JPH0474841B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a resistor trimming device for adjusting resistance value, and particularly relates to a resistor trimming device for trimming a resistor having a cylindrical shape such as a carbon film resistor or a metal film resistor. The present invention relates to a fixed resistor trimming device using a resistance element.

Conventional Technology Film resistors, which are constructed by press-fitting metal caps to both ends of a cylindrical film resistor, are generally constructed by forming a resistive film on the surface of a cylindrical insulator, and then applying a spiral-shaped resistor to the resistive element. It has a trimming step that aims to raise the resistance value to a predetermined value by performing trimming to provide a portion from which the film is removed. Conventionally, in this process, the devices for spirally trimming the resistive film as described above are roughly divided into two types: a device that grinds and removes the resistive film by rotating a thin disc-shaped grindstone at high speed, and a device that uses a laser beam to remove the resistive film by rotating it at high speed. There was a device that condensed light onto the surface to locally evaporate and remove the resistive film.

The former device using a disc-shaped grindstone was as shown in FIG. That is, a film resistor 1 having a resistance film coated on the surface of a cylindrical insulator is supplied by an appropriate aligning and supplying device (not shown) such as a vibrating parts feeder, and chucks 2 and 2 are supplied.
a, move the film resistor 1 at a constant speed in the axial direction while rotating it, and trim the resistance film in a spiral shape by applying a thin disk-shaped grindstone 3 to it while rotating at a high speed. It has a structural function of separating the disc-shaped grindstone 3 from the resistor 1 and releasing it when the resistance value is measured. Further, in FIG. 5, reference numeral 4 denotes a spindle consisting of a shaft 4a and a bearing 4b, which serves to rotate the grindstone 3. Further, 5 is 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 mechanism for applying the disk-shaped grindstone 3 to the film resistor 1, a mechanism as shown in FIG. 6 was common.

That is, the cutter holder 5 housing the spindle 4 that rotates the disc-shaped grindstone 3 is supported by the fulcrum 10, and the force with which the disc-shaped grindstone 3 is pressed against the film resistor 1 is adjusted by adjusting the position of the weight 11. , the timing at which the disc-shaped grindstone 3 is brought into contact with the film resistor 1 is determined by the cam 12. Further, in FIG. 6, 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 device, in order to generally cut a good groove, the rotating surface of the disc-shaped grindstone 3 is set at an angle θ with respect to the film resistor 1, as shown in FIG. It was adjusted to follow groove 17.

In addition, the latter device using laser light has a resistive element feeding mechanism and a spindle chuck mechanism similar to the device using the disc-shaped grindstone described above, as well as a laser oscillator and an optical system for focusing the laser beam. It consists of a device that uses a disc-shaped grindstone, with the grindstone mechanism replaced with a laser generation mechanism.

Problems to be Solved by the Invention Among such conventional trimming devices, devices using a disc-shaped grindstone and resistors trimmed with the same have the following problems.

(1) Trimming is carried out by rotating a disc-shaped grindstone 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 cause electrical In addition, as the temperature of the film resistor rises, the resistance value will be different from that at room temperature due to the temperature characteristics of the resistor film, causing a resistance measurement error when adjusting the resistance value. easy.

(2) As shown in FIG.
Because the process is carried out using only the weight of the cutting tool, the blade edge shakes, especially at the start of grooving, and the groove depth and width fluctuate. Additionally, if the disc-shaped grindstone bounces on a film resistor, groove jumps occur. These factors cause deterioration of the electrical characteristics of the film resistor as a product.

(3) In order to prevent the groove skipping and groove defects mentioned in (2) above, it is necessary to press the disc-shaped grindstone against the film resistor with more than a certain degree of force, which results in the formation of deep grooves of several tens of micrometers. . FIG. 8 shows this state, and 17 is the deep groove mentioned above. As shown in FIG. 8, 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 disc-shaped grindstone wears and its diameter becomes smaller, the groove condition deteriorates and the resistance value after trimming deviates from the target due to the timing difference between the start and end of the cut, so the cutter holder position adjustment is required, resulting in a decrease in productivity.

(5) As shown in Figure 8, 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 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 disc-shaped grindstone and a part of the blade will chip. Cause. 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 disc-shaped grinding wheel wears beyond a certain level or becomes clogged, it needs to be dressed or replaced, and at that time, detailed adjustments are required, which limits productivity.

(8) Since a single disc-shaped grindstone can only be used to trim one film resistor at a time, the number of products produced per unit time is small.

(9) In order to perform good trimming, set the rotating surface of the disc-shaped grindstone so that it forms an angle θ along the spiral groove with respect to the film resistor, as shown in Fig. 7, and then perform a trial. During trimming, the inclination of the film resistor with respect to the axial direction must be finely adjusted, and it is necessary to rely on skilled workers.

Furthermore, if the adjustment is insufficient, not only will the condition of the trimmed groove deteriorate, but also the life of the disc-shaped grindstone will be shortened.

Further, the problems of a trimming device using a laser beam and a resistor trimmed by the same will be described below using a general Q-switching YAG laser trimming device as an example.

(10) When trimming the resistive film with laser light, it is important for quality control that no resistive film remains in the spiral-shaped part where the film is removed.
Usually, it is necessary to evaluate current linearity, etc. as a substitute characteristic, which involves complicated preparation work.

(11) The throughput per unit time of this device using laser light is at most several times that of the device using the disc-shaped grindstone described above, but the device itself and repair parts are extremely expensive. It is almost unprofitable for products other than those with high added value.

Therefore, in order to solve the above-mentioned problems, the present invention uses a thread-like abrasive thread with little change over time as an abrasive material, and by scraping off almost only the resistance film, the stress on the film resistor and the generated dust are reduced. The present invention aims to provide a trimming device that is easy to maintain, inexpensive, and has high productivity.

Means for Solving the Problem In order to solve this problem, the present invention includes one or more sets of chucks that hold both ends of a cylindrical film resistor and rotate the chuck around its axis.
Distribute abrasive grains inside and/or on the surface of the fibers,
a guide pulley for running the abrasive thread in a direction perpendicular to the axis of the resistor to remove the resistance film on the surface of the resistor; unwinding the abrasive thread from a bobbin; an abrasive thread unwinding mechanism for winding the abrasive thread onto a bobbin; an abrasive thread moving mechanism for bringing the abrasive thread into contact with or releasing the abrasive thread from the surface of the resistor; and an axial movement mechanism for relatively moving in the axial direction of the resistor, and the abrasive grains of the polishing thread perform trimming to remove the resistance film on the surface of the resistor in a spiral pattern, thereby adjusting the resistance value of the resistor. It is configured to do this.

Function The trimming device of the present invention partially scrapes off the resistance film by running the filament-like abrasive material, so it is possible to scrape off only the shallow part of the surface of the film resistor, and the trimming device of the present invention is able to scrape off only the shallow part of the surface of the film resistor. Since the running speed of the polishing thread is approximately 1/10 of the circumferential speed of the disc-shaped grindstone used conventionally, there is almost no temperature rise of the grinding object, 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 well. 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. Similarly, even if the polishing thread is applied to the rotating film resistor and the polishing thread, the resistor, or both are simultaneously moved in the axial direction of the film resistor, a spiral groove can be cut in the same way. This allows for a high degree of freedom in device design. In addition, it is easy to adjust the polishing thread so that it forms an angle θ along the spiral groove with respect to the film resistor, and even non-skilled workers can easily cut the groove. will be possible.

Embodiment Hereinafter, a film resistor trimming device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 is a perspective view of a trimming unit which is the main part of an apparatus according to an embodiment of the present invention.

In Figure 1, a suitable feeding device (not shown)
The cylindrical film resistor 20 supplied by the manufacturer was held at both ends by chucks 21a and 21b, and the chucks 21a and 21b were rotatably and electrically insulated by spindle units 22a and 22b, respectively. The timing belts 25a, 25b and the timing pulley 23 are fixed to a bead (not shown) in a state in which they are driven by a suitable drive device (not shown).
a and 23b, each rotates counterclockwise when viewed from the chuck 21a side. As a result, the film resistor 20 held between these chucks 21a and 21b rotates in the same direction at an arbitrary rotation speed.
is rotated around the axis of Mercury rotors 24a and 24b electrically connect a resistance value measuring device (not shown) for measuring the resistance value of the film resistor 20 and the rotating chucks 21a and 21b. .

Further, a base 27, which is attached to a main body base (not shown) via stroke bearing units 26a and 26b and is movable in the vertical direction, moves up and down as the cam 28 rotates. Further, the base 29 is mounted on the base 27 via a linear way unit 30, is movable in the axial direction of the film resistor 20, and is connected to a ball screw unit 32 driven by a pulse motor 31.
From the chuck 21b side to the chuck 21
It is moved at a constant speed in the direction of the a side. Also, base 3
3 is connected to the base 2 via the linear way unit 34.
The spring 35 pushes the linear way unit 34 up to the stopper 36 position. Also, near the upper part of this base 33, the chuck 21a,
21b is provided. Reference numeral 37 indicates an abrasive thread used as an abrasive by the trimming device according to the present invention. For example, it is made by adding silicon carbide abrasive grains to molten nylon (trade name of DuPont), which is a polyamide-based synthetic polymer. The abrasive thread 37 is made into a thread by spreading it uniformly inside and on the surface, then spinning and drawing it into a filament. The yarn is guided by the wire and run at an arbitrary speed and tension in a direction perpendicular to the axis of the film resistor 20 held between the chucks 21a and 21b, thereby polishing and removing the resistance film on the surface of the film resistor 20. be done.

Each part of the trimming unit described above performs the operations described below to trim the film resistor 20. First, the chucks 21a and 21b hold both ends of the film resistor 20 and rotate it counterclockwise when viewed from the chuck 21a side. In this state, by pushing up the base 27 with the cam 28, the abrasive thread 37, which is being run at a given thread speed and tension, is pressed against the film resistor 20.
At the same time, by rotating the pulse motor 31, the polishing thread 37 is moved from the chuck 21b to the chuck 21a.
The resistance film of the film resistor 20 is thereby trimmed in a spiral shape. Then, when a resistance value measuring device (not shown) observes that the resistance value of the film resistor 20 has increased to a predetermined value by trimming, the solenoid 3
9 operates to release the polishing thread 37 from the film resistor 20 by pulling down the base 33, and the film resistor 20 that has been trimmed is taken out by a suitable take-out device, and each part of the trimming unit is removed. One cycle of trimming operation is completed by returning to the position before the start of trimming.

In FIG. 1, 60 is a guide rail for moving the base 29 in the axial direction of the film resistor 20.

FIG. 2 is a configuration diagram of an abrasive thread traveling unit for supplying the abrasive thread 37 to the trimming unit 40 of FIG. 1 at an arbitrary thread speed and tension. In FIG. 2, the polishing thread 3 is moved by a feed roller 42 driven by a motor 41 at an arbitrary circumferential speed.
7 is sent from the bobbin 44 to the bobbin 45 at an arbitrary speed. Numerals 43a and 43b are nip rollers that serve to press the polishing thread 37 so that it does not slip on the feed roller 42. Further, a potentiometer 46 detects the angle of the arm 49 with respect to the horizontal, and when the arm 49 is horizontal, the force of the tension of the polishing thread 37 trying to pull up the dancer pulley 47 is converted into the force of the spring 50 trying to pull it down. For balance, feedback control of the rotation speed of the motor 51 is performed, and the polishing thread 37 is supplied to the trimming unit 40 with a predetermined tension determined by the strength of the spring 50. Similarly, potentiometer 52,
The arm 53, the tension dancer pulley 54, and the spring 55 detect the tension when the bobbin 45 winds up the abrasive thread 37, and feedback-controls the rotation speed of the motor 56 so that the bobbin 45 can be wound without the abrasive thread 37 being cut. It is designed so that it can be wound up.

FIG. 3 is an enlarged perspective view of the main part of the trimming unit, and it is possible to arrange a plurality of the trimming units shown in FIG. 1 in parallel and simultaneously trim a large number of film resistors 20 using the same polishing thread 37. Show that it is possible.

FIG. 4 is an enlarged cross-sectional view showing the state of the grooves of a film resistor trimmed by the trimming device according to the embodiment of the present invention, in which the shallow grooves 57 are trimmed, and only the resistive film 58 on the surface of the resistor insulator 59 is trimmed. It shows that it has been scraped off.

In this embodiment, the polishing thread 37 is moved in the axial direction with respect to the film resistor 20.
Helical trimming can be performed by moving both in the axial direction or by using a mechanism in which both are moved relative to each other at the same time.

Furthermore, in order to hit the polishing thread 37 at an angle along the spiral groove to be trimmed on the film resistor 20, it is possible to tilt the base 33 beforehand.
Better trimming can be done.

Further, the abrasive thread 37 may have a structure in which abrasive grains are distributed and contained within the fibers and/or on the surface thereof.

Effects of the Invention The effects obtained by the resistor trimming device 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 faster than that of the conventional disc-shaped grindstone. Since a speed of about 1/10 of the circumferential speed (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 used in this device can be easily run without leaving the surface of the film resistor, groove jumping does not occur, and the tension, running speed, and push force applied to the abrasive thread by this device are If the amount is controlled to be constant, groove conditions such as groove depth and groove width will remain unchanged over time, and the electrical characteristics of the product will be maintained in good condition.

(3) In order to adjust the resistance value of a film resistor, it is necessary to
It is only necessary to scrape off only the groove (m), but the polishing thread used in this device can easily grind shallow grooves as described above. 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 resistor insulator is hardly scraped, and as a result, the amount of dust generated on the insulator is extremely reduced.

(4) This device can apply new parts to the resistor surface one after another by running the polishing thread, so the grinding force of the polishing thread remains unchanged over time and the groove condition does not deteriorate.

(5) As shown in Figure 4, 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) With this device, even if the film resistor fails to be inserted into the chuck and the film resistor rotates eccentrically, the polishing thread can move freely according to the movement of the film resistor, so the polishing thread will It will not be damaged.

(7) This device is capable of scraping only the shallow part of the surface of the insulator, so there is little wear on the polishing thread, and when replacing it, only the polishing thread needs to be replaced, and no detailed adjustments are required. Therefore, the above
In combination with 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 with one polishing thread, resulting in high productivity.

(9) Even if one or both of the abrasive thread and the film resistor are moved in the axial direction of the film resistor while applying the abrasive thread to the rotating film resistor, a spiral groove will be formed in the same way. This allows for a high degree of freedom in device design. In addition, it is much easier to adjust the polishing thread so that it forms an angle θ along the spiral groove with respect to the film resistor than with a conventional disc-shaped grindstone, and it does not require a skilled worker. With both, good groove cutting can be easily performed.

(10) Compared to trimming devices that use laser light,
Equipment costs are low, maintenance work is easy and requires no skill, and along with high productivity, operating costs are low.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a trimming unit that is the main part of a resistor trimming device according to an embodiment of the present invention, and FIG. 2 is a configuration of a polishing thread traveling unit that supplies polishing thread to the trimming unit shown in FIG. 1. 3 is an enlarged perspective view of the main parts of the trimming unit, FIG. 4 is an enlarged cross-sectional view showing the groove state of a film resistor trimmed by the trimming device of one embodiment of the present invention, and FIG. FIG. 6 is a perspective view of a conventional trimming device using a disc-shaped grindstone; FIG. 6 is a diagram showing an example of a mechanism for applying a disc-shaped grindstone to a film resistor in the trimming device shown in FIG. 5; FIG. is a diagram showing that the disc-shaped grindstone and the film resistor form an angle θ in the device of FIG. 5, and FIG. 8 shows the groove state of the film resistor trimmed by the device of FIG. FIG. 20... Film resistor, 21a, 21b... Chuck, 37... Polishing thread, 38a, 38b... Guide pulley.

Claims (1)

[Claims] 1. An abrasive thread comprising one or more sets of chucks that hold both ends of a cylindrical film resistor and rotate around its axis, and containing abrasive grains distributed inside and/or on the surface of the fibers, and the above-mentioned A guide pulley for running the abrasive thread in a direction perpendicular to the axis of the resistor to remove the resistance film on the surface of the resistor, and an abrasive thread unwinder for unwinding the abrasive thread from a bobbin and winding it onto the bobbin. a removing mechanism; a polishing thread moving mechanism for bringing the polishing thread into contact with or releasing the polishing thread from the surface of the resistor; and a shaft for relatively moving at least one of the chuck holding the resistor or the polishing thread in the axial direction of the resistor. and a directional movement mechanism, the resistor trimming is configured to perform trimming by spirally polishing and removing the resistive film on the surface of the resistor using the abrasive grains of the polishing thread, and adjust the resistance value of the resistor. Device.