JPH06333702A - Bar-shaped resistor and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve quality, to prevent the generation of a defective at the time of manufacture and to enhance productivity in a resistor, in which leads are fixed onto both end faces of a bar-shaped element. CONSTITUTION:The whole external surface of an element 2 is covered with a resistance film 3, and leads 5 are welded directly at the positions of both end faces of the element 2 in the resistance film 3. A cap which has been used is unnecessitated, thus preventing various trouble (such as trouble, in which a range that a trimming groove 4 can be formed is narrowed and performance is deteriorated) resulting from the fitting of the cap. One ends of the leads 5 are abutted and contacted with the resistance films 3 of the end faces of the element 2 through metallic foils, and currents are applied among the metallic foils and the leads 5 under the state. Accordingly, one ends of the leads 5 are welded to the resistance film 3 under the state, in which the metallic foils melted by resistance heat are extruded in the radial outward direction, thus directly fixing the leads 5 to the resistance film 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention covers the outer surface of an element formed in a rod shape with an insulator such as ceramics with a resistance film, and trims the resistance film on the outer circumference of the element with a protective film. The present invention relates to the structure of a rod-shaped resistor made of and its manufacturing method.

[0002]

2. Description of the Related Art The structure and manufacturing method of a rod-shaped resistor 21 of this type have hitherto been as shown in FIG. That is,
A resistance film 23 is formed on the entire outer surface of the element 22 by an appropriate means such as sputtering or vacuum deposition, and a trimming groove 24 for adjusting the resistance value is spirally formed on the resistance film 23 on the outer periphery of the element 22. Then, at both ends of the element 22,
A cap 25 made of iron or the like having a surface plated with copper or tin is fitted, and a lead wire 27 made of copper or the like held by a clamp body 26 is attached to an outer end surface of the cap 25.
One end of the lead wire 27 is pressed, and in that state, an electric current is applied between the lead wire 27 and the cap 25.
Is welded to the cap 25, then a protective film 28 is formed so as to cover the outer surface of the element 22 and the outer peripheral surface of the cap 25, and the resistance value, grade, etc. are displayed on the outer peripheral surface of the protective film 28. The color band 29 is printed.

[0003]

However, the structure in which the lead wires 27 are attached to both ends of the element 22 via the caps 25 has the following problems. ． After the cap 25 is fitted on the element 22, the protective film 28
The plating applied to the surface of the cap 25 is partially peeled off before the formation of the cap 25. A defective product is said to be covered with the protective film 29 as it is, and therefore, an accident in which the resistor 21 is short-circuited after being incorporated in an electronic component often occurs.

.. In this type of resistor 21, as long as the resistance value is the same, the longer the length L0 of the resistance film 23 is, the more the heat dissipation is promoted to improve the durability, and the current noise is reduced to improve the quality. Cap 2
Since the length L0 with which the trimming groove 24 can be provided becomes shorter by fitting 5 in the above, it was not possible to achieve both miniaturization and quality improvement at the same time.

Particularly, as the size of the resistor 21 becomes smaller, the proportion of the cap 25 to the entire length of the resistor 21 increases, so that the problem of this quality has been conspicuous. ． In addition to the step of fitting the cap 25 to the element 22, a gap is formed between the cap 25 and the element 22, so that cleaning / coating prior to applying the protective film 28 can be performed.
Productivity was low because it took time to dry.

[0006] As a means for providing the protective film 28, a heat-adhesive powder coating material such as epoxy which has a property of adhering when the coating surface is heated is used, and the element 22 after trimming is heated in a coating tank. To roll it,
Although powder coating is applied to the outer peripheral surface of the element 22, in that case, a gap 31 is formed at the end of the cap 25.
Occurs, the air in the gap 31 becomes bubbles due to heat,
This emerges on the surface of the protective film 29 and the pinhole 3
2 occurs, which deteriorates the appearance and causes pinholes 3
From 2 on, moisture or minute dust may adhere to the resistance film 23.

It is an object of the present invention to provide a rod-shaped resistor and a method for manufacturing the same which solve these problems.

[0008]

To achieve this object, the entire outer surface of a rod-shaped element made of an insulating material is covered with a resistance film, and the resistance film on the outer circumference of the element is spirally trimmed. Along with being covered with a protective film, one end of each lead wire is fixed to the resistance film on both end faces of the element.

Further, as a method of manufacturing the resistor described in claim 1, as described in claim 2, after forming a resistance film on the entire outer surface of the rod-shaped element made of an insulating material, the element is formed. After the resistance film on the outer periphery of the element is spirally trimmed or before the trimming, one end of the lead wire is brought into contact with the end face of the element via the metal foil, and in that state, the metal foil and the lead are connected. A structure in which one end of the lead wire is welded to a resistance film on the end surface of the element by applying a current between the wire and a protective film covering the trimmed portion on the outer peripheral surface of the element. I chose

[0010]

According to the structure of claim 1, since the conventionally used cap is unnecessary, defective products are generated due to the existing cap, that is, the surface of the cap. The effect that can prevent the occurrence of pinholes in the protective film when the plated pieces peeled from the plating layer applied to the film adhere to the resistance film or when the protective film is formed by applying a heat-adhesive powder paint Have.

Further, since the portion of the resistance film where the conventional cap is fitted can be trimmed, the length of the trimmed portion of the resistance film can be increased without changing the size of the element. Even if the size of the resistor is the same as the conventional one, it is possible to promote heat dissipation, improve durability and reduce current noise.
Therefore, the quality can be improved without increasing the size of the resistor.

Furthermore, in the manufacturing process, the process of fitting the cap can be omitted, and the cleaning and drying can be performed quickly, and the productivity of the resistor can be improved. By the way, since the resistance film is made of metal such as carbon, nickel, or chrome, the lead wire can be directly welded to the resistance film.

According to a second aspect of the present invention, one end of the lead wire is brought into contact with the resistance film on the end face of the element via the metal foil, and in this state, a current is applied between the metal foil and the lead wire. When applied, the resistance heat generated at the contact point between the metal foil and the lead wire melts the contact point between the metal foil and the lead wire, and one end of the lead wire extrudes the melted metal foil to the outside of the radius. Weld to the resistance film with.

In this case, since the metal foil merely overlaps with the resistance film at the end face of the element, no current flows through the resistance film. Therefore, according to the method of claim 2, since the lead wire can be directly fixed to the resistance film without damaging the resistance film, a resistor having the lead wire directly fixed to the resistance film at the end face of the element is provided. , Has the effect of being easily manufactured.

[0015]

Embodiments of the present invention will now be described with reference to the drawings. 1 to 3 show a small-sized resistor 1 embodying claim 1, and the resistor 1 includes an element 2 made of an insulator in which a resistance film 3 is formed on the entire outer surface. While the trimming groove 4 is spirally formed on the resistance film 3 on the outer peripheral surface 2a of the element 2, one end of the lead wire 5 extending concentrically with the element 2 is formed on the resistance film 3 on both end surfaces 2b of the element 2. Each is fixed, and the entire outer peripheral surface of the element 2 is protected by the protective film 6
Covered with.

On the end surface 2b of the element 2 on the portion of the resistance film 3 around the end of the lead wire 5, a ring body 7 generated in the attaching step of the lead wire 5 described later is welded.
The protective film 6 may be formed so as to cover the entire end surface 2b of the element 2 as shown by the chain double-dashed line in FIG. Thus, since the lead wire 5 is directly fixed to the resistance film 3 without using a cap as in the conventional case,
It is possible to prevent problems caused by fitting the cap as in the past, that is, the plating applied to the cap is peeled off and the plated piece is attached to the resistance film, and the pinhole is generated in the protective film. , Trimming groove 4
It is possible to lengthen the length L0 that can be formed to improve the quality, and further to speed up the washing / drying process in manufacturing.

In the resistor 1 described above, the resistive film 3 is formed on the element 2 by an appropriate means such as sputtering, and then the resistive film 3 is formed.
Are trimmed, and then the lead wires 5 are attached to both end faces of the element 2.
Is fixed, then washed and dried, and then the protective film 6 is formed by an appropriate means such as applying a heat-adhesive paint in a state where the whole is heated. The display is printed in that order.

Then, the step of fixing the lead wire 5 can be carried out by using a thin metal tape (metal foil) 8 for an electrode as shown in FIGS. This point will be described below. On the metal tape 8, a horizontal bridge portion 9 extending in parallel at a constant pitch P, a vertical bridge portion 10 extending in a state of being connected to the horizontal bridge portion 8a, and a crossing point of both the horizontal bridge portions 9 and the vertical bridge portion 10. The circular abutting portion 11 formed in the above is formed at a constant pitch P by punching,
This metal tape 8 is attached by two pairs of feed rollers 9 and 1
The pitch P is intermittently transferred.

The diameter d1 of the contact portion 8c is the same as that of the lead wire 5.
The diameter d2 is substantially the same as or larger than the diameter d2, and is smaller than the diameter of the element 2. In addition, when the lead wire 5 is made of copper, the metal tape 8 is made of iron. By forming the lead wire 5 and the metal tape 8 from different materials, a current is applied in a state where they are in contact with each other. When this happens, resistance heat is generated at the contact point between the two. When selecting the materials for the lead wire 5 and the metal tape 8, it is preferable to make the specific heat and the thermal conductivity as different as possible.

A portion where the left and right bridge portions 8a of the metal tape 8 are connected to the contact portion 8c, and a vertical bridge portion 8
The angle θ formed by the three points where b is connected to the upper end of the abutment portion 8c is approximately 120 degrees, in other words, the three portions that are equally spaced along the outer circumference of the abutment portion 8c. From
The three bridge portions 8a and 8b are set to extend laterally and upward.

Among the portions between the feed rollers 9 and 9, the element 2 is held at one of the portions sandwiching the metal tape 8 in a posture extending in a direction orthogonal to the surface of the metal tape 8. The 1st clamp body 10 which was made into the metal tape 8
It is arranged so that it can be moved toward and away. On the other hand, a lead wire 5 is attached to the first clamp body 10 at a portion opposite to the first clamp body 10 with the metal tape 8 interposed therebetween.
The second clamp body 11 which is concentric with the element 2 grasped by and is grasped by the second clamp body 11 is disposed so as to be movable toward and away from the metal tape 8. One of the two feed rollers 9 is electrically connected, and the power supply 13 and the switch 14 are inserted into the circuit 12 thereof.

For example, the diameter d2 of the lead wire 5 is 0.
In the case of 45 mm, the thickness of the metal tape 8 is 0.1
mm, the total width W1 of the metal tape 8 is about 5 to 10 mm, the diameter d2 of the abutting portion 8a is about 0.6 to 1.0 mm, and the width dimension W2 of each bridge portion 8a, 8b is about 0.3 to.
The length L1 of the vertical bridge portion 8a is set to about 0.5 mm.
It is preferable to set it to about 6 to 1.0 mm.

In the above structure, the element 2 is moved toward the metal tape 8 by the first clamp body 10 when the metal tape 8 is stopped while the metal tape 8 is intermittently transferred by one pitch P. At the same time, the lead wire 5 cut into a certain size is moved toward the metal tape 8 by the second clamp body 11, and the lead wire 5 is attached to the contact portion 8c of the metal tape 8 overlapping one end surface of the element 2. One end of the bridge is pressed, and in that state, electric current is applied between the feed roller 9 and the second clamp body 11, and between the metal tape 8 and the lead wire 5, left and right and upper three bridge portions 8a, A current is applied via 8b.

Then, the contact portion 8c of the metal tape 8
Resistance heat is generated at the contact portion between the lead wire 5 and the lead wire 5, the contact portion 8c and one end portion of the lead wire 5 are melted, and one end portion of the lead wire 5 is crushed and deformed, and the melted contact portion is melted. 8c is pushed outward in the radius, one end of the lead wire 5 is welded to the resistance film 3 at the end face 2b of the element 2, and the welded contact portion 8c surrounds one end of the lead wire 5. The bridge portions 8a, 8b of the metal tape 8 formed on the ring portion 7 are melted by heat.

In this case, since the metal tape 8 only overlaps the one end face 2b of the element 2 and no current flows through the resistance film 3, the resistance film 3 is not damaged by the current. Then, the lead wire 5 by the second clamp body 11
By releasing the clamp, the second clamp body 11 is separated from the metal tape 8, and the first clamp body 10 is separated from the metal tape 8, and the fixed lead wire 5 is removed from the metal tape 8. The fixing of the lead wire 5 to the one end surface of the element 2 is completed.

Further, a transfer mechanism for the metal tape 8 and a second clamp body 11 having the same construction as shown in the figure are arranged on both sides of the first clamp body 10, and the same operation as described above is performed. The lead wire 5 is fixed to the other end surface of the element 2. Thus, since the metal tape 5 is used as an electrode, the lead wire 5 can be directly fixed to the resistance film 3 reliably and efficiently without damaging the resistance film 3. .

By the way, when the current is applied, the contact portion 8
Since the vertical bridge portion 8b extending downward from c is melted, the current flows from the left and right bridge portions 8a and the upward vertical bridge portion 8b to the contact portion 8c. Therefore, as in the embodiment, the left and right bridge portions 8a and the upward vertical bridge portions 8b are arranged.
When the portions where and are connected to the abutment portion 8c are arranged at equal intervals along the circumferential direction, current flows evenly through the bridge portions 8a and 8b, so that the abutment portion 8c is melted in a uniform state,
The lead wire 5 is firmly welded and each bridge portion 8
The a and 8b can be reliably melted and lost.

It is preferable that the strength of the electric current is slightly higher than that in the conventional case where a cap is used. FIG. 9 shows an embodiment in which the intersection of the left and right bridge portions 8a and the vertical bridge portion 8b is used as the abutment portion 8c. Also in this embodiment, the bridge portion 8a extending laterally from the abutment portion 8c and the upward direction. The angle θ formed by each root with the vertical bridge portion 8b extending to is set to about 120 degrees so that the current flows evenly through the three bridge portions 8a and 8b.

In the case of the embodiment of FIG. 9, for example, when the diameter of the lead wire 6 is 0.45 mm, the metal tape 8 has a total width of about 5 to 10 mm and a thickness of 0.07 m.
The width W2 of each bridge portion 8a, 8b is 0.4 to about m.
The length L1 of the vertical bridge portion 8b is about 0.7 mm.
It is preferably set to about 4 to 0.7 mm. It goes without saying that the metal tape may have other forms.

[Brief description of drawings]

FIG. 1 is a front view of a resistor with a protective film shown in phantom.

FIG. 2 is a side view taken along line II-II of FIG.

FIG. 3 is a cross-sectional view of a main part of a resistor.

FIG. 4 is a perspective view of an essential part of a device for fixing lead wires.

FIG. 5 is a side view of an apparatus for fixing lead wires.

6 is an enlarged view of FIG. 5 taken along line VI-VI.

FIG. 7 is a cross-sectional view showing a welded state of a lead wire.

8 is a sectional view taken along line VIII-VIII of FIG.

FIG. 9 is a diagram showing another example of the metal tape.

FIG. 10 is a diagram showing a conventional resistor and its manufacturing method.

[Explanation of symbols]

 1 resistor 2 element 3 resistance film 4 trimming groove 5 lead wire 6 protective film 8 metal tape (metal foil) 8a, 8b bridge part 8c contact part

Claims (2)

[Claims] 1. A resistance film covering the entire outer surface of a device formed in a rod shape with an insulator, and a resistance film on the outer periphery of the device is spirally trimmed and covered with a protective film,
A rod-shaped resistor characterized in that one end of a lead wire is fixed to each of the resistance films on both end faces of the element. 2. A resistor film is formed on the entire outer surface of a rod-shaped element made of an insulating material, and the resistor film on the outer periphery of the element is spirally trimmed, or before trimming is performed. , One end of the lead wire is brought into contact with the end face of the element through a metal foil, and a current is applied between the metal foil and the lead wire in this state, so that one end of the lead wire is A method for manufacturing a rod-shaped resistor, comprising welding to a resistance film on an end face, and then forming a protective film on the outer peripheral surface of the element to cover the trimmed portion.