SMTA International Conference Proceedings


Authors: Andrei Naumov, Dave Mahon and Anton Kitai
Company: GSI Lumonics Inc.
Date Published: 9/22/2002   Conference: SMTA International

Abstract: In the printed circuit board industry, the growing demand for a higher number of circuit components to be contained in smaller circuit areas requires that some of the passive components (resistors, capacitors, etc) are now embedded within the board. This allows for tighter component placement with lower via counts and has also increased the reliability of these devices.

For thick film resistors, the resistor paste for embedded resistors is usually screen-printed on the surface of the PWB laminate (either copper or dielectric) that is patterned according to the circuit design. Current technologies require wet paste that is oven cured after placement. This paste process results in a resistor with a tolerance of 10-50% from the target value.

Thin film resistors deposited on the PWB also show variation in their values. Resistor trimming is required to bring this tolerance down to about 1-5% as required by the PWB design. This paper discusses the implementation of passive resistor trimming for large panel manufacturing.

Key words: Laser trimming, PWB, embedded resistors.

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