JPS63262890A - Manufacture of printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a printed circuit board, and more particularly, to a method for manufacturing a highly reliable printed circuit board using a metal substrate as a base material. It is.

[Conventional technology]

In recent years, metal-based printed circuit boards that utilize the excellent heat dissipation properties of metal substrates have become important as printed circuit boards. However, since metals generally have conductivity, if a printed circuit is provided directly on a metal substrate, a short circuit will occur between the circuits, so it is necessary to insulate the substrate. Particularly in the case of those having through holes, it is necessary to insulate the base material including the through hole drilled in the metal base material.

For example, Japanese Patent Application Laid-Open No. 60-214587 describes a method for manufacturing a metal-based printed circuit board with through-holes, in which a cured resin is used to fill the metal base material in the area where the through-holes are arranged in order to insulate the metal base material from the metal base material. A method of manufacturing a metal-based printed circuit board is shown in which a hole is formed, and then a through hole for forming a through hole is formed in the hole portion to form a through hole. However, this method requires drilling twice to form the through hole, which causes problems such as increased cost due to increased man-hours and difficulty in forming high-density circuits. Apart from this, conventionally, due to its excellent economic efficiency, it has been possible to insulate the metal substrate from the conductor layer constituting the circuit by forming an insulating layer on the metal substrate using electrodeposition paint. Although this is often done, it is important to ensure reliability, especially since the adhesion between the conductor layer, which is generally formed by chemical plating, and the electrodeposited coating is weak, so it is necessary to ensure sufficient insulation for highly reliable printed circuit boards. was not obtained.

Although various conventional methods have been proposed for insulating the metal base material and the conductor layer constituting the circuit, there has been no printed circuit that is fully satisfactory in terms of reliability and economic efficiency. No method for manufacturing the plate has been proposed yet.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above-mentioned problems, and it solves the above-mentioned problems of the conventional printed circuit board manufacturing method. A method for producing a printed circuit board that can produce a highly reliable metal-based printed circuit board with high density and economically, in which a layer and a conductive layer formed by plating on the layer are connected with high adhesion. The purpose is to provide.

[Means for solving problems]

The above objects of the present invention are achieved by the present invention as follows.

(1) forming an insulating layer containing alkaline earth metal carbonate powder on the surface of the metal substrate; (2) eluting the carbonate powder of the insulating layer by acid treatment to roughen the surface of the insulating layer; (3) forming a plating catalyst layer on the roughened insulating layer; and (4) forming a conductor layer by plating on the plating catalyst layer. A method for manufacturing a printed circuit board, comprising:

(Function) In the printed circuit board of the present invention obtained by carrying out each of the steps (+) to 4) above, sufficient adhesion between the conductive layer and the insulating layer can be ensured, so that the printed circuit board has high reliability. It is possible to manufacture circuit boards with high density and economical efficiency.

In a basic embodiment of the present invention, an insulating layer containing alkaline earth metal carbonate powder is first formed on the surface of a metal substrate. From the economic point of view, it is advantageous to form such an insulating layer by, for example, electrocoating using an electrocoating liquid containing an alkaline earth metal carbonate powder.

Here, as the metal base material, for example, aluminum, iron,
A film or substrate made of metal such as copper or an alloy thereof is used. These substrates may be subjected to a desired pretreatment, such as anodization of aluminum. Moreover, when providing a through hole, it is preferable to provide a hole that will become a through hole in the base material in advance.

Examples of electrodeposition coating liquids include emulsions such as epoxy, polyester, silicone emulsion, acrylic, styrene-butadiene, and vinyl acetate, which are widely known in this type of technical field, and water-soluble phenol resin coatings. , water-soluble melamine resin, etc. are used.

Further, examples of the alkaline earth metal carbonate powder include calcium carbonate, magnesium carbonate, barium carbonate, and the like. These may be used alone or in combination of two or more, and calcium carbonate, which is easily soluble in acids, is particularly preferably used. A relatively fine carbonate powder is suitable for the carbonate powder, and the number of fine particles is approximately 10. Below, those below a few are particularly preferred.

Next, the carbonate powder in the insulating layer is dissolved and removed by acid treatment to roughen the surface of the insulating layer. This roughening forms irregularities on the insulating layer, ensuring sufficient adhesion with the conductor layer to be plated later. As the acid, sulfuric acid, hydrochloric acid, chromic acid, nitric acid, oxalic acid, etc. can be used. These acids may be used alone or two or more types may be mixed to form a mixed acid.

During this surface roughening, if the amount of carbonate powder is too small, the surface of the insulating layer will not be sufficiently roughened, and in the opposite case, the film strength of the insulating layer will tend to gradually decrease. It is preferable to contain carbonate powder in an amount of about 1 to 40% by weight based on the weight of the entire layer.

Next, a plating catalyst layer is formed on the thus roughened insulating layer, and then a conductive layer in a desired pattern is formed on the catalyst layer to complete the printed circuit board.

The formation of such a plating catalyst layer and conductor layer can be carried out without any particular difference from conventional methods.

For example, the plating catalyst can be appropriately selected and used depending on the type of plating metal, and a typical example is palladium chloride.

Plating is preferably carried out using chemical plating using a chemical plating solution such as chemical copper or chemical nickel, or electroplating. Of course, it is also possible to use chemical plating and electroplating together if necessary.

(Example) Hereinafter, examples of the present invention will be described with reference to the drawings as necessary.

Example 1 The printed circuit board illustrated in FIG. 1 was fabricated as follows.

First, a desired metal base material as shown in FIG. 1 was prepared.

In this example, an aluminum substrate 1 on which an alumite film 2 having a thickness of IO scale was formed by anodic oxidation in 10% sulfuric acid was used as the metal base material.

Next, carbonate powder 4 with an average particle size of 3 (:aCO3
Using a commercially available acrylic anion electrodeposition coating liquid (manufactured by Honey Kasei Co., Ltd., AL-80ON) in which powder was dispersed, 1
By performing electrodeposition coating under the conditions of 50V and 1 minute,
An insulating layer 3 having a thickness of 20 μm was formed as shown in FIG. The content of CaCO3 powder in the insulating layer 3 thus obtained is approximately 1
It was 0% by weight.

Next, after sufficiently drying and curing the insulating layer 3 at 180° C. for 30 minutes, the insulating layer 3 was coated with Cr03 of 50 g/7
Then, the surface of the insulating layer 3 was roughened by immersing it in a mixed acid containing 200 m1/A of H2SO4 at 50 DEG C. for 5 minutes.

Next, a plating catalyst layer was formed on the insulating layer 3 by immersing the surface-roughened lid base material in a commercially available chemical plating catalyst solution (manufactured by Hitachi Chemical Co., Ltd., H5IOIB) for 10 minutes.

Thereafter, the base material on which the catalyst layer was formed was coated with CuSO4.5
H20 is 10g/j, EDTA/4Na is 30g
/A,H[:)10 is 3g/! So, pl (= 12.5
Plating was carried out by immersing the conductive layer 5 in a chemical copper plating solution at 70° C. for 10 hours to obtain a printed circuit board having a desired pattern of conductive layer 5 in which the copper layer was formed to a thickness of 30 μm. Note that patterning of the conductor layer was carried out by previously forming a plating-resistant resist layer of a desired pattern on the catalyst layer according to a conventional method.

Five printed circuit boards were produced in this way, and their properties were evaluated by measuring the peel strength of the conductor layer, measuring the electrical resistance, and conducting a solder heat resistance test on each board.

Example 2 A printed circuit board similar to Example 1 was prepared in the same manner as in Example 1 except that the content of Calcilla carbonate powder in the insulating layer (based on the entire insulating layer) was changed to 1% by weight. Characteristic evaluations similar to those were performed.

Example 3 A printed circuit board similar to Example 1 was prepared in the same manner as Example 1 except that the content of calcium carbonate powder in the insulating layer was changed to 40% by weight, and the same characteristics evaluation as in Example 1 was carried out. I did it.

Example 4 A printed circuit board similar to Example 1 was produced in the same manner as in Example 1 except that the content of calcium carbonate powder in the insulating layer was changed to 50% by weight, and the same characteristics evaluation as in Example 1 was carried out. I did it.

Example 5 A printed circuit board similar to Example 1 was prepared in the same manner as Example 1 except that the average particle size of the calcium carbonate powder was changed to 1 scale, and the same characteristics evaluation as in Example 1 was performed. .

Example 6 A printed circuit board similar to that in Example 1 was prepared in the same manner as in Example 1 except that the average particle size of the calcium carbonate powder was changed to 50 μm, and the same characteristics were evaluated as in Example 1.

Example 7 A printed circuit board similar to Example 1 was prepared in the same manner as in Example 1 except that the average particle size of the calcium carbonate powder was changed to 300)Lll, and the same characteristics evaluation as in Example 1 was performed. Nawata.

Comparative Example 1 A printed circuit board similar to Example 1 was prepared in the same manner as in Example 1 except that calcium carbonate powder was not used, and the same characteristics evaluation as in Example 1 was performed.

The printed circuit boards of these Examples and Comparative Examples all have sufficient electrical insulation strength of 1097 cm or more, and there was no abnormality such as blistering even in the solder heat resistance test conducted at 260°C for 60 seconds or more. However, as shown in FIG. 3, the printed circuit board of the comparative example in which calcium carbonate powder was not used had low peel strength of the conductor layer and had insufficient reliability. On the other hand, the printed circuit board of the example had sufficient reliability due to the high peel strength of the conductor layer. In addition, FIG. 4 shows the relationship between the particle size and peel strength of calcium carbonate powder.

Example 8 A printed circuit board with through holes illustrated in FIG. 2 was produced as follows.

After laminating and curing copper foil 7 with a thickness of 35 mm on both sides of the aluminum substrate 1 using a commercially available epoxy prepreg adhesive (manufactured by Toshiba Chemical Co., Ltd., TLB-551) 6, holes 8 are drilled in the through-hole forming areas using an NO drilling machine. First, a metal substrate was prepared as shown in FIG. 2, in which a top-thick alumite film 2 was formed on the exposed surface of the substrate in the hole by anodizing in 10% sulfuric acid.

Next, using the same electrodeposition coating liquid as in Example 1, the holes 8 are
After forming an insulating layer 3 with a thickness of 20μ on the exposed part of the base material,
The same surface roughening treatment as in Example 1 was performed.

Next, the laminated portion of the insulating layer 3 and the copper foil 7 is sequentially subjected to the same catalytic treatment and plating treatment as in Example 1 to form the conductive layer 5. By patterning the copper foil and the conductor layer, a printed circuit board with through holes as shown in the second figure was obtained.

The copper foil 7 and the conductor layer 5 are patterned by laminating a commercially available photosensitive dry film (manufactured by DuPont, T-1010) on the conductor layer 5, and then exposing and developing the dry film into a desired pattern. Then, unnecessary portions of the conductor layer and copper foil were removed by etching using a ferric chloride solution.

The thus obtained printed circuit board had high reliability in through-hole connection, and was also excellent in heat resistance and moisture resistance.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to manufacture a highly reliable printed circuit board with excellent adhesion strength between a conductor layer and an insulating layer at high density and economically.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic cross-sectional views of printed circuit boards according to examples of the present invention, and Figure 3 shows peel strength and calcium carbonate powder content of printed circuit boards according to examples of the present invention and comparative examples. FIG. 4 is a diagram showing the relationship between the peel strength of a printed circuit board and the particle size of calcium carbonate powder according to an example of the present invention.

Claims (1)

[Claims] 1. (1) forming an insulating layer containing alkaline earth metal carbonate powder on the surface of a metal substrate; (2) eluting the carbonate powder of the insulating layer by acid treatment; (3) forming a plating catalyst layer on the roughened insulating layer; (4) performing plating treatment on the plating catalyst layer; 1. A method for manufacturing a printed circuit board, comprising the step of forming a conductor layer.