JPS6171692A - Method of producing printed circuit board and 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 Field of the Invention The present invention relates to a method for manufacturing a printed wiring board in which a conductor is formed by S electrolytic plating, and to the printed wiring board.

Prior art JP-A-58-128791 filed by the present inventors
According to Japanese Patent Publication No. 58-134497, a photosensitive resin film is attached to an insulating substrate, baked, and developed to form a permanent mask, and a conductor is formed by electroless plating in the area excluding the permanent mask. A method for manufacturing a printed wiring board and the printed wiring board are described.

Problems that the invention aims to solve As electronic components become smaller and more LSIs and display elements are mounted on wiring boards, the spacing between conductors formed on wiring boards and the width of the conductors are becoming smaller. It's progressing rapidly. In addition, surface mounting is becoming more and more popular as a mounting method for electronic components on wiring boards.

Conventionally, fully additive methods focused on screen printing to form plating resist layers, but
As shown in the above-mentioned publication, a photoresist method has been proposed and is becoming popular.

However, with the development of office automation equipment, when mounting electronic components on both sides of a printed wiring board, it is becoming increasingly common to arrange LSIs on one side and display tubes such as liquid crystals on the other side. This is inconvenient for some people. In other words, LSI terminals are drawn out from the board with a step, whereas display tube terminals are provided directly on the back of the board and hardly protrude from the board surface, so they do not work well with conventional wiring boards. I couldn't respond.

Means for Solving the Problems The present invention involves dispersing a catalyst that reacts catalytically with the reduction of metal cations in an electroless plating solution in an insulating substrate, or using an insulating substrate with catalysts attached to both the front and back surfaces. As a base material, photosensitive resin films with different film thicknesses are pasted on the front and back sides of this insulating substrate, and a photographic film is placed on the surface of this photosensitive resin film, irradiated with ultraviolet rays, and developed to form a photosensitive resin. The film is formed as a plating resist layer, and this insulating substrate is immersed in an electroless plating solution to form an It body layer with a substantially uniform thickness except for the plating resist layer. The thickness of the plating resist layer is approximately the same as that of the plating resist layer.
This is a method of manufacturing a board.

In addition, another invention uses an insulating base material containing a catalyst or having a catalyst attached to the front and back surfaces, and plating resist layers having different thicknesses are formed on the front and back surfaces of this base material, excluding the plating resist layer of this insulating substrate. An electroless plating layer with a uniform thickness is formed at the location, and the thickness of this plating layer is almost the same as the thickness of the plating resist layer with a smaller thickness, and the plating layer and the plating resist layer on the other side are This is a printed wiring board on which a step is formed.

Example Embodiments of the present invention will be described based on the drawings.

Reference numeral 1 denotes an insulating substrate, and the insulating substrate 1 contains a dispersed catalyst 2 that reacts catalytically with the reduction of metal cations in the electroless plating solution, or the catalyst 2 is attached to both the front and back surfaces of the insulating substrate 1. An insulating substrate is used as a base material 3, and Hitachi Chemical Co., Ltd. is applied to the surface of this base material 3! ! A 30u thick photosensitive resin film 4 of the lSR-3000 type is pasted, and a 70μ thick film of the same product is attached to the back side.
A thick photosensitive resin film 5 is attached. That is, photosensitive resin films 4.5 having different thicknesses are attached to both the front and back sides of the base material 1, respectively.

A photographic film 6.7 is placed on the substrate 1 in close contact with the photosensitive resin films 4 and 5, and is irradiated with ultraviolet light 8. A reverse pattern of the conductor pattern is formed on the photographic film 6.7. When the ultraviolet rays 8 are irradiated, the photosensitive resin films 4A and 5Δ in the irradiated areas are cured, and the opaque areas 6A and '7A of the photographic film 6.7 do not transmit the ultraviolet rays and are blocked. Photosensitive resin films 4B and 5B are not cured.

After irradiating with ultraviolet rays 8 and spraying trichlorethylene on both the front and back surfaces of this insulating group Fi10, uncured portions 4B of the photosensitive resin film 4.5 are formed.

5B is dissolved, hardened parts 4△ and 5A remain as they are, and the plating resist! 111.12.

At this time, the plating resist layer 1 formed on the front and back surfaces of the base material
The thickness of 1.12 is smaller on the front side (30μ) and larger on the back side (70μ).

Next, this substrate 10 is immersed in a solution consisting of sodium dichromate and borofluoric acid to chemically roughen the exposed surface 13 of the substrate to improve the adhesion of the plating.

After that, electroless plating solution with the following composition: Copper sulfate pentahydrate 10q/1 Ethylenediaminetetraacetic acid 30g/l Caustic soda PH becomes 12.5 Formalin (37%) 3m/2
The insulating substrate 10 was immersed in a solution heated to a temperature of 70'C for about 3 hours, and the copper plating film thickness was 30μ (formed on the surface side). When the plating layer has grown to the same thickness as the deposited resist layer, the substrate 10 is removed from the plating solution and the printed wiring board 20 is removed. Since the thickness of this conductor 111 is uniform (30 μm) on the front and back surfaces, a flat surface 21 with almost the same thickness as the plating resist 11 and no unevenness is obtained on the front side, and the plating resist 12/ ) (Since it is as thick as 70μ, a step 22 is formed.

Further, another invention uses an insulating base material 3 containing a catalyst 2 or having a catalyst 3 attached to the front and back surfaces, and a plating resist having different thicknesses, for example, 30 μm on the front side and 70 μm on the back side, on both the front and back surfaces of the base material 3. 811.12. Plating resist!
! ! As for 11.12, a plated resist of any thickness can be obtained by using a photosensitive resin film and developing it, or by adjusting the coating film thickness when using a liquid resist. The insulating substrate 10 on which plated resist layers 11 and 12 with different thicknesses are formed on the front and back surfaces is immersed in the electroless plating solution described in WI, and the thickness is approximately the same as that of the thinner plated resist layer 30 μ on the front side. Sanometsu thickness 30μ
A printed wiring board 20 is obtained.

Effects of the Invention In the present invention, the thickness of the plating resist layer formed on the front and back surfaces of an insulating substrate is varied, and an electroless plated conductive layer having the same thickness as the plating resist layer of a small thickness is formed. , the front surface of the substrate is formed into a planar shape 21, and the back surface side is formed with a step 2.
2 was formed. Therefore, like the display tube 21, the main body 22
If the terminal 23 does not protrude too much from the main body 32, the terminal 33 is placed on the front side of the insulating board, such as the LSI 31.
If you install electronic components with protruding parts on the back side where a step is formed, positioning can be performed reliably, soldering work can be performed reliably, and solder bridging phenomenon can be prevented even if the spacing between conductors is narrow. , it has the effect of increasing creepage distance and improving insulation properties.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a printed wiring board of the present invention with a display tube mounted on the front side and an LSI mounted on the back side, Figs. 2 and 3 are cross-sectional views of the base material, and Fig. 4 is a photosensitive resin film mounted. Figure 5 is a cross-sectional view of the pasted photo film and irradiation with ultraviolet rays, Figure 6 is a cross-sectional view of the plated resist layer formed.
FIG. 7 is a cross-sectional view of the present invention. In the drawings, 1 is an insulating substrate, 2 is a catalyst, 3 is a base material, and 4
．． 5 is a photosensitive resin film, 6.7 is a photographic film, 8
11.12 is a plating 1/cyst, 14 is a conductor, and 20 is a printed wiring board. Patent applicant: Hitachi Capacitor Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Procedures Amendment (voluntary) June 13, 1985

Claims (2)

[Claims] (1) An insulating substrate containing a catalyst or a catalyst attached to the front and back surfaces is used as a base material, photosensitive resin films of different thicknesses are pasted on the front and back surfaces of this base material, and a photographic film is placed on top of this photosensitive resin film. After applying ultraviolet rays and developing it,
A cured photosensitive resin film is formed as a plating resist layer, and this substrate is immersed in an electroless plating solution to form a conductive layer with a substantially uniform thickness except for the plating resist layer. A method for manufacturing a printed wiring board, characterized in that the thickness is formed to be approximately the same thickness as a plating resist layer having a small thickness. (2) Using an insulating base material containing a catalyst or having a catalyst attached to the front and back surfaces, plating resist layers with different thicknesses are formed on the front and back surfaces of this base material, and the entire surface of the insulating substrate except for this plating resist layer is uniform. A thick conductive layer is formed by electroless plating, and the thickness of this conductive layer is almost the same as the thickness of the thinner plating resist layer, and a step is formed from the other plating resist layer. A printed wiring board characterized by: