Browse Prior Art Database

Memory Module With Polyimide Alpha Barrier

IP.com Disclosure Number: IPCOM000061472D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Ameen, JG: AUTHOR [+3]

Abstract

A polyimide layer is used as an alpha barrier in a memory module. Alpha particle emission from ceramic substrates can cause faulty operation of the memory circuit chip(s) mounted to the substrates. It is customary in conventional memory modules to provide an alpha barrier layer after chip mounting that covers the exposed ceramic substrate's circuitized surface surrounding the chip(s) C-4 (controlled chip collapse connection) joints to minimize the emission effects. However, because of the plastic nature of the type barrier used, the barrier often seeps between the surface-mounted chip and substrate creating stresses during subsequent processing that cause failure of the solder bond between the chip and substrate pads.

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Memory Module With Polyimide Alpha Barrier

A polyimide layer is used as an alpha barrier in a memory module. Alpha particle emission from ceramic substrates can cause faulty operation of the memory circuit chip(s) mounted to the substrates. It is customary in conventional memory modules to provide an alpha barrier layer after chip mounting that covers the exposed ceramic substrate's circuitized surface surrounding the chip(s) C-4 (controlled chip collapse connection) joints to minimize the emission effects. However, because of the plastic nature of the type barrier used, the barrier often seeps between the surface-mounted chip and substrate creating stresses during subsequent processing that cause failure of the solder bond between the chip and substrate pads. By using a polyimide as the alpha barrier, it can be applied prior to the chip-mounting operation to the circuitized surface of the substrate except for the Cr-Cu-Cr circuit pads thereof at the chip-mounting site(s). After curing, the polyimide results in a solid-type layer with no residue at the chip-mounting site(s). Moreover, the so formed polyimide layer, in addition to providing the alpha barrier function, can also function as an etch-resistant mask for the subsequent removal of the top Cr of the pads, and/or can be circuitized, thus providing a second level of circuitry for the module.

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