Solder Friendly Thermoplastic Blends

In order to miniaturize products and to improve productivity in the electronics industry, a method of soldering resinous electronic parts has been developed for affixing parts, such as connectors, switches, relays and coil bobbins to printed circuit board (PCB). This method is addressed as surface-mount technology. 

However, the thermoplastic compositions exposed to a lead-free solder that are used as insulators begin to fail. Loss of insulating ability, which generally occurs after failure, renders the thermoplastic composition unreliable for these types of applications. 

A solder resistant high-temperature composition that does not suffer from this drawback has been developed. The blend is composed of poly-(arylene ether) (PAE), PPS, and GFs. The PAE has an intrinsic viscosity (IV) less than or equal to about 0.15 dlg as determined in chloroform at 25°C. The use of the low IV PAE permits improved blending, which leads to improved high-temperature properties. Homopolymers of PAE are those containing 2,6-dimethylphenylene ether units. Suitable copolymers include random copolymers containing, for example, 2,6-dimethylphenylene ether units. In combination with 2,3,6-trimethyl-l,4-phenylene ether units or alternatively, copolymers derived from the copolymerization of 2,6-dimethylphenol with 2,3,6-trimethylphenol. Partially crosslinked PPS, as well as mixtures of branched and linear PPS, may be used in the high-temperature compositions. 

The composition advantageously displays a thermal resistance effective to withstand the high temperatures encountered in a reflowing oven. Further, the high-temperature compositions more closely match the thermal shrinkage of PBT, which is presently used in solder connector applications. 

The thermal performance is improved without any changes to existing processing equipment, such as molding machines, dies, molds, or extrud- 

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B. Liu. Lead free solder friendly thermoplastic blends and methods of manufacture thereof. US Patent 7 037 986, assigned to General Electric Company (Pittsfield, MA), May 2, 2006. 

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