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Laser trimming is the manufacturing process of using a laser to adjust the operating parameters of an electronic circuit. Laser-trimmed precision thin-film resistor network from Fluke, used in the Keithley DMM7510 multimeter. Ceramic backed with glass hermetic seal cover. Laser trim marks are visible in the grey resistive material.
The high power of the discharge, above 5 kilowatts for less than a microsecond, can melt and vaporise materials. Thin-film resistors may have their value altered by a discharge path forming across them, or having part of the thin film vaporized; this can be problematic in precision applications where such values are critical. [17]
With laser trimming two modes are used; either passive trimming, where each resistor is trimmed to a specific value and tolerance, or active trimming, where the feedback is used to adjust to a specific voltage, frequency or response by laser trimming the resistors on the circuit while powered up.
The resistance of both thin and thick film resistors after manufacture is not highly accurate; they are usually trimmed to an accurate value by abrasive or laser trimming. Thin film resistors are usually specified with tolerances of 1% and 5%, and with temperature coefficients of 5 to 50 ppm/K .
Catastrophic optical damage (COD), or catastrophic optical mirror damage (COMD), is a failure mode of high-power semiconductor lasers.It occurs when the semiconductor junction is overloaded by exceeding its power density and absorbs too much of the produced light energy, leading to melting and recrystallization of the semiconductor material at the facets of the laser.
Laser-assisted device alteration (LADA) is a laser-based timing analysis technique used in the failure analysis of semiconductor devices. The laser is used to temporarily alter the operating characteristics of transistors on the device.
The final resistor value is determined by design and can be adjusted by laser trimming. Once the hybrid circuit is fully populated with components, fine tuning prior to final test may be achieved by active laser trimming. A hybrid PCB on a ceramic substrate with laser trimmed thick film components DEC J-11 microprocessor using a hybrid PCB
A: preset resistor, B: preset resistor (alternate), C: preset potentiometer, D preset potentiometer (alternate), E: preset inductor, F: preset capacitor. In circuit diagrams, the symbol for a variable component is the symbol for a fixed component with a diagonal line through it terminating in an arrow head.