Coextrusion Solutions in Thermoformed ESD Packaging.

Thermoformers of rigid protective trays used to ship componentry for hard-disk drives, semiconductors, and other sensitive electronics stand to benefit from technology being licensed by Eastman Chemical Co., Kingsport, Tenn. It offers sheet coextrusion know-bow based on combinations of its Eastar PETG and Eastastat antistatic PETG grades. These multi-layer sheet structures can protect electronics against electrostatic discharge (ESD) while avoiding both contamination from sloughing of conductive carbon particles and the outgassing that can occur when conductive carbon-black filler is used.

J.P. Kuijpers, Eastman's market manager for electrical/electronics packaging, says coextrusion is more cost-effective than typical ESD-protective trays that are formed from monolayer sheet of costly ESD grades.

For example, Kuijpers says Eastastat GSP12, an inherently dissipative polymer (IDP) alloy, can be used as the skin layers of a tri-layer coextrusion along with standard Eastar 6763 as the core. The core provides strength and thermoformability, while skins provide ESD protection at low cost. That opens potential for downgauging, Kuijpers adds.

Alternatively, the IDP skins could be coextruded around a core layer of Eastastat GSP32, a conductive copolyester that uses carbon black as the filler. That coextrusion allows trays to have low surface and volume resistivities while encapsulating the carbon-black layer to seal off particulates or corrosive outgassing from contact with sensitive componentry.

Use of copolyester in the core layer also is said to improve formability and increase scope for designing precision detail (e.g. ribs and pins) and higher draw depth into packages in order to better nest and secure parts during shipment.