Advance in Bonding Allows LCPs to Replace Ceramic and Metal in Air-Cavity Sensor Packaging

Sensor Expo, Rosemont, Ill., June 12, 2007 – RJR Polymers has developed a series of proprietary epoxies that are the first to work across a wide variety of liquid crystal polymer (LCP) grades for use in fabricating air-cavity packaging for sensors and other electronics. This bonding technology allows packaging made of Vectra® LCP from Ticona, the engineering polymers business of Celanese Corporation, to replace packaging made of ceramic and metal. The LCP packaging provides for improved designs and significant cost savings.

LCP air-cavity packaging is a containment system that protects sensors, microelectromechanical systems (MEMS), integrated circuits and other elements from environmental and mechanical influences. Such packaging, which is typically less than 38 mm long and 38 mm wide, usually involves a housing, a lid and a lead frame encapsulated in the housing. Sensor applications for RJR air-cavity packages include automotive pressure, temperature and fuel sensors, medical diagnostics, cell phone base stations, wireless networks, radios and optical systems (including communications and cameras). “We chose Vectra LCP because it gives our sensor packages the many properties they need,” says Dick Ross, RJR president and CTO. “It allows them to meet demanding thermal specifications for reflow soldering (to 280°C) and repeated thermal cycling from -65°C to +150°C. It also has excellent resistance to water vapor, high dimensional stability, and the ability to form extremely thin yet strong walls, among other performance properties. The challenge in using LCP is to process and adhere it properly.”

RJR offers a systems approach to LCP packaging that includes custom epoxy formulations and manufacture, molding LCP packaging elements, applying epoxy to the package, and providing equipment to customers to seal packages. RJR specializes in B-staging, in which epoxy is preapplied to parts. Customers then reheat the parts so the epoxy flows and the parts can be joined to other components.

“We find that LCP air-cavity packages equal or exceed the performance and reliability of ceramic packages,” said Ross. “This polymer also helps us speed prototype design, lower tooling costs and create new design options and far greater flexibility when compared to ceramic packaging.

“Dimensional uniformity is a problem with ceramic packaging because of its high shrinkage during manufacture. As a result, designers tend to favor two-dimensional (X, Y) ceramic shapes. Vectra LCP allows us to create 3-D packaging having rounded contours and complex features, so we can make more sophisticated and efficient products.”

RJR’s LCP molding operation uses a patented method to seal leads from the lead frame as they pass through the package sidewall. This involves placing a small amount of epoxy on the frame during molding to form a strong metal-to-plastic bond.

About RJR Polymers
RJR Polymers, Inc. is a global company headquartered in Oakland, Calif., that furnishes custom package, adhesive and sealing technologies for the manufacture of air-cavity packages. It began operation in 1984 and now employs more than 100 people. It operates a 90,000-sq.-ft. production facility and has sales offices in Korea, Taiwan, Malaysia, and France.

About Ticona and Celanese
Ticona, the engineering polymers business of Celanese Corporation, produces and markets a broad range of high performance products , and achieved net sales of $915 million in 2006. Ticona employs approximately 2,000 individuals at production, compounding and research facilities in the USA, Germany and Brazil. As a global leader in the chemicals industry, Celanese Corporation makes products essential to everyday living. Our products, found in consumer and industrial applications, are manufactured in North America, Europe and Asia. Net sales totaled $6.7 billion in 2006, with over 60% generated outside of North America. Known for operational excellence and execution of its business strategies, Celanese delivers value to customers around the globe with innovations and best-in-class technologies. Based in Dallas, Texas, the company employs approximately 8,900 employees worldwide.