JPH02122688A - Manufacture of printed circuit board - Google Patents

Abstract

PURPOSE:To enable formation of fine circuit pattern by forming a copper foil circuit patterned with etching resist on a copper-clad board, applying electroplating resist to it, and electroplating holes and the copper foil. CONSTITUTION:A hole 4 is made through a substrate 1 sandwiched by copper foils 2, then catalyst 3 is applied on the inner wall of the hole 4 and the opposite faces of the substrate 1. Then the opposite faces of the substrate 1 are coated with etching resist 5 and subjected to exposure, development and etching. Thereafter, liquid photoresist is applied entirely on the opposite faces of the substrate, then it is dried, exposed, developed and hardened thus forming a plating resist 6. Then the etching resist 5 is removed. Thereafter, electroless copper plating is carried out on the inner wall of the hole 4 and the copper foil 2 thus forming a through-hole and a circuit pattern. Then solder mask 8 is printed on parts except a mounting pad, lands and through-holes thus producing a predetermined printed circuit board.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a printed wiring board, and particularly to a method for manufacturing a printed wiring board having through holes.

[Conventional technology]

Conventionally, the subtractive method and additive method have been used as methods for manufacturing printed wiring boards, but in particular, the additive method has been used to form fine lines as the density of printed wiring boards continues to increase. It has attracted attention in recent years because it is easy to use.

Additive methods include a part-additive method in which only through-holes are formed by electroless plating, and a full-additive method in which both through-holes and circuit patterns are formed by electroless plating.

In the part-additive method, as shown in Figure 2, the hole 4
After performing catalytic treatment on the copper-clad substrate 1 with the holes drilled therein, the copper foil 2 is etched using a photosensitive dry film to form a circuit pattern. A printed wiring board is formed by forming a plating mask 6 and forming copper plating 7 on holes 4 and lands and pads by electroless plating.

In addition, in the full additive method, generally, as shown in FIG. 3, holes 4 are formed in a substrate 1 containing an adhesive and a catalyst, and after a plating resist 6 is formed, the holes 4 and the substrate are formed by electroless plating. Copper plating 7 is applied to portions of 1 that are not covered with plating resist 6 to form through holes and circuit patterns. Furthermore, a solder mask 8 was printed to form a predetermined printed wiring board.

[Problem to be solved by the invention]

The above-described conventional method for manufacturing a printed wiring board using the additive method has the following drawbacks.

(1) In recent years, there has been remarkable progress in increasing the density of printed wiring boards, and what used to be one or two wires between 0.1-inch grids is now becoming mainstream with three wires. Along with this, the width of the circuit pattern is also 0.1 inch with a lattice spacing of 2
From about 200μm for main wiring to 100μm for three wirings
The pattern has been miniaturized to ~150 .mu.m, and it is thought that in the future, as the number of interconnects increases to 4 to 6, ultra-fine patterns of 100 .mu.m or less will become available. However, the miniaturization of circuit pattern widths, on the other hand, increases the electrical resistance of circuit patterns that should be conductors, reduces the electrical margin for stable operation of electronic devices, and makes circuit design more complex and difficult. It ends up.

In the above-mentioned part-additive method, a circuit pattern is formed only with copper foil, and usually silver foil with a thickness of 35 μm is used. However, as circuit patterns become finer in this way, there is a problem in that a 35 μm thick copper foil has high electrical resistance. To improve this problem, the copper foil thickness was increased by 50 mm.
A method of increasing the thickness to .mu.m or 70 .mu.m has also been used, but in this case, the amount of etching becomes large, making it difficult to form fine patterns.

(2) Surface mounting of mounting technology is now a commonly used technology. Qu is a typical surface mount component.
There is an ad Flat I'ackage (abbreviated as QFP), but the pitch between QFP pads has been reduced year by year, and now even 0.5 dragon pitch is used. In this case, the pad spacing of the printed wiring board is 0.2 to 0.
．． It becomes narrower at 25 Iom. Furthermore, now f&0.4Il1
The pitch between QFP pads is becoming narrower and narrower, and the pad spacing on printed wiring boards is also 0.15 to 0.20 mm.
It seems that it will gradually become narrower.

As described above, when the pitch between pads becomes narrow, in the above-mentioned part-additive method, bridging and the like are likely to occur due to plating deposited between the pads, which requires a considerable number of repair man-hours and significantly reduces yield.

(3) Since the fully additive method uses a special base material with adhesive layout and catalyst, it is also effective in terms of material cost.
Material supply destinations are limited.

(4) In addition, in order to reduce material costs, a method is used in which a base material without catalyst is used and treated with catalyst after drilling, but in this case, the catalyst remains between the circuits and the insulation resistance decreases significantly.

An object of the present invention is to provide a method for manufacturing a printed wiring board that allows the formation of fine circuit patterns, is compatible with surface mounting, has high insulation resistance, and can be supplied stably at low cost.

[Means to solve the problem]

The method for manufacturing a printed wiring board of the present invention includes the steps of drilling holes in a substrate having copper foil laminated on both the front and back surfaces and subjecting it to catalyst treatment;
A step of depositing etching resist on both the front and back surfaces of the substrate and etching away the exposed portion of the copper foil, forming a plating resist on the removed portion of the copper foil, and after removing the etching resist, The method includes a step of depositing plating on the hole and copper foil to form a through hole and a circuit pattern, and a step of covering a predetermined portion of the circuit pattern with a solder resist.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) to 1(f) are sectional views showing the order of steps for explaining the manufacturing method of the first embodiment of the present invention.

In the first embodiment, as shown in FIG. 1(a), a hole 4 is first formed in a substrate 1 on which copper foil 2 is laminated on both the front and back sides, and then a catalyst 3 is placed on the inner wall of the hole 4 and on the front and back sides of the substrate 1. Adhesion is formed on both sides.

Next, as shown in FIG. 1(b), on both the front and back surfaces of the substrate 1,
As the etching resist 5, for example, a dry film resist is laminated and exposed, developed, and etched.

Next, as shown in FIG. 1(c), a photo-developable liquid resist is applied to the entire surface of both the front and back surfaces of the substrate, dried, exposed, developed, and hardened to form a plating resist 6.

Next, as shown in FIG. 1(d), the etching resist 5
Peel and remove.

Next, as shown in FIG. 1(e), electroless copper plating is performed to deposit copper plating 7 on the inner wall of the hole 4 and the copper foil 2, thereby forming a through hole and a circuit pattern.

Next, as shown in FIG. 1(f), a solder mask 8 was printed on the parts excluding the component mounting pads, lands, and through holes to obtain a predetermined printed wiring board.

In the second embodiment, as shown in FIG. 1(a), holes 4 are formed and a catalyst 3 is deposited on a substrate 1, as shown in FIG. 1(b), similar to the first embodiment. As the etching resist 5, for example, a dry film resist is laminated,
Expose, develop, and etch.

Next, as shown in FIG. 1(C), a plating resist 6 is applied to the entire surface of both the front and back surfaces of the substrate 1, and after curing, both the front and back surfaces of the substrate 1 are polished to remove the plating applied on the etching resist 5. Remove resist 6.

Thereafter, the etching resist 5 was peeled off and the electroless copper plating 2 solder mask 8 was printed in the same manner as in the first embodiment to obtain a predetermined printed wiring board.

〔Effect of the invention〕

As explained above, the present invention involves forming a copper foil circuit pattern using an etching resist on the copper foil of a board on which the copper foils are laminated together, then forming a plating resist, and depositing plating on the hole and the copper foil. By doing so, the following effects can be achieved.

(1) Since general copper-clad laminate boards can be used, inexpensive printed wiring boards can be stably supplied.

(2) Printed wiring boards compatible with surface mounting can be supplied.

(3) Printed wiring boards compatible with miniaturization of circuit pattern width can be manufactured.

[Brief explanation of the drawing]

FIGS. 1(a) to (f) are cross-sectional views showing the manufacturing method of the first embodiment of the present invention in the order of steps, and FIG. 2 is a cross-sectional view showing an example of the conventional method for manufacturing a printed wiring board. 3 are cross-sectional views illustrating another example of the conventional method for manufacturing a printed wiring board. 1...Substrate, 2...Copper foil, 3...Catalyst, 4...
Hole, 5... Etching resist, 6... Plating resist, 7... Copper plating, 8... Solder mask.

Claims (1)

[Claims] A step of drilling a hole in a substrate with copper foil laminated on both sides and subjecting it to catalyst treatment, a step of depositing an etching resist on both the front and back sides of the substrate and etching away the exposed portion of the copper foil, forming a plating resist on the removed portion of the foil; depositing plating on the hole and the copper foil after removing the etching resist to form a through hole and a circuit pattern; 1. A method for manufacturing a printed wiring board, comprising the step of covering a circuit pattern with a solder resist.