JP2001085207A - Laser trimming method of chip resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a trimming length of a trimming groove shorter than that just at a predetermined resistance value and keep it since then, by a method wherein the trimming rate of the resistive film is set in such a manner where it is made lower just before the resistive film reaches to a prescribed value than the other time. SOLUTION: It is controlled by a center control circuit that the trimming rate of a trimming groove 5 provided to a resistive film 2 is set lower at a time when the resistance of the film measured by a resistance measuring device gets slightly smaller than a prescribed value than at the preceding time. That is, a trimming rate at which a trimming groove 5 is cut in the resistive film 2 is kept high until the resistance of the resistive film 2 gets a certain value slightly smaller than a prescribed value and then set lower when the resistance gets a certain value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip resistor having at least one resistive film formed on the surface of a chip-shaped insulating substrate. The present invention relates to a laser trimming method for adjusting a predetermined resistance value within an allowable range by forming a trimming groove by irradiating a light beam.

[0002]

2. Description of the Related Art Generally, when a trimming groove for adjusting the resistance value is formed in a resistive film by irradiating the resistive film with a laser beam, the resistive film and a laser beam to be irradiated on the resistive film are formed. It is well known that the laser beam is intermittently applied to the resistive film at appropriate time intervals while moving at an appropriate speed relative to each other.

In this case, conventionally, the relative moving speed of the resistive film and the laser beam irradiated to the resistive film, that is, the trimming speed, and the interval of the intermittent irradiation of the laser beam are kept constant over the entire length of the trimming groove. In other words, the trimming groove is engraved at a constant trimming speed over the entire length of the trimming groove with the laser beam irradiation interval kept constant. There was a problem.

[0004]

That is, in the conventional laser trimming method, when the trimming speed is increased, the time required for laser trimming for one resistive film is shortened, and the work efficiency can be improved. Since the engraved length of the trimming groove per one intermittent irradiation of the laser beam increases, and the rate of change in the resistance value increases, the accuracy of adjusting the resistance film to a predetermined resistance value decreases. . Further, when the trimming speed is reduced, the engraved length of the trimming groove per one intermittent irradiation of the laser beam is reduced,
As a result, the rate of change of the resistance value is reduced, so that the accuracy of adjusting the resistance film to a predetermined resistance value can be improved, but on the other hand, the time required for laser trimming for one resistance film becomes longer, and the work efficiency becomes longer. In the conventional trimming method, both the improvement of the trimming accuracy and the improvement of the work efficiency cannot be achieved at the same time.

An object of the present invention is to provide a laser trimming method which solves this problem.

[0006]

In order to achieve this technical object, the present invention provides a method of manufacturing a semiconductor device comprising the steps of: "a resistive film formed on a surface of an insulating substrate is provided with a trimming groove formed by intermittent irradiation of a laser beam; In engraving to a predetermined value, of the trimming speed at the time of engraving the trimming groove, the trimming speed from immediately before the resistance value of the resistive film reaches a predetermined value, and thereafter, from the trimming speed earlier than this. Slow down. "

[0007]

As described above, by making the trimming speed of the trimming speed before and after the resistance value of the resistive film reaches a predetermined value lower than the trimming speed before this, the laser beam intermittently becomes intermittent. Since the engraved length of the trimming groove per irradiation can be made smaller immediately before the resistance value of the resistive film reaches a predetermined value, and can be made larger before this, laser trimming for the resistive film can be performed by: Immediately before and after the resistance value reaches the predetermined value, the change can be performed in a state where the rate of change of the resistance value is small, but before that, the change can be performed in a short time.

Therefore, according to the present invention, the effect of shortening the time required for laser trimming for one resistive film and improving the accuracy of adjusting the resistive film to a predetermined resistance value can be reliably achieved. Have.

The intermittent emission device of the laser beam used for the laser trimming generally stores the power of the laser beam to be emitted next while emitting the laser beam. The power of the laser beam is intermittent emission of the laser beam, that is, the power of the laser beam is proportional to the interval of the intermittent irradiation of the laser beam. However, delaying the resistance value of the resistive film from immediately before reaching the predetermined value thereafter has a greater thermal effect on the terminal end portion of the trimming groove in the resistive film, so that the shape of the trimming groove at the terminal end portion is increased. As a result, the stability of the laser trimming is reduced.

On the other hand, according to the present invention, among the trimming speeds at which a trimming groove is formed, the trimming speed after the time immediately before the resistance value of the resistive film reaches a predetermined value is set. In addition to making the trimming speed slower than before, the interval between the intermittent irradiation of the laser beam and the interval immediately before and after the resistance value of the resistive film reaches the predetermined value is made shorter than the interval before this. It is to provide that.

As described above, the interval between the intermittent irradiation of the laser beam and the interval immediately before and after the resistance value of the resistive film reaches the predetermined value is made shorter than the interval before this, so that the power in the laser beam is reduced. Since the resistance value of the resistive film can be lowered from immediately before reaching a predetermined value and thereafter, and the thermal effect on the terminal end of the trimming groove in the resistive film can be reduced, the trimming speed of the resistive film can be reduced. The disadvantage of delaying the resistance value immediately before reaching the predetermined value or later, that is, the fact that the shape of the trimming groove becomes wider at the end thereof can be reliably eliminated, and the stability of laser trimming can be improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

In FIG. 1, reference numeral A denotes a material substrate in which a large number of chip-type insulating substrates 1 are vertically and horizontally arranged and integrated, and a portion of each insulating substrate 1 on the surface of the material substrate A has a resistance. A membrane 2 and main electrodes 3 at both ends thereof;
An undercoat 4 made of glass covering the resistance film 2 is formed.

When forming the resistive film 2, the main electrode 3 and the undercoat 4, the main electrode 3 is first formed by screen printing of the material paste and baking thereafter, and then the resistive film 2 is formed. After the material paste is formed by screen printing and subsequent firing, the undercoat 4 is formed by screen printing of the material paste and subsequent firing. After the resistance film 2 is formed, The main electrode 3 may be formed.

Then, the resistive film 2 on the upper surface of each insulating substrate 1 in the material substrate A is irradiated with a laser beam emitted from a laser beam emitting device 11 from above the cover coat 4 by reflection of a galvanometer mirror 12. Thus, the trimming groove 5 is formed so as to extend in an L-shape toward the resistance film 2 from the starting end 5a located outside the side edge 2a of the resistance film 2.

That is, the central control circuit 13 includes the resistance film 2
The total resistance value of the probe 15
The L-shaped trimming groove 5 is formed by controlling the actuator 16 for moving the laser beam emitting device 11 and the galvanomirror 12 as appropriate, using the output from the resistance value measuring device 14 for detecting the contact by detecting the L-shaped trimming groove 5. Laser trimming, in which the film 2 is engraved until the total resistance value reaches a predetermined resistance value V, is performed.

In this laser trimming, the total resistance value of the resistance film 2 is changed along the curve B from an initial resistance value V0 to a predetermined resistance value V as shown in FIG. Rise.

Therefore, the central control circuit 13 determines that the trimming speed when the trimming groove 5 is to be carved is such that the resistance value detected by the resistance value measuring device 14 is smaller than a predetermined resistance value V. After the time when the resistance value V1 becomes lower by ΔV, the trimming speed is set to the trimming speed M earlier than the above.
The speed at which the trimming groove 5 is cut, that is, the speed M2 lower than 1, that is, the trimming speed is lower than the predetermined resistance value V by a small value ΔV in the resistance film 2. Control is performed so that the speed is increased to M1 until the resistance value V1 is reached, and is decreased to M2 thereafter.

Thus, the engraved length of the trimming groove 5 per one intermittent irradiation of the laser beam is reduced immediately before the resistance value of the resistive film 2 reaches the predetermined value V, and increased before the resistance value reaches the predetermined value V. Therefore, the laser trimming of the resistive film 2 can be performed in a state where the rate of change of the resistance value is small immediately before the resistance value reaches the predetermined value V and thereafter, while shorter than before. Can be done in time.

The central control circuit 13 controls the trimming speed when the trimming groove 5 is cut.
In addition to performing the above-described control when the resistance value detected by the resistance value measuring device 14 becomes a resistance value V1 lower than the predetermined resistance value V by a slight value ΔV,
Thereafter, the interval of the intermittent irradiation of the laser beam is controlled to be faster than the interval before the above.

This makes it possible to lower the power of the laser beam from immediately before the resistance value of the resistance film 2 reaches the predetermined value V and thereafter, so that the power of the resistance film 2 with respect to the terminal end portion 5b of the trimming groove 5 is reduced. The effect of reducing the trimming speed from immediately before the resistance value of the resistive film 2 reaches the predetermined value V to a later time, that is, the shape of the trimming groove 5 becomes wider at the terminal end 5b. Can be surely eliminated.

The laser trimming is performed by moving the material substrate A vertically and horizontally on an XY table (not shown) while moving all the insulating substrates 1 on the material substrate A.
Do about.

Next, a portion of each insulating substrate 1 on the surface of the material substrate A is coated with a further cover coat 6 made of glass.
Or after forming a two-layer cover coat composed of a middle coat made of glass and an overcoat made of glass, the material substrate A is divided along a vertical dividing line A1 and a horizontal dividing line A2. Then, each of the insulating substrates 1 is divided.

Next, after forming side electrodes on the left and right end surfaces of each of the insulating substrates 1, by immersing in a plating solution and performing a plating process, for example, the surface of each of the main electrodes 3 and each of the side electrodes is formed. Then, a metal plating layer composed of a base nickel plating layer and an upper solder or tin plating layer is formed to complete the chip resistor.

The starting end 5a of the trimming groove 5 is located at a position inside the side edge 4a of the undercoat 4 and close to the side edge 2a of the resistive film 2, so that the length of the trimming groove 5 can be reduced. , The time required for laser trimming can be further reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state in which laser trimming is performed.

FIG. 2 is an enlarged plan view of a part of a material substrate.

FIG. 3 is an enlarged sectional view taken along line III-III of FIG. 2;

FIG. 4 is an enlarged view of a main part of FIG. 2;

FIG. 5 is a diagram illustrating a relationship between a resistance value and a trimming time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Resistive film 2a Side edge of resistive film 3 Main electrode 4 Undercoat 5 Trimming groove 5a Start end of trimming groove 5b End of trimming groove

Claims (2)

[Claims] 2. The method according to claim 1, wherein the trimming groove formed by intermittent irradiation of a laser beam is formed in the resistance film formed on the surface of the insulating substrate so that the resistance value of the resistance film becomes a predetermined value. A laser trimming method for a chip resistor, wherein a trimming speed of the trimming speed before and after the resistance value of the resistive film reaches a predetermined value is made lower than a trimming speed before the resistance value. 2. A step of engraving a trimming groove by intermittent irradiation of a laser beam on a resistive film formed on a surface of an insulating substrate so that a resistance value of the resistive film becomes a predetermined value. During the trimming speed, the trimming speed after the time immediately before the resistance value of the resistive film reaches a predetermined value is made slower than the trimming speed before this, and the resistance of the resistive film during the intermittent irradiation of the laser beam is reduced. A laser trimming method for a chip resistor, characterized in that an interval immediately before the value reaches a predetermined value and thereafter is shorter than an interval before the value.