TWO-LAYER TYPE PRINTED CIRCUIT BOARD AND MANUFACTURING METHOD THEREOF

PROBLEM TO BE SOLVED: To obtain a very fine circuit pattern at a high yield by specifying the number and max. length of through-holes piercing a two-layer type printed circuit board and conductive metal layer to reach the surface of an insulation film. SOLUTION: A conductive metal layer 2 is formed on an insulation film 1 and chemically adsorbed pref. through a water soln. to pin-holes through which the film 1 is exposed, i.e., defects of this metal layer 2 and, if required, to bored throughholes to expose the film 1, and then the electroplating is made to obtain a two-layer type printed board. It is specified that the number and max. length of pin-holes of this board are 10 holes/m or less and 10 microns or less as measured with the transmitted light and steromicroscope. Thus it is possible to produce a fine pattern with through-holes of 80 microns or less pitch at a high yield which was difficult to mass-produce, whereby more highdensity and more high-integration degree electric and electronic apparatus are expectable.