JPH03175691A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To obtain a printed circuit board excellent in circuit yield rate and cheap by applying liquid-form photosensitive resin not containing solvent on the surface of a board, and then coating it with film-form photo sensitive resin. CONSTITUTION:A hole is made in a board, where copper foils are junctioned to the obverse and the reverse, and a conductive layer 2 and a through hole 3 are made, and alkali separating resin paste 4 is filled in the hole 3, and after hardening the resin paste 4 adhering onto the conductive layer 2 at the surface is removed by belt sander, buff polishing, or the like. Next, liquid-form photosensitive resin 5, which does not contain solvent capable of being developed with alkali, is applied on the obverse and the reverse of the board 1, and film-form photosensitive resin 6 capable of being developed with alkali is overlaid on the obverse and the reverse of the board 1. Next, the photosensitive layer is exposed to do development with alkali, whereby an etching resist is made, and the exposed part of copper not covered with the etching resist and the resin paste is removed by etching, and the etching resist and the resin paste 4 are exfoliated and removed, thus a specified printed wiring board can be obtained.

Description

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

[Conventional technique]

Conventionally, methods for producing through-hole printed wiring boards can be roughly divided into two types: photo printing methods that form etching resists through exposure and development steps, and screen printing methods that use screen plates to form etching resists. be.

In recent years, as electronic devices have become more compact and highly functional, printed wiring boards have become more sophisticated with circuit patterns such as three ICC pins, small through holes with a diameter of 0.3 mm, and landless through holes. The adoption of high-density products such as For this reason, in order to cope with higher density, the photo printing method is increasingly being adopted in the manufacturing method of through-hole printed wiring boards.

Conventionally, as manufacturing methods capable of forming landless through-holes, pattern plating methods and hole-filling methods in which panel-plated through-holes are filled with resin such as varnish have been generally employed. As the pattern plating method, a photo printing method is often applied, and as a hole filling method, a screen printing method is used to mainly manufacture one or two ICC pits.

[Problem to be solved by the invention]

The conventional printed wiring board manufacturing method described above has the following drawbacks.

(1) The pattern plating method is a long and complicated process, and
Since expensive pattern plating equipment is required, there is the problem of high manufacturing costs, which makes it difficult to use for printed wiring boards that require cost competitiveness such as double-sided boards and 4-layer boards, and highly multi-layered boards with 6 or more layers. We had no choice but to limit our efforts to fields where wiring density is more important than board cost.

(2) On the other hand, the hole-filling method is a short and simple process, and the manufacturing cost is relatively low. However, the hole-filling method is mainly a method of forming an etching resist by screen printing, and uses a film-like photosensitive resin. The photo printing method used is
It was only partially implemented. This is due to the following problem in the method using a film-like photosensitive resin.

■After filling resin such as varnish into the through-hole, it is necessary to remove the resin on the surface, which is done by mechanical polishing such as a belt sander, but in this case, the surface is highly uneven and scratches are likely to occur. However, the film-like photosensitive resin could not follow these irregularities, resulting in poor circuit yield. ■Second
As shown in Figure (a), the filled resin paste 14 tends to make dents on the surface of the substrate 1, but the film-like photosensitive resin 16 cannot follow these dents, and there is a gap between the resin paste 14 and the resin paste 14. A space is created. For this reason, after etching, as shown in FIG. 2(b), wire breakage tends to occur at a corner of the through ball 3, resulting in poor yield.
It was difficult to manufacture inexpensive printed wiring boards.

An object of the present invention is to provide a method of manufacturing a printed wiring board that has a high circuit yield and is inexpensive.

[Means to solve the problem]

The method for manufacturing a printed wiring board of the present invention includes filling a resin paste into the hole of a substrate having a conductive layer formed on the inner wall and surface of the hole and curing the resin paste, and then adhering the resin onto the conductive layer on the surface of the substrate. a step of removing the paste; a step of applying a solvent-free liquid photosensitive resin to the surface of the substrate and then depositing a film-like photosensitive resin to form a photosensitive resin layer; and a step of forming a photosensitive resin layer on the photosensitive resin layer. a step of exposing and developing through a mask to form an etching resist; a step of selectively etching away the exposed portion of the conductive layer using the etching resist as an etching mask; and removing the resin paste and the etching resist 1. The process includes the steps of:

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1(a) to 1(g) are cross-sectional views illustrating a manufacturing method according to an embodiment of the present invention in the order of steps.

In the first embodiment, as shown in FIG. 1(a), holes are first made in a substrate 1 with copper foil bonded to the front and back surfaces, the copper panel plating is dissolved, and a conductive layer 2 and a through hole 3 are formed. .

Next, as shown in FIG. 1(b), an alkaline removable resin paste 4 is filled into the through holes 3 and hardened. v! There are two types of 1-fat paste 4: an ultraviolet curing type and a thermosetting type. However, the thermosetting type contains a solvent in the resin paste 4, so air bubbles are likely to form when the solvent dries, and the thermosetting type does not contain any solvent. Ultraviolet curing type is preferable. Next, conductive layer 2 on the surface
The resin paste 4 adhering to the top is removed by belt sander, puff polishing, etc.

Next, as shown in FIG. 1C, a liquid photosensitive resin 5 that can be developed with an alkali and does not contain a solvent is applied to the front and back surfaces of the substrate 1 to a thickness of 2 to 5 μm using a roll coater.

Next, as shown in FIG. 1(d), a film-like photosensitive resin 6 that can be developed with alkali is applied to the front and back surfaces of the substrate 1 using a laminator, and the liquid photosensitive resin 5 and the film-like photosensitive resin 6 are coated on the front and back surfaces of the substrate 1. Form a photosensitive resin layer.

Next, as shown in FIG. 1(e), the photosensitive resin layer is exposed to light and developed with alkali to form an etching resist of the photosensitive resin layer.

Next, as shown in FIG. 1(f), the exposed portions of the copper that are not covered with the etching resist and resin paste are removed by etching.

Next, as shown in Fig. 1(g), etching resist and resin paste 4 are applied. 11 pieces were removed to obtain a predetermined printed wiring board.

In the second embodiment, first, as shown in FIG. 1 (a), holes are made in a substrate 1 with copper foil bonded to the front and back surfaces, copper panel plating is applied, and a conductive layer 2 and a through hole 3 are formed. .

Next, as shown in FIG. 1(b), an alkaline removable resin paste 4 is filled into the through holes 3 and hardened. There are two types of resin paste 4: ultraviolet curing type and thermosetting type.The thermosetting type contains a solvent in the resin base I, so when this solvent dries, air bubbles tend to form spaces, and the solvent content is less likely to occur. The resin paste 4 adhering to the conductive layer 2 on the surface is then removed by belt sander, puff polishing, or the like.

Next, as shown in FIG. 1(c), a liquid photosensitive resin 5 containing no solvent of a solvent developable type such as 1,1.1-)lichloroethane is prepared.
2 to 5 μm using a roll coater on the front and back surfaces of substrate 1.
Apply.

Next, as shown in FIG. 1(d), an alkali-developable film-like photosensitive resin 6 is applied to the front and back surfaces of the substrate 1 using a laminator. Form a photosensitive resin layer.

Next, as shown in FIG. 1(e), the photosensitive resin layer is exposed, the film-like photosensitive resin 6 is developed with an alkali, and the liquid photosensitive resin 5 is developed with a solvent to form an etching resist by the photosensitive resin layer. form.

Next, as shown in FIG. 1(f), the exposed portions of the copper that are not covered with the etching resist and resin paste are removed by etching.

Next, as shown in FIG. 1(g), the etching resist and resin paste 4 were peeled off to obtain a predetermined printed wiring board.

In this embodiment, since the resin paste 4 is not dissolved during development, even when forming landless through holes,
Through holes can be formed without going down from the base material surface of the substrate 1.

〔Effect of the invention〕

As explained above, the present invention provides the following effects by forming a liquid photosensitive resin layer containing no solvent on the surface of a substrate and then applying a film-like photosensitive resin.

(1) Since the liquid photosensitive resin is applied without containing liquid material, the liquid photosensitive resin penetrates into the unevenness of the surface, resulting in a high circuit yield and making it easy to manufacture fine patterns such as ICC tough patterns. can.

(2) Since the liquid photosensitive resin penetrates into the recesses of the resin paste, there is no occurrence of cross-sections at the through-hole corners even in landless through-holes, resulting in high yields and highly reliable through-holes. Hole printed wiring boards can be manufactured.

(3) Since the process is short and simple, it can be manufactured at low cost.

[Brief explanation of drawings]

FIGS. 1(a) to (g) are cross-sectional views showing the manufacturing method according to the embodiment of the present invention in the order of steps, and FIGS. 2(a) and (b) are examples of the conventional method for manufacturing printed wiring boards. FIG. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Conductive layer, 3... Through hole, 4... Resin paste, 5... Liquid photosensitive resin, 6
...Wilm-like photosensitive resin.

Claims (1)

[Claims] A step of filling a resin paste into the hole of a substrate having a conductive layer formed on the inner wall and surface of the hole and curing it, and then removing the resin paste adhering to the conductive layer on the surface of the substrate; A step of applying a liquid photosensitive resin that does not contain a solvent and then depositing a film photosensitive resin to form a photosensitive resin layer, and exposing the photosensitive resin layer to light through a mask and developing it to form an etching resist. a step of selectively etching away exposed portions of the conductive layer using the etching resist as an etching mask; and a step of removing the resin paste and the etching resist. Method of manufacturing the board.