Tokyo--Toshiba Corporation today announced an environmentally sophisticated package for transistor ICs that can be easily recycled and which does not require treatment with flame retardants. The new package, the industry's first thermoplastic package for transistors, is a major step toward a new generation of environmentally-friendly device packages for the semiconductor industry.

The new packages is made from polyphenylene sulfide (PPS), a thermoplastic that has been optimized for precision molding and high temperature operation. PPS does not require treatment with bromine flame retardant, which releases dioxin, and produces minimum waste in the manufacturing process. It is recyclable, and can even re-used for transistor packaging. The new package will initially be applied to power transistors, with samples available from October. Mass production will start in January 1999.

Most semiconductor packages are made of epoxy, a thermoset compound. Epoxy compounds melt only at very high temperatures, making re-use or recycling of waste materials from the molding process impractical. Incineration of used products is also difficult, due to the chemical doping the compounds undergo in order to retard burning at high operating temperatures. Consequently, most used epoxy packaging ends up as landfill.

Thermoplastics melt and can be molded, characteristic supporting their use and re-use in injection molding and making them an attractive alternative for IC packages. However, they are also highly viscous, causing them to deform and break the very fine bonding wires on ICs, and also have poor adhesion.

Toshiba, working with Idemitsu Materials Co., Ltd., chose PPS for its high heat resistance and low flammability, and improved its suitability for packaging transistor ICs. Their PPS has the lower viscosity required for damage-free molding, is unaffected by the heat generated in soldering, and remains viable in highly humid conditions. These qualities, plus fine tuning of the temperature and speed of the plastic injection process, realized a new package without any increase in production costs. Testing also confirmed that use of recycled PPS for the package does not affect transistor reliability.

The new package is the latest in Toshiba's continuing efforts to develop innovative thermoplastic packages. It follows on the norbornene-type resin package for opto semiconductors the company announced in 1996. Toshiba continues to expand application of thermoplastics to other semiconductors, in support of achieving environmentally-friendly manufacturing and products.