1990-02-01

A Novel Method for Eliminating Damaging Leaks in Molded Electronic Components 900772

Forty billion dollars are lost each year due to the failure of various components in a vast array of electronic devices. These failures result in downtime for part replacement, product liability issues, and critical safety ramifications. Many of the failures are caused by corrosion due to the migration of moisture or solder flux through leak paths inherent in electronic connectors and other parts, typically at the interface between metal leads and plastic housings into which they are molded.All industry standard approaches to preventing these failures have severe limitations and drawbacks. The approaches include discarding parts that fail a leak test, employing elaborate hermetically sealed encasements, or applying surface sealants. Each method of solving the problem creates other problems: costly high scrap rates, heavy, bulky assemblies, or introduction of a foreign material through surface sealants. The use of surface sealants is also labor intensive, since each part must be handled individually.An entirely new approach to sealing leak paths in electronic components has been developed. The processing and material characteristics of this new sealant eliminate all of the problems associated with conventionally used techniques in a unique and cost-effective manner. The product is a 100% reactive low viscosity acrylic sealant which cures to form a tough, flexible, thermoset plastic with excellent environmental resistance. The process involves air evacuation of the leak paths, followed by filling of the voids with sealant. Polymerization subsequently occurs via an anaerobic cure mechanism, thus only when confined and away from air does hardening take place. Sealant exposed to air, e.g. on the surface of the parts, will remain liquid and is readily removed by an aqueous wash.Material is put in the leak path itself, and only in the leak path, leaving no surface deposit or residue. Therefore, part geometry is not changed, design parameters and assembly processes are facilitated, and subsequent adverse effects on solderability and electrical characteristics due to chemical contamination are eliminated. A batch process is used, obviating the need for handling parts individually, thus vastly improving efficiency and productivity.

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