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Post Solder Cleaning Process for Cermet Resistor Products

IP.com Disclosure Number: IPCOM000038944D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Anschel, M: AUTHOR

Abstract

Electronic modules comprising circuitized substrates, which include cermet resistors, occasionally experience corrosion resistor drift during testing because of poor adhesion of silicon resin top seal which serves as an encapsulant for the cermet resistor. The poor adhesion is due to surface contaminants which are not removed prior to top seal and encapsulation. The result is the formation of an occluded corrosion cell. The employment of ultrasonic agitation and mechanical spray system during cleaning and subsequent rinses provides sufficient cleaning to prevent corrosion resistor drift. Contaminants which cause resistor drift are typically incurred during handling, e.g., fingerprints, flux, lint, etc. Basic lead carbonate (2PbCO3 $ Pb(OH)2), caused by a combination of factors, is also a common contaminant.

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Post Solder Cleaning Process for Cermet Resistor Products

Electronic modules comprising circuitized substrates, which include cermet resistors, occasionally experience corrosion resistor drift during testing because of poor adhesion of silicon resin top seal which serves as an encapsulant for the cermet resistor. The poor adhesion is due to surface contaminants which are not removed prior to top seal and encapsulation. The result is the formation of an occluded corrosion cell. The employment of ultrasonic agitation and mechanical spray system during cleaning and subsequent rinses provides sufficient cleaning to prevent corrosion resistor drift. Contaminants which cause resistor drift are typically incurred during handling, e.g., fingerprints, flux, lint, etc. Basic lead carbonate (2PbCO3 $ Pb(OH)2), caused by a combination of factors, is also a common contaminant. Resistor drift is also caused by ionic conduction. Sources for ionic conduction are fingerprints and carbonic acid. Silicon resin sealing systems have poor adhesive qualities in general and do not adhere well to the above residual contaminants and cure to the desired polymeric properties. The conditions under which cermet corrosion and resistor drift occur are as follows: 1) The presence of oxygen, ions and water (residual or penetrating coating). 2) Ready motions of ions through the coating. 3) Ionic transfer reactions (corrosion) at the polymer/metal interface. 4) Water and topseal do not displace eac...