Browse Prior Art Database

Electrolytic Process for Substrate Manufacturing

IP.com Disclosure Number: IPCOM000061363D
Original Publication Date: 1986-Jul-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Dunkel, WE: AUTHOR [+2]

Abstract

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'.

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Electrolytic Process for Substrate Manufacturing

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'. As shown in the figure, solder-bridging can be eliminated by replacement of the wave soldering operation through application of the well-known immersion metallization technique to provide an electrolytic exchange process for coating sensitive parts. Such a process would leave the copper C-4 pads coated with a thin (in the nanometer range) protective metallized coating that would ensure them sufficient shelf life and the ability to employ solder balls, as required in the C-4 process, without additional different cleaning steps. The electrolytic exchange process may be introduced into present substrate manufacturing lines at minimal...