Use of photosensitive stratum to create through-hole connections in circuit boards

A method of making electrically conductive connections by means of through-holes between two circuits on opposite sides of a substrate comprising the steps:

• (a) laminating a supported plastic photo-hardenable toner-receptive stratum to a surface of the substrate whereby the through-hole is covered by the supported stratum;
• (b) removing the support from the stratum and applying a pressure differential across the stratum by subjecting the stratum to vacuum via the through-hole;
• (c) maintaining the pressure differential across the stratum by which the stratum covering the through-hole collapses into the through-hole and adheres to the walls thereof;
• (d) exposing the photo-hardenable stratum imagewise by which selected areas thereof, excluding the areas covering the through-hole, are rendered toner nonreceptive;
• (e) adhering copper particles having an average diameter of 0.5 to 250 microns to the toner-receptive image areas including the through-hole walls;
• (f) hardening the copper metallized areas by heating to a temperature up to about 180.degree. C. and/or by radiating with radiation actinic to the photo-hardenable stratum;
• (g) providing an electrically conductive printed circuit and connecting through-holes by plating electrolessly, soldering or conjoining the metallized or catalyzed area.

A method of making electrically conductive connections by means of through-holes between two circuits on opposite sides of a substrate comprising the steps

• (a) laminating a supported plastic photo-hardenable toner-receptive stratum to a surface of the substrate whereby the through-hole is covered by the supported stratum;
• (b) applying a pressure differential across the supported stratum covering the through-hole such that the pressure on the supported side of the stratum exceeds the pressure within the through-hole;
• (c) while maintaining the pressure differential across the stratum, removing the support from the stratum, by which the stratum covering the through-holes collapses into the through-holes and adherently coats the walls to a thickness of at least 0.00005 inch (0.0013 mm);
• (d) exposing the photo-hardenable stratum imagewise by which selected areas thereof, excluding the area covering the through-hole, are rendered toner nonreceptive;
• (e) adhering copper particles having an average diameter of 0.5 to 250 microns to the toner-receptive image areas including the through-hole walls;
• (f) hardening the copper metallized areas by heating to a temperature up to about 180.degree. C. and/or by radiating with radiation actinic to the photohardenable stratum;
• and
• (g) plating electrolessly, soldering or conjoining the metallized or catalyzed areas.