JPH0664965B2 - Electronics - Google Patents

Description

The present invention relates to an electronic device such as a push button switch in which a conductor strip integrally formed with a fixed contact, a terminal and the like is insert-molded in a synthetic resin.

FIG. 1 is a cross-sectional view showing an example of a thin push button switch. Fixed contacts 2, 2, 3 and a movable contact 4 are arranged in a housing 1 made of synthetic resin, and when the push button 5 is pressed, the contact 2, 3 is closed and the switch is turned on. Particularly, the case 1 will be described with reference to FIG.
Two sets of conductor strips 6 and 7 are buried in the insert 14 by insert molding, the fixed contacts 2 and 2 are integrally formed with the conductor strip 6, and the portions protruding to the outer wall of the housing 1 are terminals 8 and 8. Has become. Similarly, the fixed contact 3 and the terminals 9 and 9 are integrally formed with the conductor strip 7. FIG. 3 is a cross-sectional view of essential parts showing the arrangement of the molds when molding the casing 1, 11 is a lower mold, and 12
Indicates the upper mold.

When the molding synthetic resin is injected in this state, the lower surface of the fixed contact 2 is not supported by any part of the mold, so that it is in a state of being easily moved downward, and the fixed contact 2 of the fixed contact 2 is in the molding process. The height may drop a little and a slight gap may be formed between the upper mold and the molding material, and the conductive material on the surface of the fixed contact 2 in order to cover the upper surface of the fixed contact. There is a drawback such as that is blocked.

FIG. 4 shows a pin 13 on the lower mold 11 in order to eliminate the above defects.
And the fixed contact 2 is sandwiched between the pin 13 and the upper die 12 so as to prevent the fixed contact 2 from moving up and down during molding, and shows the arrangement of the mold. is there. At the same time, in this molding method, since the perforations 10 are formed on the lower surface of the housing 1 as shown in FIG. 5, after the switches and the like are assembled, the terminals of the switches are soldered onto the printed wiring board by an automatic soldering device. At the time of attachment, there is a drawback that the flux for soldering blown from the lower surface in a spouting state penetrates through the perforations 10 and even into the inside of the housing 1. In order to prevent this, the inside of the perforations 10 is prevented. It was necessary to take preventive measures such as injecting an adhesive or the like into the above to block it in advance.

The present invention is intended to eliminate the above-mentioned drawbacks. Hereinafter, the case forming process of the embodiment will be described with reference to FIG. 6 and subsequent figures. FIG. 6 shows the structure of the switch, which is common to FIG. The part is shown by the same number, and a slight thin portion 17 is formed between the innermost part 16 of the perforation 15 formed in the bottom wall 14 of the housing 1 and the fixed contact 2. The thickness of the thin portion 17 is arbitrary, but may be 0.5 mm inside or outside, for example.

Since the plan view of the housing 1 is the same as that shown in FIG. 2, the conductor strip 6,
Explaining the structure of 7 with reference to the same figure, the conductor strips 6 and 7 are both embedded in the bottom wall 14 of the housing 1 and each of them forms a separate electric circuit. The parts protruding to the side surface of the housing 1 are terminals 8, 8 and 9, 9. One conductor strip 6 is bent upward at the ends of the pair of branch strips 6a and 6a, and is exposed on the surface of the bottom wall 14 as the fixed contacts 2 and 2. The other conductor strip 7 is one branch strip. It is bent upward at the end of 7a and is exposed on the surface of the bottom wall 14 as the central contact 3.

Next, the molding process of the housing 1 will be described.
The figure is a cross-sectional view of the main parts showing the arrangement state of the injection molding die before molding, and 11 and 12 are the lower die and the upper die of the die, respectively, and the protrusion of the lower die 11 when the die is closed. There is a gap D between the tip of the pin 18 and the fixed contact 2 of the conductor strip to be embedded. The molten molding material passes through the runner 19 for injection provided on the side of the molding die closed in such a state and the molding material in the molten state becomes a cavity.
When injected into 20, the molding material flows in as shown by the arrow, and when passing through the narrow portion 21 having the gap D between the pin 18 and the fixed contact 2, the molding material flow path is changed. Since the pressure is narrowed, the pressure of the molding material becomes high. Therefore, fixed contact 2
Is pressed in the direction of the upper die 12, and therefore the fixed contact 2 and the upper die 12
The molding process is completed without forming a gap between and.
Although not shown, the structures of the molds of the other fixed contacts 2 and 3 are the same as above.

As described above, according to the present invention, the fixed contacts 2, 2 and 3 are exposed on the surface of the inner fixed surface 1a of the housing 1, and the fixed contacts 2, 2 and 3 are exposed from the fixed portion bottom surface 1b of the housing 1. The perforations 15 ... Are formed until they are close to the lower surface, and the innermost part 16 of the perforations 15 is formed.
A continuous thin portion 17 integrated with the housing bottom wall 14 is interposed between the fixed contacts 2, 2 and 3 and the lower surfaces of the fixed contacts 2, 2 and 3. By providing such a structure, the conductor strips 6 and 7 are provided to the housing 1. In the insert molding process, the fixed contacts 2, 2 and 3 are positioned by the pressure of the molten molding material in the narrow portion 21 of the gap D, so the fixed contacts 2, 2 and 3 are always located from the inner bottom surface 1a. When an electronic component that is buried so as to be exposed at a certain height and that is assembled by incorporating movable contacts and the like into the housing 1 is attached to a printed wiring board or the like by automatic soldering or the like, a capillary phenomenon occurs even in a minute gap. Since it is possible to completely prevent the penetration of flux such as cleaning liquid that permeates in the hole, and also to prevent the fixed contact from being exposed in the hole, the fixed contact can be connected to the fixed contact through the solder flux etc. Short circuit with the circuit pattern on the electronic device mounting board Etc. can be prevented insurance property in which a marked effect.

In the above-mentioned embodiment, the case having a rectangular shape has been described. However, the case may have a polygonal shape, and the fixed contacts may face each other on the same plane. Good. Further, the conductor strips to be embedded are not limited to two circuits, and three or more circuits may be provided with a step if necessary and insert-molded in the bottom wall of the housing. Needless to say, also belongs to the scope of claims of the present invention.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of a conventional electronic component, FIG. 2 is a plan view of a housing, FIG. 3 is a sectional view of a main part of a mold, and FIG. 4 is a schematic view of a mold in another conventional example. Partial sectional view, FIG. 5 is a sectional view of an essential part of a housing by the mold of FIG. 4, FIG. 6 and the following are related to the present invention, and FIG. 6 is a sectional view showing a structure of an electronic component according to the present invention, 7 and 8 are cross-sectional views of the main part of the mold. 1 …… Case 1a …… Inner bottom 1b …… Outer bottom 2,3 …… Fixed contact 6,7 …… Conductor strips 8,9 …… Terminal 14 …… Case bottom wall 15 …… Perforated 16 …… Maximum Inner part 17 ... Thin part

Claims (1)

[Claims] 1. A bottomed tubular casing integrally formed of synthetic resin, a fixed contact insert-molded into the casing so that the surface is exposed from the bottom wall of the casing, and a retractable arrangement in the casing. In an electronic device having a push button and a movable contact that is disposed in the housing and conducts a predetermined fixed contact among the contacts by pressing the push button, the bottom wall of the housing is close to the bottom surface of each fixed contact. The electronic device is characterized in that the perforation is formed, and a space between the perforation and the fixed contact is closed by a thin portion integrated with the housing bottom wall.