JPH0572083B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to surface mounting on a printed circuit board, etc., in which the resistance value is made variable by rotating a slider on a resistor formed on an insulating substrate. Concerning possible variable resistors.

Conventional technology Conventionally, this type of variable resistor is shown in Fig. 4A.
The one shown in FIG. 4C is known. however,
This variable resistor is not suitable for mounting with flow solder.

In this variable resistor, 1 is an insulating substrate, and a hole 1a is formed approximately in the center. 2
is an arc-shaped resistor, and is formed around the hole 1a on the surface of the insulating substrate 1. Reference numerals 3 and 4 denote external electrodes, which are formed by baking silver paste or the like over the surface, end surface, and bottom surface of the insulating substrate 1, respectively. are electrically connected to the other end of the resistor 2, respectively. Reference numeral 5 denotes an electrode made of a metal plate, and a cylindrical central shaft 6 is integrally formed by a method such as drawing. This electrode 5 is arranged and fixed from the bottom surface to the end surface of the insulating substrate 1, and the central shaft 6 is inserted through the hole 1a of the insulating substrate 1.
Reference numeral 7 denotes a slider, which has a hole 7a formed approximately in the center thereof and a contact point 7b which contacts the resistor 2 in its outer circumferential portion. Reference numeral 8 designates a metal rotor, which has a hole 8a formed approximately in the center, a driver groove 8b formed on the top surface, and a protrusion 8c formed at one end of the outer periphery of the bottom surface. Further, a U-shaped notch 7c is formed on the upper surface of the slider and engages with the projection 8c. The slider 7 and the rotor 8 are connected to the center shaft 6
By caulking the tip of the rotor 8 into the hole 8a of the rotor 8, the rotor 8 rotates with the insulating substrate 1.

In this variable resistor, the slider 7 and rotor 8 are rotated by a driver or the like using the driver groove 8b, and the contact 7b is slid on the resistor 2 to adjust the resistance value.

Further, variable resistors shown in FIGS. 5A and 5B are also conventionally known. This variable resistor has a main body housed in a case 13, and can be mounted using flow solder. The same parts as those of the variable resistor shown in FIGS. 4A to 4C are denoted by the same numbers, and the explanation thereof will be omitted.

In this variable resistor, 9, 10, 11 are electrodes made of metal plates, and the electrodes 9, 10 are attached to the end face of the insulating substrate 1 and electrically connected to both ends of the resistor 2, respectively. In addition, the electrode 11
is electrically connected to the cylindrical central shaft 12. The slider 7 and the rotor 8 are connected to the center shaft 1
By caulking the tip of the rotor 2 into the hole 8a of the rotor 8, it is made to rotate together with the insulating substrate 1. Reference numeral 13 denotes a resin case having an opening on the top surface, in which the electrodes 9, 10, and 11 are led out to the outside, the surface of the insulating substrate 1 is exposed on the inner bottom surface, and the insulating substrate 1 is insert-molded. . The electrodes 9, 10, 11 led out to the outside are bent toward the bottom side of the case 13. A heat-resistant cover film 14 is fixed to the periphery of the opening of the case 13 to seal the opening. In this variable resistor, since a transparent material is used for the cover film 14, the inside can be seen through the cover film 14 in FIG. 5A.

This variable resistor is mounted on a printed circuit board or the like by flow soldering or the like, then breaks the cover film 14 with a screwdriver or the like, rotates the slider 7 and rotor 8 using the driver groove 8b, and connects the contact 7b.
slide it onto the resistor 2 to adjust the resistance value.

Problems to be Solved by the Invention However, the two conventional variable resistors described above each have the following problems.

That is, in the conventional variable resistors shown in FIGS. 4A to 4C, the resistor 2 and slider 7 are exposed to the outside, so they can be easily bonded to printed circuit boards, etc. by flow soldering, which is highly productive. It is not possible to implement
It had to be mounted using reflow solder or the like. Furthermore, even when mounting is performed using reflow solder, flux may scatter onto the resistor 2 and the slider 7, causing poor contact.

Furthermore, since the conventional variable resistor shown in FIGS. 5A and 5B has its main body housed in the case 13, it can be mounted using flow solder, but it requires a large number of parts and is difficult to manufacture. It was complicated and expensive. Furthermore, when the cover film 14 is torn with a screwdriver or the like, fragments of the cover film 14 may be scattered inside and outside the case 13, causing poor contact with the variable resistor itself, or causing damage to the set equipment in which the variable resistor is mounted. It may have had a negative impact on. Furthermore, once the cover film 14 is torn, the resistor 2 and the slider 7 are exposed to the outside, making it impossible to repair or clean the setting device again.

Means for Solving the Problems Therefore, in the variable resistor according to the present invention, in order to maintain a sealing effect even after adjustment and to withstand mounting by flow soldering, the substrate portion of the slider is modified. An arm portion that is overlapped at least twice and has a contact portion at the tip is formed around the substrate portion, and the arm portion is bent parallel to a straight line connecting the center of the substrate portion and the contact portion to insulate the contact portion. Protruding toward the substrate side, applying a resin coating to at least the overlapping surface of the substrate portion facing the contact portion,
Furthermore, the slider and the rotor are integrally fixed by insert-molding the substrate portion onto the rotor.

Function In the above configuration, at least the substrate portion of the slider has a double structure at the joint portion between the rotor and the slider, and at least the overlapping surface of the substrate portion facing the contact portion is coated with resin. Since the circuit board is sealed and insert molded into the rotor, the contact area between the resistor and the slider contact area is reliably sealed, preventing the intrusion of flux, etc., and can be mounted using flow solder. It also has excellent environmental resistance. In addition, since the contact part of the slider is formed by bending the arm part parallel to the straight line connecting the center of the board part and the contact part, the mold releases the contact part during insert molding, allowing stable molding. be able to.

Note that it is effective to seal the contact area between the resistor and the contact section by simply forming a resin coating layer on the overlapping surface of the substrate section facing the contact section. By forming a resin coating layer or appropriately interposing an elastic body between the bottom of the rotor and the surface of the insulating substrate, it is possible to further improve the internal sealing performance.

Embodiments Hereinafter, embodiments of the variable resistor according to the present invention will be described with reference to the drawings. Note that the same parts as those shown in the prior art section are given the same numbers, and the explanation thereof will be omitted.

Figure 1A to Figure 1E, Figure 2A, Figure 2B
and FIG. 3 show an embodiment of a variable resistor according to the present invention.

In this variable resistor, 15 is a rotor, and a slider 16, which will be explained below, is made of synthetic resin as appropriate.
It is insert molded. This rotor 15 has a hole 15a formed almost in the center, a driver groove 15b on the top surface, and a bottom portion 2' on which the slider 16 of the resistor 2 slides (the portion shown by the chain line in FIG. 1C). an annular inner skirt portion 15c facing the surface of the insulating substrate 1 on the inner side;
An annular outer skirt portion 15d facing the surface of the insulating substrate 1 outside the portion 2' of the resistor 2 is formed.

A slider 16 is formed by pressing a conductive metal plate, and is composed of a base plate 16a and a pair of arm portions 16d located around the base plate 16a. The substrate portion 16a is bent at the end portion 16b to form a double structure, and a central hole 16c is formed. The arm portions 16d, 16d extend in the circumferential direction, and have contact portions 16e, 16e at their tips. These contact portions 16e, 16e are connected to the substrate portion 16a.
The arm portions 16d, 16d are bent toward the insulating substrate 1 along straight lines B, which are parallel to the straight line A connecting the center of the contact portions 16e, 16e. moreover,
The slider 16 is integrally fixed to the rotor 15 by insert molding a substrate portion 16a into the rotor 15.

Note that as the material for the rotor 15, by using a heat-resistant resin such as a thermosetting resin with excellent heat-resistant properties or a thermoplastic resin such as PPS resin, it is possible to prevent the properties from deteriorating due to the heat of soldering. be able to.

By the way, the contact portions 16e, 16e are located at the dashed-dotted line position in FIG. 2A in a free state, and when mounted on the insulating substrate 1, they are bent in the direction of arrow C and shifted to the solid line position. That is, in the present invention,
Arms 16d, 16 on straight lines B, B parallel to straight line A
d is bent, so the contact portions 16e, 16e
moves vertically in the direction of arrow C. If the arm portions 16d, 16d are bent at an angle with respect to the straight line A, in order for the contact portions 16e, 16e to be located at the solid line position when attached to the insulating substrate 1, free In the state, the contact portion 16e, 1
6e must be shifted in the direction of arrow D from the position indicated by the dashed dotted line. In molding the rotor 15, the contact portion 1 is placed in the space of the mold E shown in FIG. 2A.
6e, 16e and the arm portions 16d, 16d, but if the contact portions 16e, 16e
If the contact portions 16e and 16e are in a free state and are shifted in the direction of arrow D from the position of the dashed dot line,
And it becomes impossible to accommodate the arms 16d, 16d in the space of the mold E. That is, in the present invention, the arm portions 16d,
16d is bent so that the contact portions 16e, 16e move vertically in the direction of arrow C, making it possible to mold the rotor 5.

Note that the holes 15e formed in the rotor 15,
15e is a trace of a pin that supports the slider 16 during molding.

On the other hand, in this embodiment, as shown in FIG. 2B, since the contact portions 16e, 16e are divided into arc shapes,
There is no mutual interference between the contact portions 16e, 16e, and they can mutually operate freely, improving contact reliability.

17a is an inner elastic body, 17b is an annular outer elastic body, both of which are annular, and the inner elastic body 1
7a is fixed to the surface of the insulating substrate 1 facing the inner skirt portion 15c of the rotor 15, and the outer elastic body 1
7b is fixed to the surface of the insulating substrate 1 facing the outer skirt portion 15d of the rotor 15. As the material for the inner elastic body 17a and the outer elastic body 17b, an insulating silicone elastomer that can withstand the temperature of flow solder and the solvent of flux cleaning can be used.The method of fixing it to the insulating substrate 1 is screen printing. , drawing method, dipping, etc. can be used.

Reference numeral 18 indicates an intersection between the resistor 2 and the outer skirt portion 15d of the rotor 15.

The rotor 15, which integrally holds the slider 16 by insert molding, is rotatably mounted on the insulating substrate 1 by protruding the tip of the central shaft 6 from the hole 16c of the slider 16 and caulking it. It is being

The variable resistor having the above configuration has the contact portion 16
The space between the insulating substrate 1 and the rotor 15, where the components e and 16e are located, is configured in a sealed state. That is, the joint portion between the rotor 15 and the slider 16, which has conventionally not been kept airtight, is connected to the substrate portion 16a of the slider 16.
It has a structure that can maintain airtightness by double layering and insert molding. Further, an inner elastic body 17a and an outer elastic body 17b are interposed between the inner skirt portion 15c and the outer skirt portion 15d formed on the rotor 15 and the surface of the insulating substrate 1, respectively, to maintain a sealed state.

Furthermore, in the present invention, in order to improve the sealing performance of the contact portions 16e, 16e, at least the contact portions 16e, 16 of the slider substrate portion 16a shown in FIG.
A resin coating layer was formed on the overlapping surface portion X facing e. The reason why a resin coating layer was formed on the part
This is because it penetrates into the sealed portion between the hole 16c of the slider 16 and through the portion X.
The reason that flux and solvent penetrate through these parts is that these parts are made of metal joined together. In FIG. 1E, the part marked Y is a combination of resin and elastic body, and the part marked Z is a combination of metal and resin, so there is no flux or solvent penetration. In addition, the slider 16
The contact portions 16e, 16 are the overlapping surface portions of
The flux and solvent also permeate into the portion X' on the opposite side from e, but since the overlapping area of the substrate portion 16a is large in this portion, the permeation of the flux and solvent does not pose a problem. Therefore, in the present invention, a resin coating layer is formed on at least the overlapping surface portion X of the slider substrate portion 16a facing the contact portions 16e, 16e.

As the type of resin coating layer, silicone resin, fluororesin, epoxy resin, etc. can be adopted.

In addition to these resins, coating with silicone rubber or the like having excellent elasticity can also provide the same effect.

As a method for forming the resin coating layer on portion X, the entire assembled variable resistor is
A method of immersing the rotor in the coating liquid, a method of dropping the coating liquid onto the upper surface of the rotor 15 using a dispenser, etc. can be adopted. Alternatively, a resin coating layer may be formed in advance on the overlapping surfaces of the slider substrate portions 16a before insert molding on the rotor 15, or the rotor 15 with the slider 16 insert molded thereon may be immersed in a coating liquid in advance. It is also possible to adopt a method of storing the information.

In addition, in this method of immersing the entire variable resistor in the coating liquid, not only the portion X but also the portions X′,
A resin coating layer is also formed on Y, Z, etc., and it goes without saying that the hermeticity of these parts, which have already been maintained, is further improved. Note that poor solder wetting caused by the coating liquid adhering to the electrodes 3, 4, and 5 can be resolved by appropriately selecting the concentration of the coating liquid.

Therefore, in the variable resistor of the present invention, the resistor 2 and the slider 16 are isolated from the outside, and mounting with flow solder or flux cleaning with a solvent is possible.

Next, the structure of the external electrode 3 will be explained. Note that although the external electrode 3 will be described below, the same applies to the external electrode 4.

The external electrode 3 has a lower layer 30a as shown in FIG.
It is composed of three layers: a first plating layer (middle layer) 30b and a second plating layer (upper layer) 30c.
The lower layer 30a has silver or silver-palladium alloy printed and baked on the surface, and silver printed and baked on the back and end surfaces.
It is baked and has a thickness of, for example, 2 μm. The first plating layer 30b is made of nickel or a nickel alloy, and has a thickness of, for example, 2 μm.
The second plating layer 30c is made of tin or a tin-lead alloy, and has a thickness of, for example, 4 μm.

The first plating layer 30b functions as a barrier against the lower layer 30a to prevent silver corrosion, and has the effect of improving solder resistance. The second plating layer 30c has the function of increasing solder wettability and improving soldering characteristics, and also has the function of omitting preliminary soldering.

In the manufacturing process of the external electrode 30, first, the lower layer 30a is formed on the front, back, and end surfaces of the insulating substrate 1, and the resistor 2 is formed. Next, a plating resist 25 (indicated by a two-dot chain line in FIG. 3) is applied on the resistor 2, and a first plating layer 30b and a second plating layer 30 are formed.
c is formed, and then the plating resist 25 is removed.

The above is one embodiment of the variable resistor according to the present invention, and it goes without saying that the design can be changed without departing from the spirit of the present invention.

For example, regarding the sealing structure between the surface of the insulating substrate 1 and the rotor 15, various structures can be considered, such as interposing an elastic body such as an O-ring instead of the inner elastic body 17a and the outer elastic body 17b. Further, the slider 16 may be made of separate pieces assembled by welding or the like instead of being bent.

On the other hand, the plating layers 30b and 30c are not limited to the above-mentioned materials; the plating layer 30b may be made of a material that improves solder resistance, and the plating layer 30c may be made of various materials as long as they have excellent soldering properties. be able to.

Effects of the Invention As is clear from the above description, the variable resistor according to the present invention has the substrate portions of the slider overlapped at least twice and insert-molded on the rotor, and facing at least the contact portions. Since the overlapping surfaces are coated with resin, the sealing of the contact area between the contact part of the slider and the resistor is extremely good, and it goes without saying that mounting by flow soldering is possible, as shown in Figures 5A and 5A. It is easier and cheaper to manufacture than the conventional variable resistor shown in FIG. 5B. Further, there is no need to take the trouble of tearing the cover film after mounting, and there is no problem of the torn cover film scattering and causing poor contact. Furthermore, since it has a permanently sealed structure, it has excellent environmental resistance, and the set equipment can be re-modified and re-cleaned after mounting. Moreover, in the case of the slider, the arms are bent parallel to the straight line connecting the center of the substrate and the contact portion to form the contact portion, so the contact portion and the arm portion are housed in the space of the mold, and the sliding It is possible to insert mold the mover into the rotor.

[Brief explanation of the drawing]

FIG. 1A is a plan view showing one embodiment of the variable resistor according to the present invention, FIG. 1B is a side sectional view thereof, and FIG. 1C is a plan view showing the state with the slider and rotor removed. , Fig. 1D is a side sectional view of the X-X' section of Fig. 1C, Fig. 1E is a side sectional view showing the resin coating part, and Fig. 2A is a side sectional view showing the integrally fixed rotor and sliding part. A side sectional view of the child, FIG. 2B is its bottom view,
FIG. 3 is a side sectional view showing details of the external electrode.
Figure 4A is a plan view showing a conventional variable resistor;
FIG. 5B is a side sectional view thereof, FIG. 4C is a bottom view thereof, FIG. 5A is a plan view showing another conventional variable resistor, and FIG. 5B is a side sectional view thereof. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Resistor, 3, 4... External electrode, 15... Rotor, 16... Slider, 16
a...Base part, 16d...Arm part, 16e...Contact part, X...Resin coating part.

Claims (1)

[Scope of Claims] 1. A variable resistor in which a rotor having a slider fixed thereto is rotatably mounted on an insulating substrate on which an arcuate resistor on which the slider slides is formed. , The substrate portions of the slider are overlapped at least twice, and an arm portion having a contact portion at the tip is formed on the periphery of the substrate portion, and an arm portion is formed in parallel with a straight line connecting the center of the substrate portion and the contact portion. The contact portion is made to protrude toward the insulating substrate by bending the arm portion, a resin coating is applied to at least the overlapping surface of the substrate portion facing the contact portion, and the substrate portion is insert-molded to the rotor to achieve sliding movement. A variable resistor characterized in that a rotor and a rotor are integrally fixed.