Electrolytic Process for Substrate Manufacturing
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Substrate processing operations prior to 'chip join' include 'pinning', 'substrate fluxing', 'tinning' (wave solder), 'UV inspection', 'perchlorethylene cleaning', 'stand-off', 'final inspection', 'quality control' and 'stocking', in that order. The 'tinning' operation acts to prevent further exposure of the copper C-4 pads on the substrate to oxidation and potentially degraded solderability at 'chip-join'. The wave soldering process becomes increasingly subject to lowered process yields due to 'solder bridging', however, as the lines, lands, studs, pins, etc., get smaller and closer together on the substrate. This article discloses an alternative approach to tinning (wave soldering) which ensures that the C-4 pads remain solderable between the substrate build operations and 'chip-join'.