JPS63107086A - Manufacture of double-sided printed wiring board - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing a double-sided printed wiring board using a conductive paste.

[Prior art and its problems]

Conventionally, as a method of manufacturing printed wiring boards at low cost, there is a method of screen printing a circuit pattern using conductive paste on an insulating sheet. When forming a circuit pattern in two layers using this method, after screen printing the first layer circuit pattern with conductive paste, overprint an insulating layer and a through stand (conductive paste that makes the two layers of circuit patterns conductive). Then, a method is used in which the circuit pattern of the second layer is overprinted.

However, such conventional manufacturing methods have the following problems. ■In the screen printing method, between the pins (2,5+n+
) The limit is the formation of one or two lines, and it is not possible to handle high-density wiring.■ To reduce the conductor resistance of the circuit, it is necessary to increase the printing thickness of the conductive paste, but the screen printing method If the thickness is increased, the conductive paste tends to shake, so there is a limit to how thick the printing can be made. ■Since the two-layer circuit pattern is insulated by insulating paste printing, layer thickness variations, pinholes, etc. occur, causing problems with the reliability of the glabella insulation. ■Due to overprinting, printing and firing must be repeated several times, resulting in many steps and high costs. Furthermore, printing is difficult because printing occurs on uneven surfaces.

[Means for solving problems and their effects]

The present invention provides a method for manufacturing a double-sided printed wiring board that solves the problems of the prior art as described above. A UV-impermeable insulating sheet is prepared, a photosensitive dry film is laminated on both sides of the insulating sheet, and both photosensitive dry films are exposed and developed according to the circuit pattern, thereby creating a circuit formed on both sides. The method is characterized in that the concave portions and the holes according to the pattern are filled with a conductive paste, and then the conductive paste is hardened.

That is, in the present invention, it is possible to form a fine circuit pattern by forming a circuit pattern using a dry film photo method.
By forming recesses in accordance with the circuit pattern through development and filling the recesses with conductive paste, sagging does not occur even when the printing thickness is increased. Furthermore, by using an insulating sheet as the glabellar insulator, the reliability of the glabellar insulation is increased and the number of printing and firing steps is reduced.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS.

First, prepare an insulating sheet 1 that does not transmit ultraviolet light as shown in (al). This insulating sheet 1 will be used as an insulator between the eyebrows of the circuit pattern that will be formed on both sides of the sheet later, and the circuit pattern on both sides should be conductive. Holes 2 are pre-formed at the locations.For example, a colored polyester film is suitable as the material.Although not shown, this insulating sheet 1
Positioning marks (holes, etc.) are placed at specified positions around the
is provided.

Next, a photosensitive dry film 3 shown in the arrow (marked above) is laminated on both sides of the ultraviolet-impermeable insulating sheet 1.
This film 3 usually has a base film 4 on one side,
Since the protective film 5 is pasted on the other side, with the base film 4 peeled off, this is laminated on both sides of the UV-impermeable insulating sheet 1 (as shown in C1).The photosensitive dry film used here No. 3 is a negative type, and the film thickness is preferably 50 μm or more.

Since the protective film 5 transmits ultraviolet rays, a photomask 6 having a predetermined circuit pattern is placed over it as shown at +d+, and in this state both surfaces are irradiated with ultraviolet rays.

When applying the photomask 6, the positioning marks described above are used to position the insulating sheet 1 so that the holes 2 are at predetermined positions on the circuit pattern.

After exposure, development is performed, washed with water, and dried, resulting in a pattern as shown in (ill). In other words, the exposed portion of the photosensitive dry film 3 is removed, forming recesses 7 on both sides in accordance with the circuit pattern, and the recesses Hole 2 of insulating sheet 1 is exposed within 7.

Next, the recesses 7 and holes 2 are filled with conductive paste 8 using a double-sided roll coater or a squeegee.
become that way. As you can see, the thickness of the conductive paste 8 is the same as that of the photosensitive dry film 3, so
By using the thick photosensitive dry film 3, the printing thickness of the conductive paste 8 can be increased.

Next, after the conductive paste 8 is baked and hardened, the photosensitive dry film 3 is peeled off, and the conductive paste adhering to areas other than the circuit pattern is removed.

As a result, the circuit pattern formed by the conductive paste 8 is clearly finished without any sagging at the edges.

After that, as required (as shown in hl), a solder resist layer 9 is formed by laminating a coverlay film or printing solder resist ink, and Ni5Cu plating 10 is applied on the land corresponding to the component mounting area. If soldering can be performed directly on 8, plating 10 is not necessary.

With the above steps, a double-sided printed wiring board is completed.

In addition, if a flexible film is used as the UV-impermeable insulating sheet and a flexible rubber-based conductive paste is used as the conductive paste, flexible double-sided printed wiring boards can be manufactured using the roll-to-roll method. It can be manufactured efficiently.

〔Effect of the invention〕

As explained above, according to the present invention, dry film
By adopting the photo method, it is possible to form lines with 2 to 5 bin intervals, and since the conductive paste is filled into the recesses according to the circuit pattern formed by exposing and developing the photosensitive dry film, printing of the conductive paste is possible. No blurring occurs even when the thickness is increased, so fine circuit patterns can be formed. Furthermore, since the circuit pattern is printed on both sides of the insulating sheet, reliable glabellar insulation can be obtained, and since the number of printing and firing steps is small, there are other advantages such as high productivity.

[Brief explanation of the drawing]

FIGS. 1(a) to (hl) are cross-sectional views showing the manufacturing method of a double-sided printed wiring board according to an embodiment of the present invention in the order of steps. Photosensitive dry film, 6~Photomask, 7~Figure 1

Claims (1)

[Claims] Prepare a UV-impermeable insulating sheet with holes formed in advance at the positions where the circuit patterns to be formed on both sides should be conductive, laminate photosensitive dry films on both sides of the insulating sheet, and place both photosensitive dry films into the respective circuits. Manufacture of a double-sided printed wiring board characterized by exposing and developing according to the pattern, thereby filling the recesses and the holes formed on both sides with a conductive paste according to the circuit pattern, and then hardening the conductive paste. Method.