Abstract: Through-holes in a substrate are masked during plating of the substrate by substantially filling the through-holes with a liquid material, followed by applying a photoimageable material to an external surface of the substrate, forming a predetermined pattern in the photoimageable material, circuitizing the predetermined pattern and then removing both the photoimageable material and the liquid material from the through-holes.

Abstract: A method and apparatus is described for reworking a printed circuit board having plugged vias and plated through holes. The printed circuit board, supported by a movable local support, is heated from only the bottom side by a heating device near the area on the PCB that contains the plated through hole or holes to be reworked. The heating device is removed when the solder in the plugged PTH is completely melted. At that time, blast air is turned on to remove and blow off the excess solder in the PTH. The compressed air is more effective in displacing the molten solder than is vacuuming, and has less chance of damaging the PCB than do conventional reworking methods, due to the non-contact nature of the invention.

Abstract: A method and apparatus is described for reworking a printed circuit board having plugged vias and plated through holes. The printed circuit board, supported by a movable local support, is heated from only the bottom side by a heating device near the area on the PCB that contains the plated through hole or holes to be reworked. The heating device is removed when the solder in the plugged PTH is completely melted. At that time, blast air is turned on to remove and blow off the excess solder in the PTH. The compressed air is more effective in displacing the molten solder than is vacuuming, and has less chance of damaging the PCB than do conventional reworking methods, due to the non-contact nature of the invention.

Abstract: An improved photoimagable cationically polymerizable epoxy based coating material is provided. The material includes an epoxy resin system consisting essentially of between about 10% and about 80% by weight of a polyol resin which is a condensation product of epichlorohydrin and bisphenol A having a molecular weight of between about 40,000 and 130,000; between about 20% and about 90% by weight of an epoxidized octafunctional bisphenol A formaldehyde novolak resin having a molecular weight of 4,000 to 10,000; and if flame retardancy is required between about 35% and 50% by weight of an epoxidized glycidyl ether of tetrabromo bisphenol A having a softening point of between about 60 C. and about 110 C. and a molecular weight of between about 600 and 2,500. To this resin system is added about 0.