JPH0374483B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a film resistor in which a resistance film of carbon, metal, etc. is deposited on an insulating substrate such as an insulator. The present invention relates to a method for adjusting the resistance value of a film resistor.

BACKGROUND ART Conventionally, this type of resistance value adjustment has been performed by a method as shown in FIG. That is, both ends of a film resistor 1, which has a resistance film coated on the surface of a cylindrical insulator, are gripped by a chuck 2, the film resistor 1 is rotated and fed in the axial direction, and a thin disk-shaped cutting wheel 3 is attached to it. By applying the material while rotating it at high speed, a spiral groove was formed and the resistance value was adjusted (this is called trimming). Also, in Figure 3,
A spindle 4 includes a shaft 4a and a bearing 4b, and serves to rotate the grindstone 3. 5 is a cutter holder that houses the spindle 4, and the spindle 4 is connected to a motor 6,
It is rotationally driven by a large pulley 7, a small pulley 8, and a belt 9.

As a method of applying the cutting wheel 3 to the film resistor 1, a configuration as shown in FIG. 4 has been common. That is, the cutter holder 5 containing the spindle 4 that rotates the cutting wheel 3 is supported by the fulcrum 10, and the force with which the cutting wheel 3 is pressed against the film resistor 1 is adjusted by adjusting the position of the weight 11. Put the cutting wheel 3 on the film resistor 1
I was trying to find the right timing to hit it. Further, in FIG. 4, 13 is a cutter holder holder, 14 is a weight shaft, 15 is a cam lever, and 16 is a fulcrum.

In addition, in this adjustment method, in order to generally cut a good groove, the rotating surface of the cutting wheel 3 is made to form an angle θ with respect to the film resistor 1 as shown in FIG. It was adjusted to match.

Problems to be Solved by the Invention This conventional resistance value adjustment method has had the following problems.

(1) Grooves are formed by applying a high-speed rotating cutting wheel to the film resistor, which applies thermal and mechanical stress to the film resistor, leaving fine cracks on the edges of the groove, and causing damage to the film resistor. becomes a factor in deterioration of electrical characteristics. Furthermore, as the temperature of the film resistor increases, the resistance value becomes different from that at room temperature due to the temperature characteristics of the resistance film, which tends to cause a resistance value measurement error when adjusting the resistance value.

(2) As shown in Fig. 4, since the contact between the cutting edge of the cutting wheel 3 and the film resistor 1 is made only by the weight of the cutter holder 5, etc., the edge of the cutting edge sometimes shakes when cutting the groove. occurs and the groove depth and groove width fluctuate. Additionally, if the cutting wheel bounces on the film resistor, it will cause groove jumping. These factors cause deterioration of the electrical characteristics of the film resistor as a product.

(3) To prevent groove skipping and groove defects mentioned in (2) above,
It is necessary to press the cutting wheel against the film resistor with more force than a certain level, which results in the formation of a deep groove of several micrometers. This situation is shown in FIG. 6, where 18 is the deep groove mentioned above. As shown in FIG. 6, the thickness of the portion of the resistance film 20 existing on the surface of the insulator 19 constituting the film resistor 1, including the surface roughness of the insulator 19, is several μm or less. Therefore, the mechanical bending strength of the resistor body is extremely reduced due to the deep groove 18 described above. This is undesirable because it may cause the film resistor to break, for example, when the film resistor is inserted into a printed circuit board using an insert machine. In addition, by cutting the insulator deeply, a large amount of insulator dust made of alumina etc. is generated, but this dust is not only harmful to the human body, but also clogs the precision parts of other machines and is not functioning normally. It becomes a factor that impedes the functions.

(4) When the diameter of the cutting wheel becomes smaller due to wear, the condition of the groove deteriorates and the cutting resistance value changes due to the timing difference between the start and end of cutting, so it is necessary to adjust the position of the cutter holder. , resulting in a decrease in productivity.

(5) As shown in Figure 6 above, since the edges of the grooves become sharp, they easily damage the resistance films of other film resistors and the plating of terminal caps during product transportation, and the edges of the grooves lack confidence. The resistance value may change, or the plating of the terminal caps of other film resistors may adhere to the resistance film, resulting in deterioration of electrical characteristics.

(6) If you fail to insert the film resistor into the chuck and the film resistor rotates eccentrically due to eccentric chucking, an impact will be applied to the cutting edge of the cutting wheel, causing part of the blade to chip. . If a part of the blade is chipped in this way, the condition of the groove will deteriorate significantly, and if production continues without noticing, a large number of defective products will be produced.

(7) If the cutting wheel wears out beyond a certain level or becomes clogged, dressing or replacement is required, and fine adjustments are required at that time, which limits the ability to increase productivity.

(8) Since the resistance value can be adjusted only one film resistor at a time using a single cutting wheel, the number of products produced per unit time is small.

(9) In order to cut a good groove, set the rotating surface of the cutting wheel so that it forms an angle θ along the spiral groove with respect to the film resistor, as shown in Figure 5, and then cut a trial groove. The inclination of the film resistor with respect to the axial direction must be finely adjusted while doing so.
Must rely on skilled workers. In addition, if the adjustment is insufficient, not only will the groove condition deteriorate, but
The life of the cutting wheel will also be shortened.

Therefore, in order to solve the above-mentioned problems, the present invention uses a cutter that does not change much over time and cuts almost only the resistance film, thereby reducing the stress applied to the film resistor and the generated dust. It is.

Means for Solving the Problem In order to solve this problem, the present invention uses a thread-like abrasive material made by adding abrasive grains to the raw material or adhering it to the surface thereof, and applying a predetermined tension to the thread-like abrasive material. The structure includes a pulley and a drive device that run at high speed, and a chuck having multiple sets grips and rotates a large number of film resistors while applying the thread-like grinding material to them, and the film resistor and the thread-like grinding material are The present invention is characterized in that at least one of the objects is moved in the axial direction of the film resistor, and a spiral groove is cut in the resistance film of the film resistor to adjust the resistance value.

Effects According to this configuration, the resistance film is partially scraped off using the filament-like grinding material, so it is only necessary to scrape off a shallow part of the surface of the film resistor, and the running speed of the grinding material is lower than that previously used. Since approximately 1/10 of the circumferential speed of the cutting wheel is sufficient, there is almost no temperature rise in the grinding part, so no thermal stress is applied to the resistor. Further, mechanical stress such as fine cracks does not remain on the edge of the groove. Due to these factors, the electrical characteristics will not deteriorate. In addition, since the abrasive object can be easily moved without leaving the surface of the film resistor, groove jumping does not occur, and if the tension applied to the abrasive object, the running speed, and the amount of pushing are controlled at a constant level, Groove conditions such as groove depth and groove width remain unchanged over time, and electrical characteristics are maintained favorably. Furthermore, since the cut groove is shallow as described above, the mechanical bending strength of the resistor body does not deteriorate, and the product is not damaged by impact when inserted into a board with an insert machine. Since only a shallow portion of the surface of the film resistor is scraped, the insulator is hardly scraped, and as a result, the amount of dust on the insulator is extremely reduced. Further, since a large number of film resistors held by a large number of chucks can be adjusted simultaneously using a single thread-like grinding object, productivity per unit time can be increased.

Embodiment An embodiment of the present invention will be described above with reference to the drawings.

First, in FIG. 1, 21 is an abrasive thread as a filament-like abrasive material made by adding abrasive grains to a raw material or adhering them to the surface thereof, such as nylon (trade name of Dupont), which is a polyamide-based synthetic polymer. Silicon carbide is bonded to the surface of the 22 is a cylindrical film resistor with a resistive film coated on its surface. Then, the film resistor 22 is gripped by the right chuck 23a sent in the axial direction by the feed cam 26 and the right chuck 23b supported by the spring 28, and is caused to revolve together with the disk 24 (angular velocity W ₂ ). On the other hand, by rotating the large gear 25 slightly slower than the disk 24 (angular velocity W ₁ ), the small gear 27 rotates (angular velocity W ₃ ), and the film resistor 22 rotates. The chuck 23a is pushed by the feed cam 26, and the film resistor 22 is fed in the axial direction. Chuck 23 with the same mechanism as above
A, 23b are provided in large numbers, and the film resistors 22 are continuously supplied. A groove for guiding the abrasive thread 21 is provided in the mountainous portion of the disk 24, which has a number of valleys on the outer circumferential surface in which the film resistors 22 are housed, and a drive device such as a motor ( pulleys 29 on which the abrasive threads 21 driven by (not shown) are arranged vertically at a predetermined speed;
It runs through 30. Also, pulley 29,3
0 gives an appropriate tension to the abrasive thread 21.

With the above mechanism, the abrasive thread 21 can continuously groove the resistance films of a large number of film resistors 22 in a spiral shape, thereby adjusting the resistance value.

FIG. 2 is a diagram showing the state of the grooves of a film resistor whose resistance value has been adjusted in this way.A shallow groove 31 is formed on the surface of the resistor, and this shallow groove 31 is almost entirely formed by the resistance film. Scrape off only 32, insulator 3
The surface of No. 3 is only shallowly scratched.

Furthermore, in the above embodiment, a case has been described in which a part of the resistance film 32 on the film resistor 22 is cut off by the abrasive thread 21 by feeding the film resistor 22 in its axial direction. The abrasive thread 21 may be moved in the axial direction of the film resistor 22, or even both the abrasive thread 21 and the film resistor 22 may be moved.

As described above, the resistance value adjustment method of the present invention involves gripping a large number of film resistors 22 by a large number of sets of chucks 23a and 23b, and polishing the resistors while being applied with a predetermined tension and running at a predetermined speed. Press the thread 21 against the film resistor 22 and press the abrasive thread 2
By moving at least one of the film resistor 1 and the film resistor 22 in the axial direction of the film resistor 22, the resistance film 32 of an arbitrary portion on the film resistor 22 is scraped off to form a spiral groove. This is a new and unprecedented technical means of adjusting values.

Effects of the Invention The effects obtained by the method for adjusting the resistance value of a film resistor according to the present invention configured as described above are as described below.

(1) It is only necessary to scrape off almost only the resistance film on the surface of the film resistor, that is, only the shallow part, using the abrasive thread (thread-like grinding material), and the running speed of the abrasive thread is the same as the circumferential speed of the conventional cutting wheel. Since a speed of about 1/10 of that (approximately 300 m/min) is sufficient, there is almost no temperature rise in the grinding section. Therefore, no thermal stress is applied to the resistor, and no measurement error occurs when adjusting the resistance value. Further, mechanical stress such as fine cracks does not remain on the edge of the groove. Due to these factors, the electrical characteristics will not deteriorate.

(2) Since the abrasive thread can be easily run without leaving the surface of the film resistor, groove jumping does not occur, and if the tension applied to the abrasive thread, running speed, and pushing amount are controlled at a constant level, Groove conditions such as groove depth and groove width remain unchanged over time, and the electrical characteristics of the product are maintained well.

(3) In order to adjust the resistance value of a film resistor, it is necessary to
It is sufficient to remove only the groove m), but as described above, using an abrasive thread makes it easy to grind the shallow groove. Since the groove cut out in this manner is shallow, the mechanical bending strength of the resistor body does not deteriorate, and the product will not be damaged by impact when inserted into a board with an insert machine. Furthermore, since only a shallow portion of the surface of the film resistor is scraped, the insulator is hardly scraped, and as a result, the amount of dust generated on the insulator is extremely reduced.

(4) As the abrasive thread runs, new parts come into contact with the resistor surface one after another, so the cutting force of the abrasive thread remains unchanged over time and the groove condition does not deteriorate.

(5) As shown in Figure 2, the edges of the grooves do not become sharp, so they are less likely to damage other resistors or the edges of the grooves themselves become chipped.
Deterioration of the electrical characteristics of the resistor can be prevented.

(6) Even if you fail to insert the film resistor into the chuck and the film resistor rotates eccentrically, the abrasive thread can move freely according to the movement of the film resistor, so there is no risk of damage to the abrasive thread. There isn't.

(7) Since only the shallow part of the surface of the insulator is removed, there is little wear on the abrasive threads, and when replacing them, only the abrasive threads need to be replaced, and no detailed adjustments are required. Therefore, in addition to the above points (5) and (6), productivity can be increased.

(8) The resistance values of multiple film resistors held by multiple sets of chucks can be adjusted simultaneously using one abrasive thread.

(9) Even if one or both of the abrasive thread and the film resistor are simultaneously moved in the axial direction of the film resistor while applying the abrasive thread to the film resistor that is being rotated, a spiral groove will be formed in the same way. This allows for a high degree of freedom in device design. Also,
Adjustment when setting the abrasive thread to form an angle θ along the spiral groove with respect to the film resistor is much easier than with conventional cutting wheels,
Even a non-skilled worker can easily perform good groove cutting.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a method for adjusting the resistance value of a film resistor according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of the surface of the resistor showing the state of the grooves obtained by the method of the present invention. , FIG. 3 is a diagram showing a conventional method for adjusting the resistance value of a film resistor, FIG. 4 is a perspective view showing an example of a mechanism for applying a cutting wheel to a film resistor in the conventional method, and FIG. FIG. 6 is an enlarged sectional view of the surface of the resistor showing the state of the kerf obtained by the conventional method. 21... Polishing thread, 22... Film resistor, 23a
...Left chuck, 23b...Right chuck, 24...
...Disk, 25...Large gear, 26...Feed cam, 28...Spring, 29,30...Pulley, 3
1...Shallow groove, 32...Resistive film, 33...Insulator.

Claims (1)

[Claims] 1 Using a thread-like abrasive material made by adding abrasive grains to the raw material or adhering it to its surface, it is equipped with a pulley and drive device that runs at a predetermined speed while applying a predetermined tension to the thread-like abrasive material. The film resistor is gripped and rotated while the thread-like ground material is applied to the film resistor, and at least one of the film resistor and the thread-like ground material is moved in the axial direction of the film resistor. A method for adjusting the resistance value of a film resistor, characterized by adjusting the resistance value by cutting a spiral groove in the resistance film of the film resistor.