An LS laser trimmer system automates and improves your circuit adjustment. The system can trim thick- and thin-film-resistors as well as SMD-resistors and -capacitors. You can trim to a certain resistance (passive trim), or the attributes of the whole circuit can be taken into account (active or functional trim). The comparison parameter is then e.g. an output voltage, a frequency or a switching level. A laser trim system normally consists of the following components:
laser source
control computer with software
beam positioning (deviation) unit
circuit handling
prober unit
measuring unit for active/passive trim
For trimming, the circuit board is placed under the positioning unit and contacted electrically. The deviation unit moves the laser beam to the component to be trimmed and trims it until the programmed nominal value is reached. A lateral laser cut in a resistor narrows the current flow path, thereby increasing the resistance. Removing part of the top electrode of a capacitor decreases the capacitance. During the trim the relevant parameter is measured continuously or sequentially via IEEE bus and compared with the nominal value. When the parameter reaches the nominal value the trim cut stops automatically. Various types of cut and the appropriate selection of laser parameters enable a precise trim of the circuit board, with excellent long-term stability. For instance, a resistance value can be increased to a multiple of its initial value.