JPH01110703A - Variable resistor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain the title variable resistor, having excellent heat-resisting property, which can be mounted by flowing soldering at low cost by a method wherein a carbon resistive material, containing diallyl phthalate resin as bonding resin, is integrally molded on the surface of the substrate consisting of diallyl phthalate resin. CONSTITUTION:The title variable resistor, provided with a substrate 1 having a resistive body formed on the surface, is constituted by integrally molding the carbon resistive body 6 formed in the prescribed shape on the surface of the resin substrate 1. Said carbon resistive body 6 contains diallyl phthalate resin as bonding resin, and the resin substrate 1 is made of diallyl phthalate resin. For example, the above-mentioned carbon resistive body 6 is formed using the paste consisting of black lead of 8.0-70.0wt.% as the main ingredient, an inorganic filler of 0-40.0wt.% as a resistance regulating agent, bonding resin of 30.0-70.0wt.%, a thermosetting agent of 1.0-5.0wt.% for bonding resin, and a proper quantity of ethyl carbitol acetate as a solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable resistor equipped with a substrate having a resistor on its surface, and a method for manufacturing the same.

Next and so on.

Conventionally, variable resistors have used an alumina substrate for the substrate and a cermet resistor whose main component is Ruoffi for the resistor, and although the reliability is relatively high, the alumina substrate is more expensive than the resin substrate. Moreover, the cermet resistor is also expensive, and as will be explained below, the manufacturing process is complicated, resulting in an overall high cost.

In addition, when using a relatively inexpensive carbon-based resistor, if the substrate is made of Bakelite, glass/epoxy resin, or polyphenylene sulfide resin, which are conventionally used for boat fishing, these substrate materials have a heat resistance of 180 to 250.
℃, making it impossible to mount using flow soldering. Therefore, a combination of a carbon-based resistor and an alumina substrate is considered, but since the resistor area is small in the chip volume, the adhesion of the resistor to the substrate is insufficient, making it impossible to obtain linear characteristics. There are problems, and the cost increases due to the use of an alumina substrate.

On the other hand, in terms of manufacturing methods, a common method for fixing resistors to the surface of a substrate is to perform screen printing directly on the surface of the substrate. That is, a resistor paste was screen printed in a predetermined shape on the surface of a molded resin substrate in which lead terminals were embedded in advance, dried, and baked to fix the resistor.

According to this manufacturing method, in the process of fixing the resistor to the surface of the resin molded board, a small number of prototypes are first manufactured for each loft of the resistor paste, and the resistance value, etc. of the resistor of the prototype is determined. They had to check the characteristics of the product and confirm that its resistance characteristics were within specifications before mass production could begin.

The composition of resistor paste components differs depending on the loft, and the resistance characteristics of the resistor will change if the composition of the components and printing, drying, and baking conditions differ, so make sure that the resistance characteristics are within the specifications. Otherwise, all the manufacturing lofts will end up with defective products. However, by the time we manufactured the prototype and checked the resistance characteristics of the resistor,
It took 2 to 4 hours, and the production equipment had to be stopped during that time, resulting in poor productivity.

Moreover, even after mass production, the resistor paste must be dried on the resin molded substrate in which the lead terminals formed integrally with the hoop terminals are embedded. Therefore, there was a problem that a large space was required and the production equipment became large. Furthermore, if there are irregularities on the surface of the resin molded substrate on which the resistor paste is printed, there is another problem in that the resistance characteristics of the formed resistor will vary.

In order to solve the above-described problems, the variable resistor according to the first invention is formed into a predetermined shape, and a carbon-based resistor containing diallyl phthalate-based resin as a binder resin is used. ,
It is characterized by being integrally molded onto the surface of a substrate made of diallyl phthalate resin.

Further, the method for manufacturing a variable resistor according to the second invention includes: (a) printing a carbon-based resistance paste containing diallyl phthalate-based resin as a binder resin on a heat-resistant film in a predetermined shape, drying it; a step of preparing a transfer sheet on which a carbon-based resistor is formed by baking; (b) a step of accommodating and positioning the transfer sheet together with lead terminals in a mold; (C) melting diallyl in a mold. (d) forming a resin molded substrate in which lead terminals are embedded inside and a carbon-based resistor and a heat-resistant film are fixed to the surface by filling and solidifying a phthalate-based resin; (d) the carbon-based resin; The method is characterized in that it includes a step of peeling off the heat-resistant film from the resin molded substrate, leaving the resistor behind.

In the first invention, a diallyl phthalate resin is used as a binder resin for a carbon-based resistance paste, and a diallyl phthalate resin is used for the substrate, which improves heat resistance and allows mounting by flow soldering. It is possible and the materials are inexpensive.

Furthermore, in the second aspect of the invention, printing, drying, and baking of the carbon-based resistance paste containing diallyl phthalate resin as the binder resin are performed on a heat-resistant film, and the drying and baking of the carbon-based resistance paste is performed on a heat-resistant film. This is done by folding the sex film in a zigzag pattern at intervals or winding it up on a reel. Therefore, after the production equipment is downsized, the resistance characteristics of the resistor formed on the transfer sheet are checked and confirmed to be within the specifications after the process of preparing the transfer sheet. Only the transferred sheet is transferred to the next process. The transfer sheet preparation process is performed as a preliminary step to the next series of processes, and if the transfer sheet preparation process has been performed in advance, the next process of manufacturing the variable resistor can be performed immediately. . In this case, the production of a prototype is unnecessary.

After the transfer sheet whose resistance characteristics have been checked is housed in a mold together with lead terminals and positioned, the mold is filled with molten diallyl phthalate resin and solidified to form a resin molded substrate. The resin molded board has lead terminals embedded in it and also on its surface!
The carbon-based resistor and the heat-resistant film are molded in a fixed state. When only the heat-resistant film is peeled off from this resin molded substrate, a resin molded substrate having a carbon-based resistor formed on its surface is manufactured. Thereafter, a variable resistor is manufactured by assembling and adjusting sliders and the like on this resin molded substrate.

long cover Next, embodiments of the present invention will be described based on the accompanying drawings.

FIGS. 2(A) and 2(B) are a plan view and a vertical sectional view showing an example of a resin molded substrate used in a variable resistor according to the present invention. In the figure, 1 is a resin molded substrate, in which lead terminals 3, 4.5 are embedded, and a carbon-based resistor 6 is molded on the surface thereof so as to be exposed on the same plane. A hole 1a is formed approximately in the center.

The substrate 1 is molded from diallyl phthalate resin having the composition described below with reference to Table 1.

The carbon-based resistor 6 provided on the surface of the substrate 10 has a substantially arc shape, and one end of each lead terminal 3.4 is buried in the substrate 1 while being electrically connected to both ends of the carbon-based resistor 6. The other ends of the lead terminals 3.4 are completely led out to the outside of the substrate 1.

The lead terminal 5 has an annular collector electrode part 5a integrally formed at one end, and the outer peripheral part of the collector electrode part 5a is connected to the substrate 1.
It is buried in the inner periphery of the hole 1a, and the other end is led out to the outside of the substrate 1.

A slider (not shown) is rotatably attached to the resin molded substrate 1 configured in this manner while being electrically connected to the collector electrode portion 5a of the resin, and the contacts of the slider are made of a carbon-based resistor. A variable resistor of the type that slides on the surface of 6 is constructed.

Fig. 2(C) shows that in order to make a chip type variable resistor,
The lead terminals 3, 4, and 5 are bent from the side surface of the board 1 to the back side, so that surface mounting on a printed circuit board or the like is possible.

Here, one embodiment of a method for manufacturing a variable resistor having the above configuration will be described.

As shown in FIG. 1(A) and FIG. 3, the belt-shaped heat-resistant film 7 is wound up on a reel 8, and the reel 8 also coats the surface of the heat-resistant film 7 with carbon-based resistance paste. 9 are screen printed on the shape of the resistor 6 turned over at regular intervals. For the heat-resistant film 7, for example, a polyimide film is used, and for the resistance paste 9, for example, a carbon paste having the composition described below with reference to Table 1 is used. Feed holes 7a are formed at both ends of the heat-resistant film 7 at regular intervals. The feed holes 7a are used to ensure feeding of the heat-resistant film 7 at regular intervals, determine the printing position of the resistive paste 9, and align the positions of the resistor and the mold, which will be described later.

In order to dry the resistance paste 9 printed on the heat-resistant film 7, the heat-resistant film 7 is folded in a zigzag pattern or wound onto a reel so that the resistance paste 9 printed at intervals does not come into contact with each other. , the resistive paste 9 is allowed to dry naturally or by force. In this example, forced drying is performed at 150° C. for about 5 minutes.

After the resistance paste 9 is dried, the heat-resistant film 7
is placed in an electric furnace, and the resistive paste 9 is baked onto the heat-resistant film 7. In this example, 260℃, about 15
It can be baked under the conditions of minutes. The resistor paste 9 is baked to form a resistor 6 that can be firmly fixed to the resin molded substrate 1.

At this stage, the resistance characteristics of the resistor 6 formed on the heat-resistant film 7 are checked to see if they are within the specifications, and the composition of the resistor paste 9 and the conditions of printing, drying, and baking are good. It will be confirmed whether The resistance characteristics of the resistor 6 are checked for all or some samples of the resistor 6.

If the resistance characteristics of the resistor 6 are within the specifications, the resistor 6 is wound onto a reel 10 and used as a transfer sheet 11. Transfer sheet 11
At this stage, various types of variable resistors are prepared, and it is possible to immediately respond to changes in variable resistor types.

Next, as shown in FIG. 1(B) and FIG.
The transferred sheet 11 and the lead terminals 3 and 4
．． 5 and the mold 12. It can be accommodated and positioned within I3. The lead terminals 39 and 4 are integrally connected to the hoop terminal 14, and the lead terminal 5 is integrally connected to the hoop terminal 15, respectively, and wound up on the reel 16. Feed holes 14a and 15a are formed in the hoop terminals 14 and 15, respectively, and the feed holes t
Hoop terminals 14.15 are fed at regular intervals by the hoop terminals 15a and 15a and housed in the mold 12.13. The lead terminals 3, 4.5 are formed in the groove 13a formed in the mold 13,
13b and 13c and are positioned. On the other hand, the transfer sheet 11 is positioned so that the feed holes 7a formed in the heat-resistant film 7 are fully inserted into the protrusions 13d protruding from the mold 13.

When the transfer sheet 11 and the lead terminals 3, 4.5 are positioned, the mold 12.13 is closed, and then the mold 12
．． The molten diallyl phthalate resin is filled in 13 and solidified.

By solidifying the resin, as shown in FIG. 5, a resin molded substrate 1 with lead terminals 3, 4.5 embedded therein and a carbon-based resistor 6 and a heat-resistant film 7 fixed on its surface is completed. In this way, the resin molded substrate 1
are sequentially molded using molds 12.13 and connected to hoop terminals 14.15 and heat-resistant film 7,
It is sent out from molds 12 and 13.

The resin molded substrate 1 is subjected to heat treatment, degassing, etc. as necessary [see FIG. 1(B)].

Next, as shown in FIG. 6, the heat-resistant film 7 is peeled off from the resin molded substrate 1 connected by the hoop terminals 14 and 15. At this time, the carbon-based resistor 6 formed on the surface of the heat-resistant film 7 is embedded and fixed to the surface of the resin molded substrate 1 so as to be exposed on the same plane. will not be peeled off from the surface of the substrate. Further, since the carbon-based resistor 6 has a uniform thickness formed on the heat-resistant film 7 and is fixed (transferred) to the surface of the substrate 1 as it is, there is no variation in resistance characteristics.

Next, the heat-resistant film 7 is peeled off and a rotor having a slider (not shown) is attached onto the carbon-based resistor 6 exposed on the surface of the resin molded substrate 1. This slider is electrically connected to and rotatably attached to the flapper electrode portion 5a of the resin keeled substrate 1. In this way,
After the necessary parts are attached to the resin molded board 1,
Hoop terminals 14 and 15 that connect resin molded boards l
are completely cut from lead terminals 3, 4.5, respectively, and a variable resistor is manufactured. The lower terminals 3, 4.5 are on the board 1
If it is bent from the side surface to the back surface, it can be made into a surface mount type element.

Here, the compositions of the carbon-based resistor 6 and the substrate 1 and their effects will be described in detail with reference to Table 1.

As a carbon-based resistor, the main component is graphite 8.0~
70. Out%, inorganic filler as resistance adjuster 0~
40.0wt%, binder resin 30.0-70.0wt%
, thermosetting agents (e.g. tertiary-butylbenzoate).

(organic peroxide such as simicle peroxide, butyl peroxide) in a ratio of 1.0 to 5.0 to the binder resin.
A paste obtained by adding an appropriate amount of ethylcarpitol acetate as a solvent to wt% was used.

As a substrate, diallyl phthalate resin 4 is used as the main component.
0 wt%, inorganic filler 30 wt%, short glass fiber 30
The mixture was prepared by mixing, kneading, and pulverizing each component in an amount of 1 to 5 wt% of the thermosetting agent as described above based on the diallyl phthalate resin.

2. As is clear from Table 1 above, Examples ■ and ■ have smaller temperature coefficients of resistance (TCR) than Comparative Examples Example■
In Comparative Example (2), air bubbles were generated on the board, in Comparative Example (2), the board was deformed, and in Comparative Example (2), the board was discolored, and the board was not able to withstand flow soldering.

Furthermore, in each of Examples (1) and (2), there was almost no change in resistance value even after ultrasonic cleaning with triethane, and the results were good.

Although the variable resistor and the manufacturing method thereof according to the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the gist.

For example, the variable resistor is not limited to the form shown in FIG. 2, but may also be of the form in which the resistor is formed on the inner surface of the cylinder.Moreover, the variable resistor itself may have a lead terminal. It may be attached to the substrate by caulking or other methods without molding.

Furthermore, after printing and baking a resistor paste on a heat-resistant film, an electrode paste made of a good electrical conductor is printed and baked on top of the area where it will be connected to the lead terminal, ensuring electrical connection between the resistor and the lead terminal. You may also do this.

Further, the heat-resistant film is preferably a polyimide film having excellent heat resistance and two-dimensional stability, but may also be a film molded from an imide-based resin composite material or a material having excellent heat resistance.

Other methods include adding a chemical treatment process to the transfer sheet on which the carbon-based resistor is formed to make the heat-resistant film easier to peel off from the resistor, or removing the resistor on the heat-resistant film using a silane coupling agent or silicone. It is also possible to treat with a primer to increase the adhesion between the resistor and the substrate and improve the transferability.

As is clear from the above explanation, according to the first invention, a carbon-based resistor containing a diallyl phthalate resin as a binder resin is used as a resistor, and a diallyl phthalate resin is used as a substrate. Therefore, not only can it be manufactured at a low cost, but diallyl butarate resin has good heat resistance and can be mounted using flow soldering, and the variable resistor has good characteristics with a small rate of change in resistance value. be able to.

Further, according to the second invention, the carbon-based resistor formed on the transfer sheet is transferred to the surface of the resin molded substrate at the same time as the resin molded substrate is molded.
At the stage of molding the transfer sheet, that is, the resistance characteristics of the carbon-based resistor transferred to the surface of the resin molded substrate can be checked on the transfer sheet, making it possible to mass-produce prototypes. Therefore, it is not necessary to stop the production equipment to check the resistance characteristics of the carbon-based resistor, and productivity is greatly improved and variable resistors can be provided at a lower cost. Further, the drying work of the resistor paste can be carried out in a narrow space, and there is no need for a space to store resin molded substrates before forming resistors, and the space of the entire production facility can be reduced. Furthermore, since the carbon-based resistor formed on the transfer sheet and containing diallyl phthalate resin as a binder resin is transferred as is to the mold substrate made of diallyl phthalate resin, variations occur in the resistance characteristics of the resistor. Therefore, it is possible to provide a high quality variable resistor with excellent resistance characteristics.

[Brief explanation of the drawing]

FIG. 1 is for showing the manufacturing process of a variable resistor according to the method of the present invention, and FIG. 1 (A) is a manufacturing process diagram of a transfer sheet;
FIG. 2B is a process diagram of manufacturing and assembling the resin molded substrate. Figure 2 is for showing one embodiment of the variable resistor according to the present invention, where (A) is a plan view, (B) is a vertical sectional view, and (C) is a surface mount type. FIG. Figures 3150-f$6 are for explaining the manufacturing method of the variable resistor shown in Figure 2, Figure 3 is a perspective view for explaining the manufacturing process of the transfer sheet, and Figure 4 is a resin mold. An exploded perspective view for explaining the process of molding the substrate, FIG. 5 is a perspective view showing the state of the resin molded substrate after molding, and FIG. 6 is a perspective view for explaining the process of peeling off the heat-resistant film from the resin molded substrate. It is a diagram. DESCRIPTION OF SYMBOLS 1... Resin molded board, 3, 4.5... Lead terminal, 6... Carbon-based resistor, 7... Heat resistant film, 9... Resistance paste, 11... Transfer sheet, 1
2.13... Molding mold, 14.15... Hoop terminal. Patent applicant Murata Manufacturing Co., Ltd.

Claims (2)

[Claims] (1) In a variable resistor equipped with a substrate provided with a resistor on the surface, a carbon-based resistor formed in a predetermined shape is integrally molded on the surface of the resin substrate, and the carbon-based resistor 1. A variable resistor comprising diallyl phthalate resin as a binder resin, and a resin substrate made of diallyl phthalate resin. (2) A step of printing a carbon-based resistance paste containing diallyl phthalate resin as a binder resin in a predetermined shape on a heat-resistant film, drying it, and baking it to prepare a transfer sheet on which a carbon-based resistor is formed. and accommodating and positioning the transfer sheet together with the lead terminals in a mold, and filling the mold with molten diallyl phthalate resin and solidifying it, so that the lead terminals are embedded inside and the surface is The method is characterized by comprising the steps of: molding a resin molded substrate to which a carbon-based resistor and a heat-resistant film are fixed; and peeling off the heat-resistant film from the resin-molded substrate, leaving the carbon-based resistor. Manufacturing method of variable resistor.