Resistor Trimming

Click here to go to our main page on resistors

Click here to go to our page on resistor math

Click here to go to our page on thin-film resistors

Click here to go to our page on thick-film resistors

After processing, thick and thin-film resistors will always have some statistical variation from their intended value. In the case of separate chip resistors, parts can be measured, then binned into 10%, 5% or even 1% tolerances (standard RETMA values). In larger format thick-film or thin-film networks where the resistors are just one small detail in complex artwork, often the final part will not work if the resistor value deviates too much, and out-of-spec resistors means scrapped parts. The alternative is to trim the resistors into the correct value. In laser trimming, a YAG laser is used to ablate the resistor material from the substrate, raising its resistor value.

Resistor Trimming Rule of thumb: Note that you can only trim a resistor up in value, not down.


There are three ways to laser-trim resistors, shown below. Plunge-cut gives the "fastest" resistor change, but from a reliability point-of-view, it may , may , L-cut, edge trim, etc.

Resistor Trimming

In a "poor-man's version" of laser trimming that is sometimes used in prototype shops, you can abrade a resistor with emery paper to raise its value. Here you are actually decreasing the effective thickness of the resistor, rather than altering the number of squares. Thin-film resistors will have to be re-stabilized after this step, since you would be removing the oxide layer.

Author : Unknown Editor