JPS634921B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a small chip type variable resistor that is directly attached to a circuit board such as a printed circuit board.

Traditionally, this type of small variable resistor is
Both ends of the wiper contact electrode and the resistor that come into contact with the wiper of the variable resistor are connected from one main surface of the resistor substrate on which the wiper contact electrode and the resistor are formed through one side of the resistor substrate. It is generally known that the variable resistor is connected to a wiper electrode and a fixed electrode arranged in a row at one end of the other main surface. The spacing between the electrodes became narrow, and there was a risk that the electrodes would short-circuit when attaching the variable resistor to the printed circuit board.

Therefore, as shown in FIGS. 1a and 1b, a part of the wiper contact electrode 11 is removed from the resistor substrate 12.
A part of the fixed electrodes 16, 16 extends through the side surface of one end to the back surface, passes around the hole 14 on the back surface by the conductive path 13, and positions the extended end 15 at the other end, while being connected to the resistor. It has been proposed that the conductive path 13 is extended to the back surface of one end through the side surface of the resistor substrate 12, and the conductive path 13 is further overcoated with a highly insulating resin.

By doing the above, it is possible to prevent short circuits when soldering the variable resistor to the printed circuit board, but in the variable resistors shown in FIGS. 1a and 1b,
While forming the conductive path 13 in a narrow space,
This conductive path 13 must be overcoated, which inevitably limits miniaturization, and high printing accuracy is required for printing the conductive path 13 and overcoat, which reduces printing man-hours and product yield. I had a problem with the height.

In addition, in all conventional chip-type variable resistors, the mounting members such as the wiper 1 or 12 are made of materials to which solder easily adheres, and these variable resistors are often used together with other electronic components such as chip resistors and chip capacitors. It is not possible to perform soldering by a dip method in which soldering is performed by immersing the product in molten solder, and soldering is performed by a reflow method using cream solder, which has the drawback of increasing the number of man-hours by one.

Furthermore, in conventional chip-type variable resistors, the wiper 11 (in the case of FIG. 1a) does not have a stopper to restrict its rotating position, and when adjusting these variable resistors, the wiper 11 comes off the resistor 5 and resists the resistance. When the wiper 11 is slid on the main surface 6 of the resistor substrate (FIG. 1 c) several times, the wiper 11 is scraped and the metal powder adheres to the main surface 6 of the resistor substrate and is fixed. There was a problem of a short circuit occurring between the electrode 3 and the wiper electrode 4, and the wiper had to be very nervous when sliding.

The present invention has been made in view of the above-mentioned circumstances regarding conventional small variable resistors, and its purpose is to:
The direction in which the terminal board conducts to the wiper is drawn out is opposite to the direction in which the fixed electrodes are drawn out from both ends of the resistor, increasing the distance between the terminal board and other fixed electrodes, while the stopper The purpose is to regulate rotation and to enable mounting on a circuit board such as a printed circuit board using a dip method.

For this reason, the present invention provides a variable resistor in which a wiper is rotatably attached to one main surface of a resistor substrate using a screw, and a screw to which solder does not easily adhere is connected to a hole provided in the wiper and a screw that is difficult to adhere to solder. In addition to being inserted into the wiper mounting hole, a terminal plate is provided on the other main surface side of the resistor board with a metal layer on which solder does not easily adhere to the metal plate, and the terminal plate is inserted into the hole provided in the portion where the metal layer is formed. It is characterized in that the tip of the screw is inserted and plastically deformed onto the metal layer, so that the plastically deformed portion of the screw can freely come into sliding contact with the metal layer.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In Figure 2a, Figure 2b and Figure 2c,
21 is a resistor board, 22 is a wiper, 23 is a screw,
24 is a terminal board.

The resistor substrate 21 is made of an insulating material such as Bakelite or ceramic, and approximately in the center thereof, there is a
A wiper attachment hole 21a is provided for attaching the wiper 22 with a screw 23.

As shown in FIG. 3a, a ring-shaped wiper contact electrode 25 is formed on one main surface of the resistor substrate 21 around the wiper mounting hole 21a, and a part of the wiper contact electrode 25 is It is drawn out to an extraction electrode 25a provided approximately at the center of one end of the main surface having a substantially square shape.

An arc-shaped cermet resistor 26 having a constant width is formed on the outer periphery of the wiper contact electrode 25 concentrically with the wiper mounting hole 21a.
Both ends of the resistor substrate 21 are drawn out into notches 28 and 28 provided at both ends of the one end side surface 21b of the resistor substrate 21 by conductive films 27 and 27, respectively.

On the other hand, on the other main surface of the resistor substrate 21,
As shown in FIGS. 3b and 3c, fixed electrodes 29, 29 are formed near the notches 28, 28, and a groove passing through the wiper mounting hole 21a is formed between these fixed electrodes 29, 29. 31 is formed.

A terminal plate 24 is fitted into the groove 31, and a connecting part 24a formed at one end is narrower than the other part.
is drawn out onto the lead electrode 25a through the hole 21c provided in the resistor substrate 21, and the connecting portion 24a is soldered to the lead electrode 25a.

Further, the other end of the terminal plate 24 is connected to the resistor board 2
The resistor substrate 21 is made to protrude toward the one main surface side of the resistor substrate 21 through a groove 32 provided in the other end side surface 21d of the resistor substrate 21 so as to be continuous with the groove 31.

The terminal plate 24 is provided with a round hole 24b so as to be concentric with the wiper mounting hole 21a of the resistor board 21 when the terminal plate 24 is attached to the resistor board 21 as described above.

A cladding layer 33 made of a material to which solder does not easily adhere, such as stainless steel or aluminum, is formed on the outer periphery of the round hole 24b of the terminal plate 24.

Returning again to FIG. 2a, FIG. 2b, and FIG. 2c, the screw 23 is made of stainless steel or other material with an oxide film formed on the surface to which solder does not easily adhere, and its large diameter head 23a has a driver groove 23b into which an adjustment driver (not shown) is inserted.
has.

A wiper 2 made of a metal material such as stainless steel to which solder does not adhere easily is provided on one main surface of the resistor substrate 21.
2, and insert the screw 23 into the hole 22 of the wiper 22.
a. The wiper 22 is rotatably attached to the resistor board 21 by inserting it into the wiper mounting hole 21a of the resistor board 21 and the round hole 24b of the terminal board 24, and by plastically deforming one end of the wiper to the outside and caulking it. .

At this time, the cross-sectional shape of the lower part of the head 23a of the screw 23 is made into a rectangular shape, for example, and the hole 22a of the wiper 22 into which this lower part is fitted is also shaped accordingly, so that the wiper 22 and the screw 23 rotate together. .

Therefore, when the screw 23 is rotated, the wiper 22 also rotates, and the sliding portion 22a protrudes to a position whose distance from the center of rotation is equal to the distance from the center of the wiper mounting hole 21a to the center portion of the resistor 26. teeth,
It slides on the resistor 26.

The wiper 22 also has a sector-shaped protrusion 22b protruding radially outward in order to regulate its rotation angle, and the protrusion 22b is connected to a terminal protruding from one main surface of the resistor board 21. Projecting end 24 of plate 24
It can be stopped by c.

In the above manner, the wiper 22 is electrically connected to the wiper contact electrode 25, the extraction electrode 25a, and the terminal plate 24, but the soldered portion 24d of the terminal plate 24 is formed on the other end side surface 21d of the resistor board 21. As can be seen from FIG. 2c, the resistor substrate 21
Fixed electrode 2 formed on one end side surface 21b side of
It is far from 9,29.

Therefore, when attaching the small variable resistor to a printed circuit board or the like, the soldered portion 24 of the terminal board 24
d and the fixed electrodes 29, 29 are almost never short-circuited to each other.

Also, the rotation angle of the wiper 22 is determined by the protrusion 22b.
is abutted against the protruding end 24c of the terminal plate 24 as shown by the dashed line in FIG. 3b, and the wiper 22
The sliding part 22a comes off the resistor 26 and the sliding contact part is scraped, and the scraped powder from the wiper 22 is removed from the resistor board 2.
There is no possibility that it will stick to 1 and cause a short circuit accident.

Furthermore, a cladding layer 33 made of a material to which solder does not easily adhere is formed on the terminal board 24, and
Since the screws 23 and wiper 22 are also made of materials that do not easily adhere to solder, the variable resistor is temporarily fixed to a printed circuit board (not shown) with adhesive or the like, and other materials such as chip resistors and chip capacitors are Together with the components, it can be soldered to a printed circuit board using the Demp method.

Furthermore, the soldered portion 24d of the terminal board 24 is away from the fixed electrodes 29, 29 as described above, and the caulked portion of the screw 23 is the groove 31 provided in the resistor board 21, so the resistor The printed circuit board to which the variable resistor is attached does not protrude from the other main surface of the substrate 21, and there is a pattern of the printed circuit board between the soldered portion 24d and the portions to which the fixed electrodes 29, 29 are soldered. can pass through the substrate, making it possible to further increase the density of the circuit pattern on the printed circuit board.

In the above explanation, basic embodiments of the present invention have been described, but the present invention is not limited to the above embodiments, and various configurations can be made within the scope of the gist of the present invention.

As is clear from the detailed description above, the present invention provides a terminal plate that is connected to a wiper in a direction opposite to a direction in which a fixed electrode of a resistor is drawn out with respect to a resistor board. The wiper, which is difficult to solder to, is rotatably attached to the resistor board by using a clad layer made of a material that does not easily adhere to solder, and screws, so that the electrodes of the variable resistor are arranged in a triangular shape. It is possible to almost eliminate short-circuit accidents between electrodes when mounting on a printed circuit board, etc., and since no solder adheres to the cladding layer, screws, or wiper of the terminal board, soldering by the depth method is possible.

In addition, since the wiper stopper is provided using the terminal board, if the rotational position of the wiper deviates from the resistor and the shavings adhere to the resistor board, causing a short circuit between the electrodes. Problems like this will also be resolved.

[Brief explanation of the drawing]

1a, 1b, and 1c are a plan view, a bottom view, and a plan view of a resistor substrate of a conventional small variable resistor, and FIG. 2a is an example of a small variable resistor according to the present invention. A plan view of the embodiment, FIG. 2b is a sectional view taken along the line -' of FIG. 2a, FIG. 2c is a bottom view of FIG. 2a,
Figure 3a is a plan view of the resistor board, Figure 3b is the third
FIG. 3c is a bottom view of FIG. 3a. 21...Resistor board, 21a...Wiper mounting hole, 2
2...wiper, 23...screw, 24...terminal board, 24c
...Protruding end, 25... Wiper contact electrode, 26... Resistor, 33... Cladding layer.

Claims (1)

[Scope of Claims] 1. In a variable resistor in which a wiper is rotatably attached to one main surface of a resistor substrate with a screw, a screw to which solder does not easily adhere is connected to a hole provided in the wiper and the resistor substrate. In addition to being inserted into the wiper mounting hole, a terminal plate is provided on the other main surface side of the resistor board with a metal layer on which solder does not easily adhere to the metal plate, and the terminal plate is inserted into the hole provided in the portion where the metal layer is formed. A small variable resistor, characterized in that the tip of the screw is inserted and plastically deformed onto the metal layer, so that the plastically deformed portion of the screw can freely come into sliding contact with the metal layer. 2. One end of the terminal plate is made to protrude from the other main surface of the resistor board toward one main surface, and a protrusion protruding in the radial direction of the wiper is abutted against the protruding end. A small variable resistor according to claim 1.