Post Solder Cleaning Process for Cermet Resistor Products
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
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.