JPH0423287Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to improvement of a variable resistor.

(Prior Art) As shown in FIGS. 3 and 4, a conventional variable resistor has a resistance film 12 made of ruthenium oxide or the like formed on a substrate 11 made of an electrically insulating material such as ceramic, glass, or resin. It has a structure in which a slider 14 having a contact piece 13 that contacts and slides on a resistive coating 12 is rotatably mounted on a substrate 11,
By rotating the slider 14, the resistance coating 1 of the contact piece 13 is removed.
The resistance value is adjusted by varying the contact position with 2.

(Problem to be solved by the invention) However, when this conventional variable resistor is attached and fixed to a circuit board using jet solder (melting point 200 to 260°C), the solder is not applied to the resistive coating 12. The flux used in the process evaporates, and the vaporized material scatters and solidifies, obstructing the contact between the resistive coating 12 and the contact piece 13, causing the resistor to lose its function, or causing a change in the resistance value. It had the disadvantage of being

(Purpose of the invention) The present invention was devised in view of the above-mentioned drawbacks, and it is possible to reliably adjust the resistance value to the desired value without losing the function as a resistor. It is an object of the present invention to provide a variable resistor that can eliminate the need for a subsequent flux cleaning step.

(Means for Solving the Problems) The present invention provides a variable resistor in which a slider having a contact piece that contacts and slides on the resistive coating is attached to an insulating substrate having a resistive coating. The feature is that the outer surface is coated with a coating film that scatters when exposed to heat of 200°C or higher.

(Example) Next, the present invention will be explained in detail based on the example shown in FIGS. 1 and 2.

Figures 1 and 2 show an embodiment of the variable resistor of the present invention, in which 1 is a substrate made of an electrically insulating material such as ceramic, glass, or resin, and its upper surface is made of ruthenium oxide, carbon, etc. Resistive coating 2
is formed.

The resistive film 2 has an arcuate shape, and one end thereof is connected to a terminal 5 formed at the end of the insulating substrate 1 for connection to an external circuit. This resistive film 2 is formed on the insulating substrate 1 by employing a conventionally known thin film method or thick film method.

Further, a slider 4 made of metal such as stainless steel or aluminum is placed on the insulating substrate 1, and the slider 4 is rotatably attached to the insulating substrate 1 via a caulking pin P. There is. This slider 4 has a rotation operation part 6 on its head for rotating the slider 4, and a contact piece 3 that contacts the resistance coating 2 on the insulating substrate 1 on the lower surface of the outer periphery. When a rotational force applying member such as a screwdriver is inserted into the rotation operation section 6 and the slider 4 is rotated, the contact piece 3 comes to contact and slide on the resistance coating 2. The slider 4 is formed from a single metal plate using a conventionally known press forming method.

The slider 4 also connects to the insulating substrate 1 via a caulking pin P and a metal portion 8 formed on the bottom surface of the insulating substrate 1.
It is electrically connected to a terminal 9 for connecting to an external circuit at the end of the terminal 5 and terminal 9.
In the meantime, the resistance of this variable resistor is derived.

The outer surface of the resistive coating 2 is covered with a coating film 10, and the coating film 1
0 isolates the resistive coating 2 from the outside air.

The coating film 10 is made of a material that scatters when heated at 200° C. or more, specifically, a fluorine-based resin such as Teflon, and is deposited on the outer surface of the resistive film 2 by a conventionally well-known thick film method. . This coating film 10 completely isolates the resistance film 2 from the outside air, and connects the variable resistor with jet soldering (melting point approximately 200 to 260).
℃) to prevent the flux used in the soldering process from adhering to the resistive film 2, and also to prevent the coding film 10 itself from being scattered by the heat of the jet solder, thereby preventing the coding film 10 from adhering to the resistive film 2. This serves to remove flux adhering to the ing film 10 to the outside.

In this way, the variable resistor of the present invention is attached and fixed to the circuit board using jet solder, and then a rotating force applying member such as a screwdriver is inserted into the rotating operation part 6 of the head of the slider 4, and the slider 4 is slid. By rotating the element 4 and varying the contact position of the contact piece 3 with the resistive coating 2, the desired resistance value can be adjusted.

Although the method of soldering the variable resistor to the printed circuit board described above was explained using solder jet bonding, for example, even when bonding the variable resistor using a solder reflow method, it is not necessary to melt the solder. Since the coating film is scattered by heat, there is no need to use different variable resistors depending on the soldering method, resulting in a highly versatile variable resistor.

(Effects of the invention) According to the variable resistor of the present invention, the outer surface of the resistance film is coated with a coating film that scatters when heated at 200°C or more, so the variable resistor can be attached to the circuit board using jet solder. When bonding, the flux used in the soldering process does not fly and adhere directly to the resistive coating, and the flux attached to the coating film is removed by the heat of the solder jet (approximately 200 to 260°C). Since the flux is scattered to the outside, it is scattered and removed to the outside together with the coating film.As a result, after the variable resistor is soldered to the circuit board, a cleaning process is required to remove the flux that has adhered to the resistive film. It can be omitted, and furthermore, the contact between the resistive coating and the contact piece of the slider is not hindered in any way by the flux.

In addition, since there is no flux adhering to the resistance coating, the resistance value of the variable resistor can be determined simply by changing the contact position between the contact piece of the slider and the resistance coating. You can reliably adjust the resistance value to the desired value just by moving it.

Note that the present invention is not limited to the above-described embodiments, and various changes can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of the variable resistor of the present invention, FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1, and FIG.
The figure is a plan view showing a conventional variable resistor, and FIG. 4 is a sectional view taken along the line A--A in FIG. 3. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Resistance film, 3... Contact piece, 4... Slider, 10... Coating film.

Claims (1)

[Scope of utility model registration request] A variable resistor comprising an insulating substrate having a resistive coating and a slider having a contact piece that slides in contact with the resistive coating, and is soldered to a printed circuit board, wherein A variable resistor whose surface is covered with a coating film that scatters due to heat of 200°C or more during soldering.