JPS6027164B2 - Laser trimming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser trimming method for adjusting the resistance value of a resistor using laser light.

Conventionally, adjusting the resistance value of a resistor by laser trimming involves removing a portion of the resistor by laser irradiation, creating a groove in the resistor, or cutting off a certain portion of the resistor to increase the resistance value of the entire resistor. Adjustment means have been used to match the resistance value of the resistor to a predetermined resistance value.

For this reason, pulsed laser light is used that provides a higher energy peak value and is easier to process. In order to improve trimming accuracy with this method, apart from the resistor pattern, the number of resistor parts to be removed with one pulse is reduced.

In other words, the purpose is to reduce the resistance value that changes with one pulse. However, the trimming accuracy is about 0.05
% or less, in addition to the increase in resistance due to the removal of the resistor, the increase in resistance due to a change in the material of the resistor with a time delay becomes a problem. In other words, during the laser trimming process, the resistance value of the resistor becomes -0.0 of the predetermined resistance value.
Even if you turn off the laser as soon as it falls within 1%, the resistance value will continue to increase due to changes in the material of the resistor, and eventually the resistance value of the trimmed resistor will be reduced to a trimming accuracy of 0.05%. It is difficult to put it in. Conventional laser trimming does not take into account changes in resistance value that are accompanied by time delays due to changes in the material of the resistor irradiated with laser light. The purpose of the present invention is to focus on the phenomenon of increase in resistance value due to material change of the resistor due to laser beam irradiation, which was not considered in the conventional laser trimming described above, and to perform highly accurate laser trimming by utilizing this phenomenon. This is what we are trying to do.

In conventional laser trimming, the part of the resistor that is irradiated with the laser beam is heated to a high temperature, and the resistance value changes rapidly due to changes in the resistor material immediately after the laser beam is turned off, resulting in poor trimming accuracy. drop down. In the present invention, instead of using laser light to remove the resistor, the laser light is weakened and the resistor is heated to a low temperature to gently promote chemical changes, mainly oxidation of the resistor material. This is an attempt to perform accurate laser trimming. The laser beam may be focused on one point on the resistor or may be scanned over a certain area. The laser beam may be pulsed or continuous wave (hereinafter referred to as CW), but CW is suitable for performing highly accurate trimming in accordance with the gist of the present invention.

The energy peak value of the laser beam is not constant depending on the resistor pattern, material, trimming resistance value, trimming accuracy, trimming time, etc., but in general, as the energy peak value increases, the resistance value change per unit time of the resistor increases, and the resistance value changes over a short period of time. It is possible to perform trimming for large resistance value changes, but the trimming accuracy decreases. FIG. 1 schematically shows a laser trimming system according to the present invention.

Reference numeral 1 designates a laser oscillator, and a laser beam 2 oscillated from this is directed downward by a mirror 3 and focused onto a resistor 5 by a lens 4.

The resistance value of the resistor 5 is detected by two loops 6, and the signals thereof are input to the control circuit 101. The control circuit 1 is interrelated with the laser oscillator 1 and the table control circuit 11.

The table control circuit 11 drives the table 7 via the motor 8. The resistor 5 is fixed to the table 7 and moves together.
9 is a surface plate on which the table 7 and the motor 8 are placed. Now, fix the resistor 5 on the table 7 and connect the probe 6 to the resistor 5.
The laser beam 2 from the laser oscillator 4 is focused on the trimmed part of the resistor 5 by the lens 4, and the table 7 is driven while the resistance value is measured by the control circuit 10 (in this case, the table 7 must be (No need to drive)
. When the resistance value of the resistor 5 matches a predetermined resistance value, a signal is sent from the control circuit 10 to the laser oscillator 1 and the laser beam 2 is output.
At the same time, the feeding of the table 7 is stopped through the control circuit 11. FIG. 2 shows an example of the resistor 5 shown in FIG.

5 resistance board, 52 electrode, 53 resistor, 54a,
54b indicates a laser light spot.

The probe 6 shown in FIG. 1 is followed by the electrode 52 of FIG. The laser spots 54a and 54b are 54
It may be fixed at one point a, or it may be scanned between 54a and 54b as shown in FIG. When a thin film resistor (width 50 mm) was irradiated with a CW laser beam with an average output of several mW, it was confirmed that the trimming accuracy could be controlled to 0.05% or less.

In conventional laser trimming, which adjusts the resistance value by removing the resistor with laser light, it is difficult to achieve trimming accuracy of 0.05% or less.

This is because a strong laser beam is used to remove the resistor, and a chemical change in the resistor material appears immediately after trimming, resulting in an increase in the resistance value of the resistor. In the present invention, as described above, the chemical change in the resistor material is controlled by controlling the intensity and irradiation time of the laser beam, and the trimming accuracy is improved by utilizing the change in resistance value based on this chemical change. , {110.0
It has the following advantages: a trimming accuracy of 5% or less can be obtained; a laser oscillator with a 2M output is sufficient; and three, conventional laser trimming bags can be used.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the laser trimming method according to the present invention, and FIG. 2 is a plan view of a resistor. Explanation of symbols, 1: laser oscillator, 2: laser beam, 3: mirror, 4: lens, 5: resistor, 6: probe, 7: table, 8: motor, 10: control circuit, 11: table control circuit, 52: Electrode 53: Resistor, 54a, 54b
:Laser spot. 1, 2, and 2 figures

Claims (1)

[Claims] 1 Detecting the resistance value of the resistor with a detection means, and condensing a laser beam obtained from a laser oscillator with energy capable of causing a change in the material of the resistor without removing the resistor using a condensing optical system. When the resistance value detected by the detection means reaches a predetermined resistance value, the laser beam obtained from the laser oscillator is stopped to irradiate the resistor body locally. A laser trimming method characterized by adjusting the resistance value by changing the material.