| 摘要 |
PURPOSE: To perform brazing rejection covering by providing a photosensitive negative brazing rejection varnish on the entire surface of a printed circuit board, providing a mask in the range of a through-hole and/or a brazing pad, and performing exposure phenomenon. CONSTITUTION: A negative brazing rejection varnish 5 is provided for a printed circuit board with a conductor path 2, a through-hole 3, and a brazing pad 4 on an electrically insulated substrate 1 and a photosensitive layer 6 with silver halide as a base is provided on an entire surface. Laser beams Ls are applied obliquely for exposing a hole wall to be exposed by laser beams, thus causing a light-transmitting gelatin layer 60 to remain. The exposed non-light- transmitting range 600 is mainly made of a silver metallic mask. The mask 600 is removed by melting gelatin, a non-exposed range 50 of the varnish 5 is developed, and only the exposure range 50 is left. The through-hole 3 and the brazing and 4 are selectively covered with a tin/lead alloy without problem in succession by a high-temperature tin-plating method. |
