JPH01312894A - Manufacture of al plate for use with printed circuit board - Google Patents

Abstract

PURPOSE:To make a surface on which an insulation layer should be formed have excellent electric resistance and excellent contact with the insulation layer by performing an anodic oxidation processing in a specific condition in an electrolyte with phosphoric acid as its main ingredient. CONSTITUTION:An anode oxidation processing is performed on an Al plate 1 for 5 to 15min. with a bath voltage kept at a constant voltage from 10 to 30V, in an electrolyte of phosphoric acid density of 50 to 150g/l and of bath temperatures of 25 to 35 deg.C, and an anode oxidation surface layer 2, 0.2 to 1.0mum in film thickness, is formed at least on one surface. When a bath voltage is kept at a constant voltage in this way, an anodic oxidation surface layer having a uniform barrier layer can be obtained and insulation is improved. By performing an anodic oxidation processing in an electrolyte with phosphoric acid as its main ingredient, its hole size becomes 300Angstrom or thereabouts. Penetration into a hole of a material constituting the insulation layer 3 becomes better, and the contact of the insulation layer with the Al plate is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION This invention relates to a method for manufacturing aluminum plates used for printed circuit boards.

In this specification, the term "aluminum" includes not only pure aluminum but also aluminum alloys.

Conventional technology printed circuit boards include one side of an aluminum plate,
Some circuit metal foils made of copper, aluminum, etc. are bonded via an insulating layer made of thermosetting resin, thermoplastic resin, etc. Conventionally, the above-mentioned aluminum plates for circuit boards have been roughened by mechanical methods such as polishing, or by chemical or electrochemical methods in order to increase the adhesion with the insulating layer. I was using something. A printed circuit board was then manufactured by bonding metal foil to the rough surface of this aluminum plate using prepreg or thermoplastic synthetic resin film.

Problems to be Solved by the Invention However, the above-mentioned printed circuit boards have not been able to fully satisfy various required characteristics under the severe usage conditions of recent years.

This is thought to be due to the fact that the surface of the aluminum plate for circuit boards on which the insulating layer is to be formed does not have electrical insulation properties, and the adhesion between the aluminum plate for circuit boards and the insulating layer is not sufficient. .

This invention was made in view of the above circumstances, and its purpose is to provide a surface on which an insulating layer is to be formed, which has excellent electrical insulation properties, and a printed circuit board with excellent adhesion to the insulating layer. An object of the present invention is to provide a method for manufacturing an aluminum plate.

Means for Solving the Problems In the method of manufacturing an aluminum plate for printed circuit boards according to the present invention, the aluminum plate has a phosphoric acid concentration of 50 to 15.
0 g / / in an electrolyte with a bath temperature of 25-35 °C,
5 to 1 while keeping the bath voltage at a constant voltage in the range of 10 to 30 V.
Anodic oxidation treatment was performed for 5 minutes to create a film thickness of 0.000 mm on at least one side.
It is characterized by forming an anodic oxide film of 2 to 1°0.

In the above, the phosphoric acid concentration in the electrolyte is 50 g
If it is less than 150 g / /, the electrolytic voltage will increase and it will be difficult to form a uniform and stable film, and if it exceeds 150 g / /, the dissolution rate of the film in the electrolyte will increase and it will take a long time to form the film. However, the cost increases. Therefore, the phosphoric acid concentration in the electrolytic solution should be selected within the range of 50 to 150 g//, particularly preferably within the range of 90 to 110 g//.

If the bath temperature is less than 25°C, the electrolytic voltage will increase and it will be difficult to form a uniform and stable film. If the bath temperature exceeds 35°C, the dissolution rate of the film in the electrolyte will increase and the film formation will take longer. This is time consuming and costly. Therefore, the bath temperature should be selected within the range of 25 to 35°C, especially 28°C.
It is preferably within the range of ~32°C.

When the bath voltage is less than 10 V, the film formation rate decreases, and 30
If it exceeds V, the current becomes high and it is difficult to form a uniform and stable film. Therefore, the bath voltage is 10-3
Although it should be selected within the range of 0V, it is particularly preferably within the range of 15 to 25V.

If the anodic oxidation treatment time is less than 5 minutes, a film with a thickness of 0.2p or more cannot be obtained, and if the anodization treatment time exceeds 15 minutes, the effect will not change and the cost will only increase. Therefore, the anodizing treatment time should be selected within the range of 5 to 10 minutes, and particularly preferably within the range of 8 to 12 minutes.

If the thickness of the anodic oxide film is less than 0.2p1, the pores on the surface of the film will be shallow and sufficient adhesion with the insulating layer will not be obtained;
Even if the OJm is exceeded, the adhesion with the insulating layer does not improve any further, and when a printed circuit board equipped with this aluminum plate is bent, cracks occur in the film and the adhesion and insulation properties deteriorate. There are things to do. In addition, when drilling holes, the drill wears out (which shortens the life of the drill, and cracks occur in the film, reducing adhesion and insulation. Therefore, the thickness of the anodic oxide film is It should be selected within the range of 0.2 to 1.0 p, particularly preferably within the range of 0.5 to 0.7 p.

Further, in the above, the reason why the bath voltage is kept constant is as follows. That is, if the bath voltage is maintained at a constant voltage, an anodic oxide film having a uniform barrier layer can be obtained, and the insulation properties will be improved.

Further, the reason why the anodic oxidation treatment is performed in an electrolytic solution containing phosphoric acid is as follows. In other words, when anodizing treatment is performed using other methods such as sulfuric acid anodizing treatment or oxalic acid anodizing treatment, the pore diameter of the formed film surface is about 120 to 200 mm. When anodic oxidation treatment is performed in an electrolytic solution, the diameter of the pores changes color by about 300 mm, which improves the penetration of the substance that makes up the insulating layer into the pores, and improves the adhesion between the insulating layer and the aluminum plate. This is because it improves sexual performance. In addition, when anodizing is performed using other methods such as sulfuric acid anodizing or pre-anodizing, the formed film is easily hydrated by moisture, making the film brittle and hindering its adhesion. On the other hand, a film obtained by anodizing in an electrolytic solution containing phosphoric acid as a main component is less likely to be hydrated and therefore has good adhesion.

Materials used as the insulating layer for bonding metal foil to the anodized film surface of the aluminum plate manufactured by the above method include prepreg, thermoplastic resin film, thermosetting resin coating, thermoplastic resin coating, etc. There is.

Phenol resins, epoxy resins, unsaturated polyester resins, polyimide resins, etc. are used as thermosetting resins, but among these, epoxy resins or polyimide resins are used in order to exhibit the excellent adhesive properties of the phosphoric acid anodized film. It is preferable to use

Reinforcing materials for prepreg include paper, synthetic fiber cloth, glass fiber cloth, etc., but we use glass fiber woven cloth or glass fiber non-woven cloth made of E-glass, which has excellent electrical properties, as a reinforcing material. It is preferable to do so. In addition, the proportion of resin in prepreg is usually 30 to 60% by weight, but from the viewpoint of thermal conductivity and heat resistance, less is better as long as it satisfies the properties required for subsequent processing steps such as the contact force between each layer. preferable. Then, an aluminum plate, a predetermined number of prepregs, and, if necessary, metal foil are laminated and molded under heat and pressure to produce a printed circuit board.

When applying thermosetting resin to an aluminum plate, usually the liquid resin is applied directly to the aluminum plate, dried, and then
If necessary, metal foils are overlapped and molded under heat and pressure.

Common thermoplastic resins include cross-linked polyolefins, high-melting point polyolefins, polyetherimides, polyethersulfones, and fluororesins, which are either laminated to aluminum plates in the form of a film, or made into an emulsion and coated on the aluminum plate. dried. In this case as well, metal foils are laminated as necessary, and an adhesive is used between each layer as necessary. Thereafter, it is heated and press-molded at a temperature equal to or higher than the resin softening point.

Copper, aluminum, nickel, etc. are used as the metal foil, and it is preferable that the surface to be bonded to the insulating layer is subjected to a mechanical or chemical surface treatment in advance. Adhesive is usually applied to the adhesive surface of the metal foil to the insulating layer, but
In order to improve thermal conductivity, it is preferable that no adhesive be applied to the adhesive surface.

Function: According to the method of the present invention, on the surface on which the insulating layer is to be formed,
Aluminum plates with a uniform barrier layer and an anodized coating with a discoloration pore size of about 300 can be produced.

Example Examples of the present invention will be described below along with comparative examples.

Example I Made of JIS A1050 H24 material, thickness 0.5 mm
An aluminum plate was anodized under the following conditions to form an anodic oxide film with a thickness of 0.5 on one side.

Bath composition 100 g/
/(phosphoric acid concentration) Bath temperature 30℃ bath
Voltage 20V processing time
10 minutes Example 2 An aluminum plate made of JIS A3052 H34 material and having a thickness of 1 mm was anodized under the following conditions to form an anodic oxide film having a thickness of 0.5/ff on one side thereof.

Bath composition 100 g/
/(phosphoric acid concentration) Bath temperature: 30℃ bath Voltage: 25V Treatment time
10 minutes Example 3 A 1 mm thick aluminum plate made of JIS A3052) 134 material was anodized under the following conditions to form an anodic oxide film with a thickness of 0.6 on one side.

Bath composition 90 g/
l (phosphoric acid concentration) Bath temperature 28℃ bath Voltage 15V Treatment time
12 minutes Example 4 A 1 mm thick aluminum plate made of JIS A3052 H34 material was anodized under the following conditions to form an anodic oxide film with a thickness of 0.77 m on one side.

Bath composition 1 10 g
/ l (phosphoric acid 1 degree) Bath temperature 32℃ bath
Voltage 25V processing time
12 minutes Comparative Example I A 1 mm thick aluminum plate made of JIS A3052 +134 material was subjected to sulfuric acid anodic oxidation treatment under the following conditions to form an anodized film with a thickness of 20 mm on one side.

Bath composition 150g//(sulfuric acid concentration) Bath temperature 20℃ bath
Voltage 16V processing time
60 minutes Comparative Example 2 One side of a 1 mm thick aluminum plate made of JIS A1050 H24 material was roughened by ball polishing. The surface roughness R was 15/ffi.

aX Evaluation Test In order to evaluate the performance of the aluminum plate manufactured by the method of the present invention, the following evaluation test was conducted.

That is, on the rough surfaces of all the aluminum plates of Examples 1 to 4 and Comparative Examples 1 to 2, epoxy resin varnish was applied to glass fiber woven fabric (Nittobo W) so that the resin content was 41% by weight.
EA-106E) was impregnated with dry prepreg, and then a 35-cut electrolytic copper foil with one side roughened was placed on top of it with the rough surface facing the prepreg, and heated at 175°C. , heat and pressure molded for 130 minutes at a pressure of 90 kg/c- to form an anodized film (2) as shown in the drawing.
A printed circuit board consisting of an aluminum plate (1) with or without an insulating layer (3) and an electrolytic copper foil (4) was manufactured.

Then, the adhesion between the aluminum plate (1) and the insulating layer (3), heat resistance, surface resistance, and thermal conductivity of these printed circuit boards were examined.

The results are summarized in the table below.

(Margin below) In the above table, the adhesive strength was determined by immersing the obtained printed circuit board in boiling water for 2 hours and observing whether or not peeling occurred between the aluminum plate and the insulating layer (0... No peeling, ×...Peeling occurred).

In addition, the thermal conductivity was measured by hot wire thermal conductivity using a QTM type quick thermal conductivity meter manufactured by Showa Denko. Other characteristics are JI
This was carried out using SC6481.

Effects of the Invention The method for manufacturing an aluminum plate for a printed circuit board according to the present invention is configured as described above, so that a uniform barrier layer is formed on the surface on which an insulating layer is to be formed, and three
It is possible to produce an aluminum plate with an anodized coating having a discoloration pore size of about 0.00 mm. Therefore, in the aluminum plate manufactured by this method, the surface on which the insulating layer is to be formed has excellent electrical insulation properties, and in the printed circuit board equipped with this aluminum plate, the aluminum plate and the The adhesion between the insulating layer and the insulating layer is excellent. Further, the characteristics of the circuit board, such as thermal conductivity and heat resistance, are also superior to those of conventional circuit boards. As a result, a circuit board can be obtained that fully satisfies various required characteristics even under the severe usage conditions of recent years.

[Brief explanation of the drawing]

The drawing is an enlarged vertical cross-sectional view of a printed circuit board made using an aluminum plate manufactured by the method of the present invention. (1)...Aluminum plate. that's all

Claims (1)

[Claims] Phosphoric acid concentration is 50-150g/l on aluminum plate
, in an electrolytic solution with a bath temperature of 25 to 35°C, and a bath voltage of 10 to 3
An aluminum plate for printed circuit boards, characterized in that it is anodized at a constant voltage in the range of 0V for 5 to 15 minutes to form an anodic oxide film with a thickness of 0.2 to 1.0 μm on at least one side. Production method.