JPH044104B2 - - 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 trimming a film resistor, which involves scraping and trimming.

Conventional technology Conventionally, a thin disk-shaped cutting wheel has been used as the grinding object used in this type of film resistor trimming method, and film resistor trimming using this grinding wheel is as shown in Figure 4. It was done in a certain way.
That is, by grasping both ends of the film resistor 1 with the chucks 2 and 2', feeding the film resistor 1 in the axial direction while rotating it, and applying the above-mentioned cutting wheel 3 to it while rotating at high speed, it is turned into a spiral shape. I trimmed it and adjusted the resistance value. 4 is axis 4
It is a spindle consisting of a bearing 4b and a bearing 4b, and serves to rotate the cutting wheel 3.
Reference numeral 5 designates a cutter holder that houses the spindle 4, and the spindle 4 is rotationally driven by a motor 6, 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. 5 has been common. That is, the cutter holder 5 containing the spindle 4 for rotating the cutting whetstone 3 is supported by the fulcrum 10 via the cutter holder holder 13,
By adjusting the position of the weight 11, the force that presses the cutting wheel 3 against the film resistor 1 is adjusted, and the cam 12
The timing for applying the cutting wheel 3 to the film resistor 1 was determined by the following. Also, in Figure 5, 1
4 is a weight shaft, 15 is a cam lever, and 16 is a fulcrum.

Problems to be Solved by the Invention The above-mentioned disc-shaped cutting grindstone and the conventional film resistor trimming method using the same have the following problems.

(1) Trimming is performed by rotating a cutting wheel at high speed and applying it to the film resistor, which applies thermal and mechanical stress to the film resistor, leaving fine cracks on the edges of the grooves, which affect the electrical characteristics. It becomes a factor of deterioration. 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. 5, 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 blade edge is unstable, especially when starting grooving. 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) In order to prevent the groove jumping and groove defects mentioned in item (2) above, it is necessary to press the cutting wheel against the film resistor with a certain degree of force, which results in the formation of grooves as deep as several tens of micrometers. This state is shown in FIG. 6, where 17 is the deep groove mentioned above. As shown in FIG. 6, the thickness of the portion of the resistance film 19 existing on the surface of the resistor insulator 18 constituting the film resistor, including the surface roughness of the resistor insulator 18, is several μm or less. Therefore, the mechanical bending strength of the resistor body is extremely reduced due to the deep groove 17 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. Also, by cutting the resistor 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 can also clog the precision parts of other machines. Interfere with normal function.

(4) When the diameter of the cutting wheel becomes smaller due to wear, the condition of the groove deteriorates, and the resistance value after trimming deviates from the target due to the timing difference between the start and end of cutting, so it is important to adjust the position of the cutter holder. This is necessary and will lead to a decrease in productivity.

(5) As shown in Figure 6, the edges of the grooves become sharp, so it is easy to damage the resistance film of other film resistors and the plating of the terminal caps during product transportation, and the edges of the grooves themselves are also chipped, reducing the resistance value. Otherwise, the plating of the terminal caps of other film resistors may adhere to the resistive film, deteriorating the electrical characteristics.

(6) If the film resistor fails to be inserted 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. Become. If a part of the blade is chipped in this way, the condition of the groove will deteriorate significantly, and if trimming is continued without noticing, a large number of defective products will be produced.

(7) If the cutting wheel wears beyond a certain level or becomes clogged, it needs to be dressed or replaced, which requires fine adjustments and limits productivity.

The present invention aims to solve these conventional problems and provide a method for trimming a film resistor using an abrasive thread that can perform trimming by scraping off almost only the resistance film on the surface of the film resistor. It is something to do.

Means for Solving the Problem In order to solve this problem, the present invention adds abrasive grains to a synthetic polymer resin to form a filament, and the abrasive grains are dispersed and fixed inside and on the surface of the filament. This is a method that uses abrasive threads.

Function The abrasive thread used in the method of the present invention is a thread-like abrasive material, and the part of the abrasive particles contained therein that is exposed from the surface of the abrasive thread serves as a cutting edge to scrape off the resistance film on the surface of the film resistor. do. Also, if the same abrasive thread is used repeatedly for trimming,
The abrasive grains exposed on the surface of the abrasive thread wear out little by little, but the synthetic polymer resin also wears out little by little at the same time, so new abrasive grains contained inside the abrasive thread appear on the surface, maintaining the grinding power. It will be.

Since the abrasive thread is in the form of a thread, it can be easily run without leaving the surface of the film resistor, so there is no groove jumping, and it can be used in shallow areas on the surface of the film resistor (approximately where the resistance film is present). This makes it easy to trim only parts of the image.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, reference numeral 20 indicates an abrasive thread as a thread-like abrasive material used in the method of the present invention. This abrasive thread 20 is made of a polyamide-based synthetic polymer resin, such as polyamide-based nylon (trade name of Dupont) 21, in a molten state, with abrasive grains 22 added at a weight ratio of about 18% and uniformly dispersed. The abrasive grains 22 are made of silicon carbide with a grain size of approximately No. 1000 as a main component. In addition, in Fig. 1, the abrasive thread 2
0, the abrasive thread 20 of this embodiment is long and has a thread diameter of, for example, 0.3 mmφ.

FIG. 2 shows an example of a trimming method using the above-mentioned abrasive thread, where 20 is the above-mentioned abrasive thread, 21 is a cylindrical film resistor with a resistive film coated on its surface, and 22 and 22' are the above-mentioned abrasive threads. A chuck that grips both ends of the film resistor 21 and sends it in the axial direction while rotating it;
Reference numeral 23 denotes guides arranged above and below to allow the abrasive thread 20, which is sent at a predetermined speed by a drive device (not shown) such as a motor, to come into pressure contact with the surface of the film resistor 21 while applying a predetermined tension. These guide rollers 23 are provided with grooves (not shown) on their outer circumferential surfaces in order to allow the abrasive threads 20 to run along the circumferential surfaces thereof. 24
is a guide roller holder to which the guide roller 23 is attached, and this guide roller holder 2
4 is movable in the front and back (arrow A) directions with respect to the film resistor 21 so that the abrasive thread 20 can be pressed against the film resistor 21.

Then, the film resistor 21 is connected to the chucks 22 and 2.
2', and feed it in the axial direction while rotating it, and also run it along the guide roller 23 at a predetermined speed while applying a predetermined tension to the abrasive thread 20. In this state, the vehicle is allowed to run along the guide rollers 23. In this state, the guide roller 23
Guide roller holder 24 to which is attached
is moved a certain amount toward the film resistor 21, and the abrasive thread 20 is brought into pressure contact with the film resistor 21. This causes the abrasive thread 20 to helically trim the resistive coating.

FIG. 3 is a diagram showing the state of the cut grooves of a film resistor trimmed in this way.A shallow groove 25 is formed on the surface of the resistor, and this shallow groove 25
Almost only the resistive film 26 is scraped off, and the surface of the resistor insulator 27 is only shallowly scraped off.

Effects of the Invention The effects obtained by the film resistor trimming method of the present invention are as described below.

(1) It is possible to scrape off almost only the resistance film on the surface of a film resistor, that is, only the shallow part, using the abrasive thread, and the running speed of the abrasive thread is about 1/10 of the circumferential speed of the conventional cutting wheel. (almost 300
m/min) is sufficient, so there is almost no temperature rise in the grinding part. 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) For trimming to adjust the resistance value of a film resistor, it is only necessary to scrape off the portion of the resistor surface where the resistance film is present (several μm thick), but when using abrasive thread, shallow grooves can be ground as described above. It's as easy as that. Because the grooves cut out in this way are shallow, the mechanical bending strength of the resistor body does not deteriorate.
The product will not be damaged by impact when inserted into the 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 grinding force of the abrasive thread remains unchanged over time and the groove condition does not deteriorate.

(5) Since the edges of the grooves do not become sharp as in conventional resistors, it is less likely to damage other resistors or chip the edges of the grooves themselves, thereby preventing deterioration of the resistor's electrical characteristics.

(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 combination with the above points (5) and (6), productivity can be increased.

[Brief explanation of drawings]

FIG. 1 is an enlarged perspective view of a part of the abrasive thread of the present invention, FIG. 2 is a perspective view showing an example of a method for trimming a film resistor using the abrasive thread, and FIG.
An enlarged cross-sectional view showing the surface condition of a film resistor trimmed by the method shown in the figure. Fig. 4 shows a disc-shaped cutting whetstone, which is an abrasive used for conventional trimming of film resistors, and its grinding wheel. 5 is a perspective view showing a trimming method using a cutting wheel, FIG. 5 is a diagram showing an example of a mechanism for applying a cutting wheel to a film resistor in the trimming method shown in FIG. 4, and FIG. FIG. 3 is an enlarged cross-sectional view showing the surface state of a trimmed film resistor. 20...Abrasive thread, 21...Nylon, 22...
Abrasive grains.

Claims (1)

[Claims] 1. A film resistor characterized in that the resistive film is trimmed using an abrasive thread in which abrasive grains are added to a synthetic polymer resin and the abrasive grains are dispersed and fixed to the inside and surface of the thread. How to trim the vessel.