JPH0352236B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printed wiring board with selective overlay plating, and more particularly to a printed wiring board having stable electrical characteristics unaffected by the atmosphere of high-density wiring, and a method for manufacturing the same.

The printed wiring board is provided with seats, terminals, and through holes for the purpose of external connection and connection with mounted components. In order to satisfy these connection functions, a method of overlaying dissimilar metals on the copper layer is adopted, and precious metals are very often used for this overlay plating. A method of overlay plating is adopted.

As shown in FIG. 1a, according to the conventional method, desired copper patterns, that is, independent terminal patterns A1, A2, A3, A4, and a seat pattern B1 are connected to the desired portions on the insulating substrate 1 by wiring patterns. ，
Connection patterns of terminal patterns A1, A2, A3, and A4 are formed by etching B2, B3, terminal patterns C, and terminal patterns A1, A2, A3, and A4 independently of these connection patterns and lead patterns D1 to D2.

In this state after etching, the terminal pattern A1,
A2, A3, A4, seat pattern B1, B2, B
3. It is necessary to apply overlay plating only on terminal pattern C, and seat patterns B1, B2, B3,
On the wiring patterns connecting the terminal pattern C and the lead patterns D1 to D2, a conventional organic insulating film having anti-sticking properties or a protective adhesive tape coated with adhesive is adhered to the hatched areas in Fig. 1B. be protected as such.

The required areas are then plated with a double layer of nickel, gold, or a single overlay such as solder or gold (FIG. 1c). At this time, the pinning current is supplied by connecting lead patterns extending from the patterns connecting B1 to C and B2 to B3 to contact pattern E for the pinning contacts provided in the margin outside the product. It will be done.

If a protective adhesive tape is used after this, the organic insulating film remains as it is after the tape is removed (Figure 1 describes the case of an organic insulating film).Terminal pattern A
1, A2, A3, A4 with lead patterns D1 to D
In order to separate it from 2, the lead pattern is removed by mechanical cutting. For example, by means of drilling, press working, etc., lead patterns D1 to D2 and terminal pattern A are formed as shown in FIG. 1d.
1, A2, A3, A4 and lead patterns D1 to D
Drill or press work to make a hole near the outer contour line F of the lead pattern where B1 to C and B2 to B3 are extended. Alternatively, as shown in FIG. 1e, the purpose is achieved by cutting off the blank area including the lead patterns D1 to D2 by milling.

In either case of drilling or milling, the purpose of forming a lead pattern on the outer contour line F of the insulating substrate 1 can be achieved even in the process of cutting out the outer shape, regardless of the processing.

For example, when such conventional drilling is performed, the cross-sectional state is as shown in FIG. 2, and when milling is performed, the cross-sectional state is as shown in FIG. Here, since the drill advances perpendicularly to the lead pattern and rotates in one direction horizontally, " In such cases, the terminal patterns A1, A2, A3, A should be independent.
4 may be electrically short-circuited with each other, or the spacing between the patterns may become extremely narrow.

The insulating substrate 1 is made of a laminated board made by laminating and bonding glass cloth and synthetic resin, and when drilled or milled, the fractured surface 1a has large irregularities and is microscopically composed of the laminated and bonded glass cloth. Peeling occurs between resins due to mechanical impact during processing.

In addition, in the state of punching such as during press working, the copper pattern fracture surface 2a penetrates considerably into the fracture surface 1a of the insulating substrate, as shown in the cross-sectional view of FIG. The copper patterns 2 on the front and back sides are short-circuited or brought very close to each other, and the pattern gap becomes extremely small.

When a printed wiring board manufactured by such a conventional method is used, for example, in a humid atmosphere, the fractured surface 1a of the insulating substrate 1 is in a rough surface state as described above, and therefore dew condensation is extremely likely to form on the copper pattern 2. Fractured surface 2a, 2
b is close to the fracture surface 1a of these insulating substrates, and the electrical insulation between the fracture surfaces 2a and 2b of the copper patterns of the independent terminal patterns A1, A2, A3, and A4 is impaired.

Furthermore, as shown in FIGS. 2 and 4, cutting the lead pattern so that the front and back sides are perforated limits the wiring area on the back side. On the other hand, mechanical cutting requires a wide area for the portion of the lead pattern to be removed, which has the disadvantage of interfering with high-density wiring.

An object of the present invention is to eliminate the drawbacks of such conventional printed wiring boards and to provide a printed wiring board with good electrical characteristics and capable of high-density wiring.

According to the present invention, after a desired portion of a wiring board having a wiring pattern obtained by etching a surface copper layer pasted on an insulating board is covered with a peelable first film having anti-stick properties. After selectively applying overlay plating to the desired wiring pattern, the first film is removed and the desired portion including the copper circuit excluding the lead pattern is covered with a second insulating substrate having etching resistance. , a printed wiring board characterized by including a step of selectively etching away only the lead pattern is obtained.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for manufacturing a printed wiring board according to the present invention will be explained below in order of steps with reference to the drawings.

Figure 5a shows A1, A2, A3, A4 with copper patterns formed by a general etching method.
are independent terminal patterns, and B1, B2, B3,
C is the connected seat and terminal pattern, which are the parts that require overlay plating. Here, terminal patterns A1, A2, A3, A4
The terminal pattern C is connected to the B1 to C connection patterns connecting the terminal pattern C from the dowel pattern B1 by a lead pattern derived from the terminal lead pattern. External extension lead patterns B1 to E that further extend the B1 to C connection patterns and B2 to B3 connection patterns
and B2 to E are connected to the plating contact pattern E.

In Fig. 5b, a first coating having plating resistance (hereinafter referred to as 1st
(Abbreviated as ``film'')) For example, apply anti-stick screen ink or dry film as shown in the diagonal lines.

Terminal patterns A1, A2, A3, A4 and seat pattern B that require overlay plating next
1, B2, B3, terminal pattern C is coated with double layer plating such as nickel or gold plating, or commonly known overlay plating such as solder on top of the copper pattern 2, resulting in the state shown in Figure 5 c. Become.
At this time, the electricity necessary for plating is supplied by connecting external extension lead patterns provided at the tips of the B1 to C connection patterns and B2 to B3 connection patterns to a plating contact pattern E provided in a margin outside the product.

After overlay plating, the first film attached to areas that do not require gold plating is treated with a solvent such as halogenated hydrocarbon, alcohol, or ester, caustic soda, or an alkaline solution containing caustic potash. , the resist is dissolved and removed using a stripping solution compatible with the fleck resist used as the first film. As a result, the wiring pattern and lead pattern of the copper layer, which do not require gold plating, are exposed (FIG. 5d).

Next, a second etching-resistant insulating film is deposited on a desired portion including the copper layer wiring pattern excluding the lead pattern. As a result, the state shown in FIG. 5e is obtained in which the overlay plating pattern and the lead pattern are exposed.

If the exposed lead pattern is overlaid with nickel or gold, for example, the terminal pattern can be removed by dissolving and removing it with a well-known etching solution such as a solution containing ammonium persulfate or an alkaline etchant. A
1, A2, A3, and A4 become desired independent terminal patterns separated from the pattern connecting B1 and C. Also, B1-C connection pattern and B2-B
3 connection pattern is separated from the folding contact pattern E provided outside the product, and a desired pattern is formed on the insulating substrate 1 with overlay plating applied only to the desired portion (FIG. 5f). In the final process, A desired printed wiring board is obtained by cutting from the outer contour line.

As a result, the patterns 21 and 22 provided on the substrate 1 are prevented from coming into direct contact with the fractured surface 1a of the insulating substrate 1 cut along the forming contour line F as shown in the cross-sectional view of FIG. Further, patterns 23 and 41 have lead patterns, and FIG. 6 shows the state in which the lead patterns have been removed by etching. As a result, there is an advantage that the pattern 42 can be wired on the back side.

As described above, in the manufacturing method of the present invention, in order to perform partial overlay plating on a copper pattern, a lead pattern is provided in the blank area, overlay plating is performed, and then removed by etching, thereby forming a conventionally machined insulating substrate. This has the advantage that it is possible to provide high-density printed wiring boards with excellent electrical properties because the conductor pattern does not come into direct contact with the fractured surface of It is extremely effective.

[Brief explanation of drawings]

1A to 1E are plan views illustrating the manufacturing process of a conventional printed wiring board, and FIGS. 2 to 4 are sectional views of the printed wiring board obtained by the conventional method. FIGS. 5a to 5f are plan views illustrating the manufacturing process of the printed wiring board according to the present invention. FIG. 6 is a sectional view of a printed wiring board obtained by the method of the present invention. 1... Insulating substrate, 2... Copper pattern, 3... Organic insulating film layer having anti-plating properties, 4... Overlay plating applied on the copper pattern, 5... Peelable anti-plating properties Resistor film, 6...Organic insulating film having etching resistance, A1, A2, A
3, A4, C...Terminal pattern, B1, B2, B
3... Seat pattern, D1-D2... Lead pattern, E... Plated contact pattern, F... External outline, 1a... Fractured surface of insulating substrate, 2a, 2b...
Fractured surface of copper pattern.

Claims (1)

[Claims] 1. A step of providing a wiring pattern and a lead pattern for connecting the wiring patterns to each other and electrically connecting them to the outside on an insulating substrate, and selectively imparting plating resistance to a desired portion including the wiring pattern and the lead pattern. a step of selectively applying overlay plating to the desired wiring pattern; and a step of removing the plating-resistant film adhering to the desired portion;
A method for manufacturing a printed wiring board, comprising the steps of: attaching an etching-resistant insulating film to a desired portion including a copper layer wiring pattern excluding the lead pattern; and removing the lead pattern.