JPS598043B2 - How to trim IC resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION One of the methods of trimming an IC resistor to obtain a highly accurate resistance value is L-cut trimming.

An example of the L-cut shape is shown in FIG. This method uses a laser beam to cut a groove in the resistor 1 in a direction perpendicular to the direction in which the current flows (indicated by the broken line with an arrow in the figure) (in a direction that blocks the current direction), and roughly adjusts the resistance value. Fine adjustment is performed by cutting grooves in the direction parallel to the direction of current flow. In this method, turn point 2 (Turnp
oint), microcracks (M
icrocrack). The region 3 where microcracks are likely to occur is shown in FIG. 1 with crosshatched lines. The occurrence of the microcracks has serious disadvantages such as a decrease in the accuracy of resistance values and generation of noise by the resistor. The present invention provides a method for trimming an IC resistor to eliminate the above drawbacks.

That is, the present invention provides a trimming method that prevents microcracks from occurring at turn points when performing L-cut trimming on an IC resistor using a laser beam to obtain a desired resistance value. Next, a method for trimming an IC resistor according to an embodiment of the present invention will be described in detail with reference to the drawings. The resistor 11 as shown in FIG. 2 has a resistor 11 in which current flows in the direction of the arrow in the broken line in the figure, and a third
Referring to the figure, the resistance value is the initial value R. Change from R4 (3rd
The rough adjustment ends at RL (time Tl). Next, the value is finely adjusted to R2 (curve 3 in FIG. 3, time T2), and trimming is completed at the final value Rs. Resistance value R, (RL
-R7/Rs×100', 2%), the laser output is gradually decreased from the initial value Po, and is set to a certain constant value PT after a time ΔT (where (Tl+ΔT)<TL). After the time Tl at which the resistance value RL at the turn point is reached, the laser output is returned to the original laser output Po with a delay of just a few microseconds. As shown in FIG. 3, the laser output is decreased from the output Po (curve 4) at time Tl as shown by a straight line 5, and becomes PT (curve 6) at Trk level. After passing Tl, the output is returned to the original output Po (curve 4) at T2 several microseconds later. By doing the above, the micro-cracks that occur when the resistance value RL is reached can be reduced to the output PT (P
This can be prevented by setting T<P0). According to the present invention, although trimming with a laser beam has excellent points such as accuracy and speed, it also has the disadvantage of thermal processing, that is, micro-cracks that occur at the turn point in L-cut trimming. By selecting the laser power and the laser output, there is a remarkable advantage that the thermal influence on the resistor is almost eliminated and the occurrence of microcracks is prevented.

Although the present invention has been illustrated with respect to L-cut trimming, the fourth
As shown in the figure, by similarly reducing the laser output at a certain gradient at the end of trimming, it is possible to prevent microcracks from occurring at the end of trimming.

[Brief explanation of drawings]

FIG. 1 is a top view showing micro-cracks caused by L-cut trimming of an IC resistor using a laser beam, and FIGS. 2 and 3 illustrate a method of trimming an IC resistor using a laser beam according to the present invention, particularly L-cut trimming. Figure 2 is a top view of the resistor for L-cut trimming, Figure 3 is a diagram showing the relationship between laser output, time, and resistance value of the resistor to explain the L-cut trimming method, and Figure 4 is a diagram showing the relationship between laser output, time, and resistance value of the resistor to explain the L-cut trimming method. The figure is a top view of a resistor for explaining another embodiment of the method of the present invention. 1, 11...Resistor, 2...Turn point (in L cut trimming).

Claims (1)

[Claims] 1. In a method for trimming an IC resistor in which an IC resistor is subjected to L-cut trimming using a laser beam to obtain a desired resistance value, at least the desired resistance value is reached after reaching a resistance value near the turn point of the L-cut trimming. A method for trimming an IC resistor, characterized in that trimming is performed by reducing the output of a laser beam while reaching .