JPH04196389A - Wiring board - Google Patents

Abstract

PURPOSE:To enhance a plating layer which serve as a conductor in adhesive power and insulation reliability by a method wherein a conductor is formed by plating through such a manner that an organic insulating layer is given plating nucleuses before it is thermally cured and then plated after cured. CONSTITUTION:An organic insulating layer is formed on a metal board through electrophoresis, and a conductor is provided thereon through plating for the formation of a wiring board, where the conductor concerned is formed through such a manner that the organic insulating layer is given plating nucleuses before it is cured by heating and plated with metal after it is cured. A layer of epoxy resin, melamine resin, polyimide resin, or the like is used as the organic insulating layer concerned, and it is preferable on the standpoints of dielectric strength and heat-resistant properties that a polyimide resin layer is used as the organic insulating layer. Palladium, copper, silver, or the like is used as plating nucleus, and palladium is preferable from the standpoint of the prevention of oxidation at a heating process in which a polyamide acid coating is turned into imide by heating. By this setup, a wiring board where a conductor circuit is excellent in adhesive strength and insulation reliability can be obtained keeping the feature of a metal core board.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is applicable to metal core substrates which are used due to the characteristics of heat dissipation, substrate strength, high dimensional stability, etc. required for high-density mounting of elements. The present invention relates to a wiring board that has excellent adhesive strength of formed conductors and excellent insulation reliability.

(Prior Art) As electronic components become lighter, thinner, shorter, and smaller, the packaging density of components has increased significantly, and in line with this trend, substrates are also becoming more diverse. One such example is a metal core substrate, which is a metal substrate with through holes, and is used because of its features such as heat dissipation, substrate strength, and high dimensional stability.

Since the metal core board has through holes, the inner wall of the through hole and the surface must be insulated, and a conductor must be formed on it. The current manufacturing method is to drill holes in a metal plate, place glass cloth and copper foil impregnated with epoxy resin on both sides, and bond them using a hot pressure press, then drill a hole in the epoxy resin that has hardened through the flow. After that, the holes are processed in the same way as for double-sided boards, and the inner walls and surface of the holes are coated with an organic resin at the same time by electrodeposition coating, electrostatic powder coating, fluidized dipping, etc. There is a method of forming a conductor using In the former case, the positioning accuracy in drilling holes in the two layers is difficult and the process is complicated. Furthermore, since the surface layer is made of epoxy resin-impregnated glass cloth, heat dissipation performance is also reduced. The latter can be manufactured relatively easily, but the adhesion of the plating layer that serves as a conductor is weak, and the surface of the hardened organic insulating layer is roughened and plating cores are attached, followed by electroless method 7.
A method is taken to improve the adhesion of the plating layer by using the anchor effect.

However, in order to roughen the surface, strong chemicals such as a chromic acid mixture and a highly concentrated alkali are used.

For this reason, there is a risk of pinholes occurring in the insulating layer.

(Problems to be Solved by the Invention) An object of the present invention is to solve such problems by providing a metal core substrate with excellent adhesive strength and insulation properties of a plating layer serving as a conductor.

(Means for Solving the Problems) The wiring board of the present invention that achieves the above object is a wiring board that includes an organic insulating layer formed on a metal plate by electrophoresis, and a conductor formed on the organic insulating layer by plating. The conductor is characterized in that the conductor is provided by applying plating nuclei to the organic insulating layer before heat curing, and plating after curing.

The metal plate used in the present invention is not particularly limited, but usually includes aluminum, iron, silicon steel plate, anodized aluminum, copper, and copper alloy.

Doinher et al.

Examples of the organic insulating layer used in the present invention include layers made of epoxy resin, melamine resin, polyimide resin, etc., but it is preferably made of polyimide resin in terms of voltage resistance and heat resistance. The polyimide used in the present invention is not particularly limited, but from the viewpoint of adhesiveness, for example, 3.3'
-Diaminohenduphenone, 1.3-bis(3-aminophenoxy)henzene, 4.4'-bis(3-aminophenoxy)biphenyl, 2.2-bisC4-(3-aminophenoxy)phenyldipropane , 2,2-bis(
/1-(3-aminophenoxy)phenyl] -1,1
, 1,3,3,3-hexafluoropropane, bis[4
-(3-aminophenoxy) phenyl fusulfide, bis(4-(3-aminophenoxy) phenyl koketone,
Diamines such as bis(4-(3-aminophenoxy)phenyl)sulfone and, for example, ethylenetetracarboxylic dianhydride, cyclopenkune tetracarboxylic dianhydride, pyromellitic dianhydride, 3.3', 4. 4'-benzophenonetetracarboxylic dianhydride, 2.2'.

3.3'-benzophenonetetracarboxylic dianhydride, 3.3', 4.4'-biphenyltetracarboxylic dianhydride, 2.2', 3.3'-biphenyltetracarboxylic dianhydride, 2 , 2-bis(3,4-dicarboxyphenyl)propanihydride, 2,2'-bis(
2,3-dicarboxyphenyl)propanihydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3゜4-dicarboxyphenyl)sulfone dianhydride, 1.1-bis(2,3- dicarboxyphenyl)
Ethanihydride, bis(2,3-dicarboxyphenyl)methanihydride, bis(3,4-dicarboxyphenyl)methanidianhydride, 2,3,6° 7-naphthalenetetracarboxylic dianhydride, 1° 4.5.8-Naphthalenetetracarboxylic dianhydride, 1.2.5.6-Naphthalenetetracarboxylic dianhydride, 1.2.3.4-Hensentetracarboxylic dianhydride, 3,4 , 9.10-Perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7°8-phenanthrenetetracarboxylic dianhydride, etc. A polyimide obtained by heating and imidizing a polyamic acid composed of an anhydride is preferred. These may be used alone or in combination of two or more.

Furthermore, an inorganic filler may be added to the resin for the purpose of improving heat dissipation. Examples of inorganic fillers used for this purpose include alumina, phosphoric acid, boron nitride, silicon carbide, aluminum nitride, beryllium oxide, and the like.

Formation of a polyimide insulating film by electrophoresis can be performed as follows. In other words, an electrodeposition solution is prepared by neutralizing polyamic acid, which is a precursor of polyimide, with an amine, etc., and diluting it with water. Electrophoresis is performed at a voltage of 10V to 300V to form a polyamic acid film on the metal plate. Thereafter, a polyimide insulating layer can be formed by heat imidization.

Examples of the plating core used in the present invention include palladium, copper, silver, etc., but palladium is preferable from the viewpoint of preventing oxidation during heat imidization of the polyamic acid coating.

An example of a method for depositing palladium cores is shown below.

As described above (after washing the metal plate on which a polyamic acid film has been formed in an electrodeposition bath with water, it is immersed in a tin chloride colloidal solution, and then immersed in a palladium chloride aqueous solution to form palladium nuclei on the polyamic acid film. The polyamic acid is dehydrated and imidized by heat imidization, and the palladium core is immobilized on the polyimide layer.

Next, electroless copper plating is performed to form a copper conductor layer on the polyimide film. At this time, it is of course possible to use electroless plating and electroplating in combination. If necessary, the surface of the organic insulating layer may be etched with a solvent or alkali to promote exposure of the plating nucleus before electroless plating, but it is important to lightly etch the surface.

A desired circuit is formed on the plated board by techniques such as dry film or screen printing, for example, in the same way as a normal double-sided board, to obtain a metal core wiring board.

(Effects of the Invention) The wiring board of the present invention obtained in this way maintains the characteristics of the conventional metal core board, and has excellent adhesive strength and insulation multiplication properties for conductor circuits, and is industrially useful. be.

(Example) EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.

In the following examples, the adhesive strength is 5III1
Measurement result of 90° peel strength at width kg /
Convert and display in cm units. The dielectric breakdown voltage is determined by applying each AC voltage for 1 minute and when the leakage current reaches 5 mA, it is considered to be dielectric breakdown. Soldering heat resistance is 260”C2 under normal conditions.
Judgment was made based on the appearance after 0 seconds of solder immersion.

1 tsp of fruit 1,3-bis(3-aminophenoxy) as diamine
Benzene, 3.3' as tetracarboxylic dianhydride,
4.4'-Hensephenonetetracarboxylic dianhydride was reacted to obtain polyamic acid. This polyamic acid was neutralized with dimethylethanolamine, and water was added to prepare an electrodeposition solution. An aluminum plate with a hole of 0.5 diameter drilled in it was immersed in the electrodeposition solution, and the aluminum plate was used as an anode and the stainless steel plate was used as a cathode.
Electrophoresis was performed by applying the voltage for 2 seconds. After washing the substrate with water, it was immersed in a tin chloride colloid solution for 1 minute, and then immersed in a palladium chloride aqueous solution for 2 minutes. This board was heated to 120°C for 30 minutes.
Heat imidization was performed at 180°C for 30 minutes and then at 250°C for 30 minutes to form a polyimide insulating layer having plating nuclei. The insulation layer thickness was 15 μm.

Thereafter, a copper plating layer with a total thickness of 1 μm was formed by electroless plating and then by electroplating to a total thickness of 18 μm.

The adhesive strength of the plating layer is 1.5 kg/cm. The breakdown voltage was 7.5 v. There were no abnormalities in the appearance after solder immersion, both inside the through-hole and on the surface.

Back box ■1 2.2-bis[4-(3-aminophenoxy)phenyl]propane as diamine, 3.3', 4.4'-hensiphenonetetracarboxylic dianhydride as tetracarboxylic dianhydride were reacted to obtain polyamic acid. An electrodeposition solution was prepared in the same manner as in Example 1, and polyamic acid electrodeposition was performed on an aluminum plate by applying 80 V for 40 seconds, plating nuclei were added, and heating imidization was performed to form a polyimide insulation containing plating nuclei. formed a layer. The thickness of the insulating layer was 17 μm. The treated plate was immersed in a 30° CIO% sodium hydroxide aqueous solution for 20 seconds, thoroughly washed with water, and then subjected to electroless plating. The plating thickness was 18 μm. The adhesive strength of the plating layer is ], 8 kg/
cm. The dielectric breakdown voltage was 7.2 kV. There were no abnormalities in the appearance after solder immersion, both inside the through-hole and on the surface.

3.3′-diaminohendophenone as a diamine,
3.3' as tetracarboxylic dianhydride.

4.4'-hensiphenotetracarboxylic dianhydride was reacted to obtain polyamic acid. Alumina having an average particle size of 1 μm was added to the polyamic acid solution at a solid content of 50% by weight, and the mixture was kneaded using three rolls. Thereafter, an electrodeposition solution was prepared in the same manner as in Example 1, and 120 V2O was applied to an aluminum plate.
Electrodeposition was performed by applying seconds, plating nuclei were applied, and heating imidization was performed to form a polyimide insulating layer having plating nuclei. The thickness of the insulating layer was 25 μm. after that,
Electroless plating and electroplating were performed. Plating thickness is 35
It was μm. The adhesive strength of the plating layer is 1.6 kg/
cm, and the dielectric breakdown voltage was ν at 9.0. There were no abnormalities in the appearance after solder immersion, both inside the through-hole and on the surface.

This Jl Tsuji 1 Electrophoresis was performed using the electrodeposition solution obtained in Example 1 under the same electrodeposition conditions. After washing this board with water,
'C 30 minutes, 180°C 30 minutes, then 250°C 30 minutes
Imidization was performed by heating for 1 minute. The insulation layer thickness was 15 μm. It was immersed in a tin chloride colloid solution for 1 minute, and then immersed in a palladium chloride aqueous solution for 2 minutes to provide plating nuclei. A polyimide insulating layer having plating nuclei was formed. after that,
A copper plating layer with a total thickness of 1 μm was formed by electroless plating and then by electroplating to have a total thickness of 18 μm. The dielectric breakdown voltage is 7
．． 5kV, but the adhesive strength of the plating layer was 0.2kV.
g/Cm, and the appearance after solder immersion showed that peeling occurred between the insulating layer and the copper plating layer both inside the through hole and on the surface.

Electrophoresis was performed using the electrodeposition solution obtained in Example 1 under the same electrodeposition conditions. After washing this board with water, 120°C3
A polyimide insulating layer was formed by heating imidization for 0 minute, 30 minutes at 180°C, and then 30 minutes at 250°C. The insulation layer thickness was 15 μm. The treated plate was immersed in a 10% sodium hydroxide aqueous solution at 80°C for 2 minutes, thoroughly rinsed with water, immersed in a tin chloride colloid solution for 1 minute, and then immersed in a palladium chloride aqueous solution for 2 minutes to provide plating nuclei. . Thereafter, a copper plating layer with a total thickness of 1 μm was formed by electroless plating and then by electroplating to a total thickness of 18 μm. The adhesion strength of the plating layer was 1.6 kg/crn, and the appearance after solder immersion was normal both inside the through hole and on the surface, but the dielectric breakdown voltage was a low value of 0.5 kV.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd.

Claims (2)

[Claims] 1. A wiring board comprising an organic insulating layer formed by electrophoresis on a metal plate and a conductor formed by plating on the organic insulating layer, wherein the conductor is provided with plating nuclei before thermosetting the organic insulating layer. A wiring board characterized in that it is provided by plating after hardening. 2. 2. The wiring board according to claim 1, wherein the organic insulating layer is made of polyimide resin.