at 100 ° C. until the mixture became homogeneous, and was made into a solution with the solvent ethylene glycol monomethyl ether.

By dispersing a 1: 1 (mass ratio) mixture of aluminum nitride (AlN) and boron nitride (BN) in the obtained resin solution so that the total amount is 65% by volume with respect to the entire resin component. Resin composition 1R was prepared.

Synthesis Example 8: Preparation of Resin Composition 2R Add 10 parts by mass of phenoxy resin (trade name “YP-50”; manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) to 90 parts by mass of the cyanate resin mixture until uniform. A resin composition 2R was prepared in the same manner as the resin composition 1R, except that it was mixed.

Synthesis Example 9: Preparation of Composition 3R Acrylic rubber particles (trade name “Unipowder”; manufactured by JX Energy Co., Ltd.) were added in an amount of 10 parts by mass to 90 parts by mass of the cyanate resin mixture, and mixed until uniform. Except for the above, a resin composition 3R was prepared in the same manner as the resin composition 1R.

The obtained resin compositions 1 to 6, 1R to 3R are shown in Table 1. In addition, the weight average molecular weight of rubber | gum is a polystyrene conversion value measured by GPC method.

<Manufacture of laminates>
Each resin composition prepared above was applied to a copper foil for circuits so that the thickness after heating and pressing was 100 μm. Next, after the solvent was dried, it was bonded to a copper plate as a base and subjected to heat and pressure molding to produce a laminated plate.

<Confirmation of phase separation structure>
The presence or absence of the phase separation structure of the present invention in the insulating layer was confirmed by observing the cross section of the insulating layer with a scanning electron microscope.

As a result, the same phase separation structure as in FIG. 1B was confirmed in the insulating layers (Examples 1 to 6) using any of the resin compositions 1 to 6. On the other hand, no phase separation structure was confirmed in the insulating layers (Comparative Example 1 and Comparative Example 2) using the resin composition 1R or 2R. Further, in the insulating layer (Comparative Example 3) using the resin composition 3R, the same phase separation structure (reverse phase separation structure) as in FIG. 1E was confirmed.

Furthermore, the presence or absence of the phase separation structure of the present invention in the insulating layer was also confirmed by analysis means using DMA measurement.
In the DMA measurement, a circuit copper foil and a base copper plate were removed from each laminated plate by etching, and the obtained insulating layer was cut into a strip shape having a width of 3 mm and a length of 50 mm as a sample. The measurement conditions were that the temperature was raised from -50 ° C. to 350 ° C. at a rate of 5 ° C./min, and the measurement was performed in a frequency of 1 Hz and a tensile mode. The ratio between the storage elastic modulus and the loss elastic modulus thus obtained was defined as tan δ.

FIG. 7A is a graph showing the behavior of tan σ obtained by DMA measurement for an insulating layer (Example 3) using the resin composition 3, and FIG. 7B shows an insulating layer using the resin composition 3R ( It is a graph which shows the behavior of tan-sigma obtained by DMA measurement about the comparative example 3).

In the graph shown in FIG. 7A, a peak T ₁ derived from a thermosetting resin (cyanate resin) and a peak T ₂ derived from rubber are detected, and it can be seen that the phase separation structure of the present invention is formed. On the other hand, in the graph shown in FIG. 7B, since the peak derived from rubber is not detected, the added acrylic rubber particles do not form a continuous phase and are in a dispersed state as a discontinuous phase. It can be seen that no phase separation structure is formed.

In the DMA measurement for the insulating layers (Examples 1, 2, 4 to 6) using any one of the resin compositions 1, 2, 4 to 6, the thermosetting resin (cyanate resin) is derived as in FIG. 7A. Peak T ₁ and rubber-derived peak T ₂ were detected, and it was confirmed that the phase separation structure of the present invention was formed.

The results are shown in Table 2, where A is the phase separation structure of the present invention and B is the phase separation structure is not formed.

<Evaluation>
The processability, water absorption, water absorption solder withstand voltage, and heat resistant adhesive strength were evaluated by the following methods. The results are shown in Table 2. In addition, it shows that it is excellent in low water absorption, so that a water absorption is small and a water absorption solder withstand voltage is large. Moreover, it shows that it is excellent in oxidation deterioration resistance, so that heat resistant adhesive force is large.

[Machinability]
As for workability, the presence or absence of a coating film was visually observed when a dry film formed by applying each resin composition to a circuit copper foil and drying it was cut by shearing.
The results are shown in Table 2, with A indicating that the dry film was not chipped and B indicating that the dry film was chipped.
In addition, it turns out that what was not chipped in the dry film is excellent in workability, and further, it can be seen that an insulating layer obtained by curing the dry film is also excellent in workability.
[Water absorption (mass%)]
After removing the circuit copper foil and the base copper plate by etching from each laminated plate, the water absorption of the obtained insulating layer was measured by the following method.

After drying at a temperature of 100 ° C. for 24 hours, the mass of the insulating layer was measured. Thereafter, after absorbing moisture for 24 hours under the conditions of a temperature of 85 ° C. and a humidity of 85%, the mass of the insulating layer was measured again. The mass increase rate before and after moisture absorption was calculated, and this was taken as the water absorption rate.

[Water absorption solder withstand voltage (kV)]
The circuit copper foil surface of each laminate was etched to form a circuit pattern of φ20 mm. This circuit pattern was allowed to absorb water in an atmosphere of 40 ° C. and 98% for 24 hours. Next, after floating in a solder bath at 280 ° C. for 5 minutes, the breakdown voltage was measured by the following method to obtain a water-absorbing solder withstand voltage.

Measure the withstand voltage by applying an AC voltage in insulating oil between the circuit pattern of φ20mm and the copper plate on the back side. While repeating the operation of increasing the voltage by 500 V from the start voltage and applying each voltage for 20 seconds, the step-up voltage was measured and the breakdown voltage was measured.

[Heat resistant adhesive strength (MPa)]
The circuit copper foil surface of each laminate was etched to form a φ4 mm circuit pattern. The circuit pattern was allowed to stand at 200 ° C. for 1000 hours in an air atmosphere, and then the heat resistance adhesion was obtained by measuring the vertical peeling strength of the circuit pattern by the following method.

A stud pin with an epoxy adhesive was fixed vertically on a φ4 mm circuit pattern, and was cured and adhered by heating at 150 ° C. for 1 hour to prepare a sample for a tensile test. Next, the sample was fixed to a tensile tester, the stud pin was pulled in the vertical direction, and the adhesive strength was calculated from the load and adhesive area when the circuit pattern was peeled, thereby measuring the vertical peeling strength of the circuit pattern.

From Table 2, it can be seen that Examples 1 to 6 according to the embodiment of the present invention are excellent in workability.
In addition, it can be seen that Examples 1 to 6 according to the embodiment of the present invention are excellent in low water absorption because the water absorption rate is small and the water-absorbing solder withstand voltage is large.
In addition, it can be seen that Examples 1 to 6 according to the embodiment of the present invention have excellent resistance to oxidation and deterioration because of their high heat-resistant adhesive strength.

Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention in the implementation stage. In addition, the embodiments may be appropriately combined as much as possible, and in that case, the combined effect can be obtained. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be obtained as an invention.

DESCRIPTION OF SYMBOLS 1 Circuit board laminated board 1 'Metal base circuit board 2 Metal board 3 Insulating layer 4 Metal foil 4' Circuit pattern 100 Power module 11 Power device 12 Solder layer 13 Metal base circuit board 13a Circuit pattern 13b Insulating layer 13c Metal board 14 Heat dissipation Sheet 15 Heat Sink 200 Conventional Power Module 21 Power Device 22 First Solder Layer 23 Circuit Pattern 24 Ceramic Substrate 25 Metallized Layer 26 Second Solder Layer 27 Metal Substrate 28 Heat Dissipating Sheet 29 Heat Sink 101 Continuous Phase (Rubber)
102 Discontinuous phase (thermosetting resin)
103a Inorganic filler (aluminum nitride)
103b Inorganic filler (boron nitride)
111 Continuous phase (thermosetting resin)
112 Discontinuous phase (rubber particles)
113a Inorganic filler (alumina)
113b Inorganic filler (boron nitride)
121 Continuous phase (thermosetting resin)
123a Inorganic filler (aluminum nitride)
123b Inorganic filler (boron nitride)

Claims (10)

1. A circuit board laminate comprising a metal substrate, an insulating layer provided on at least one side of the metal substrate, and a metal foil provided on the insulating layer, the insulating layer comprising a resin component and an inorganic filling A laminate for a circuit board, wherein the resin component has a phase separation structure including a discontinuous phase containing a thermosetting resin and a continuous phase containing rubber.
2. The circuit board laminate according to claim 1, wherein the rubber contains at least a rubber having a weight average molecular weight of 1.5 million or less.
3. The circuit board laminate according to claim 1 or 2, wherein the rubber contains at least a rubber having a saturated structure as a main chain.
4. The circuit board laminate according to any one of claims 1 to 3, wherein the rubber contains at least acrylic rubber.
5. The circuit board laminate according to any one of claims 1 to 4, wherein a compounding ratio of the rubber in the insulating layer is 1 to 40 mass% with respect to a total mass of the resin component.
6. The circuit board laminate according to any one of claims 1 to 5, wherein the thermosetting resin contains at least a cyanate resin.
7. The circuit board laminate according to any one of claims 1 to 6, wherein the thermosetting resin contains a bisphenol type cyanate resin and a novolac type cyanate resin.
8. The circuit board laminate according to any one of claims 1 to 7, wherein a compounding ratio of the epoxy resin as the thermosetting resin is 0 to 10% by mass with respect to a total mass of the thermosetting resin. Board.
9. A metal base circuit board obtained by patterning the metal foil included in the laminated board for a circuit board according to any one of claims 1 to 8.
10. A power module comprising the metal base circuit board according to claim 9.

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