Browse Prior Art Database

End-Of-Line Ionograph Clean Modification

IP.com Disclosure Number: IPCOM000040109D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Barcak, JM: AUTHOR [+6]

Abstract

A cleaning process used on first level metallized ceramic polyimide (MCP) circuit packages was determined to be the source of a white crystal contamination on the substrate surface. Spacing violations caused by the contaminant result in defective product. Scanning electron microscopy analysis was used to characterize the contamination as lead oxide and lead carbonate hydroxide. (Image Omitted) Formation of the contaminant is a result of interactions between water-air-lead-nucleation sites, with the nucleation sites taking the form of molecules, dust, etc. Experimentation shows crystal growth is a result of the following reactions: 1. MCP substrates removed from the ionograph clean have a thin film of highly reactive D.I. water (20+ megohm) on their surface. 2. The D.I.

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End-Of-Line Ionograph Clean Modification

A cleaning process used on first level metallized ceramic polyimide (MCP) circuit packages was determined to be the source of a white crystal contamination on the substrate surface. Spacing violations caused by the contaminant result in defective product. Scanning electron microscopy analysis was used to characterize the contamination as lead oxide and lead carbonate hydroxide.

(Image Omitted)

Formation of the contaminant is a result of interactions between water-air-lead-nucleation sites, with the nucleation sites taking the form of molecules, dust, etc. Experimentation shows crystal growth is a result of the following reactions: 1. MCP substrates removed from the ionograph clean have a thin film of highly reactive D.I. water (20+ megohm) on their

surface. 2. The D.I. water absorbs carbon dioxide and oxygen from the air. 3. The carbon dioxide in the water solution forms a carbonic acid which attacks the lead on the component, forming lead oxide and

lead carbonate in solution (lead source-tin/lead solder). 4. As the thin film of the solution evaporates, the lead carbonate and lead oxide form crystals which are deposited on the surface

of the substrate. Environmental controls are used to prevent crystal formation by restricting the exposure of the MCP substrates to an inert (nitrogen) atmosphere immediately following ionograph clean and the immediate removal and drying of surface water. A nitrogen-purged enclosure (Fig. 1)...