Electroless solder plated circuit board mfg. process - avoids copper@ layer attack by solder plating soln.

摘要

Prodn. of a circuit board, having an electroless solder plated wiring pattern (1), involves (a) forming a wiring pattern (1) on a circuit board substrate (4); (b) covering a first portion (1, 2), requiring a solder coating, with an insulating mask (5); (c) electrolessly depositing a metal, which is not attacked by the solder plating soln., onto an exposed second portion (3) to form a metal mask (6); (d) removing the insulating mask (5); and (e) electrolessly plating solder alloy from an immersion bath onto the first portion (1, 2). Also claimed are (i) a circuit board having a relatively thin electrolessly plated solder alloy layer in the vias (3) and a relatively thick electrolessly plated solder alloy layer on fine contacts (1); (ii) a method of producing the above circuit board; (iii) a circuit board mfg. process in which a wiring pattern (1) and solder coatings are formed on the substrate (4), electroless copper plating is carried out on copper base contacting patterns and vias (3) of the wiring pattern and solder alloy is electrolessly plated onto the copper; and (iv) a circuit board mfg. process in which the circuit board substrate is stationary or is continuously or intermittently reciprocated in an electroless solder plating soln. ADVANTAGE - The processes avoid redn. of copper layer thickness of the wiring pattern and in the vias and improve circuit board reliability.