A method of forming solder mask, suitable for forming a solder mask on the
surface of a wiring board, is provided. The surface of the wiring board
includes a first region and a second region, and the surface of the
wiring board has a wiring pattern thereon. The method includes forming a
first sub solder mask in the first region on the surface of the wiring
board by performing a screen-printing or a photolithographic process, and
forming a second sub solder mask in the second region on the surface of
the wiring board by performing an ink-jet printing process. The method
not only improves the precision of the solder mask alignment on the
wiring board and its reliability, but also increases the production rate
and lowers the manufacturing cost.