JP4187082B2 - Metal base circuit board and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention has a high heat dissipation suitable for a hybrid integrated circuit that can mount a high heat generation electronic component or a high heat generation electronic component and a control circuit electronic component and can be applied to a high power application such as a power supply. The present invention relates to a circuit board for hybrid integration.
[0002]
[Prior art]
A metal base circuit board having a good thermal conductivity is used as a circuit board for mounting a highly heat-generating electronic component. The metal base circuit board uses a metal plate such as aluminum as a base material, and an insulating layer made of an inorganic filler-containing resin with a thickness of about several tens of μm is provided on the metal plate, and a circuit is formed on the insulating layer. Has a structure. Since the metal base circuit board has a high heat dissipation property, it is used for a high power application in which an electronic component having a large calorific value is mounted.
[0003]
In recent years, there has been a demand for a metal base circuit board with higher heat dissipation for the purpose of further increasing power in high-power applications, increasing circuit density, or expanding the field of application. Metal-based circuit boards using foil as a circuit conductor have been developed.
[0004]
However, since a metal base circuit board is generally formed of a metal different from a metal plate and a metal foil, stress is likely to occur in the vicinity of the insulating layer due to a thermal history received during manufacture. For this reason, for example, under use conditions in which thermal shock is repeated, the insulating layer may crack, and in the worst case, dielectric breakdown may occur.
[0005]
For this reason, attempts have been made to make the metal plate the same copper plate as the circuit, but there are problems such as an increase in weight and high cost, and it is hardly used at present.
[0006]
In addition, attempts have been made to use an aluminum alloy with good etching properties as a circuit conductor, but the substrate heat dissipation is not sufficient and there is a limit to the application field.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and the purpose thereof is to prevent heat from being dissipated without causing cracks in the insulating layer even under use conditions such as repeated thermal shocks or severe thermal shocks. It is an object of the present invention to provide a metal base circuit board suitable for high current applications with excellent performance.
[0008]
[Means for Solving the Problems]
The present invention is a metal base circuit board provided with a circuit made of aluminum on one main surface on an aluminum plate through an insulating layer, the aluminum purity of the circuit made of aluminum is 99.5% by mass or more, The metal base circuit board is characterized in that the etching factor of the circuit made of aluminum is 1.5 or more and 2.5 or less, preferably the thickness of the circuit made of aluminum is 300 μm or more and 1000 μm or less, more preferably 1. The metal base circuit board according to claim 1, wherein at least one metal layer selected from the group consisting of nickel, copper, and gold is provided on a circuit made of aluminum.
[0009]
Further, the present invention provides a metal base circuit in which an aluminum foil is laminated on one main surface of an aluminum plate via an insulating layer to obtain a laminate, and then the aluminum foil of the laminate is etched to form a circuit. It is a manufacturing method of a board | substrate, Comprising: The purity of the said aluminum foil is 99.5 mass% or more, It is a manufacturing method of the metal base circuit board characterized by the above-mentioned.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the metal base circuit board of the present invention, the aluminum purity of a circuit made of aluminum (hereinafter referred to as an aluminum circuit) provided on an aluminum plate through an insulating layer is 99.5% by mass or more, and the aluminum circuit The etching factor is 1.5 or more and 2.5 or less. When the above-described configuration is adopted, it is possible to improve the thermal shock resistance, which has been a defect of the conventionally known metal base circuit board made of copper for high current applications, and at the same time achieve high circuit density. That is, if the aluminum purity is less than 99.5% by weight, the thermal shock resistance may not be improved sufficiently, and if the etching factor is less than 1.5, the circuit pattern accuracy is poor and it is difficult to increase the circuit density. Moreover, those exceeding 2.5 are difficult to technically realize.
[0011]
In the present invention, the aluminum circuit is not limited to its production method as long as the aluminum purity is 99.5% by mass or more, but JIS 1000 series aluminum is preferably selected because it is inexpensive and easily available.
[0012]
In this invention, it is preferable that the thickness of an aluminum circuit is 300-1000 micrometers. In other words, when the thickness is 300 μm or more, a metal base circuit board that can withstand repeated heating and cooling under practical conditions can be obtained. However, when the thickness exceeds 1000 μm, circuit formation becomes difficult and practical. It ’s not right. Of these ranges, 300 to 500 μm is selected as a more preferable range because stress relaxation can be reliably achieved and production is not difficult.
[0013]
In the metal base circuit board of the present invention, when mounting electronic parts or forming a module by connecting circuits, an aluminum circuit is provided so that the solderability of the electronic parts, the connection of bonding wires, and the like are improved. It is preferable that a metal layer made of copper, nickel, gold-nickel or the like is provided on a part of the top. As for the method of providing the metal layer on the aluminum circuit, a conventionally known method such as a method using a composite foil of aluminum and a metal layer, a method of providing a metal layer by plating after an aluminum foil is provided on an insulating layer, etc. Apply the method.
[0014]
Moreover, the metal base circuit board of the present invention may be obtained by any manufacturing method as long as the above-described configuration is satisfied. That is, after applying an insulating layer on an aluminum plate and further affixing an aluminum foil on the insulating layer, the aluminum foil is processed by etching or the like to form a circuit, or a circuit is formed in advance by etching. Any method such as attaching this to an aluminum plate via an insulating layer may be used, but as will be described later, the former does not require specially expensive equipment and adjusts the conventional manufacturing conditions. By the modification, the metal base circuit board of the present invention can be obtained stably.
[0015]
The aluminum plate used for the metal base circuit board of the present invention may be aluminum or an alloy thereof, and the thickness may be 0.5 to 3 mm. As the insulating layer, any insulating material can be used. For example, various resins such as epoxy resin, phenol resin, unsaturated polyester resin, and polyimide resin, and glass cloth or the like are impregnated. In addition, a resin in which the resin is filled with an inorganic filler, a resin in the form of a film, or the like can be used. Of these, an epoxy resin excellent in adhesiveness with aluminum is preferably added with aluminum oxide, silicon oxide, silicon nitride, aluminum nitride, boron nitride or the like for the purpose of increasing thermal conductivity.
[0016]
About the manufacturing method of the metal base circuit board of this invention, as a result of the present inventor repeating various experimental examination regarding the material of aluminum, etching conditions, and the shape of the circuit obtained, the aluminum purity of aluminum foil is more than a specific value. At some point, the inventors have obtained knowledge that an etching factor circuit having a value range suitable for circuit formation can be formed, and the present invention has been achieved.
[0017]
That is, generally, etching of aluminum is carried out using an aqueous solution of sodium hydroxide, ferric chloride, and cupric chloride as an etching solution. However, an etching factor of 1 is usually used in an etching method that is usually used. It is known that a practical problem will occur. As a result of various investigations aimed at elucidating the cause of the present inventors, when an aluminum foil having a purity of 99.5% by mass or more is used, a sodium hydroxide-based etching solution is used as an aluminum selective etching solution, It has been found that the etching factor can be controlled within the range of 1.5 to 2.5 which is convenient for circuit formation by overetching the etching from the normal etching time.
[0018]
The manufacturing method of the metal base circuit board of the present invention is obtained by laminating an aluminum foil on one main surface on an aluminum plate via an insulating layer to obtain a laminate, and then etching the aluminum foil of the laminate. A method of manufacturing a metal base circuit board for forming a circuit, wherein the purity of the aluminum foil is 99.5% by mass or more. As described above, by using an aluminum foil having a purity of 99.5% by mass or more, a metal base circuit board according to the present invention can be obtained by changing the conventional manufacturing conditions without requiring specially expensive equipment. There is a feature that can be obtained stably.
[0019]
In the manufacturing method of the present invention, a metal layer made of copper, nickel, gold-nickel, or the like is used in advance at a desired position of the aluminum foil, so that the metal layer is used as a mask when selectively etching aluminum. As a result, it is possible to simplify the steps necessary for a conventional resin mask.
[0020]
【Example】
〔Example〕
A bisphenol A type epoxy resin (Epicoat 828 manufactured by Yuka Epoxy Co., Ltd.) containing 60% by volume of aluminum oxide is applied on an aluminum plate having a thickness of 3.0 mm so that the insulating layer has a thickness of 125 μm. A JIS 1050 aluminum (400 μm thick) foil plated with 10 μm thick copper was placed so that the aluminum layer side was in contact with the insulating layer, and pressed under heating to produce a metal base substrate.
[0021]
Next, a desired position on the copper plating was masked with an etching resist using a screen printing method to etch the copper plating layer, and then the aluminum foil was etched with a 20 wt% sodium hydroxide solution to form a circuit. At this time, the condition was excessive for 2 minutes with respect to the just etching conditions.
[0022]
As a result of measuring the etching factor of the circuit pattern of the metal base circuit board, it was 2.5, which was a desired value. It was confirmed that the dielectric breakdown voltage did not change even after the solder heat treatment evaluation shown below, and there were no insulating layer cracks.
[0023]
<Solder heat treatment evaluation method>
An evaluation substrate on which an aluminum pattern of φ20 mm was formed by etching was floated on a solder bath at 260 ° C. for 10 minutes, and then the change in dielectric breakdown voltage characteristics and the presence or absence of an insulating layer crack were evaluated.
[0024]
[Comparative Example]
For the same metal base substrate as in the example, the desired position on the copper plating is masked with an etching resist using a screen printing method, and etching is performed with a ferric chloride solution (liquid temperature 40 ° C./concentration 40 baume) under just etching conditions. The aluminum circuit was formed.
[0025]
The etching factor of the aluminum circuit of the metal base circuit board was measured and found to be 1.1.
[0026]
【The invention's effect】
The metal base circuit board according to the present invention is free from cracks in the insulating layer, excellent in heat dissipation of the substrate, and has an etching factor of 1.5 or more even under conditions of repeated thermal shock or strong thermal shock. .5 or less, the high density of the circuit is achieved, which is very useful in the industry.
[0027]
In addition, the metal base circuit board manufacturing method of the present invention does not require a particularly expensive facility for the metal base circuit board, and can be stably obtained by changing the conventional manufacturing conditions. It is very useful in industry.

Claims (4)

A metal base circuit board in which a circuit made of aluminum is provided on one main surface on an aluminum plate via an insulating layer, and the aluminum purity of the circuit made of aluminum is 99.5% by mass or more, and the circuit made of aluminum A metal base circuit board having an etching factor of 1.5 to 2.5. 2. The metal base circuit board according to claim 1, wherein the thickness of the circuit made of aluminum is 300 μm or more and 1000 μm or less. 3. The metal base circuit board according to claim 1, wherein at least one metal layer selected from the group consisting of nickel, copper and gold is provided on a circuit made of aluminum. After obtaining the laminate by laminating the aluminum foil via an insulating layer on one main surface of the aluminum plate, forming a circuit by etching by the aluminum foil of sodium hydroxide solution of the laminate, the etching factor A method for producing a metal base circuit board, which is 1.5 or more and 2.5 or less , wherein the purity of the aluminum foil is 99.5% by mass or more.