Printed circuit layout transfer system - uses flexible slightly yieldable support with etch-resistant layer only soluble in solvent

摘要

The board is coated with copper, and is selectively covered by the mask directly prior to etching the exposed surfaces of the Cu. The mask consists of a flexible substrate (3) which is only slightly stretchable, and which is covered by a homogeneous, dense layer (5) of acid resistant material. Layer (5) is insol. in water, but soluble in solvents and removable by pressure. Layer (5) is pref. wax, fat, plastics, or micro-encapsulated lacquer, and pref. contains pigments. Substrate (3) is pref. polyester foil sepd. by a silcone or wax layer (4) from layer (5), so the adhesion of layer (5) to foil (3) is reduced. Layer (5) is pref. covered by a pressure sensitive adhesive, which only functions above a specific pressure and bonds layer (5) to the Cu to form a mask which does not include layers (3,4). The advantage is that only a single masking operation is required, and a ball-point pen can be pressed onto the stack (3-6), so layers (5,6) stick to the Cu.