JP2008213426A - Metal foil, metal base circuit board, and method of manufacturing metal base multi-layered circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably supply a circuit board having high heat-radiating property and exhibiting reliability over a long period of time. <P>SOLUTION: In a metal foil with insulating layer formed by providing an insulating layer on one main surface of a metal foil, the insulating layer contains an epoxy resin, a hardening agent, a hardening catalyst and an inorganic filler, and is in B-stage status (semi-hardened status) containing 40 mass% or more of a hydrogenated epoxy resin in the epoxy resin. A metal base circuit board using the metal foil, and a manufacturing method of a metal-based multi-layered circuit board are also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a metal foil used in electronic devices, electrical devices, communication devices, automobiles, etc., a metal base circuit board using the same, and a method for manufacturing a metal base circuit board.

In response to the recent demand for higher density, smaller size, and higher reliability of electronic devices and electrical devices, a prepreg in which a base material such as a glass cloth is impregnated with a thermosetting resin varnish is prepared. A metal foil is placed on the top and bottom, heated and pressed to produce a printed wiring board, a circuit is formed by etching the metal foil to form a circuit board, and a predetermined number of the prepregs are stacked on the outside. A multi-layer substrate is provided by arranging a metal foil and heating and laminating it (see Patent Document 1).

On the other hand, a metal base circuit in which an insulating layer made of an epoxy resin or the like filled with an inorganic filler is provided on a metal plate and a circuit pattern is formed on the metal plate for the purpose of high heat dissipation from electronic components, electrical components, and circuit boards. A board is used as a circuit board for mounting a highly heat-generating electronic component (see Patent Document 2).

Also, a metal-based multilayer circuit board is known in which an insulating layer is formed on a metal base, a metal foil is pasted, and circuitization is formed a plurality of times for the purpose of higher density and higher reliability (Patent Document 3). reference).

JP 2000-95844 A JP-A-62-271442 JP 09-139580 A

However, the prepreg resin of Patent Document 1 has poor heat dissipation, and there is a limit to miniaturization and high density of the printed wiring board. Further, Patent Document 2 has almost no problem with respect to heat dissipation, but cannot be multilayered, so that there is a limit to miniaturization and high density of the printed wiring board. In Patent Document 3, there is a problem that the cured state of the insulating layer changes when it is multilayered. That is, even if there is no problem in the heat and pressure molding immediately after production due to the change over time, the curing time is shortened and the melt viscosity is increased. Therefore, it is difficult to sufficiently fill the resin of the insulating layer into the inner layer circuit, and bubbles and prepreg are peeled off, which causes a problem that the reliability of the printed wiring board such as a dielectric breakdown voltage is remarkably lowered.

As a result of various investigations in order to stably provide a circuit board that has high heat dissipation and can exhibit reliability over a long period of time, in view of the circumstances of the above-described known technology, the present inventors have found that a metal with a specific structure. The knowledge that the object can be achieved by using a foil has been obtained, and the present invention has been achieved.

That is, the present invention is a metal foil with an insulating layer in which an insulating layer is provided on one main surface of the metal foil, the insulating layer containing an epoxy resin, a curing agent, a curing catalyst, and an inorganic filler, A metal foil with an insulating layer, characterized in that the epoxy resin contains 40% by mass or more of an epoxy resin hydrogenated in the epoxy resin. Preferably, the hydrogenated epoxy resin is The metal foil with an insulating layer, wherein the epoxy equivalent is 100 or more and 300 or less, and more preferably, the curing agent is selected from the group consisting of an acid anhydride resin, a phenol resin, and dicinamide. It is the metal foil with an insulating layer, characterized in that it contains more than one kind.

The present invention is the above metal foil with an insulating layer, characterized in that the curing catalyst is an imidazole compound or a phosphorus compound, preferably, the inorganic filler is selected from the group consisting of silicon oxide, aluminum oxide, and aluminum nitride. The metal foil with an insulating layer, characterized in that it is composed of one or more selected, and the filling rate in the insulating layer after curing is 45 volume% or more and 80 volume% or less, more preferably a metal foil The metal foil with an insulating layer, wherein the foil has a thickness of 0.013 mm to 0.450 mm, and more preferably, the thermal conductivity calculated from the thermal resistance of the cured insulating layer is 1.5 W. The metal foil with an insulating layer described above, wherein the metal foil has an insulating layer of / mK or more.

The present invention also provides:
(1) a step of preparing a metal plate,
(2) A step of laminating and integrating the metal foil with an insulating layer according to any one of claims 1 to 7 via an insulating layer on the metal plate,
(3) forming a circuit from the metal foil of the metal foil with an insulating layer;
Is a method of manufacturing a metal base circuit board.

In addition, the present invention provides:
(1) preparing a metal base circuit board or a metal base multilayer circuit board;
(2) A step of laminating and integrating the metal foil with an insulating layer according to any one of claims 1 to 7 via an insulating layer on a circuit of a metal base circuit board or a metal base multilayer circuit board,
(3) forming a circuit from the metal foil of the metal foil with an insulating layer;
A method of manufacturing a metal-based multilayer circuit board comprising, preferably,
(2) The process for producing a metal-based multilayer circuit board according to (2) and (3) is repeated twice or more.

Since the metal foil of the present invention has an insulating layer under a specific state composed of the composition of the specific composition, and after curing, it exhibits a thermal conductivity in a predetermined numerical range, and has a feature with little change with time. It has an effect that it is possible to easily and stably provide a metal base circuit board and a metal base multilayer circuit board that are excellent in heat dissipation.

Since the metal base circuit board manufacturing method of the present invention uses the characteristic metal foil, it is possible to provide a metal base circuit board that is stable, high in productivity, and excellent in heat dissipation.

The method for producing a metal-based multilayer circuit board according to the present invention uses the above-described characteristic metal foil, so that it is possible to provide a metal-based multilayer circuit board that is stable, high in productivity, and excellent in heat dissipation. In addition, according to the present invention, when a highly heat-generating electronic component, which has been difficult in the past, is mounted on a metal-based multilayer circuit board having heat dissipation and electrical insulation, the density of electronic equipment is increased and the size is reduced. Since the change in the metal foil with an insulating layer over time can be reduced, problems associated with integration can be greatly reduced and cost reduction can be achieved.

The metal foil of the present invention has a structure in which an insulating layer is provided on one main surface of the metal foil. The metal foil is used as a metal plate in a metal base circuit board, which will be described later, and may form a circuit by being processed by etching or the like. Therefore, any of copper, aluminum, nickel, iron, tin, silver, and titanium is used. Alternatively, an alloy containing two or more of these metals, or a clad foil using the metal or alloy can be used. In addition, the manufacturing method of the metal foil may be one produced by an electrolytic method or a rolling method, and metal plating such as Ni plating, Ni-Au plating, or solder plating may be applied on the metal foil. From the viewpoint of adhesion to the insulating adhesive, it is more preferable that the surface of the metal foil (circuit) on the side in contact with the insulating adhesive is roughened in advance by etching, plating, or the like. In the present invention, the thickness of the metal foil is preferably 0.013 mm to 0.450 mm. If it is 0.013 mm or more, the thickness is sufficient for normal circuit formation on the circuit board. Although there is no reason to limit the upper limit, applications where the circuit thickness exceeds 0.450 mm are not practical.

The insulating layer provided on the metal foil of the present invention contains an epoxy resin, a curing agent, a curing catalyst, and an inorganic filler, is in a B-stage state, and the epoxy resin is hydrogenated into the epoxy resin. It is characterized by containing 40% by mass or more with respect to 100% by mass of the epoxy resin. By containing 40% by mass or more of the hydrogenated epoxy resin in the epoxy resin, the cured insulating layer can obtain a circuit board having excellent characteristics such as a metal base circuit board obtained after curing, particularly excellent heat dissipation characteristics. it can.

In the present invention, the B stage state (semi-cured state) refers to a state in which there is no tack in a state where the insulating layer is applied and dried and cooled to room temperature, but melts when further heated and pressurized. Further, the curing rate of the epoxy resin in the insulating layer in the B stage state is preferably about 5% to 70%, and more preferably 20% to 60%.

As the epoxy resin used for the insulating layer, bisphenol A, bisphenol F, cresol novolac, dicyclopentadiene, trisphenylmethane, naphthalene, biphenyl type and the like and hydrogenated epoxy resins thereof are generally used. There is no limit to the structure if there is. Moreover, the said epoxy resin can be used by 1 type or multiple types. In particular, when a hydrogenated epoxy resin is used, an epoxy resin obtained by hydrogenating an epoxy resin such as bisphenol A, bisphenol F type, or biphenyl type is preferable.

Moreover, regarding the hydrogenated epoxy resin, it is preferable that epoxy equivalent is 100-300. If the epoxy equivalent is 100 or more, the resin strength after curing is sufficient, and there is no problem with the electrical insulation when it is used as a circuit board. If the epoxy equivalent is 300 or less, the molecular weight is not increased, the viscosity is increased, and the addition of the inorganic filler is not difficult.

As for the curing agent, an acid anhydride resin, a phenol resin, dicinamide, or the like can be used. Moreover, since these can also be used combining 1 type or multiple types, 1 or more types are selected from the group which consists of an acid anhydride type resin, a phenol type resin, and a dicinamide. Of these, amine resins and phenol resins are preferably selected in consideration of the high temperature characteristics of the insulating layer and durability at high temperatures and high humidity. About the compounding quantity of a hardening | curing agent, 35-70 mass% is preferable with respect to 100 mass% of epoxy resins. When the compounding amount of the curing agent is 35 to 70% by mass or more, there is no problem in curing.

As the curing catalyst, an imidazole compound or a phosphorus compound is used, and one kind or a plurality of kinds are used in combination. Although there is no restriction | limiting in particular about addition amount, since it changes with hardening temperature, Generally, it is preferable that it is 0.01 to 5 mass% with respect to 100 mass% of epoxy resins. If it is 0.01 mass% or more, it will harden | cure reliably, and if it is 5 mass% or less, it will not change from a B stage state to a C stage state immediately.

As the inorganic filler, silicon oxide, aluminum oxide, aluminum nitride, silicon nitride, boron nitride, etc. can be used. However, it is spherical and can be filled with high capacity, with low dielectric constant, low thermal expansion coefficient, or semiconductor silicon. It can be selected in consideration of various factors such as close to N, and industrially, at least one selected from the group consisting of silicon oxide, aluminum oxide, aluminum nitride, and boron nitride is preferably selected. About the compounding quantity of an inorganic filler, it is preferable that the filling rate in an insulating layer is 45 volume% or more and 80 volume% or less. When the filling rate is 45% by volume or more, the heat dissipation of the insulating layer is sufficient, and when the filling rate is 80% or less, it is not difficult to form the insulating layer. Preferably, the filling rate is in the range of 50% to 75% by volume.

The insulating layer of the present invention preferably has a high thermal conductivity after curing in consideration of its use. Based on the study of the present inventor, it is preferably 1.5 W / mK or more after curing, preferably 2 W / mK or more, for application to a circuit board on which a semiconductor device such as an LED or the like is mounted. Is more preferable. In the preferred embodiment of the insulating layer of the present invention, a cured product of 1.9 to 6.5 W / mK is obtained.

The metal foil with an insulating layer of the present invention can be obtained by applying an insulating agent to be the insulating layer on the metal foil. As a method for applying the insulating agent to the metal foil, a roll coater or a gravure coater is used. And publicly known methods such as donation coater and screen printing. The insulating layer is usually a single layer or a plurality of layers. In the case of a plurality of layers, the cost is increased due to the length of the process, but there is a feature that the dielectric breakdown resistance can be improved and the thickness accuracy of the insulating layer can be improved.

The “metal foil with an insulating layer” obtained by applying an insulating layer to the metal foil is left as it is or left as necessary, and further subjected to treatment such as heating and drying to adjust to a predetermined degree of curing. It is used for storage and manufacturing of metal base circuit boards and metal base multilayer circuit boards as shown below.

The manufacturing method of the metal base circuit board of this invention is demonstrated below. That is, the present invention prepares a metal plate previously cleaned by degreasing or chemical treatment, arranges it on the insulating layer side of the metal foil with the insulating layer, heats and pressurizes it, and then integrates the circuit from the metal foil. Is a method of obtaining a metal base circuit board by forming

There are no particular restrictions on the material of the metal plate, but aluminum, copper, iron, zinc, nickel and their alloys are preferably selected in consideration of heat dissipation and adhesion of the insulating layer, and the purity is 90 mass due to adhesion problems. % Or more is preferable. Aluminum and aluminum alloys are preferably selected from the viewpoints of adhesiveness, thermal conductivity, weight and price. Furthermore, surface treatments such as roughening treatment, coupling agent treatment, primer treatment, and alumite treatment can be applied as necessary to improve the adhesion to the insulating layer. Moreover, there is no restriction | limiting in particular as thickness of a metal plate, but 0.3 mm-4.0 mm are generally used.

In order to integrate the metal foil with the insulating layer and the metal plate, a roll or a laminating press machine that can be heated and pressurized is used, which is 80 to 180 ° C., 5 to 70 kg / cm ² , 60 to 240 minutes. It is preferable to heat and pressurize under these conditions. When the heating temperature is low or the heating time is short, curing is insufficient and sufficient adhesiveness and electrical insulation cannot be ensured. On the contrary, when the heating temperature is high or the heating time is long, the resin is thermally deteriorated and the adhesiveness and the electrical insulation are lowered. In addition, when the pressure is low, the resin of the metal foil with resin cannot uniformly wet the metal plate, etc., and the adhesive force varies, and when the pressure is high, the resin of the metal foil with resin is high pressure. As a result, the electrical insulation is significantly reduced.

As a method of forming a circuit from the metal foil of the metal foil with an insulating layer, there is no particular limitation, a predetermined portion is protected with a dry film, an etching resist for screen printing, and the metal foil other than the predetermined portion is etched. The method of removing by this method is generally used.

The metal-based multilayer circuit board can be easily obtained by repeatedly stacking and integrating a metal plate or a metal base circuit board with a metal foil with an insulating layer and forming a circuit. The metal base circuit board is not necessarily limited to the one obtained by the method of the present invention, but when the one obtained by the method of the present invention is used, it can be handled with the minimum equipment and can be obtained at a low cost. This is preferable.

The metal base multilayer circuit board can be provided with through holes for connecting between conductor circuits or metal foils as required. There is no restriction | limiting in particular in the through-hole formation method, If there can be continuity between circuits, there will be no restriction | limiting in the method.

(Example 1) On a copper foil having a thickness of 35 μm, an epoxy equivalent of 201-hydrogenated bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., “YX-8000”) is used as an epoxy resin in an amount of 50% by mass. With respect to 100 parts by mass of an epoxy resin consisting of 50% by mass of an bisphenol F-type epoxy resin having an equivalent weight of 180 (manufactured by Japan Epoxy Resin, “jer-807”), phenol novolak (Maywa Kasei Co., Ltd., “HF- 3 ") 48 mass parts, spherical aluminum particles (" CB-A20 "manufactured by Showa Denko KK) having a maximum particle size of 75 µm or less and an average particle size of 21 µm and an average particle size of 0.6 µm Together with a certain spherical fine particle of aluminum oxide (manufactured by Admatechs, "AO-502"), 50% by volume (spherical rough) in the insulating layer. The particles and the spherical fine particles are blended so that the mass ratio is 65:35), and 2,3-dihydro-1H-pyrrolo (1,2-a) benzimidazole (manufactured by Shikoku Kasei Co., Ltd., “TBZ”) is used as a curing catalyst. ) Is blended with 0.05 part by weight, an insulating layer is formed so that the thickness after curing is 100 μm, dried by heating at 130 ° C. for 40 minutes, and a B-stage copper foil with an insulating layer Was made.

After the said copper foil with an insulating layer was preserve | saved in 25 degreeC atmosphere, the gel time of resin was measured at 170 degreeC. The results are shown in Table 1.

The following procedure was performed using a copper foil with an insulating layer stored at 25 ° C. for 500 hours.
The resin-coated copper foil is placed on an aluminum plate from which the adhering portion has been removed in advance so that the insulating layer faces the aluminum plate, and at 90 ° C. for 30 minutes + 130 ° C. for 90 minutes at 30 kgf / cm ² by a press machine. The insulating layer was thermally cured and integrated by heating and pressurizing to obtain a metal base substrate. The metal base substrate, the metal base circuit substrate using the same, and the like were evaluated as shown in Table 1.

In the above operation, as "evaluation of moldability"
Those with voids, resin flow, and poor bonding ×,
No defect ○
It was.

With respect to “withstand voltage”, a circular circuit pattern having a diameter of 20 mm was formed from a copper foil, and the withstand voltage between the circuit and the aluminum plate was measured by a step-up method defined in JIS C2110.

The “adhesion strength” between the circuit and the insulating layer was determined by a method defined in JIS C 6481 by processing a conductor circuit of a metal base circuit board into a 10 mm wide strip.

“Thermal conductivity” was measured by removing the metal plate and the circuit of the metal base circuit board, processing the cured insulating layer to a diameter of 10 mm and a thickness of 100 μm, using a laser flash method (apparatus used; vacuum mechanic) Co., Ltd., TC-7000).

Further, the obtained metal base circuit board was masked at a predetermined position with a dry film and the copper foil was etched, and then the dry film was removed to form a circuit to obtain an inner circuit board.

The inner layer circuit board is used as a base, the insulating layer of the copper foil with the insulating layer is disposed so as to face the circuit of the interior board, and after heating and pressure curing under the same conditions as described above, the metal in the outermost layer The foil was etched to form an outer layer circuit to produce a metal-based multilayer substrate. Further, the copper foil in a predetermined through hole portion was removed by etching in the same manner as in the above method to expose the insulating layer.

A YAG laser was used at the location where the copper foil was removed, and a hole with a diameter of 0.2 mm was made to penetrate the inner layer circuit and the outer layer circuit, and then copper plating was performed to form a through hole. On this surface, the outer layer circuit was further etched by the above-described method to obtain a metal-based multilayer circuit board.

With respect to the metal-based multilayer circuit board, (1) appearance, (2) insulation withstand voltage between the inner layer and the upper layer, and (3) adhesion between the inner layer and the upper layer were measured and evaluated in the same manner as described above.
These results are also shown in Table 1.

(Example 2) Example 1 except that 0.1 parts by mass of 1-aminoethyl-2-undecimidazole (manufactured by Shikoku Kasei Co., Ltd., “C11Z-CNS”) was added as a curing catalyst for the composition of the insulating layer. A metal-based multilayer circuit board was prepared in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

(Example 3) A metal-based multilayer was produced in the same manner as in Example 1 except that 0.2 parts by mass of triphenylphosphine (manufactured by Hokuko Chemical Co., Ltd., "TPP") was added as a curing catalyst for the composition of the insulating layer. A circuit board was prepared and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

(Example 4) The composition of the insulating layer is a bisphenol A type epoxy resin (“YX-8000”, manufactured by Japan Epoxy Resin Co., Ltd.) hydrogenated with an epoxy equivalent of 201, and the epoxy equivalent is 80% by mass. A metal-based multilayer circuit board was prepared in the same manner as in Example 1 except that 20 mass% of 4371 bisphenol F-type epoxy resin (“EP4010P” manufactured by Japan Epoxy Resin Co., Ltd.) was added. It was evaluated with. The evaluation results are shown in Table 1.

Example 5 A metal-based multilayer circuit board was produced in the same manner as in Example 1 except that bisphenol A novolak resin (Dainippon Ink Co., Ltd., “VH4240”) was used as the curing agent for the insulating layer composition. Evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Table 1.

(Example 6) A multilayer circuit board was produced in the same manner as in Example 1 except that the total amount of the inorganic filler having the composition of the insulating layer was 65% by volume, and the same method as in Example 1 was made. It was evaluated with. The evaluation results are shown in Table 1.

(Example 7) An inorganic filler having a composition of an insulating layer, a coarse particle aluminum nitride (manufactured by Denki Kagaku Kogyo) having a maximum particle size of 75 μm or less and an average particle size of 24 μm, and spherical fine particles having an average particle size of 0.6 μm The aluminum oxide (manufactured by Admatechs Co., Ltd., “AO-502”) was combined with the insulating layer to make 65 volume% (spherical coarse particles and spherical fine particles had a mass ratio of 65:35). A metal-based multilayer circuit board was produced in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

(Comparative Example 1) A hydrogenated bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., “YX-8000”) having an epoxy equivalent of 201 as the composition of the insulating layer is 20% by mass and the epoxy equivalent is 180%. A multilayer circuit board was prepared in the same manner as in Example 1 except that it was blended so as to be 80% by mass of bisphenol F-type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., “jer-807”). And evaluated in the same manner. The evaluation results are shown in Table 1. A decrease in moldability was observed, and therefore the withstand voltage decreased.

The metal foil with an insulating layer of the present invention has an insulating layer in a specific state made of a composition having a specific composition, and also exhibits a thermal conductivity in a predetermined numerical range after curing, and has a feature that changes with time are small. Therefore, it is possible to provide a metal base circuit board and a metal base multilayer circuit board excellent in heat dissipation easily and stably, which is very useful industrially.

The method for producing a metal base circuit board according to the present invention is industrially useful because it can provide a metal base circuit board that is stable, high in productivity, and excellent in heat dissipation because the characteristic metal foil is used. .

The method for producing a metal-based multilayer circuit board according to the present invention uses the above-described characteristic metal foil, so that it is possible to provide a metal-based multilayer circuit board that is stable, high in productivity, and excellent in heat dissipation, and heat dissipation. When a highly heat-generating electronic component, which has been difficult in the past, is mounted on a metal-based multilayer circuit board having electrical insulation, it is possible to achieve higher density, smaller size, or thinner electronic equipment. Since the time-dependent change of the metal foil with a layer is small, it is very useful in the industry because the problems of integration are greatly reduced and the cost can be reduced.

Claims (10)

A metal foil with an insulating layer formed by providing an insulating layer on one main surface of the metal foil, the insulating layer containing an epoxy resin, a curing agent, a curing catalyst and an inorganic filler, in a B-stage state, The metal foil with an insulating layer, wherein the epoxy resin contains 40% by mass or more of an epoxy resin hydrogenated in the epoxy resin. The metal foil with an insulating layer according to claim 1, wherein the hydrogenated epoxy resin has an epoxy equivalent of 100 or more and 300 or less. The metal foil with an insulating layer according to claim 1 or 2, wherein the curing agent contains at least one selected from the group consisting of an acid anhydride resin, a phenol resin, and dicyanamide. The metal foil with an insulating layer according to any one of claims 1 to 3, wherein the curing catalyst is an imidazole compound or a phosphorus compound. The inorganic filler is composed of one or more selected from the group consisting of silicon oxide, aluminum oxide, and aluminum nitride, and the filling rate in the insulating layer after curing is 45 volume% or more and 80 volume% or less. The metal foil with an insulating layer according to any one of claims 1 to 4. The metal foil with an insulating layer according to any one of claims 1 to 5, wherein the thickness of the metal foil is 0.013 mm to 0.450 mm. The metal foil with an insulating layer according to any one of claims 1 to 6, wherein the thermal conductivity calculated from the thermal resistance of the insulating layer after curing is 1.5 W / mK or more. (1) a step of preparing a metal plate,
(2) A step of laminating and integrating the metal foil with an insulating layer according to any one of claims 1 to 7 via an insulating layer on the metal plate,
(3) forming a circuit from the metal foil of the metal foil with an insulating layer;
A method of manufacturing a metal-based circuit board, wherein (1) preparing a metal base circuit board or a metal base multilayer circuit board;
(2) A step of laminating and integrating the metal foil with an insulating layer according to any one of claims 1 to 7 via an insulating layer on a circuit of a metal base circuit board or a metal base multilayer circuit board,
(3) forming a circuit from the metal foil of the metal foil with an insulating layer;
A method for producing a metal-based multilayer circuit board comprising: 10. The method for producing a metal-based multilayer circuit board according to claim 9, wherein the steps (2) and (3) are repeated twice or more.