JP7625530B2 - Insulating resin composition, cured insulating resin body, laminate and circuit board - Google Patents

Description

The present invention relates to an insulating resin composition and its cured product that are suitable for use in the manufacture of metal-based circuit boards. The present invention also relates to a laminate and a circuit board formed using the insulating resin composition.

A variety of circuit boards have been put to practical use as circuit boards for mounting semiconductor elements and other electronic and electrical components to form hybrid integrated circuits. Circuit boards are classified based on the board material into resin circuit boards, ceramic circuit boards, metal-based circuit boards, etc.

Resin circuit boards are inexpensive, but because the thermal conductivity of the board is low, their use is limited to applications requiring relatively low power. Ceramic circuit boards are suitable for applications requiring relatively high power due to the high electrical insulation and heat resistance characteristics of ceramics, but they have the disadvantage of being expensive. On the other hand, metal-based circuit boards have properties intermediate between the two, and are suitable for general-purpose applications requiring relatively high power, such as power sources for refrigerators, home air conditioners, automobiles, and high-speed trains.

For example, Patent Document 1 discloses a method for obtaining a circuit board having excellent stress relaxation properties, heat resistance, moisture resistance and heat dissipation properties by using a composition for circuit boards whose essential components are a specific epoxy resin, a curing agent and an inorganic filler.

JP 2008-266535 A

In recent years, the popularity of plug-in hybrid vehicles, electric vehicles, and the like has led to an increased demand for automotive quick chargers. Circuit boards used in these charger applications are used at higher voltages than conventional automotive circuit boards, and so require higher moisture-resistant adhesion and moisture-resistant insulation, as well as thermal conductivity and heat cycle resistance equal to or greater than those of conventional automotive circuit boards.

One method for improving the heat cycle resistance of circuit boards is to reduce the elastic modulus of the insulating layer to relieve thermal stress and thereby inhibit the progression of solder cracks. However, when the elastic modulus of the insulating layer is reduced, the adhesive strength between the metal foil and the insulating layer is likely to decrease under conditions of high temperature and high humidity and application of DC voltage, which may cause the metal foil to bulge.

The present invention aims to provide an insulating resin composition and its cured product capable of forming an insulating layer that has both excellent adhesion and insulating properties and a low elastic modulus in a high-temperature, high-humidity environment. The present invention also aims to provide a circuit board that has an insulating layer composed of a cured product of the insulating resin composition and has excellent moisture-resistant insulation, thermal conductivity, and heat cycle resistance.

One aspect of the present invention relates to an insulating resin composition containing an organic material and an inorganic filler. In this insulating resin composition, the organic material contains an epoxy resin, a curing agent, a phosphate ester compound having one or more hydroxyl groups in one molecule, a heavy metal deactivator, and a hindered phenol-based antioxidant, and the content of the inorganic filler is 50% by mass or more and 95% by mass or less.

In one embodiment, the curing agent may be an amine-based curing agent.

In one embodiment, the amine-based curing agent may contain a first amine-based curing agent having an amine equivalent of 300 or less and a second amine-based curing agent having an amine equivalent of 800 or more.

In one aspect, the content of the heavy metal deactivator may be 0.01 to 0.5 mass% based on the total amount of the organic material and the inorganic filler.

In one aspect, the content of the hindered phenol-based antioxidant may be 0.05 to 5 mass % based on the total amount of the organic material.

In one aspect, the content of the phosphate ester compound may be 0.05 to 0.4 mass% based on the total amount of the organic material and the inorganic filler.

In one aspect, the melting point of the heavy metal deactivator may be 250°C or lower.

Another aspect of the present invention relates to an insulating resin cured body, which is a cured body of the above-mentioned insulating resin composition.

In one embodiment, the insulating resin cured body may have a storage modulus of 500 MPa or less at 85°C.

Yet another aspect of the present invention relates to a laminate comprising a metal plate, the cured insulating resin body disposed on the metal plate, and a metal foil disposed on the cured insulating resin body.

Yet another aspect of the present invention relates to a circuit board comprising a metal plate, the cured insulating resin body disposed on the metal plate, and a circuit portion disposed on the cured insulating resin body.

According to the present invention, there is provided an insulating resin composition capable of forming an insulating layer that has both excellent adhesion and insulating properties in a high-temperature, high-humidity environment and a low elastic modulus, and a cured product thereof. According to the present invention, there is also provided a circuit board having an insulating layer composed of a cured product of the insulating resin composition, and having excellent moisture-resistant insulation, thermal conductivity, and heat cycle resistance.

FIG. 1 is a cross-sectional view showing one embodiment of a laminate. FIG. 2 is a cross-sectional view illustrating an embodiment of a circuit board.

A preferred embodiment of the present invention is described in detail below.

(Insulating resin composition)
The insulating resin composition of the present embodiment is a composition containing an organic material and an inorganic filler, and the content of the inorganic filler is 50% by mass or more and 95% by mass or less. The insulating resin composition of the present embodiment also contains, as the organic material, an epoxy resin, a curing agent, a phosphoric acid ester compound having one or more hydroxyl groups in one molecule, a heavy metal deactivator, and a hindered phenol-based antioxidant.

The insulating resin composition can form a cured body (insulating layer) that has excellent adhesion and insulating properties in a high-temperature, high-humidity environment and a low elastic modulus. Therefore, the insulating resin composition can be suitably used to form an insulating layer for a circuit board (particularly a metal-based circuit board). The reason why the above effect is achieved in this embodiment is not necessarily clear, but is thought to be as follows.

In this embodiment, the phosphate ester compound is believed to improve the dispersibility and adhesion between the resin component and the inorganic filler due to the presence of hydroxyl groups in the molecule, thereby improving moisture-resistant adhesion. In addition, the phosphate ester compound is believed to suppress the decrease in moisture-resistant insulation caused by oxidative deterioration of the insulating layer by trapping OH radicals that are generated under conditions of high temperature and high humidity and application of DC voltage.

In addition, in this embodiment, the hindered phenol-based antioxidant also plays a role in trapping radicals, and through interaction with the phosphate ester compound, it is believed that the oxidative deterioration of the insulating layer is more significantly suppressed, thereby further improving the moisture-resistant insulating properties.

In addition, migration of ionic impurities into the insulating layer is considered to be a cause of the deterioration of adhesion and insulation, but in this embodiment, the heavy metal deactivator captures metal ions, suppressing the adverse effects of migration. In particular, when a metal plate such as a metal-based circuit board is adjacent to an insulating layer, metal ions (e.g., copper ions) may leach from the metal plate to the insulating layer, but the insulating resin composition of this embodiment can form an insulating layer that can maintain excellent moisture-resistant adhesion and moisture-resistant insulation even when adjacent to a metal plate.

In this embodiment, a cross-linked structure is formed in the cured body by the epoxy resin and the amine-based curing agent, which is believed to reduce the elastic modulus of the cured body while significantly obtaining the effects of the above-mentioned phosphate ester compound, hindered phenol-based antioxidant, and heavy metal deactivator.

The epoxy resin may be any that is cured by an amine-based curing agent to exhibit an adhesive effect. Examples of epoxy resins include bifunctional epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol A/F type epoxy resin; novolac type epoxy resins such as phenol novolac type epoxy resin and cresol novolac type epoxy resin; multifunctional epoxy resins such as trisphenol methane type epoxy resin; glycidyl amine type epoxy resin; heterocyclic epoxy resins such as triglycidyl isocyanurate, hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, and other alicyclic epoxy resins.

As the epoxy resin, among the above, a bifunctional epoxy resin (bifunctional aromatic epoxy resin) and an alicyclic epoxy resin can be preferably used. By using these epoxy resins, the heat cycle resistance of the circuit board tends to be further improved. The insulating resin composition according to the present embodiment may contain at least one of a bifunctional epoxy resin and an alicyclic epoxy resin, or may contain both a bifunctional epoxy resin and an alicyclic epoxy resin.

When the insulating resin composition contains a difunctional epoxy resin and an alicyclic epoxy resin, the ratio (A ₂ /A ₁ , mass ratio) of the content A ₂ of the alicyclic epoxy resin to the content A ₁ of the difunctional epoxy resin may be, for example, 1.5 or more, preferably 2.0 or more, more preferably 2.5 or more. This tends to further improve the heat cycle resistance of the circuit board. In addition, the ratio (A ₂ /A ₁ , mass ratio) may be, for example, 8.0 or less, preferably 6.0 or less, more preferably 4.0 or less. This tends to further improve the insulating properties and adhesive properties of the cured body. That is, the ratio (A ₂ /A ₁ , mass ratio) may be, for example, 1.5 to 8.0, 1.5 to 6.0, 1.5 to 4.0, 2.0 to 8.0, 2.0 to 6.0, 2.0 to 4.0, 2.5 to 8.0, 2.5 to 6.0, or 2.5 to 4.0.

The content of the epoxy resin in the insulating resin composition may be, for example, 50% by mass or more, preferably 55% by mass or more, more preferably 60% by mass or more, and even more preferably 65% by mass or more, based on the total amount of the organic material. The content of the epoxy resin may be, for example, 90% by mass or less, preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less, based on the total amount of the organic material. That is, the content of the epoxy resin in the insulating resin composition may be, for example, 50 to 90 mass%, 50 to 85 mass%, 50 to 80 mass%, 50 to 75 mass%, 55 to 90 mass%, 55 to 85 mass%, 55 to 80 mass%, 55 to 75 mass%, 60 to 90 mass%, 60 to 85 mass%, 60 to 80 mass%, 60 to 75 mass%, 65 to 90 mass%, 65 to 85 mass%, 65 to 80 mass%, or 65 to 75 mass%, based on the total amount of the organic material.

The curing agent may be any curing agent capable of curing epoxy resin. Examples of the curing agent include amine-based curing agents, phenol-based curing agents, and acid anhydride-based curing agents. Among these, amine-based curing agents are preferred from the viewpoint of further improving moisture-resistant adhesion and moisture-resistant insulation.

The amine-based hardener may be any hardener that has an amino group and can harden epoxy resins. Examples of the amine-based hardener include aromatic amine-based hardeners, aliphatic amine-based hardeners, and dicyandiamide.

As an amine-based curing agent, an aliphatic amine-based curing agent is preferred from the viewpoint of further improving the heat cycle resistance of the circuit board.

The amine-based curing agent preferably contains a first amine-based curing agent having an amine equivalent of 300 or less and a second amine-based curing agent having an amine equivalent of 800 or more. By using two types of amine-based curing agents with different amine equivalents in combination, the crosslinked structure of the epoxy resin becomes coarse and dense during curing, and the elastic modulus of the cured body tends to decrease further.

The amine-based curing agent preferably contains an amine-based curing agent having a polyether chain, more preferably at least one of the first amine-based curing agent and the second amine-based curing agent has a polyether chain, and even more preferably both the first amine-based curing agent and the second amine-based curing agent have a polyether chain. Since an amine-based curing agent having a polyether chain has excellent compatibility with epoxy resins, the use of such an amine-based curing agent makes it easier to obtain a cured product with even better adhesion and heat resistance. The polyether chain is preferably a polyoxyalkylene chain, more preferably a polyoxyalkylene chain having an alkylene group selected from the group consisting of an ethylene group and a propylene group.

It is preferable that the first amine-based hardener and the second amine-based hardener are both aliphatic amine-based hardeners.

It is preferable that the first amine-based curing agent and the second amine-based curing agent are both curing agents having two amino groups in one molecule.

The ratio (B ₂ /B ₁ , mass ratio) of the content B ₂ of the second amine curing agent to the content B ₁ of the first amine curing agent in the insulating resin composition may be, for example, 0.2 or more, preferably 0.25 or more, more preferably 0.3 or more. This tends to further improve the heat cycle resistance of the circuit board. In addition, the ratio (B ₂ /B ₁ , mass ratio) may be, for example, 2.0 or less, preferably 1.5 or less, more preferably 1.0 or less. This tends to further improve the insulation, adhesion, and heat resistance of the cured body. That is, the ratio (B ₂ /B ₁ , mass ratio) may be, for example, 0.2 to 2.0, 0.2 to 1.5, 0.2 to 1.0, 0.25 to 2.0, 0.25 to 1.5, 0.25 to 1.0, 0.3 to 2.0, 0.3 to 1.5, or 0.3 to 1.0.

The amount of curing agent to be added may be determined based on the ratio (C ₂ /C ₁ ) of the active hydrogen equivalent (or acid anhydride equivalent) (C ₂ ) of the curing agent to the epoxy equivalent (C ₁ ) of the epoxy resin. The ratio (C ₂ /C ₁ ) is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. The ratio (C ₂ /C ₁ ) is preferably 2.5 or less, more preferably 2.0 or less, and even more preferably 1.5 or less. That is, the ratio (C ₂ /C ₁ ) may be, for example, 0.1 to 2.5, 0.1 to 2.0, 0.1 to 1.5, 0.2 to 2.5, 0.2 to 2.0, 0.2 to 1.5, 0.3 to 2.5, 0.3 to 2.0, or 0.3 to 1.5.

The phosphate ester compound has one or more hydroxyl groups in one molecule. In this embodiment, the phosphate ester compound is considered to have the effect of improving the dispersibility and adhesion between the resin component and the inorganic filler and improving the moisture-resistant adhesion due to the presence of hydroxyl groups in the molecule. In addition, the above-mentioned phosphate ester compound is considered to have the effect of suppressing the decrease in moisture-resistant insulation caused by oxidative deterioration of the insulating layer by trapping OH radicals generated under conditions of high temperature and high humidity environment and application of DC voltage.

It is more preferable that the number of hydroxyl groups in a phosphate ester compound is 1 to 2 per molecule, and even more preferable that the number is 2 per molecule.

It is preferable that the phosphate ester compound has a hydroxyl group bonded directly to the phosphorus atom. It is more preferable that the phosphate ester compound has two hydroxyl groups bonded directly to the phosphorus atom.

The phosphate ester compound preferably contains a polyether chain from the viewpoints of excellent compatibility with the epoxy resin and the curing agent, and further improving adhesion between the inorganic filler and the resin component. The polyether chain is preferably a polyoxyalkylene chain, and more preferably a polyoxyalkylene chain having an alkylene group selected from the group consisting of an ethylene group and a propylene group.

It is preferable that the phosphate ester compound contains an oxycarbonyl group, from the viewpoint of excellent compatibility with the epoxy resin and the curing agent, and further improving adhesion between the inorganic filler and the resin component.

The number average molecular weight of the phosphate ester compound is preferably 200 or more, and more preferably 400 or more. The number average molecular weight of the phosphate ester compound is preferably 2000 or less, and more preferably 1000 or less. The number average molecular weight of the phosphate ester compound indicates a value measured by size exclusion chromatography (GPC). That is, the number average molecular weight of the phosphate ester compound may be, for example, 200 to 2000, 200 to 1000, 400 to 2000, or 400 to 1000.

The phosphate ester compound may be, for example, a compound represented by the following formula (1):

In formula (1), R represents a monovalent group having a polyether chain. R may further have a polyester chain.

The content of the phosphate ester compound in the insulating resin composition may be, for example, 0.05% by mass or more, preferably 0.1% by mass or more, based on the total amount of the organic material and the inorganic filler. This makes the above-mentioned effect of the phosphate ester compound more pronounced. The content of the phosphate ester compound in the insulating resin composition may be, for example, 0.4% by mass or less, preferably 0.3% by mass or less, based on the total amount of the organic material and the inorganic filler. This suppresses the decrease in moisture-resistant insulation and moisture-resistant adhesion caused by moisture absorption and hydrolysis of the phosphate ester compound itself, and tends to further improve the heat cycle resistance of the circuit member. That is, the content of the phosphate ester compound in the insulating resin composition may be, for example, 0.05 to 0.4% by mass, 0.05 to 0.3% by mass, 0.1 to 0.4% by mass, or 0.1 to 0.3% by mass, based on the total amount of the organic material and the inorganic filler.

The heavy metal deactivator may be, for example, one that can chelate and capture metal ions (e.g., copper ions) in the insulating resin composition or its cured body.

As heavy metal deactivators, nitrogen-containing deactivators such as hydrazine-based heavy metal deactivators and triazole-based heavy metal deactivators can be suitably used.

Examples of heavy metal deactivators include dodecanedioic acid bis[N2-(2-hydroxybenzoyl)hydrazide] (product name "CDA-6", manufactured by ADEKA), N-(2H-1,2,4-triazol-5-yl)salicylamide (product name "CDA-1", manufactured by ADEKA), N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine (product name "CDA-10", manufactured by ADEKA), and 3-amino-1,2,4-triazole.

From the viewpoint of improving dispersibility in the insulating resin composition, it is preferable for the heavy metal deactivator to have a low melting point. The melting point of the heavy metal deactivator may be, for example, 250°C or less, preferably 240°C or less, more preferably 230°C or less, and even more preferably 220°C or less.

The content of the heavy metal deactivator in the insulating resin composition may be, for example, 0.01% by mass or more, preferably 0.03% by mass or more, more preferably 0.05% by mass or more, based on the total amount of the organic material and the inorganic filler. This makes the above-mentioned effect of the heavy metal deactivator more pronounced, and tends to further improve the moisture-resistant adhesion. In addition, the content of the heavy metal deactivator in the insulating resin composition may be, for example, 0.5% by mass or less, preferably 0.3% by mass or less, more preferably 0.2% by mass or less, based on the total amount of the organic material and the inorganic filler. This further improves the coatability of the insulating resin composition, and tends to further improve the moisture-resistant insulation and reliability of the circuit board. That is, the content of the heavy metal deactivator in the insulating resin composition may be, for example, 0.01 to 0.5 mass%, 0.01 to 0.3 mass%, 0.01 to 0.2 mass%, 0.03 to 0.5 mass%, 0.03 to 0.3 mass%, 0.03 to 0.2 mass%, 0.05 to 0.5 mass%, 0.05 to 0.3 mass%, or 0.05 to 0.2 mass%, based on the total amount of the organic material and the inorganic filler.

The hindered phenol-based antioxidant may be any compound having a hindered phenol structure. By having a hindered phenol structure, the compound is less likely to decompose (e.g., hydrolyze) even in a high-temperature, high-humidity environment, and the adverse effect of the decomposition on moisture resistance is suppressed.

Examples of hindered phenol-based antioxidants include compounds represented by the following formula (2-1), compounds represented by the following formula (2-2), and compounds represented by the following formula (2-3).

In the formula, R ¹ represents an alkyl group having 1 to 25 carbon atoms (preferably an alkyl group having 10 to 20 carbon atoms).

The content of the hindered phenol-based antioxidant in the insulating resin composition may be, for example, 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.15% by mass or more, based on the total amount of the organic material. This makes the above-mentioned effects of the hindered phenol-based antioxidant more pronounced, and tends to further improve the moisture-resistant adhesion and moisture-resistant insulation. The content of the hindered phenol-based antioxidant in the insulating resin composition may be, for example, 10% by mass or less, preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 4% by mass or less, based on the total amount of the organic material. This tends to further improve the thermal conductivity of the insulating resin composition. That is, the content of the hindered phenol-based antioxidant in the insulating resin composition may be, for example, 0.01 to 10 mass%, 0.01 to 7 mass%, 0.01 to 5 mass%, 0.01 to 4 mass%, 0.05 to 10 mass%, 0.05 to 7 mass%, 0.05 to 5 mass%, 0.05 to 4 mass%, 0.1 to 10 mass%, 0.1 to 7 mass%, 0.1 to 5 mass%, 0.1 to 4 mass%, 0.15 to 10 mass%, 0.15 to 7 mass%, 0.15 to 5 mass%, or 0.15 to 4 mass%, based on the total amount of the organic material.

The insulating resin composition may further contain other components as organic materials in addition to the above.
Examples of other components include surface modifiers such as coupling agents, leveling agents, defoamers, wetting agents, stabilizers, and curing accelerators.

The inorganic filler is not particularly limited, and any known inorganic filler used in applications requiring insulation and thermal conductivity can be used without any particular restrictions.

Examples of inorganic fillers include inorganic fillers composed of aluminum oxide, silica, aluminum nitride, silicon nitride, boron nitride, etc.

From the viewpoint of suppressing the decrease in moisture-resistant insulating property caused by hydrolysis of the inorganic material, it is preferable that the inorganic filler contains as a main component an inorganic material selected from the group consisting of aluminum oxide, silica, silicon nitride, and boron nitride. The content of the inorganic material in the inorganic filler is preferably 60 mass% or more, more preferably 70 mass% or more, and even more preferably 80 mass% or more, based on the total amount of the inorganic filler.

For example, when the inorganic filler contains a large amount of aluminum nitride, hydrolysis of the aluminum nitride may occur in a high-temperature and high-humidity environment, resulting in a decrease in insulating properties. For this reason, the content of aluminum nitride in the inorganic filler is preferably 40 mass% or less, more preferably 30 mass% or less, and even more preferably 20 mass% or less, based on the total amount of the inorganic filler. As described above, by using an inorganic material selected from the group consisting of aluminum oxide, silica, silicon nitride, and boron nitride as the main component, the decrease in insulating properties caused by such hydrolysis is significantly suppressed.

The shape of the inorganic filler is not particularly limited and may be particulate, scaly, polygonal, etc., and is preferably particulate.

The maximum particle size of the inorganic filler may be, for example, 250 μm or less, preferably 200 μm or less, more preferably 150 μm or less. This tends to further improve the insulation of the cured body. The minimum particle size of the inorganic filler is not particularly limited, but from the viewpoint of further improving the thermal conductivity, it may be, for example, 0.05 μm or more, preferably 0.1 μm or more. In this specification, the maximum particle size and minimum particle size of the inorganic filler refer to the d90 diameter and d10 diameter in the volume-based particle size distribution, which are measured by a laser diffraction particle size distribution measuring device.

The inorganic filler may contain two or more inorganic fillers with different average particle diameters. For example, the inorganic filler may contain a first inorganic filler with an average particle diameter of 25 μm or more and a second inorganic filler with an average particle diameter of 4 μm or less. With such an inorganic filler, the gaps in the first inorganic filler are filled with the second inorganic filler, thereby increasing the packing density and further improving the thermal conductivity of the hardened body. In this specification, the average particle diameter of the inorganic filler refers to the d50 diameter in the volume-based particle size distribution. The volume-based particle size distribution is measured using a laser diffraction particle size distribution measuring device.

The average particle diameter of the first inorganic filler is preferably 30 μm or more, more preferably 40 μm or more. The average particle diameter of the first inorganic filler may be, for example, 200 μm or less, preferably 150 μm or less. With such an average particle diameter, the above-mentioned effects are more pronounced. That is, the average particle diameter of the first inorganic filler may be, for example, 30 to 200 μm, 30 to 150 μm, 40 to 200 μm, or 40 to 150 μm.

The average particle diameter of the second inorganic filler is preferably 3.5 μm or less, more preferably 3 μm or less. The average particle diameter of the second inorganic filler may be, for example, 0.05 μm or more, preferably 0.1 μm or more. This makes the above-mentioned effects more pronounced. That is, the average particle diameter of the second inorganic filler may be, for example, 0.05 to 3.5 μm, 0.05 to 3 μm, 0.1 to 3.5 μm, or 0.1 to 3 μm.

The inorganic filler may further contain a third inorganic filler having an average particle diameter of more than 4 μm and less than 25 μm. Such a third inorganic filler makes the above-mentioned effects more pronounced.

The content of the inorganic filler in the insulating resin composition is 50% by mass or more, preferably 55% by mass or more, more preferably 60% by mass or more, based on the total amount of the insulating resin composition. This tends to further improve the moisture-resistant adhesion and thermal conductivity of the cured body. In addition, the content of the inorganic filler in the insulating resin composition is 95% by mass or less, preferably 90% by mass or less, more preferably 85% by mass or less, based on the total amount of the insulating resin composition. This makes it easier to obtain a cured body with improved adhesion and insulation properties in a high-temperature and high-humidity environment, and tends to further improve the heat cycle resistance of the circuit board. That is, the content of the inorganic filler in the insulating resin composition may be, for example, 50 to 95% by mass, 50 to 90% by mass, 50 to 85% by mass, 55 to 95% by mass, 55 to 90% by mass, 55 to 85% by mass, 60 to 95% by mass, 60 to 90% by mass, or 60 to 85% by mass, based on the total amount of the insulating resin composition.

(Insulating resin hardened body)
The insulating resin cured body according to the present embodiment is a cured body of the insulating resin composition described above. The insulating resin cured body can form an insulating layer that has excellent adhesion and insulating properties in a high-temperature and high-humidity environment and a low elastic modulus.

The storage modulus of the insulating resin cured body at 85°C is preferably 500 MPa or less, more preferably 400 MPa or less, even more preferably 300 MPa or less, and even more preferably 200 MPa or less. Such an insulating resin cured body can realize a circuit board with even better heat cycle resistance.

The method for producing the insulating resin cured body is not particularly limited. For example, the insulating resin cured body can be produced by heat treating the insulating resin composition to harden it. The heat treatment may be carried out in one step or two steps. By carrying out the heat treatment in two steps, the insulating resin cured body can be formed via a semi-cured body of the insulating resin composition.

When the heat treatment is performed in one step, the heat treatment temperature may be, for example, 150 to 250°C, preferably 160 to 240°C, and the heat treatment time may be, for example, 2 to 15 hours, preferably 2.5 to 10 hours.

When the heat treatment is carried out in two stages, the temperature of the first stage heat treatment may be, for example, 60 to 130°C, preferably 65 to 100°C, and the heat treatment time may be, for example, 0.3 to 8 hours, preferably 0.5 to 5 hours. The temperature of the second stage heat treatment may be, for example, 150 to 250°C, preferably 160 to 240°C, and the heat treatment time may be, for example, 2 to 15 hours, preferably 2.5 to 10 hours.

By carrying out a heat treatment while maintaining the insulating resin composition or a semi-cured product thereof in a predetermined shape, it is possible to obtain an insulating resin cured product having a predetermined shape. For example, an insulating resin composition can be applied to a metal plate, metal foil can be laminated thereon as necessary, and the composition can be cured to form a layered insulating resin cured product on the metal plate.

(Laminate)
The laminate according to the present embodiment includes a metal plate, a cured insulating resin body disposed on the metal plate, and a metal foil disposed on the cured insulating resin body. In the laminate according to the present embodiment, the metal plate and the metal foil may be separated by the cured insulating resin body, and the cured insulating resin body may function as an insulating layer.

The metal material constituting the metal plate is not particularly limited, and examples thereof include aluminum, aluminum alloys, copper, copper alloys, iron, stainless steel, etc. The metal plate may be composed of one type of metal material, or may be composed of two or more types of metal materials. In addition, the metal plate may have a single-layer structure or a multi-layer structure.

The thickness of the metal plate is not particularly limited, and may be, for example, 0.5 to 3.0 mm, from the viewpoint of being suitable for producing circuit boards.

The metal material constituting the metal foil is not particularly limited, and examples include copper, aluminum, nickel, etc. The metal foil may be composed of one type of metal material, or may be composed of two or more types of metal materials. In addition, the metal foil may have a single-layer structure or a multi-layer structure.

The thickness of the metal foil is not particularly limited, and may be, for example, 5 μm to 1 mm, from the viewpoint of being suitable for producing circuit boards.

The thickness of the cured insulating resin body is not particularly limited, and may be, for example, 50 μm to 300 μm from the viewpoint of being suitable for producing circuit boards.

The method for producing the laminate is not particularly limited. For example, the laminate can be produced by a method including a step of applying an insulating resin composition onto a metal plate and curing or semi-curing the composition, and a step of bonding a metal foil onto the cured or semi-cured insulating resin composition (i.e., an insulating resin cured body or semi-cured body). The method may further include a step of curing the semi-cured body of the insulating resin composition. The bonding of the metal foil may be performed by, for example, a roll lamination method, a lamination press method, or the like.

The laminate can also be produced by a method including the steps of applying an insulating resin composition onto a metal foil and curing or semi-curing the composition, and bonding a metal plate onto the cured or semi-cured insulating resin composition (i.e., the insulating resin cured body or semi-cured body). The method may further include the step of curing the semi-cured body of the insulating resin composition.

Figure 1 is a cross-sectional view showing a preferred embodiment of a laminate. The laminate 10 shown in Figure 1 comprises a metal plate 1, a metal foil 3, and an insulating layer 2 composed of a cured insulating resin interposed between the metal plate 1 and the metal foil 3. By processing the metal foil 3 of the laminate 10 into a predetermined pattern, a circuit board can be easily formed.

(Circuit board)
The circuit board according to the present embodiment includes a metal plate, a cured insulating resin body disposed on the metal plate, and a circuit section disposed on the cured insulating resin body. In the circuit board according to the present embodiment, the metal plate and the circuit section may be separated by the cured insulating resin body, and the cured insulating resin body may function as an insulating layer.

The metal plate can be, for example, the same as the metal plate in the laminate described above.

The circuit portion may be made of a metal material. Examples of the metal material constituting the circuit portion include the same metal material as the metal foil described above. The circuit portion may be the metal foil described above processed into a predetermined pattern.

The thickness of the circuit portion is not particularly limited, and from the standpoint of heat resistance and processability, it may be, for example, 5 μm to 1 mm.

The thickness of the insulating resin cured body is not particularly limited, and may be, for example, 50 μm to 300 μm from the standpoint of thermal conductivity and insulating properties.

The circuit board preferably has a volume resistivity between the circuit part and the metal plate at 85°C and 85% RH of 1.0 x 10 ⁹ Ω·cm or more, and more preferably 5.0 x 10 ⁹ Ω·cm or more, after a DC voltage of 500 V is continuously applied between the circuit part and the metal plate for 1000 hours in an environment of 85°C and 85% RH. Such a circuit board can be said to be a circuit board that is particularly excellent in moisture-resistant insulation.

The method for manufacturing the circuit board is not particularly limited. For example, the circuit board can be manufactured by a method including a step of processing the metal foil of the above-mentioned laminate into a predetermined pattern. The method for processing (etching) the metal foil is not particularly limited, and a conventionally known method may be applied.

Figure 2 is a cross-sectional view showing a preferred embodiment of a circuit board. The circuit board 20 shown in Figure 2 comprises a metal plate 1, a circuit section 4, and an insulating layer 2 composed of a cured insulating resin interposed between the metal plate 1 and the circuit section 4. The circuit board 20 may be, for example, a metal foil 3 of a laminate 10 processed into the circuit section 4.

The above describes a preferred embodiment of the present invention, but the present invention is not limited to the above embodiment.

Example 1
(Synthesis of phosphate ester compounds)
90 g of methoxypropanol and 0.3 g of potassium hydroxide were charged into an autoclave, and after replacing with nitrogen, the temperature was raised to 100°C, and 1,914 g of propylene oxide was injected over 3 hours while stirring. After that, the mixture was stirred at 90 to 100°C for 30 minutes, cooled, neutralized with phosphoric acid water, dehydrated, and filtered to obtain polypropylene glycol monomethyl ether.

400 g of polypropylene glycol monomethyl ether, 100 g of succinic anhydride, and 2 g of tetramethylammonium chloride were charged into an autoclave, and after replacing with nitrogen, the temperature was raised to 100°C, and 58 g of propylene oxide was injected while stirring. After stirring for 2 hours at 100°C, 558 g of an oily product was obtained.

1.8 g of water was added to 558 g of the above oily product, and 14 g of phosphorus pentoxide was added in small portions over about 30 minutes while maintaining the temperature at 50° C. After that, the mixture was stirred at the same temperature for about 1 hour to obtain a phosphate ester compound (P-1) having two hydroxyl groups bonded to the phosphorus atom and having a polyether chain.
The number average molecular weight of the obtained phosphate ester was measured by size exclusion chromatography and found to be 510. The mobile phase was tetrahydrofuran, and the measurement was performed with an RI detector (refractometry) at a flow rate of 1.0 ml/min, and the value was calculated in terms of polystyrene. The hydroxyl groups bonded to the phosphorus atoms were confirmed by comparing the results of size exclusion chromatography of the obtained sample with the results of mass analysis by LC/MS and the results of structural analysis by ¹ H-NMR and ¹³ C-NMR.

(Preparation of insulating resin composition)
Bisphenol A/F type epoxy resin (manufactured by Mitsubishi Chemical Corporation, "YD-6020") 2.2 parts by mass, bisphenol A type hydrogenated epoxy resin (manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd., "YX-8000") 6.7 parts by mass, aliphatic amine (manufactured by Huntsman, "D-400", amine equivalent 200), 2.4 parts by mass, aliphatic amine (manufactured by Huntsman, "D-2000", amine equivalent 1040), 1.6 parts by mass, alumina (manufactured by Denka Company, "DAS45", maximum particle diameter 70 μm, average particle diameter 45 μ m), 30.5 parts by mass of alumina (Denka "DAS10", maximum particle size 21 μm, average particle size 10 μm), 30.5 parts by mass of alumina (Sumitomo Chemical "AA2", maximum particle size 5 μm, average particle size 2 μm), 26.0 parts by mass of alumina (Sumitomo Chemical "AA2", maximum particle size 5 μm, average particle size 2 μm), 0.1 parts by mass of heavy metal deactivator (ADEKA "CDA-6", melting point 212 ° C.), 0.1 parts by mass of hindered phenol-based antioxidant 1 (ADEKA "ADEKA STAB AO-50"), and 0.2 parts by mass of phosphoric acid ester compound (P-1) were added. The mixture was kneaded with a planetary mixer (Thinky "Awatori Rentaro AR-310", rotation speed 2000 rpm) to prepare an insulating resin composition.

(Circuit board manufacturing)
The insulating resin composition was applied onto an aluminum plate having a thickness of 1.5 mm (manufactured by Amano Aluminum Co., Ltd., "A1050 1.5 mm thickness") and dried at 120° C. for 15 minutes to bring the plate into a B-stage (semi-cured) state. The amount of the insulating resin composition applied was adjusted so that the thickness of the insulating layer after curing would be 100 μm.

Then, a 70 μm thick copper foil (manufactured by Furukawa Electric Co., Ltd., "Electrolytic copper foil 70 μm thick") was placed on top of the semi-cured body of the insulating resin composition, and the laminated body was heat-treated at 180°C for 6 hours using a heat press method to harden the semi-cured body, thereby obtaining a laminate.

Next, after masking predetermined positions with an etching resist, the copper foil was etched using a sulfuric acid-hydrogen peroxide mixed solution as an etching solution. The etching resist was removed, and the substrate was washed and dried to obtain a circuit board with a circuit section made of copper foil.

Example 2
The amount of "DAS45" added was changed to 30.4 parts by mass, the amount of "DAS10" added to 30.4 parts by mass, the amount of "AA2" added to 25.8 parts by mass, and the amount of heavy metal deactivator ("CDA-6") added to 0.4 parts by mass. Except for the above, an insulating resin composition and a circuit board were obtained in the same manner as in Example 1.

Example 3
The amount of "YX-8000" added was changed to 1.0 part by mass, and the amount of the heavy metal deactivator ("CDA-6") added was changed to 0.02 part by mass. Except for the above, an insulating resin composition and a circuit board were obtained in the same manner as in Example 1.

Example 4
As a heavy metal deactivator, 0.1 parts by mass of "CDA-10" (manufactured by ADEKA, melting point 227°C) was used instead of "CDA-6". Except for the above, an insulating resin composition and a circuit board were obtained in the same manner as in Example 1.

Example 5
As a heavy metal deactivator, 0.1 parts by mass of "CDA-1" (manufactured by ADEKA, melting point 320°C) was used instead of "CDA-6". Except for the above, an insulating resin composition and a circuit board were obtained in the same manner as in Example 1.

Example 6
An insulating resin composition and a circuit board were obtained in the same manner as in Example 1, except that the amount of the hindered phenol-based antioxidant 1 ("ADK STAB AO-50") added was changed to 0.4 parts by mass.

Example 7
An insulating resin composition and a circuit board were obtained in the same manner as in Example 1, except that the amount of the hindered phenol-based antioxidant 1 ("ADK STAB AO-50") added was changed to 0.02 parts by mass.

Example 8
As a hindered phenol-based antioxidant, 0.1 parts by mass of "ADK STAB AO-60" (manufactured by ADEKA Corporation) was used in place of "ADK STAB AO-50." Except for the above, an insulating resin composition and a circuit board were obtained in the same manner as in Example 1.

<Example 9>
The amount of "YD-6020" added was changed to 1.3 parts by mass, and the amount of "YX8000" added was changed to 7.6 parts by mass. In addition, as the curing agent, 4.0 parts by mass of a novolac curing agent (manufactured by Meiwa Kasei Co., Ltd., "MEH-8000H") was used instead of the amine curing agents ("D-400" and "D-2000"). Except for the above, an insulating resin composition and a circuit board were obtained in the same manner as in Example 1.

Example 10
The amount of "YD-6020" added was changed to 6.9 parts by mass, the amount of "YX8000" added to 20.7 parts by mass, the amount of "D400" added to 7.2 parts by mass, and the amount of "D2000" added to 4.8 parts by mass. In addition, instead of alumina ("DAS45", "DAS10" and "AA2"), 60.3 parts by mass of boron nitride ("XGP" manufactured by Denka Co., Ltd., maximum particle diameter 90 μm, average particle diameter 30 μm) was used. Except for the above, an insulating resin composition and a circuit board were obtained in the same manner as in Example 1.

Example 11
The amount of "YD-6020" added was changed to 1.2 parts by mass, the amount of "YX8000" added to 3.6 parts by mass, the amount of "D400" added to 1.2 parts by mass, the amount of "D2000" added to 0.8 parts by mass, the amount of "DAS45" added to 32.6 parts by mass, the amount of "DAS10" added to 32.6 parts by mass, and the amount of "AA2" added to 27.9 parts by mass. Except for the above, an insulating resin composition and a circuit board were obtained in the same manner as in Example 1.

<Comparative Example 1>
An insulating resin composition and a circuit board were obtained in the same manner as in Example 1, except that no heavy metal deactivator was added.

<Comparative Example 2>
An insulating resin composition and a circuit board were obtained in the same manner as in Example 1, except that no hindered phenol-based antioxidant was added.

<Comparative Example 3>
Instead of the hindered phenol-based antioxidant, 0.1 parts by mass of a phosphorus-based antioxidant (manufactured by ADEKA Corporation, "ADEKA STAB 2112") was used. Except for the above, an insulating resin composition and a circuit board were obtained in the same manner as in Example 1.

<Comparative Example 4>
Instead of alumina ("DAS45", "DAS10" and "AA2"), 12.0 parts by mass of boron nitride ("XGP" manufactured by Denka Company, maximum particle size 90 μm, average particle size 30 μm) was used. Except for the above, an insulating resin composition and a circuit board were obtained in the same manner as in Example 1.

<Comparative Example 5>
The amount of "DAS45" added was changed to 100.0 parts by mass, the amount of "DAS10" added was changed to 100.0 parts by mass, and the amount of "AA2" added was changed to 95.0 parts by mass. Except for the above, an insulating resin composition and a circuit board were obtained in the same manner as in Example 1.

<Comparative Example 6>
An insulating resin composition and a circuit board were obtained in the same manner as in Example 1, except that 0.2 parts by mass of a phosphoric acid ester compound not having a hydroxyl group in the molecule (manufactured by Johoku Chemical Industry Co., Ltd., "JC-224") was added instead of the phosphoric acid ester compound (P-1).

The formulations of the insulating resin compositions of the examples and comparative examples are shown in Tables 1 and 2. The maximum particle size and average particle size of the inorganic fillers used in the examples and comparative examples were determined by the following method.

[Measurement of inorganic filler]
Measurements were performed using a laser diffraction particle size distribution analyzer SALD-200 manufactured by Shimadzu Corporation. Specifically, 50 cc of pure water and 5 g of inorganic filler were added to a glass beaker, stirred with a spatula, and then dispersed in an ultrasonic cleaner for 10 minutes. The inorganic filler dispersion was added drop by drop to the sampler section of the device with a dropper, and the absorbance was allowed to stabilize until it could be measured. Measurements were performed when the absorbance stabilized. In the laser diffraction particle size distribution analyzer, particle size distribution was calculated from the data of the light intensity distribution of diffracted/scattered light by particles detected by the sensor. The maximum particle size was d90, and the average particle size was d50.

The insulating resin compositions obtained in the examples and comparative examples, and the circuit board obtained in Example 1 were evaluated by the following methods. The results are shown in Tables 1 and 2.

[Measurement of storage modulus of insulating resin cured body]
Measurement was performed using "RSA-III" manufactured by TA Instrument. Specifically, the insulating resin composition was applied onto a PET film so that the thickness after curing was 200 μm, and cured by heating at 180° C. for 6 hours to prepare an insulating resin cured body. The prepared insulating resin cured body was processed to a width of 4 mm and a length of 5 cm to obtain a measurement sample. The obtained sample was used to measure the storage modulus at a measurement frequency of 1 Hz, and heated from -50° C. to 150° C. at a heating rate of 7° C./min. The storage modulus at 85° C. was obtained from the measurement results.

[Measurement of thermal conductivity of cured insulating resin]
The thermal conductivity was calculated from the thermal diffusivity, specific gravity and specific heat. Specifically, the thermal conductivity was determined by the laser flash method using a measurement sample obtained by processing the insulating resin cured body to a width of 10 mm, length of 10 mm and thickness of 1 mm. The measurement device used was a xenon flash analyzer (LFA447 NanoFlash manufactured by NETZSCH). The specific gravity was determined by the Archimedes method. The specific heat was determined by using a differential scanning calorimeter (manufactured by TA Instruments, "Q2000") to raise the temperature from room temperature to 300°C at a heating rate of 10°C/min under a nitrogen atmosphere.

[Evaluation of moisture-resistant insulation]
For the laminates obtained in the examples and comparative examples, the copper foil was etched to prepare a circular electrode with a diameter of 20 mm, which was used as a measurement sample. Next, a DC voltage of 500 V was applied between the circular electrode and the metal plate for 1000 hours under conditions of 85°C and 85% RH. After the voltage application, the volume resistivity between the circular electrode and the metal plate was measured at 85°C and 85% RH for the measurement sample. This measurement was performed using an insulation degradation system ("SIR13" manufactured by Kusumoto Chemicals Co., Ltd.).

[Evaluation of Moisture Resistant Adhesion]
For the laminates obtained in the examples and comparative examples, the copper foil was etched to prepare a circular electrode with a diameter of 20 mm, which was used as a measurement sample. Next, a direct current voltage of 500 V was applied between the circular electrode and the metal plate for 2000 hours under the conditions of 85°C and 85% RH. The case where the electrode part had blistered within 1500 hours from the start of voltage application was evaluated as C, the case where the electrode part had blistered between 1500 and 2000 hours was evaluated as A, and the case where the electrode part had not blistered even after 2000 hours was evaluated as AA. The presence or absence of blistering was visually confirmed.

[Evaluation of heat cycle resistance]
For the laminates obtained in the examples and comparative examples, the copper foil was etched to prepare electrodes, which were used as measurement samples. A chip resistor with a chip size of 2.0 mm x 1.25 mm was soldered between the electrodes of the circuit board, and a heat cycle test was performed 2000 times, with one cycle being -40°C for 15 minutes to +150°C for 15 minutes, in accordance with the JIS-C-0025 temperature change test method. The total number of chip resistors was 20 for each example and comparative example. After the test, the presence or absence of cracks in the soldered parts was observed under a microscope. The cases where the cracks in the soldered parts were 30% or more were evaluated as C, the cases where the cracks in the soldered parts were 10% or more but less than 30% were evaluated as A, and the cases where the cracks in the soldered parts were less than 10% were evaluated as AA.

As shown in Tables 1 and 2, in the examples, it was confirmed that an insulating layer having both a low elastic modulus and high thermal conductivity could be formed, and a circuit board having excellent moisture-resistant insulation, moisture-resistant adhesion, and heat cycle resistance could be obtained.

According to the present invention, an insulating layer can be formed that has both excellent adhesion and insulation properties in a high-temperature, high-humidity environment and a low elastic modulus. According to the present invention, a circuit board having the above insulating layer and excellent moisture-resistant insulation, thermal conductivity, and heat cycle resistance can be obtained. Therefore, the present invention can be suitably used in fields where heat cycle resistance, moisture-resistant insulation, heat dissipation, etc. are required (for example, circuit boards for on-board filling machines, etc.).

1...metal plate, 2...insulating layer, 3...metal foil, 4...circuit portion, 10...laminate, 20...circuit board.

Claims (9)

Contains an organic material and an inorganic filler,
the organic material contains an epoxy resin, a curing agent, a phosphoric acid ester compound having one or more hydroxyl groups in one molecule, a heavy metal deactivator, and a hindered phenol-based antioxidant;
The content of the inorganic material selected from the group consisting of aluminum oxide, silica, silicon nitride, and boron nitride in the inorganic filler is 80 mass% or more based on the total amount of the inorganic filler;
The content of the inorganic filler is 50% by mass or more and 95% by mass or less,
the content of the phosphate ester compound is 0.05 to 0.4 mass% based on the total amount of the organic material and the inorganic filler,
The content of the heavy metal deactivator is 0.01 to 0.5 mass% based on the total amount of the organic material and the inorganic filler,
The insulating resin composition has a content of the hindered phenol-based antioxidant of 0.05 to 10 mass % based on the total amount of the organic material . The insulating resin composition according to claim 1, wherein the curing agent is an amine-based curing agent. The amine-based curing agent is
a first amine-based curing agent having an amine equivalent of 300 or less;
a second amine-based curing agent having an amine equivalent of 800 or more;
The insulating resin composition according to claim 2 , comprising: 4. The insulating resin composition according to claim 1, wherein the content of the hindered phenol-based antioxidant is 0.05 to 5 mass % based on the total amount of the organic material. The insulating resin composition according to any one of claims 1 to 4 , wherein the melting point of the heavy metal deactivator is 250°C or lower. An insulating resin cured product, which is a cured product of the insulating resin composition according to any one of claims 1 to 5 . 7. The insulating resin cured product according to claim 6 , which has a storage modulus at 85°C of 500 MPa or less. A metal plate;
The insulating resin cured body according to claim 6 or 7 , which is disposed on the metal plate;
A metal foil disposed on the insulating resin cured body;
A laminate comprising: A metal plate;
The insulating resin cured body according to claim 6 or 7 , which is disposed on the metal plate;
A circuit portion disposed on the insulating resin cured body;
A circuit board comprising:

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