JPS63179501A - Manufacture of variable resistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention relates to 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. The present invention relates to a method for manufacturing a surface-mountable variable resistor.

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As shown in FIG. 1, an arc-shaped cermet resistor 5 is formed on the upper surface of the insulating substrate 1, and a slider (not shown) is rotatable on the insulating substrate 1 so as to slide on the resistor 5. It is provided with the unit installed. The slider is rotatably attached to the center hole 2 of the insulating substrate 1 via an electrode (not shown).

Furthermore, external electrodes 6, 6 made of a silver-palladium alloy are provided at both ends of the resistor 5. As shown in FIG. 10, this external electrode 6 is made by first printing and baking silver-palladium alloys 6a and 6b on the front and back surfaces of the insulating substrate 1, and then depositing and baking a silver-palladium alloy 60 on the end surface. Then, the resistor 5 is printed and baked.

Ming tries to decide. ,.

However, in the above-mentioned variable resistor, a silver-palladium alloy is used as the external electrode 6 in order to prevent the silver from diffusing into the solder and improve the solder heat resistance. It has problems in that it is expensive and it is impossible to reliably prevent silver corrosion. In addition, the film thickness of the silver-palladium alloy 60 provided on the end face inevitably becomes thick, and the glass frit is exposed on the surface, which impairs the properties of soldering, and requires complicated preliminary soldering. There is.

Means for Solving the Problem Therefore, in the method for manufacturing a variable resistor according to the present invention, a plating resist for masking the resistor when plating the external electrode is applied to both ends of the insulating substrate and It is characterized in that it is provided so as to cover the edge of the center hole.

In other words, in the present invention, the external electrode is covered and protected with at least one plating layer. Therefore, even if cheap silver is used for the external electrode, silver cracks will not occur.
Moreover, during this plating process, the plating resist is provided so as to cover both edges of the insulating substrate and the edge of the center hole, so the adhesion of the plating resist at the edges is strengthened, and during the barrel plating process, the plating resist Even if there is a collision, the plating resist on the edges will not peel off.

1 to 5 show a variable resistor manufactured according to the present invention.

This variable resistor is composed of an insulating substrate 10 and a slider 20 installed on the surface of the insulating substrate 10.

The insulating substrate 10 is made of molded and sintered alumina, has a center hole 11, and has an arc-shaped cermet resistor 15 and an annular collector electrode 17 formed on its surface. Both ends of the resistor 15 and the collector electrode 17 extend to one end of the substrate 10, and are connected to external electrodes 16.16, which will be described in detail below.
．． It is electrically connected to 18.

As shown in FIG. 2, the slider 20 has a dish-shaped portion 21, a cylindrical portion 22 provided at the center, and an arm portion 23 provided at the outer periphery. This slider 20 is constructed by inserting the cylindrical part 22 into the center hole 11 of the insulating substrate 10 and caulking it on the back side, so that the dish-shaped part 21 comes into contact with the collector electrode 17 and the lower part of the arm part 23 A contact portion 24 protruding from the resistor 15 is rotatably attached to the resistor 15 in contact with the contact portion 24 .

Next, the structure of the external electrode 16 will be explained.

As shown in FIG.
The bottom layer 16a on the surface side is made of silver or Print and bake silver-palladium alloy to form the bottom layer 1 on the end side.
The bottom layer 6a'' and the bottom layer 16a'' on the back side are printed and baked with silver, and each has a thickness of, for example, 15 μm.

The first plating layer 16b is made of nickel or a nickel alloy, and has a thickness of, for example, 2 μm. The second plating layer 16c is made of tin or a tin-lead alloy, and has a thickness of, for example, 4 μm.

The first plating layer 16b is the bottom W 16a, 16a.
'q16a- functions as a barrier to prevent silver cracks and has the effect of improving solder heat resistance. The second plating layer 16c has the effect of increasing solder wettability and improving soldering characteristics, and also has the effect of omitting preliminary soldering.

In the manufacturing process of the external electrode 16, first, the insulating substrate 10 is
The bottom layer 16a, 16a', 16a is on the front surface, end surface, and back surface of
“Form 17, form 15 Gio 61, then form 1
A plating resist 25 is placed on the 5° collector electrode 17 (FIG. 3).

(indicated by the two-dot chain line in Figure 4). Subsequently, a first plating layer 16b and a second plating layer 16c are formed, and then the plating resist 25 is removed.

In this plating process, the plating resist 25 is also applied to both end edges 10a of the insulating substrate 10 and the edge 11a of the center hole 11. The plating process is performed on the sheet 10' before it is cut into individual insulating substrates, as shown in FIG. Therefore, the plating resist 25 is actually applied up to the upper portion 10a at the edge 10a of the insulating substrate located at the end of the sheet 10°.

As described above, by applying the plating resist 25 so as to cover both end edges 10a of the insulating substrate 10 and the edge 11a of the center hole 11, the adhesion of the plating resist 25 at the edges 10a and 11a is improved. , Peeling due to media collision during barrel plating is eliminated.

Therefore, the plating does not adhere to the resistor 15 from the peeled portion and the resistance value does not change.

On the other hand, the external electrode 18 of the collector electrode 17 also has a three-layer structure similar to the external electrode 16. Further, reference numeral 19 denotes an idle electrode, and this idle electrode 19 also has a three-layer structure similar to the external electrode 16.

In addition, in the present invention, the second plating Jil 16c is not necessarily necessary, and the lowermost layer 15a, L6a'
.

It is sufficient that at least the first plating J116b is completely formed on the plating layer 16a''. Furthermore, the materials of the plating layers 16b and 16c are not limited to those mentioned above, and various materials can be used.

6 to 8 show another variable resistor manufactured according to the present invention.

In this variable resistor, an electrode 30 is provided in place of the collector electrode in the variable resistor shown in FIG.
The slider 20 is rotatably attached by caulking the upper part of the outer electrode 16 of the cermet resistor 15.
．． Reference numeral 16 is made into a three-layer structure using the same manufacturing process as those shown in FIGS. 1 to 5.

Effects of the Invention As is clear from the above explanation, according to the present invention, since the external electrode is plated, the plating layer acts as a protective barrier, and even if silver is used as the electrode, it is possible to prevent silver corrosion. This makes it possible to improve the soldering heat resistance by preventing this from occurring, and it is not necessary to use an expensive silver-palladium alloy as the electrode. Moreover, since the plating resist was provided so as to cover both edges of the insulating substrate and the edge of the center hole during the plating process, the adhesion of the plating resist at the edges was strengthened, eliminating the risk of peeling. There is no problem such as plating adhering to the resistor from the exposed part and changing the resistance value.

[Brief explanation of the drawing]

1 to 5 show a variable resistor manufactured by the manufacturing method according to the present invention, in which FIG. 1 is a central sectional view of the variable resistor, FIG. 2 is a perspective view of a slider, and FIG. The figure is a plan view of the insulating substrate, Figure 4 is a sectional view taken along line A-A showing details of the external electrode, and Figure 5
The figure is a cross-sectional view of the insulating substrate sheet in the middle of the manufacturing process. 6 to 8 show another variable resistor manufactured by the manufacturing method according to the present invention, FIG. 6 is a plan view, FIG. 7 is a central sectional view, and FIG. 8 is a bottom view. . Figure 9 is a perspective view of the insulating substrate of a conventional variable resistor;
The figure is a sectional view showing the external electrode. DESCRIPTION OF SYMBOLS 10... Insulating substrate, 10a... Edge, 11... Center hole, lla... Edge, 15... Cermet resistor, 16... External electrode, 16g... Surface side most lower layer, 1
68゛... Bottom layer on the end side, 16a''... Bottom layer on the back side, 16b, 16c... Plating layer, 17... Collector electrode, 18... External electrode, 20... Slider , 25
...Plating resist.

Claims (1)

[Claims] (1) In a method for manufacturing a variable resistor in which a slider that slides on the resistor is rotatably attached to an insulating substrate on which an arcuate resistor is formed, the external electrode is plated. 1. A method for manufacturing a variable resistor, comprising: providing a plating resist for masking the resistor during plating so as to cover both edges of an insulating substrate and the edge of a center hole.