JPH0632375B2 - Printed wiring board manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a printed wiring board.

[Background technology]

Through holes are formed in the printed wiring board for component mounting. As described above, in order to obtain a printed wiring board having through holes, it has been conventionally performed as shown in FIGS. 2 (a) to (g).

That is, as shown in FIG. 2 (a), an aluminum base copper clad laminate (aluminum CCL) 50 is prepared. This aluminum-based copper-clad laminate 50 is based on an aluminum substrate 501 and has an alumite layer 50 on both sides thereof.
2, an adhesive layer 503, and a copper foil 504 are sequentially laminated. As shown in FIG. 2 (b), a hole 51 for a through hole is made in the aluminum-based copper-clad laminate 50. As shown in FIG. 2 (c), the inner wall surface of the through hole hole 51 is subjected to electrolytic etching to smooth the aluminum substrate portion and the alumite layer portion exposed on the inner wall surface. As shown in FIG. 2 (d), the alumite layer 52 is formed on the smoothed aluminum substrate and the alumite layer portion by performing the alumite treatment. Further, as shown in FIG. 2 (e), powder electrostatic coating is applied to form a powder electrostatic coating layer 53 on the alumite layer 52. As shown in FIG. 2 (f), electroless copper plating is applied to form an electroless copper plating layer 54 on the inner wall surface of the through hole hole 51 and on the copper foil 504. After that, perform tenting (filling the holes for through holes),
As shown in Fig. 2 (g), by applying an etching resist to form a desired electric path and then etching, the resist is removed and the tenting is removed. Was formed,
That is, a printed wiring board in which the through hole 51 'and the electric path 55 are formed can be obtained.

As described above, the printed wiring board with through holes was manufactured. According to this method, when the holes 51 for through holes are opened, as shown in FIG.
Incorporate a metal foil such as No. 4 (the part B in the figure is the part involved.
In the figure, arrow A indicates the drilling direction. In some cases, the wound metal foil comes into contact with a metal substrate such as the aluminum substrate 501, resulting in poor insulation between the metal foil and the metal substrate. Therefore, in the obtained printed wiring board, insulation failure between the conductor layer of the through hole and the metal substrate has occurred. Also, when chemical conversion treatment such as alumite treatment is performed with the metal foil such as the copper foil attached, the metal foil such as the copper foil dissolves, and thus a protective mask for the metal foil such as the copper foil is required. The work of attaching and removing the protective mask was required. Moreover, when powder electrostatic coating or the like is applied in the state where the metal foil such as copper foil is attached, the paint adheres to the surface of the metal foil such as copper foil, so that it is necessary to remove it. In addition, there is a drawback that work such as tenting is required, there are many work steps, and productivity is poor.

On the other hand, as a method for obtaining a printed wiring board with through holes which does not cause insulation failure due to the winding of the metal foil and has good productivity, there are conventionally methods shown in FIGS. 4 (a) to 4 (f).

In the case of this method, first, as shown in FIG. 4 (b), an insulating resin layer 72 is formed on both surfaces of the aluminum substrate 71 shown in FIG. ),
A hole 73 for a through hole is formed in the aluminum substrate 71. Then, as shown in FIG. 4 (d), an alumite layer 74 is formed on the inner wall surface of the through hole 73 by chemical conversion treatment, and subsequently, as shown in FIG. 4 (e), an electroless plating layer is formed. 75 is formed, and then a mask (not shown) for covering a necessary portion is provided, electroplating is performed, the mask is removed, and an unnecessary portion of the electroless plating layer 75 is removed. ), The holes 73 for through holes are covered with the electroplating layer 76 to form through holes, and a wiring electric circuit (not shown) can be formed.

However, the alumite layer formed by chemical conversion treatment on the surface portion of the aluminum substrate has good adhesion, but since it is porous, the plating solution easily enters the layer during electroless plating and easily absorbs moisture and has an insulating property. However, there is a drawback in that the conductive layer formed on the conductive layer formed on the surface of the conductor layer is cracked due to a decrease in strength or a weakness against heat cycle or thermal shock, resulting in cracks. It is hard to say that it is practical if the insulation is deteriorated or conduction is poor.

[Object of the Invention]

In view of the above circumstances, the present invention does not cause insulation failure due to the winding of the metal foil at the time of drilling a through hole,
Highly productive, the insulating layer on the inner wall of the through hole is
It is a solid product with no concern about insulation failure or conduction failure. Furthermore, it can sufficiently support the high density of printed wiring boards and keeps the excellent heat dissipation of the aluminum substrate. It aims at providing the method which can obtain the printed wiring board with a through hole.

[Disclosure of Invention]

In order to achieve the above-mentioned object, the present invention provides a printed wiring board having through holes formed with holes for through holes in an aluminum substrate having insulating resin layers formed on both surfaces thereof, and forming a hole on the inner wall surface of the holes. An alumite layer is formed by treatment, and a crack generation treatment is applied to the alumite layer, and then an electrodeposition coating layer is formed on the alumite layer by electrodeposition coating, and then on the electrodeposition coating layer and the insulating resin. The gist is a method for producing a printed wiring board, which is characterized in that a conductor layer is formed on the layer by a plating method.

Hereinafter, the present invention will be described in detail with reference to the drawings showing an embodiment thereof.

FIGS. 1 (a) to 1 (i) show an embodiment of a method for manufacturing a printed wiring board according to the present invention.

As shown in FIG. 1 (a), an aluminum substrate (metal substrate) 1 is prepared.

As shown in FIG. 1 (b), an adhesive layer (insulating resin layer) 2 is formed by applying an adhesive agent to both surfaces of the aluminum substrate 1.

As shown in FIG. 1 (c), holes 3 for through holes are formed using a mold or the like.

Deburring and surface roughening of the adhesive layer 2 are performed. This is performed by using any of sandpaper, buffing, liquid honing, etc., or by using them in combination.

As shown in FIG. 1 (d), electrolytic polishing is performed to remove the protrusions on the inner wall surface of the through-hole 3 and smooth the inner wall surface.

As shown in FIG. 1 (e), by performing the alumite treatment (chemical conversion treatment), the alumite layer 4 is formed on the aluminum substrate portion exposed on the inner wall surface of the through hole hole 3.
To form.

A thermal shock (heat shock) of 100 deg or more is applied to cause cracks in the alumite layer 4.

As shown in FIG. 1 (f), the electrodeposition coating layer 5 is formed on the alumite layer 4 by applying the electrodeposition coating. Through these steps, an insulation treatment layer including the alumite layer 4 and the electrodeposition coating layer 5 is formed on the inner wall surface of the through hole.

As shown in FIG. 1 (g), electroless copper plating is applied to form an electroless plating layer having a thickness of about 1 μm on the insulating treatment layer (the electrodeposition coating layer 5 in this embodiment) and the adhesive layer 2. Form layer 6.

As shown in FIG. 1 (h), after the pattern resist 7 is printed, electrolytic copper plating is performed to form an electrolytic copper plating layer 8 on a desired portion (inner wall surface of the through hole hole and a portion to be an electric path). Form.

 The pattern resist 7 is removed.

By etching the entire surface, the unnecessary electroless copper-plated layer 6 is dissolved and removed, leaving only the desired portion of the conductor layer composed of the electroless copper-plated layer and the electrolytic copper-plated layer 8. A printed wiring board having through holes 3'and electric paths 8'as shown in FIG.

As described above, in the method for manufacturing this printed wiring board, the through hole is drilled in the state where the metal foil such as the copper foil is not attached to the metal substrate such as the aluminum substrate.
Metal foil such as copper foil does not get caught. Therefore, in the obtained printed wiring board, insulation failure between the conductor layer of the through hole and the metal substrate will not occur. Also, since the chemical conversion treatment such as alumite treatment is performed in the state where the metal foil such as the copper foil is not attached to the metal substrate such as the aluminum substrate, there is no fear that the metal foil such as the copper foil will be dissolved (the adhesive may affect Not to receive). Therefore, a protective mask for metal foil such as copper foil becomes unnecessary, and the mounting of the protective mask,
The work process of removal can be omitted. In addition, since the metal foil such as copper foil is not applied to the metal substrate such as the aluminum substrate, the coating such as electrodeposition coating is performed, so there is no fear that the paint will adhere to the surface of the metal foil such as copper foil. It is possible to omit the work step for removing the paint. Further, the conductor layer (electric path) on the insulating resin layer and the conductor layer of the through hole can be simultaneously formed by the semi-additive method (plating method using electroless plating and electroplating), and the work steps such as tenting can be omitted. As described above, compared with the conventional manufacturing method, the number of working steps is small throughout and the productivity is good.

In this embodiment, after the alumite layer is formed, heat shock is applied to previously generate cracks in the alumite layer, and then electrodeposition coating is applied. Therefore, the electrodeposition coating material penetrates into the cracked portion to improve the insulation reliability, and it becomes difficult for the alumite layer to crack again after the printed wiring board is completed.

As the method for forming the conductor layer, the semi-additive method is used in the above-mentioned embodiment, but the full-additive method using only electroless plating may be used. As the paint used for electrodeposition coating, acrylic melamine, epoxy-based electrodeposition coating, etc. are used. An adhesive for forming an insulating resin layer is used in order to ensure adhesion between the metal substrate and the conductor layer.
A mixture of a silicone-modified epoxy resin and NBR as a main agent and a curing agent, and a silicone-modified epoxy resin and NBR as a main agent as disclosed in JP-A-59-81368. A compound containing a borohydride amine complex, a compound shown in JP-A-59-81370 containing a silicon-modified epoxy resin and NBR as a main component, and an aromatic polyamine as a curing agent and a curing accelerator. It is preferable to use.

Next, the above embodiment will be described more specifically.

(Example) An adhesive having the following composition was applied to both surfaces of an aluminum substrate in an amount of 70 μm each and cured under the conditions of 150 ° C. and 60 minutes.

[Composition of adhesive]

Silicon modified epoxy resin 100 parts by weight NBR 100 parts by weight Alumina 100 parts by weight Curing agent and solvent Appropriate amount Using a mold, holes for through holes having a diameter of 1 mm were opened.

After polishing both surfaces with # 600 waterproof paper, liquid honing was used to roughen the surface and simultaneously remove burrs.

The treated body was made into an anode using a 5% sodium hydroxide solution, and electropolishing was performed at a DC voltage of about 1-2 V for 5 minutes.

Alumite treatment was performed for 60 minutes at a current of 1.5 A / dm ² using a 10% sulfuric acid solution, and a thickness of about 30 μ was formed on the aluminum substrate portion exposed on the inner wall surface of the through hole.
m alumite layer was deposited.

Immediately after putting in the furnace at 150 ℃ for 5 minutes, 10 ℃
A heat shock was given by putting it in the water.

Acrylic melamine (Electron NO3500R manufactured by Kansai Paint Co., Ltd.) was used as the electrodeposition paint, and after the electrodeposition was applied at a voltage of DC 180 V for 10 minutes, the paint was applied at 180 ° C.
Cured for 30 minutes at a thickness of approximately 15 μm on the alumite layer
Was applied.

By electroless copper plating on the entire surface, an electroless copper plating layer having a thickness of about 1 μm was deposited on the electrodeposition coating layer and the adhesive layer.

By screen-printing the alkali-soluble resist, masking the parts other than the part that will be the electric path on both sides, and then performing electrolytic copper plating, the thickness of the desired part (the inner wall surface of the through hole and the part that will be the electric path) will be approximately Three
A 5 μm electrolytic copper plating layer was deposited.

The alkali-soluble resist was dissolved and peeled off with a 5% sodium hydroxide solution.

By etching the entire surface with an etching solution, the unwanted electroless copper plating layer is dissolved and removed, leaving only the desired portion of the conductor layer consisting of the electroless copper plating layer and the electrolytic copper plating layer, and forming a through hole and electric path. The printed wiring board thus obtained was obtained.

The electrical performance of the through holes of the printed wiring board obtained as described above was measured. The measurement was carried out at a portion where conductor layers of 1 cm × 1 cm centering on the through hole were formed on both surfaces.

As a result, the withstand voltage between the conductor layer of the through hole and the aluminum substrate was 1000 V or more, and the insulation resistance between the conductor layer of the through hole and the aluminum substrate was 10 ° MΩ or more. From this result, according to the method for producing a printed wiring board according to the present invention, in the obtained printed wiring board, insulation failure between the conductor layer of the through hole and the metal substrate does not occur, and the insulating property is extremely high. I understand.

The method for manufacturing the printed wiring board according to the present invention is not limited to the above-mentioned embodiment.

〔The invention's effect〕

The method for manufacturing a printed wiring board according to the present invention described above is extremely practical because it can simultaneously achieve the following effects (1) to (5).

Effect (1) Insulation failure due to the inclusion of metal foil during drilling for through holes does not occur.

This is because, in the case of the present invention, since the through hole is drilled in a state where the metal foil is not attached to the aluminum substrate, the metal foil is not rolled up during the drilling.

Effect (2) High productivity.

This is because when an insulating film is formed on the inner wall surface of a hole for a through hole, there is no metal foil only on the surface of the aluminum substrate, and there is no metal foil, so it is necessary to attach / remove a metal mask protective mask or to attach paint to the metal foil. This is because it is not necessary to remove and the troublesome tenting work can be omitted.

Effect (3) The insulating layer on the inner wall surface of the through hole is strong and has sufficient insulation. An insulating layer that is strong and has a sufficient insulating property does not cause insulation failure or conduction failure.

This is due to the layer structure in which the insulating layer is formed by subjecting the alumite layer formed by chemical conversion treatment to crack generation treatment and then applying the electrodeposition coating layer.

The alumite layer formed by oxidizing the surface of the aluminum substrate by chemical conversion treatment (anodic oxidation) has good adhesion, but since it is porous, the plating solution easily enters the layer during electroless plating and absorbs moisture. Insulation is easily deteriorated, or cracks are vulnerable to heat cycle or thermal shock, and there is a drawback that the conductive layer formed thereon has cracks and poor conduction, but in the case of the present invention, Since the electrodeposition coating layer is formed after the crack generation process is performed and the cracks and micropores are sealed, it is strengthened without the occurrence of new cracks and the porosity is eliminated. Therefore, moisture absorption and residual plating solution do not occur, and the insulation is sufficient.

Effect (4) It is possible to sufficiently cope with the high density of the printed wiring board.

Since the alumite layer and the electrodeposition paint layer of the chemical conversion treatment can be sufficiently formed with a small thickness, even if an insulating layer is provided on the inner wall surface of the hole for a small through hole, the layer thickness will be thin and the hole will be clogged. You can avoid the situation. The higher density of the printed wiring board is accompanied by the smaller diameter of the through hole, which can be sufficiently dealt with.

Effect (5) The excellent heat dissipation of the aluminum substrate is not impaired.

This is because the electrodeposition coating layer in the present invention is naturally formed only on the alumite layer, the electrodeposition coating layer is not formed on the aluminum substrate surface, and the substrate surface is covered with an unnecessarily thick film. This is because the excellent emissivity due to the high thermal conductivity of aluminum is retained.

[Brief description of drawings]

1 (a) to 1 (i) are explanatory views showing an embodiment of a method for manufacturing a printed wiring board according to the present invention, and FIGS. 2 (a) to 2 (g) are explanations showing a method for manufacturing a conventional printed wiring board. FIGS. 3 and 4 are explanatory views showing a state after forming holes for through holes in a conventional printed wiring board manufacturing method, and FIGS. 4 (a) to (f) are explanatory drawings showing another conventional printed wiring board manufacturing method. It is a figure. 1 ... Aluminum substrate (metal substrate), 2 ... Adhesive layer (insulating resin layer), 3 ... Through hole, 4,5 ...
Insulation layer, 6, 8 ... Conductor layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshinaga Yamakawa, 12-1 Satsuki-cho, Kanuma City, Tochigi Prefecture, Kanuma Plant, Toyo Giken Co., Ltd. (72) Hideo Miyagi, 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works (72) Inventor Toshiyuki Suzuki 1048, Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Masami Takagi, 1048, Kadoma, Kadoma City, Osaka Matsushita Electric Works, Ltd. (56) References JP-A-52-59852 (JP, A) JP-A-51-132458 (JP, A) JP-A-53-111471 (JP, A) JP-A-55-19853 (JP, A) JP-A-57-126193 (JP , A) Japanese Patent Sho 58-35376 (JP, B2)

Claims (1)

[Claims] 1. To obtain a printed wiring board having through holes, holes for through holes are formed in an aluminum substrate having insulating resin layers formed on both sides, and an alumite layer is formed on the inner wall surface of the holes by chemical conversion treatment. Then, after subjecting the alumite layer to a crack generation treatment, an electrodeposition coating layer is formed on the alumite layer by electrodeposition coating, and then a plating method is applied on the electrodeposition coating layer and the insulating resin layer. A method for producing a printed wiring board, which comprises forming a conductor layer.