JPS63246889A - Manufacture of printed wiring 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 <Industrial Application Field> The present invention relates to a method for manufacturing a through-hole printed wiring board, and particularly to an exposure apparatus for a printed wiring board used in the manufacturing.

<Prior Art and Problems to be Solved by the Invention> Two typical manufacturing methods of through-hole printed wiring boards that have been used in the past will be described.

'The tenting method and the solder through-hole method both use a dry film as a photosensitive resin, but due to constraints from the thickness and photosensitive characteristics of the dry film, the resolution for both line-to-line widths is 50 to 60 μm. However, in reality, there are problems with embedding into unevenness such as dents and scratches on the copper foil surface on which the dry film is laminated. Both line widths are thought to be 80 to 100 μm. In addition, in terms of cost, the dry film itself is expensive in the tenting method, and in the solder through-hole method, the process is complicated and expensive, such as applying solder plating after using the dry film, and it is difficult to combine with the solder resist that is applied later. Adhesion is also poor.

On the other hand, when manufacturing through-hole printed wiring using a liquid resin that is cured by ultraviolet light, it is different from the dry film method and has good adaptability to unevenness on the copper foil surface, but conventional exposure equipment When exposed to light, it is difficult to uniformly expose and harden the resin inside the through-holes because the light is perpendicular to the substrate surface, so some of the resin flows out from inside the through-holes during the subsequent development process, resulting in etching. As a result, some of the copper plating inside the through-holes was removed, impairing the continuity reliability of the through-holes.

An object of the present invention is to provide a method for manufacturing a printed wiring board that can solve the above-mentioned problems. However, in conventional exposure, a negative film (a film with transparent circuit parts) is stacked on both sides of the substrate as a photomask, and vertical light is applied to perform the first exposure. Next, thin metal plates having a hole diameter slightly larger than the hole diameter of the through hole are stacked on both sides. The hole diameter at this time must not be larger than the land diameter used in the first exposure. Any material may be used for the thin metal plate, but preferably a thin stainless steel plate is suitable, and one with a slightly convex warp to the board will reduce the amount of lifting from the board. preferable. The second exposure is OO
UV light is irradiated at an angle of 450 degrees.

By irradiating the UV light, the wall surface of the through hole is also exposed to the UV light, and the inside of the through hole is also exposed. It is appropriate to use a method of sufficiently cooling the UV clamp with cold water during this exposure. With the air cooling method, the heat from the UV rung cannot be removed sufficiently, so the temperature under the rung gets too high, and as a result, the photosensitive resin thermally polymerizes, making it impossible to form an image faithful to the photomask during the next development process. Therefore, it is better not to use air-cooled UV rungs. In this way, the inside of the through-hole is covered with the photocured resin, so that the inside of the through-hole will not be etched even after the etching process.

<Example> The present invention will be described in more detail below based on the illustrated example.

FIGS. 1(a) to 1(d) show cross sections of a substrate according to the present invention. Figure 1(a) shows a copper-clad laminated base material consisting of a base material (■) and a copper foil (■), after the through-hole copper plating has been completed and a photosensitive liquid has been applied and dried on the entire surface including the inside of the through-hole. Consists of through-hole copper plating (■) and photosensitive resin (■) that is cured by dry ultraviolet light.

FIG. 1(b) shows the state of the first exposure, and the photomask ■
is placed on the photosensitive resin, and ultraviolet rays are irradiated from above and below in a direction perpendicular to the base material 1, and the irradiated photosensitive resin 1 is photocured. Next, FIG. 1(C) shows the state of the second exposure, in which a photomask ■ that irradiates only the through holes with ultraviolet rays is placed on the photosensitive resin 5, and the inside of the through holes is exposed by irradiating diagonally. Lightly cure the resin. The photomask used here preferably has a thickness of 0.1 to Q, 2 mm.
A thick stainless steel plate is best. The exposure machine used for this second exposure uses UV silane of 80-120 W/cm (length), and it is necessary to remove the generated heat by water cooling to prevent the temperature of the substrate surface from rising. . As shown in FIG. 2, the UV lamp (2) uses a parabolic mirror (2) to approximate parallel light beams, and irradiates both sides of the substrate at an angle of 50 to 45 degrees with the light beam. When irradiating with ultraviolet rays, a hole made by Hook Co., Ltd. at the end of a photomask (2) is hooked onto the top of the glass plate (2), and the substrate is passed between the UV clamps.

When the photosensitive resin exposed to the inner wall of the through hole is developed in this way, a photosensitive resin layer completely covering the inner wall of the through hole is obtained, as shown in FIG. It is durable enough.

Note that even if the order of the first exposure and the second exposure is switched, there is no change in the effect obtained.

<Effects of the Invention> The method of through-hole printing according to the present invention is carried out as described above, and compared to dry film, photosensitive liquid is used to reduce the material cost and to embed copper foil into uneven surfaces. It is possible to shorten manufacturing time by being able to expose the inside of the through hole (second exposure) on both sides at the same time, and to reduce the occurrence of circuit defects, thereby improving the yield. A method for manufacturing a hole printed wiring board can be provided.

[Brief explanation of the drawing]

FIGS. 1(a) to (dJ are partially enlarged cross-sectional views of the through-hole portion showing the steps of manufacturing the through-hole printed wiring board according to the present invention, and FIG. 2 is the exposure of the photosensitive resin on the inner wall of the through-hole according to the present invention. FIG. 3 is a flowchart according to the present invention. ■-Base material, ■-Copper foil, ■-Copper plating, ■-Photosensitive liquid, l-
Photocured photosensitive liquid (resin), ■-photomask film, ■-7 first mask metal plate, ■-UV rung, ■-parabolic reflector, ■-glass, ■-Hook and above, agent and patent attorney. Takeshi Sugiyama (and 1 other person) No. 1 Figure 3vXJ No. 2

Claims (1)

[Scope of Claims] 1. After applying copper plating to the entire surface including the through holes of a double-sided copper-clad laminate having predetermined through holes, applying an ultraviolet curable resin to the entire surface and drying it, a photomask is applied. In the method of manufacturing a printed wiring board, in which a wiring pattern is formed by irradiating ultraviolet rays onto an ultraviolet curing resin through etching, the irradiation of ultraviolet rays includes a first exposure with vertical light and an oblique exposure toward the inner surface of the through hole. A method for producing a printed wiring board, comprising: second exposure to light. 2. The oblique light of the second exposure has an angle of 5° to 45° with respect to a parallel line on the inner surface of the through hole of the double-sided copper-clad laminate. A method for manufacturing a printed wiring board according to item 1.