JPH0455548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a method for manufacturing a through-hole wiring board, which includes a step of etching conductor parts in non-circuit parts using a photosensitive etching resist.

(b) Conventional technology The conventional manufacturing method for through-hole wiring boards includes:
There are hole-filling methods and solder stripping methods, but these methods have disadvantages such as through-hole chipping and increased chemical costs. Recently, a method has been proposed in which a photosensitive etching resist is formed on a circuit portion including through holes by an electrodeposition coating method, thereby eliminating the drawbacks of the above method and forming a high-density wiring pattern. With this electrodeposition coating method, the photosensitive etching resist reliably adheres to the inner surface of the through hole, and the thickness of the resist film can also be easily controlled. For example, it becomes possible to form 20 to 30 wiring lines between the pins of an IC. In this method, the entire surface of the substrate is exposed to light with a photosensitive etching resist exposed on circuit parts including through holes, and the etching resist placed on the circuit parts is photocured. Thereafter, unnecessary coatings are removed and etching is performed to remove non-circuit conductor parts (copper, etc.).

(c) Problems to be Solved by the Invention However, in the above conventional method using a photosensitive etching resist, when the entire surface of the substrate is exposed, the inner wall of the through hole may not be irradiated with sufficient light. FIG. 5 shows this situation. A conductor portion 2 made of a material such as copper is formed on the entire surface of the substrate 1 and the inner wall of the through hole, and a photosensitive etching resist 3 is further formed on the circuit portion including the inner wall of the through hole by an electrodeposition coating method. , the entire surface of the substrate is exposed to light by the ultraviolet lamp 5. At this time, the circuit section on the surface of the board 1 is exposed to ultraviolet light 5a.
However, the inner wall of the through hole 4 is not sufficiently irradiated. For this reason, the etching resist 3 on the inner wall of the through hole is not sufficiently hardened.
When cleaning the substrate, there was a possibility that the uncured etching resist would peel off from the inner wall of the through hole.

An object of the present invention is to provide a method for manufacturing a through-hole wiring board in which the inner walls of the through-holes are sufficiently exposed during exposure and the reliability of the through-hole portions can be increased.

(d) Means for solving the problem In this invention, after forming a conductor part on the entire surface of a board including through holes, a photosensitive etching resist is exposed only in the circuit part including through holes, and then a photosensitive etching resist is etched on one side of the board. A process of placing a diffused reflection plate on one side and fully exposing the other side to light is performed on both the upper and lower surfaces of the substrate, and the conductor portions in areas other than the photo-cured etching resist are removed by etching to form a circuit pattern. shall be.

(e) Effect The operation of this invention will be explained with reference to FIG.

FIG. 1 shows the exposure process of this invention. This exposure process differs from the conventional exposure process shown in FIG. 5 in that a diffused reflection plate 6 is disposed on the substrate surface opposite to the position where the ultraviolet lamp 5 is disposed.
When the ultraviolet light 5a irradiated from the ultraviolet lamp 5 to the substrate 1 passes through the through hole 4, the ultraviolet light 5a
As in the conventional case shown in the figure, the inner wall of the through hole is not sufficiently irradiated. However, it is diffusely reflected by the diffused reflection surface 6a and reaches the inner wall of the through hole. Therefore, as shown in the figure, the inner wall of the through hole is sufficiently irradiated with the diffusely reflected light, and the amount of irradiation is substantially the same as the amount of irradiation to the circuit portion on the surface of the substrate 1. The subsequent steps are exactly the same as the conventional manufacturing method. That is, the conductor portions other than the circuit portion including through holes are removed by etching to form a circuit pattern, and furthermore, the etching resist 3 covering the circuit portion is removed.

(f) Embodiment FIG. 2 shows a method for manufacturing a through-hole wiring board according to the present invention in the order of steps. Each step will be explained below.

A...Materials such as glass epoxy, paper epoxy, paper phenol, etc. are prepared to form the substrate 1.

B...Drill holes at predetermined locations on the board 1.

C: The inner wall of the hole and the entire front and back surfaces of the substrate 1 are subjected to known chemical plating to form a plating film 7.

D...Furthermore, an electroplated layer 8 is formed on the plating film deposited by the above chemical plating.

E...Furthermore, the area other than the circuit portion on the electroplated layer 8 is covered with a suitable insulating film 9. This insulating film 9 is formed by a screen printing method or the like.

F...Subsequently, the above substrate is immersed in an electrodeposition liquid, and electrodeposition is performed using the electroplating layer 8 as one electrode. Although any known electrodeposition solution can be used, in the present invention, one containing a photosensitizer that is hardened by ultraviolet irradiation is used. Through this step, a photosensitive etching resist 10 is formed in the circuit portion including the through holes.

G...Next, place the above board on the diffuse reflection plate 6,
An ultraviolet lamp 5 is placed above and irradiates ultraviolet rays 5a. As a result, the photosensitive etching resist 10 on the surface of the substrate is cured, and the ultraviolet rays 5a transmitted through the through-holes are diffusely reflected by the diffusely reflecting surface 6a of the diffusely reflecting plate 6a, and the inner walls of the through-holes 4 are uniformly irradiated and hardened.

H...The diffused reflection plate 6 is placed on the top surface of the substrate, and the ultraviolet lamp 5 is placed below the substrate 1 to irradiate the back surface of the substrate with ultraviolet rays 5a. As a result, the photosensitive etching resist 10 on the back surface of the substrate is cured, and the ultraviolet rays transmitted through the through holes 4 are diffusely reflected by the diffuse reflection surface 6a of the diffuse reflection plate 6 and irradiate the inner walls of the through holes. In step G, the etching resist 10 on the inner wall of the through hole is in a hardened state, but in step H, the etching resist 10 inside the through hole is further completely hardened.

I...Remove the diffused reflection plate 6 and the ultraviolet lamp 5, remove the insulating film 9 with a weak alkaline solution, and remove the conductor part 8 in the non-circuit part by an etching process.

J...Furthermore, the etching resist 10 of the circuit portion is removed to complete the formation of the circuit pattern, and processing such as solder resist (not shown) is performed to complete the manufacture of the board.

Among the above manufacturing directions, since the photosensitive etching resist 10 is formed by the electrodeposition coating method in step F, a resist film with a uniform thickness is reliably formed on all circuit surfaces including through holes. be able to. Since the diffused reflection plate 6 is used for exposure in the steps G and H, the etching resist film on the inner wall of the through hole can be irradiated with sufficient ultraviolet rays.

FIG. 3 shows a part of the manufacturing method of the present invention using a photographic method. In the manufacturing method shown in FIG. 2 above,
In the step E, the insulating film 9 is formed by printing, and in the step F, the etching resist 10 is formed only on the circuit area, but in the manufacturing method shown in FIG. 3, the above step E is replaced. Then, an etching resist 10 is formed over the entire surface of the substrate (E').
Then, in place of the step F, a negative film 19 covering the non-circuit portion is placed on the substrate, and the process proceeds to the steps G and subsequent steps. With this method as well, it is possible to reliably form an etching resist having a uniform thickness, as in the method shown in FIG. 2, and it is also possible to reliably harden the etching resist on the inner wall of the through hole.

FIG. 4 shows an example of application of the manufacturing method according to the present invention. A diffuse reflection plate 6 is sandwiched between the first substrate 1 and the second substrate 1' as shown in the figure, and the substrates are irradiated with ultraviolet rays from both above and below. Both the upper and lower surfaces of the diffused reflection plate 6 are constituted by diffused reflection surfaces. In the steps G and H in FIG. 2, by exposing the two substrates from both the top and bottom through the diffuse reflection plate 6 in a sandwich structure, the two substrates can be processed simultaneously in one exposure process. It becomes possible. Therefore, after completing this process, if the two substrates 1 and 1' are reversed upside down and exposed again, the exposure process for the two substrates will be completed in two exposure steps. In other words, it can be considered that the exposure of one substrate is substantially completed in one exposure process, and the efficiency can be improved.

In the above embodiments, the photosensitive etching resist was formed on the circuit portion including the through holes using an electrodeposition coating method, but in the present invention, the photosensitive etching resist was formed on the circuit portion including the through holes. It is not necessary to necessarily use an electrodeposition coating method to form this etching resist. Of course, it is also possible to form the etching resist using other methods.

(g) Effects of the Invention As described above, according to the present invention, when exposing a photosensitive etching resist formed exposed on a circuit portion including through holes, a diffused reflection plate is placed on one side of the substrate. Since the light is diffusely reflected by the diffused reflection plate and reaches the photosensitive etching resist in the through hole, the resist can be sufficiently irradiated with light. Therefore, it is possible to easily prevent peeling of the resist on the inner wall of the through hole due to insufficient exposure to light, and there is an advantage that the reliability of the through hole can be reliably improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the manufacturing method of the present invention. Fig. 2 is a diagram for explaining the manufacturing method according to the present invention step by step, Fig. 3 is a diagram showing a modification thereof, and Fig. 4 is a diagram for explaining a method for performing the manufacturing method of the present invention more efficiently. This is a diagram. FIG. 5 is a diagram for explaining a conventional manufacturing method. 1...Substrate, 2...Conductor portion, 3...Etching resist, 4...Through hole, 6...Diffuse reflection plate.

Claims (1)

[Claims] 1 After forming a conductor part on the entire surface of the board including through holes, expose the photosensitive etching resist only on the circuit part including through holes, then place a diffused reflection plate on one side of the board, and A method for manufacturing a through-hole wiring board, characterized in that a step of exposing the entire surface of the board to light is carried out on both the upper and lower surfaces of the board, and conductor parts in areas other than the photo-cured etching resist area are removed by etching to form a circuit pattern.