JPH02280399A - Printed wiring board and its manufacturing method - 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 (Field of Industrial Application) The present invention relates to a printed wiring board for mounting components using a chip mounting method and a through-hole method, and a method for manufacturing the same.

(Background of the Invention) A chip mount component mounting method is known in which a chip component without a lead wire is directly soldered to a circuit conductor portion on the surface of a printed wiring board. Also known is a through-hole component mounting method in which components with lead wires or lead terminals (discrete components) are inserted into through holes of a wiring board and the components are connected to circuit conductor portions of the wiring board by soldering. It is also known to apply both of these methods to a common printed wiring board.

When using the chip mounting method, conventionally, ream solder is used. Figures 3A-3C show the steps of this method, and the method will be explained with reference to these figures. First, solder plating (plating thickness of about 8 μm or more) is applied to the circuit conductor portion 2 of the wiring board 1 to form a plating layer 3, and after this plating, a fusing treatment is performed (FIG. 3A). When mounting chip components on this wiring board 1, this plating layer 3
A cream solder 4 is applied to a thickness of 100 to 300 LLm, and the chip component 5 is fixed thereon using the viscosity of the cream solder 4 (FIG. 3B). Then heat the whole thing (
(reflow) and soldering (Fig. 3C). However, this method requires the accurate application of an appropriate amount of cream solder to the predetermined location, which is not only cumbersome, but also expensive as it requires tools such as special ream solder and its printing frame. There was a problem with becoming.

Furthermore, in the through-hole method, immersion soldering is usually used to suck up the solder into the through-hole. Therefore, it is preferable to solder chip components using the chip mount method according to the immersion soldering method, since the discrete components with lead wires and the chip components can be soldered in a single immersion soldering operation, which reduces the number of work steps. That is, in this case, the chip component is fixed in a predetermined position with an adhesive and then brought into contact with molten solder. However, in this case, a sufficiently thick solder plating layer (plating thickness of 100 μm) is applied to the surface conductor for chip mounting.
In order to perform smooth and reliable soldering, it is necessary to form a certain degree of soldering. Conventionally, this solder plating layer is formed in a single plating process, so if thick solder plating is applied to the chip mount surface conductor, thick solder plating will also be formed on other conductor parts. . The third diagram is a sectional view showing a printed wiring board plated with thick solder as described above. In this figure, 6 is a chip mounting surface conductor part, 7 is a solder plating formed here, 8 is a through hole part, and 9 is a solder plating formed here. In this way, a thick solder plating layer is also formed inside the through-hole portion 8, and especially by fusing the solder flows into the through-hole, the inner diameter of the through-hole portion 8 becomes smaller, and the leads of the leaded component are The problem arises that it cannot fit into the through hole, or that it becomes difficult to fit into the through hole.

”(Objective of the Invention) The present invention was made in view of the above circumstances, and it does not require the use of cream solder when mounting components using the chip mounting method or the through-hole method (dip soldering is prohibited by law). A printed wiring board that makes it possible to solder chip components and leaded discrete components in a single process, without the risk of inconveniences such as the leads of leaded components not being able to enter through holes, making mounting difficult. The primary purpose is to provide the following.

A second object of the present invention is to provide a method for manufacturing this printed wiring board.

(Structure of the Invention) According to the present invention, the first object is to provide a printed wiring board for mounting components using both the chip mounting method and the through-hole method. This is achieved by a printed wiring board characterized in that the thickness is thicker than the thickness of the solder plating layer in the through-hole portion.

The second purpose is to provide a method for manufacturing a printed wiring board for mounting components using a chip mounting method and a through-hole method: (1) covering the surface conductor portion for chip mounting and the through-hole portion with a plating resist; (2) The process of performing the first solder plating on the surface: ■ The process of covering the through-hole part with solder resist; The process of performing the second solder plating on the surface ■ The process of removing the plating resist; A method for manufacturing a printed wiring board, characterized in that the thickness of the solder plating layer is thicker than the thickness of the solder plating layer of the through hole portion,
This is achieved by

(Embodiment) FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is an operation flowchart showing the manufacturing process thereof.

In Fig. 2, the reference numeral 20 is a double-sided copper-clad laminate, in which a circuit is formed on the inner layer and a multi-layer pressed board is coated with copper foil 2 on both sides.
2.22 are laminated (step 100). This laminated plate 20 is cut into appropriate dimensions, and holes 24 for through holes are punched or drilled at predetermined positions (step 102). This laminate 20 is subjected to pre-treatment such as removing paris generated during drilling of the through-hole holes 24 and purifying the inner walls of the holes 24, and then subjected to electroless copper plating treatment to coat the laminate with electroless copper. A plating layer 26 is formed (step 104).

As a result, conductivity is imparted to the inner wall of the hole 24 and the surface of the laminate 20. Then electrolytic copper plating is done (step 1)
06), a copper plating layer 28 having an appropriate thickness (for example, about 25 to 35 μm) is formed on the electroless copper plating layer 26.

On the other hand, parts that do not need to be plated with solder are covered with plating resist 30 (step 108). For example, this plating resist 30 is applied by means such as printing. That is, the laminated plate 20 has through-hole holes 2
4 and the part 32 that will become the chip mount conductor part 32
A: The surface is covered with a plating resist 30 except for the portion that will become the electrical circuit.

In this manner, the laminate 20 is electrolytically solder plated with the portions not to be solder plated covered with the plating resist 30 (step 110), and a solder plating layer 34 is formed on the electric circuit portion.

Next, this laminate 20 is coated again with plating resist 36 except for the portion 32A that will become the chip mounting conductor portion 32 (step 112). And this laminated board 20 has 2
The third solder plating process is performed (step 114). As a result, a second solder plating layer 34A is formed on the portion 32A that will become the chip mount conductor portion 32, and the total thickness of the solder plating layer 34. It is thicker than the thickness of the plating layer 34, and the total thickness is about 1100u.

The plating resist 30.36 is then removed (step 1
16) and is further etched (step 118).
). At this time, the solder plating layers 34 and 34A act as a metal etching resist, and only the parts excluding the electrical circuit parts such as the solder-plated through holes and chip mounting conductor parts are etched, and the copper foil 22 is removed. Ru. After this etching, the solder plating layers 34, 34A are melted by heat treatment and subjected to fusing treatment (step 120). This process prevents short circuits between circuit edges that have overhangs due to etching.
etc. will be planned. As a result, a through hole 38 is formed by the solder plating layer 34 of the through hole hole 24, and the two solder plating layers 34.34A are integrated on the chip mounting conductor portion 32 to form a thick solder plating layer 34B. Since the solder plating layer 32 formed in the through hole 38 is thin, the inner diameter of the through hole 38 does not become excessively small, and the chip mounting conductor portion 3
Solder plating layer 3 of sufficient thickness (approximately 100 μm) for 2
2B is formed.

Thereafter, parts unrelated to component mounting are covered with a solder resist (step 122), and as a final processing step, outline cutting and inspection are performed (step 124) to complete the printed wiring board.

When mounting components on this wiring board, as shown in FIG. The lead 44 of the component is inserted and held, and immersed in the molten solder from its underside. In this immersion soldering method, the molten solder enters between the chip component 40 and the solder plating layer 34B to solder the chip component 40, and is also sucked up into the through hole 38 by capillary action to form the lead 44. Solder.

The second coating with plating resist 34 in step 112 can be accomplished in a variety of ways. for example,
Techniques such as screen printing can be used. Alternatively, the plating resist 34 may be formed using a dry film resist. In this case, the photoresist is thermocompression bonded to the substrate surface while peeling off the carrier film, and then the image is baked by exposing the surface to ultraviolet light to form the plating resist. do. At this time, the holes that will become the through holes 38 are covered with a plating resist 34.

(Effects of the Invention) As described above, the first invention is such that the thickness of the solder plating layer of the surface conductor part for chip mounting is thicker than the thickness of the solder plating layer of the through hole part. To prevent the inner diameter from becoming small due to an excessive amount of solder entering the hole, to allow the leads of discrete components to easily enter the through-hole, and to enable easy mounting of day-discrete components according to the immersion soldering method. In addition, chip components can be mounted using dip soldering at the same time as discrete components, which simplifies component mounting.

Further, according to the second invention, the print used in the first invention can provide a method for manufacturing a wiring board.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an embodiment of the present invention, Fig. 2 is an operation flow chart showing the manufacturing process, Fig. 3 is an explanatory diagram of a conventional method using cream solder, and Fig. 4 is a cross-sectional view of an embodiment of the present invention. FIG. 2 is a cross-sectional view of a conventional printed wiring board. 20... Laminate board, 24... Hole for through hole, 30.36... Plating resist, 32... Conductor part for chip mount, 34. 34A, 34B... Solder plating layer, 38...
・Through hole, 40...Chip component, 44...Lead. Patent applicant Nippon Avionics Co., Ltd. Agent Patent attorney Fumio Yamada Attorney Patent attorney Hiroshi Yamada Figure 1 Figure 2 Figure 4

Claims (2)

[Claims] (1) In a printed wiring board for mounting components using both the chip mount method and the through-hole method, the thickness of the solder plating layer on the surface conductor for chip mount is smaller than the thickness of the solder plating layer on the through-hole portion. A printed wiring board characterized by being thicker. (2) In a method for manufacturing a printed wiring board for mounting components using the chip mounting method and the through-hole method, a step of covering the chip mounting surface conductor portion and the through-hole portion with plating resist; b. (c) A process of covering the through-hole portion with solder resist; (d) A process of performing second solder plating on the surface; (e) A process of removing the plating resist; Solder plating of the surface conductor portion for chip mounting. A method for manufacturing a printed wiring board, characterized in that the thickness of the layer is thicker than the thickness of the solder plating layer in the through-hole portion.