JPS6226293B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a push button switch in which a terminal conductor is insert molded into a synthetic resin housing.

FIG. 1 shows an example of a push button switch, in which a contact 2 fixed in a housing 1 and a terminal 3 led out to the outside are integrally formed by a conductor strip 4 made of a metal material. The conductor strip 4 is insert molded into a casing made of synthetic resin.

In the conventional method, a hoop-shaped conductor strip 4 is placed in the cavity of a mold for molding, and a molten synthetic resin is injected into the cavity to fill the cavity. As the resin hardens, the conductor strips 4 are embedded within the hardened housing. However, in this method, as shown in FIG. 2, the synthetic resin forming the wall 5 of the housing 1 shrinks during the curing process, so the synthetic resin separates from the conductor strip 4, creating a slight gap 5a. It is inevitable that it will occur. Therefore, when assembling a pushbutton switch using the completed housing 1 and connecting the switch to a circuit on a printed wiring board, it is necessary to use flux for soldering, especially when this is done by an automatic soldering device. is sprayed from the bottom of the printed wiring board,
flux enters through said gap in the housing;
It has the disadvantage that it adheres to contacts and other parts, degrading electrical performance. Such flux is
Generally, rosin (vegetable natural resin) is dissolved in alcohol, thinner, etc., and because its surface tension is low, it easily penetrates into gaps due to capillary action. At this time, it is possible to prevent flux from entering by applying grease, etc. to the base of the terminal outside the casing in advance, but this method requires an extra step of applying grease, etc. However, it was not always possible to prevent it completely.

The present invention seeks to eliminate the drawbacks mentioned above.
The embodiment will be described in detail below with reference to the drawings. In FIG. 3, 6 is a hoop-shaped conductor strip made of a metal plate such as a brass or phosphor bronze plate, which connects a central contact 7a and a plurality of peripheral contacts 7b, 7b. It is formed by stamping in one piece, and the figure shows a portion of it. A coating film 8 of epoxy resin is applied in advance in the width direction of the conductor strip 6 in the vicinity of the base of the terminal portion of the portion of the conductor strip 6 to be buried in the housing.
By forming and naturally drying the conductor strip 6, the coating film 8 becomes a semi-polymerized state and is well adhered to the conductor strip 6. Next, the conductor strip 6
The conductor strip 6 is inserted into the molded body 9 made of epoxy resin by insert molding into the molded body 9 made of epoxy resin as shown in FIG. 4, and the portion 10 is a conductor. After being separated from the strip 6, it becomes a terminal portion. FIG. 5 is a side view of FIG. 4, and FIG. 6 is an enlarged sectional view of the portion where the conductor strips 6 are buried.

In the case of molding according to the above-mentioned process, when the coating film 8 of the epoxy resin is in a half-polymerized state, the coating film 8 is already in a state of being adhered to the surface of the conductor strip 6, and this When the epoxy resin for molding is injected in this state, the epoxy resin for molding and the coating film 8 are easily integrated because they are both of the same resin. Next, during the curing process, the coating film 8 is already in a good adhesive state with the conductor strip 6 as described above, so even if the epoxy resin shrinks, the conductor strip 6, the coating film 8 and the epoxy for molding There is no separation between the conductor strip 6 and the molded body 9, and therefore no gap is created between the conductor strip 6 and the molded body 9, allowing for good insert molding. In the above embodiments, an epoxy resin is used as the synthetic resin for molding, but the invention is not necessarily limited to this, and for example, polyacetal resin or the like may be used.

As described above, in the present invention, a coating film of epoxy resin is formed in advance in the width direction of the conductor strip in the vicinity of the base of the terminal part of the portion of the conductor strip to be embedded in the casing. This has the effect that there is no gap between the housing and the conductor strip in some parts, and flux does not enter the contact area when the push button switch is soldered to the printed circuit board, improving the performance of the push button switch. It is.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a push button switch, FIG. 2 is a sectional view showing a buried part of a conductor strip by a conventional molding method, FIG. 3 and the following are related to the present invention, and FIG. 4 is a top view showing a state of insert molding, FIG. 5 is a side view of FIG. 4, and FIG. 6 is a sectional view of the main part of FIG. 5. 6... Conductor strip, 7a, 7b... Fixed contact, 8...
...Coating film, 9...Synthetic resin molded body, 10...Terminal portion.

Claims (1)

[Claims] 1. In a method for manufacturing a push button switch in which a conductor strip made of a metal material integrally formed with a fixed contact and a terminal part is insert-molded into a housing made of synthetic resin, the terminal of the part of the conductor strip embedded in the housing is A coating film of epoxy resin is formed in advance in the width direction of the conductor strip near the base of the conductor strip, and after this coating film is air-dried to a semi-polymerized state, a synthetic resin resin is injected into the conductor strip and inserted. A method for manufacturing a push button switch characterized by molding.