JPS6236332B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switch board and a method for manufacturing the same, and an object of the present invention is to provide a switch board with high wear resistance in the switch contact portion, high corrosion resistance, and high reliability. Our goal is to provide the following.

Generally, rotary switches used for detecting the position of a type wheel in a printer, detecting the number of rotations in a counter, etc. are required to have extremely good wear resistance. Figures 1 and 2 show this type of switch, that is, a disk-shaped substrate 52 is attached to a rotating shaft 51 that drives a type wheel 50, and contacts on the substrate 52 rotate at high speed together with the rotating shaft 51. On the pattern 53, a contact 54 made of a highly conductive and springy metal piece...
A general example of a high-speed rotary switch is shown in which the rotational position of the type wheel 50 is detected by making elastic contact with the type wheel 50.

The conventional board structure used in this type of switch has a structure that eliminates unevenness on the contact surface of the contactor 54.
The surface of the substrate 52 and the contact pattern 53 are located on the same plane to improve wear resistance as described above. However, since this contact pattern 52 is formed using a transferable method, it requires a large number of printing processes, transfer processes, and peeling processes, which complicates the manufacturing process. (Because the contact pattern is formed by printing or plating, the thickness is thinner than that of a metal plate.) Therefore, it is difficult to guarantee a long life.

On the other hand, in order to solve this problem, it is possible to embed a thin metal plate punched into a predetermined shape into the substrate, but if fine strips are punched out to form a precise pattern, the insert molding process In addition, it is extremely difficult to prevent deformation and position the strips in the process, and if the fine strips are buried with their surfaces exposed so that they are flush with the substrate surface, the adhesion between the strips and the substrate will be reduced. Deteriorate. On the other hand, it is also possible to bond a thin metal plate to the board using the die stamping method, but since the substrate material requires a certain degree of hardness, the surface of the contact pattern made of the thin metal plate is stamped to the same height as the board surface. This was difficult and resulted in unevenness on the substrate surface.

Therefore, in order to eliminate the above-mentioned drawbacks, as shown in FIG. 3, protrusions 61 corresponding to the contact pattern are formed on a thin metal plate 60 by embossing, and this thin metal plate 60 is made of insulating synthetic resin. A switch board which is embedded in a board 63 by integral molding and whose contact point is a protruding part 61 which is exposed so as to be located substantially on the same plane as the surface of the board 63 was proposed by the applicant of this application in U.S. Pat. It was proposed as a number.
Although the switch board disclosed in this prior application is easy to manufacture and has excellent wear resistance, it has the disadvantage that the yield of precious metal plating applied to the surface of the thin metal plate 60 is poor.

The problem is that if the surface of the protrusion 61 is plated with the thin metal plate 60 buried in the substrate 63, the resin (substrate 63) will be easily attacked by the plating solution, and the resin (substrate 63) will not have adequate hardness and corrosion resistance. In addition to the difficulty in selecting the resin, acidic liquid that penetrated between the substrate 63 and the thin metal plate 60 during the plating process (this is due to poor bonding between the substrate 63 and the thin metal plate 60, The thin metal plate 60 has holes 6 for connecting the upper and lower resins.
2...) cannot be completely removed during the cleaning process and remains, and this remains on the thin metal plate 60 over time.
This causes corrosion of the switch board, reducing the reliability of the switch board. Therefore, the thin metal plate 60 is connected to the substrate 63.
A method is adopted in which through-metal plating is applied before embedding the projecting portion 61, but the partial plating method in which only the surface of the protruding portion 61 is selectively plated is difficult to manufacture a mask for applying the plating resist because the thin metal plate 60 has irregularities. ,
The alignment of the mask is extremely difficult and impractical, and for this reason, the entire surface of the thin metal plate 60 is plated with extremely expensive precious metals such as gold, and this is buried in the substrate 63. The yield was extremely poor.

Therefore, the applicant further submitted a patent application filed in 1983.
No. 117478 proposed a switch board in which precious metal plating was applied only to the contact pattern protrusions to improve the yield of precious metal plating. As shown in FIG. 5, this switch board is made by forming a protrusion 42 corresponding to the contact pattern on a thin metal plate 41 by embossing, and coating the entire surface of the thin metal plate 41 with an insulating paint (insulating paint) that serves as a plating resist. After forming a film of resin) 45, only the insulating resin 45 on the surface of the protrusion 42 is removed by machining such as cutting and polishing, and then base plating 46 and noble metal are applied only to the surface of the protrusion 42 where the metal is exposed. Apply plating 47 in sequence.

After that, the thin metal plate 41 is introduced into a molding machine, and the flat part of the thin metal plate 41 is formed into a substrate 4 made of insulating synthetic resin.
At the same time, only the surface of the protruding portion 42 is placed on the same plane as the surface of the substrate 48, and finally, a connecting piece in which a number of metal disks are connected is pressed using a press processing machine. By cutting the switch board, an independent switch board can be obtained. Note that Fig. 5b is the same as A in Fig. 5a.
-A sectional view, and in the figure, 49 is a center hole for shaft insertion.

Now, the switch substrate for the rotary switch manufactured in this way has various advantages such as excellent wear resistance and a good yield of precious metal plating, but it has been found that there are some problems in corrosion resistance. Ta. In other words, normally a copper-based alloy is used for the thin metal sheet, nickel plating is used as the base plating, and gold is used as the precious metal plating.Due to the difference in ionization tendency, the nickel plating part is the most likely to corrode, followed by copper, which is the least likely to corrode. Since it becomes gold, if corrosion occurs, corrosion of the nickel metal will progress first.

Therefore, for example, if a pinhole exists in the noble metal plating layer, the nickel plating will corrode, and the corrosion will progress at or near the contact pattern, potentially reducing the reliability of the switch board.

By the way, if the thin metal plate, base plating, and noble metal plating are cut and exposed by press working on the end face of the substrate, corrosion is extremely likely to start in this part. In this case, even if there is a pinhole in the noble metal contact pattern and corrosion is likely to occur, the resistance of the corrosion current in this part is high and the end face of the switch board has a lower resistance value, so corrosion will occur on the end face. In this case, the corrosion progresses proactively and intensively, and the corrosion of the contact pattern portion is inhibited.

The present invention has been made in view of the above points, and will be described below with reference to an embodiment shown in FIG.

In this embodiment, a thin metal plate 1 is embossed (protruded) using a press machine to form protrusions 3 that match the contact pattern, and then the entire surface of the thin metal plate 1 made of a copper alloy is coated with nickel or the like. A first base plating 2 is applied using a metal that has a greater ionization tendency than the thin metal plate 1. Thereafter, an insulating paint 5 is applied to the entire surface of the protrusion 3, and the insulating paint 5 and the first base plating 2 of the protrusion 3 are removed by machining such as cutting or polishing, and the surface of the protrusion 3 is removed. A second base plating 6 is applied to only the first base plating 2 using the same metal as the first base plating 2, and a precious metal plating 7 such as gold is applied thereon.

Next, the metal thin plate 1 is embedded in a substrate 8 made of insulating synthetic resin, the protrusion 3 and the surface of the substrate 8 are positioned on substantially the same plane, and finally the substrate 8 including the protrusion 3 is A predetermined amount of the outer periphery is cut and removed to obtain a switch board having a structure as shown in FIG. As a result, the base platings 2 and 6 are all connected and exposed at the end surface of the substrate 8. Further, all the noble metal plating 7 plated in the shape of the contact pattern reaches the end face.

With such a structure, it is possible to electrochemically suppress corrosion in the contact pattern portion and around the contact pattern by corrosion of the end surface of the substrate 8. In other words, generally when dissimilar metals are joined, these two
When an electrolyte, such as water droplets, is supplied between the seed metals, a so-called local battery is formed and a current flows, and metals with a large tendency to ionize are eluted, which causes rust. In the case of the present invention, the end surface of the substrate 8 is more open than the contact pattern part and the area around the contact pattern, and the internal resistance of the local battery is smaller, so it is possible to suppress rusting from around the pinholes in the contact pattern part. can.

As detailed above, the advantages of the present invention are as follows: (a) Since the protrusions formed by embossing are used as contacts, it is easy to form protrusions (contacts) including fine patterns, and it is possible to easily form protrusions (contacts) during and before molding. There is no risk of deformation of the contact part during the process, and compared to a configuration in which a variety of fine metal strips are buried, positioning and deformation prevention during molding is much easier, and the contact part is not connected to the protruding part (contact). Since the other thin metal plate parts are buried in the board, the adhesion between the contacts and the board is very good. Overall, this is a smooth, wear-resistant, long-life switch board that uses thin metal plates as contacts. However, it has an extremely simple structure, is easy to manufacture, and can be provided at low cost.

(b) After coating the entire surface of the thin metal plate with insulating paint, the paint on the surface of the protrusion is removed by polishing, cutting, etc., and precious metal plating is applied only to the exposed surface of the protrusion. , there is no wastage of expensive precious metal materials, and the yield is very high.

(c) The insulating paint that is in close contact with the thin metal plate can be selected from one that has good adhesion to the substrate, and therefore it can be expected that the adhesion between the thin metal plate and the substrate will be extremely good.

(d) As corrosion progresses on the end surface of the substrate, corrosion on the surface of the contact pattern can be inhibited, and a switch substrate with high reliability in corrosion resistance can be provided.

Overall, it is possible to provide a switch board that has good corrosion resistance and abrasion resistance, is easy to manufacture, and is inexpensive, and has a remarkable effect that it has great industrial value.

In the above-mentioned embodiments, a rotary switch used for detecting printed characters in a printer was explained as an example, but the switch board of the present invention is not limited to this, and can be used for various encoder switches or slide switches. Of course, it can also be applied to

[Brief explanation of the drawing]

Figures 1 and 2 relate to the first conventional example;
The figure is an explanatory view of the main parts of a switch used in a printer, Figure 2 is a plan view of the switch board, Figures 3 and 4 relate to the second conventional example, and Figure 3 is a plane view of a thin metal plate. 4 are sectional views of essential parts of the switch board, FIG. The figures relate to an embodiment of the present invention, in which figure a is a plan view and figure b is a plan view.
is a cross-sectional view taken along line A-A in FIG. 1...Thin metal plate, 2...First base plating, 3...
...Protruding portion, 5...Insulating paint, 6...Second base plating, 7...Precious metal plating, 8...Substrate.

Claims (1)

[Scope of Claims] 1. A first base plating made of a metal having a higher ionization tendency than the thin metal plate and an insulating paint are laminated on the entire surface of a thin metal plate, excluding the protrusions, on which a protrusion is formed by embossing, The protrusion includes:
A second base plating made of the same metal as the first base plating and a noble metal plating are formed, and the protrusion is further embedded in a substrate made of an insulating synthetic resin so that it is located on substantially the same plane as the substrate surface. . A switch board, wherein each plating layer on the thin metal plate including the protrusion is exposed at the end surface of the board. 2. A first step of forming a protrusion on a flat thin metal plate by embossing, and a second step of applying a first base plating to the entire surface of the thin metal plate using a metal that has a higher ionization tendency than the thin metal plate, A third step of applying an insulating paint to the entire surface of the thin metal plate that has been plated with the first base plating, and machining such as cutting and polishing the surface of the protrusion to remove the insulating paint and the first base plating on the surface of the protrusion. a fourth step of removing the metal; and a fifth step of applying noble metal plating after applying a second base plating with the same metal as the first base plating to the surface of the protrusion where the metal was exposed in the fourth step; The sixth step is to embed the thin metal plate that has gone through the five steps in a substrate made of insulating synthetic resin by outsert molding, and to position the protrusion surface and the substrate surface substantially on the same plane.
and a seventh step of cutting and removing a predetermined amount of the outer periphery of the substrate including the protrusion.