Solder Mask Protective Coating for Flexible Printed Circuits
Original Publication Date: 1988-Nov-01
Included in the Prior Art Database: 2005-Feb-15
A method is described of laying down a solder mask on a flexible printed circuit which also acts as a protective layer on the conductors beneath it. The method has production advantages over conventional methods; capital costs are lower, registration is more accurate, and coverage for fine pitching is superior. When bent, the flexible circuit coating has good resistance to fracture. The figures show the sequence of process steps. An electrically insulating material 1 is deposited upon a flexible substrate 2, which has an electrical circuit 3 on one or both of its sides. The insulating material 1 is photosensitive, and by using a suitable photomask (4) and developing solutions, apertures 5 are created to expose the underlying copper circuitry 8 in selected areas 6.