JPS584999A - Manufacturing method for printed wiring boards - 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 involves forming a wiring pattern with a conductive foil on at least one side of an insulating substrate such as an insulating plate or an insulating film, and placing a wiring pattern over a coating resin layer in a hole penetrating the insulating substrate. Coating forms a conductive layer.

This invention relates to a method of manufacturing a printed wiring board that has both sides electrically connected.

Conventional printed wiring boards are based on copper-clad laminates, which are made by pasting copper foil on one side of an insulating board such as a paper-phenol resin laminate, and this copper foil is selectively etched or selectively plated to meet the requirements. A wiring pattern is formed, and then the lead attachment holes of the mounted components or the through holes between both sides of the base are processed by drilling, punching, etc., and the other side without the wiring pattern is coated with epoxy resin, melamine resin, etc. After that, the through holes are filled with a conductive material such as conductive paint.

harden. Next, a solder resist is formed leaving the soldering area on the wiring pattern surface, or a smooth, soldering heat-resistant coating is formed on the insulating surface, and resistive paint or conductive paint is printed on the insulating surface.

An overcoat is applied over the entire surface of these conductive and resistive paints.

Page 3 In printed wiring boards manufactured by such a conventional method, conductive paint is applied directly to each through hole, so the conductive paint seeps into the inside of the insulating substrate from the through hole wall, which has a rough surface due to processing. Also, through the conductive paint layer,
Moisture penetrates inside the insulating substrate extremely easily, so in many cases where multiple through holes are placed close together and with different potential differences, electrical short circuits are likely to occur, impairing the function of the printed wiring board. There was a risk.

The present invention eliminates these conventional drawbacks,
Examples thereof will be described below with reference to the drawings.

As the insulating substrate 1, a paper-based phenolic resin laminate 1 a paper-based epoxy resin laminate, a glass cloth-based epoxy resin laminate, a glass cloth-based polyimide resin laminate, a polyimide film, a polyester film, a polyparabanic acid film, and The glass mat base material is mainly used for molding plates such as amorphous polyester resin, polybutadiene film, triazine resin, BT (bismaleimide triazine) resin, diallyl phthalate resin, monocuring unsaturated polyester resin, etc. with a thickness of 1.6. The thickness range is 0.025
A copper clad board having a thickness of 10 to 50 μm attached to one or both sides of a copper foil having a thickness of 10 to 50 μm is used. Of course, this copper foil can also be formed by electroplating or chemical plating. By selectively removing unnecessary portions of the copper foil of this copper clad plate or similar structure using etching technology or selectively applying plating, the necessary circuit pattern 2 is formed as shown in FIG. get. The first example) shows the case where the copper foil adhesive layer 3 was left as is. Next, as shown in Fig. 2 (m), out of the forming part of one circuit pattern 2, the other part is insulated so that the part necessary for soldering or use as an electrical contact point is left in a more limited form. 4. Perform the adhesive resin coating 4. At this time, if there is a surface on which the 1-circuit pattern 2 does not exist, the same insulating resin coach and ink 5 are applied to this surface as well.

The direction of the second figure corresponds to the first figure), and the resin coating 4 may be omitted. Next, holes for component leads, terminal insertion holes, and through hole connections for through-hole connections are punched out or drilled to a diameter of 1.0118 mm, with a diameter range of 1.0118 mm.

Open as 0.4 to 2,011. Then, an insulating resin coating 7 is applied to the through-holes 6 for through-hole connection and, if necessary, to the holes for inserting component leads and terminals. Methods include applying it by hand and applying it using a pin.

By making the apertures of the perforated mask concentric circles and matching the diameter to the hole, it was possible to screen print on the hole walls using a squeegee without applying the coating to the front and back surfaces of the insulating plate. In this way, a coating resin layer can be formed on the entire insulating surface of the surface of the printed wiring board (the insulating surface of the gap between the copper foil conductors and the surface of the wall where the holes are formed). Epoxy resins are well-known as coating resins, and in fact have electrical properties and moisture resistance equivalent to or better than most insulating substrates for printed circuit boards. An example of an epoxy resin that is easy to use is Epikote 828.As a curing agent, an aromatic amine type curing agent is easy to cure at a relatively low temperature and is superior in terms of electrical properties and hygroscopicity. Use of an aliphatic amine resin curing agent in combination with a diluent is undesirable because it reduces the electrical properties of the coating resin layer. As a solvent, butyl cellosolve acetate, butyl calpitol or the like is used, and the working range is a viscosity of 90 to 160 poise for surface printing and 10 to 100 poise for pore wall coating. The curing conditions range from 12° to 220°C, but if there is a subsequent heat processing step, it is more energy-saving to leave it in a semi-cured state at 120°C for about 15 minutes. The printing thickness is 10-16μ.

Next, the through holes 6 are coated with conductive paint or plated. Plating can be applied using known through-hole plating techniques such as copper sulfate bath electroplating and alkaline electroless plating bath (for example, Shipley's A626 solution).
is applicable. However, these platings stick to the wiring board surface, so we printed a plating resist on the wiring board surface.
It takes time to cure and then to peel off after plating. The cost of conductive paint is less than 1/4 of that of a plating bath, and there are 7 pages. 1. Since selective coating is easy by direct printing, there is no need to print a metal resist on the wiring board surface. By using a mask with through holes and printing with a squeegee, the conductive paint conductor 8 can be formed over the land on one surface and the hole wall. However, it is not possible to form even the land on the back side.Therefore, by printing conductive paint 8a on the insulating surface of the single-sided printed wiring board that has no wiring pattern, single-sided wiring and through-hole connection can be achieved. It is highly efficient and can reduce the cost to less than 1/2 compared to the 7I double-sided wiring board using the butterbur method.

In this way, the insulating surface of the printed wiring board is not directly exposed to the outside air, the plating solution, or the solder bath, so the penetration of the plating solution, moisture, and humidity into the insulating substrate is reduced, and it can be used even in high humidity. Insulation resistance is maintained 2 to 3 orders of magnitude higher than before. It also has the advantage of eliminating peeling of the conductor that occurs due to repeated thermal shocks such as in a solder bath.In addition, it is possible to select a through-hole conductor that is cheaper than plating on a cheaper double-sided wiring board, and even rough holes can be used for hole processing. For,
Since the cost is low, it has very high practical value.

[Brief explanation of the drawing]

FIGS. 1(M), 2), FIGS. 2C&), 2), FIGS. 3 and 4 are sectional views for explaining a method according to an embodiment of the present invention. 1...Insulating base, 2...Copper foil, 3...
...adhesive layer. 4.6. ...Coating resin layer, 6...
・Through hole, 7...Coating resin layer, 8...
...Conductive paint.

Claims (2)

[Claims] (1) On the wiring pattern surface of an insulating substrate on which a wiring pattern made of conductive foil is formed on at least one side. The soldering process is characterized in that after a first coating resin layer is provided leaving a planned portion, a through hole is formed in the insulating base, and a second coating resin layer is formed on the insulating surface surrounding the hole. A manufacturing method for printed wiring boards. (2) A conductive paint layer is overlaid on the second coating resin layer, and the end thereof is extended to at least one side so as to be in direct contact with the conductive foil, and a through hole that does not come into direct contact with the insulating substrate. A method for manufacturing a printed wiring board according to claim 1, in which connection is made.