JPS625692A - Manufacture of 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 The present invention relates to a method for manufacturing a circuit board in which conductors are formed by electroless plating. Recently, the miniaturization of electronic components and
As integrated circuit components such as C were increasingly used, the distance between conductive patterns was reduced, and as a means of obtaining a plated resist layer.

A photomask method is effective.

In the present invention, the photosensitive resin film used in the photomask method has strong alkali resistance (the plating solution is highly alkaline).
Using a film that suffers less thermal deterioration when immersed in the solder layer (no cracks occur due to heat, and less deterioration of the insulation resistance of the film), this film is used as a permanent metal resist to form printed wiring boards. It is configured to remain as it is.

This permanent plating resist is formed with a reverse pattern of conductors, so that conductors are formed in locations where this resist 1- is not attached. A feature is that the thickness of this conductive layer is thinner than the thickness of the mesh resist.

The conventional manufacturing method for printed wiring boards using the additive method uses an insulating board such as a catalyst-containing epoxy glass laminate as a base material, prints a reverse conductor pattern of epoxy resin on the surface of this base material, and then removes this board. When immersed in an electrolytic copper plating solution, copper plating is deposited at locations other than those where the electrolytic conductor pattern is printed. The thickness of this copper plating increases in proportion to the time the substrate is immersed, so the thickness can be freely controlled. This method of forming a plating resist layer by sink printing has its limits when the conductor patterns become narrower and closer to each other, and the printing may be misaligned.

There were problems such as meandering and adjacent patterns coming into contact with each other, and it was not possible to reduce the defective rate.

In the printed wiring board of the present invention, the plating resist is applied by using a heat-resistant and chemical-resistant photosensitive resin film instead of using an epoxy resin sink printing method. It is used to make a permanent photo print and perform the action of a metsukire cyst.

The embodiment of the present invention will be described based on the aspect. Reference numeral 21 is a base material, and this base material 1 is mixed with a catalyst 2 that promotes copper deposition when immersed in an electroless copper plating solution. 3 is a photosensitive resin film having excellent heat resistance and chemical resistance (for example, 5R-106 manufactured by Hitachi Chemical Co., Ltd.), and this film 3 is laminated on the surface of the base material 1. The thickness of this film is greater than the thickness of the adhesion layer.

Since the standard film thickness is about 30 μm, a suitable film thickness of 40 μm or more may be used in this case.

A negative film 4 on which a conductive pattern has been printed is placed on the photosensitive resin film 3 and irradiated with light, whereby the film 3 is cured by the transmitted light through the transparent portion 6 of the negative film 4. After this, a heat treatment is performed to accelerate the hardening of the film.

After cooling and returning to room temperature, the uncured portion 8 of the film 3 is developed with a chemical such as trichloroethane, so that only the cured portion 7 remains on the base material 1. In other words, the mesh resist layer 9 has been formed.

When the base material 10 on which the plating resist layer 9 is formed is immersed in a known electroless copper plating layer, as one hour passes, copper plating is deposited in areas where the plating resist 9 is not formed in proportion to the immersion time. A conductor 11 is formed. The thickness of the conductor 11 is thinner than the thickness of the plating resist layer 9, and a step is created between the conductor layer 11 and the plating resist layer 9.

In the printed wiring board of the present invention, the plating resist layer 9 attached to the surface is made thicker than the conductor layer 11, so that the terminal portion 21 of the flat-back type electronic component 20 can be placed on the printed wiring board.
Since the position of the ffi child component is determined, subsequent soldering work can be performed reliably, and mistakes such as the electronic parts moving during soldering work can be prevented. Further, even if the distance between adjacent conductors becomes narrow, the creepage distance between the conductors can be increased, so this invention is effective in improving insulation properties.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the base material of the present invention, and FIG. 2 is a sectional view of the base material laminated with a photosensitive resin film. Figure 3 is a sectional view showing the state in which a negative film is placed and exposed to light to be printed, Figure 4 is a sectional view showing the state in which the film is developed and hardened and formed as a plating resist, and Figure 5 is a cross-sectional view showing a state in which a conductor layer thinner than the film thickness is formed. FIG. 6 is a sectional view in which electronic components are set. In the drawing, ■ indicates the base material, 2 indicates the catalyst mixed in the base material, and 3 indicates the catalyst mixed in the base material.
4 is a photosensitive resin film, 4 is a negative film, 5 is irradiated light, and 6 is a transparent part of the negative film. 7 is a cured portion of a photosensitive film, 9 is a permanent plating resist, 11 is a conductor, 20 is an electronic component, and 21 is a terminal portion of the electronic component.

Claims (1)

[Claims] 1. Form a plating resist layer with a pattern opposite to that of the conductor on an insulating base material, and immerse this substrate in an electroless plating solution to form a conductor pattern with a thickness thinner than the thickness of the plating resist layer. A method of manufacturing a circuit board characterized by leaving a resist layer as it is as a solder resist, placing terminals of electronic components on a conductive pattern surface, and performing soldering.