Method for Laser Direct Writing of PWB Circuit Patterns Using Thick Film Conductive Pastes
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
The present method uses laser beam exposure of a thick film paste to circuitize a printed wiring board (PWB) or ceramic substrate for hybrid circuit fabrication. Process simplification, overall cost reduction and increased energy efficiency results from using the selective beam annealing method rather than conventional IR curing to produce the conductive traces. The replacement of the screening step with a laser- writing step introduces enormous flexibility into the circuit design and eliminates the need for expensive and time-consuming stencil or screen photographic work. This method also makes available the use of the thermally sensitive substrates, such as FR-4, which cannot survive the elevated temperatures necessary for IR curing.