ANAHEIM, CALIF. — Electronic-assembly trends toward chip-scale packaging present opportunities for polymer suppliers and have drawn established solder makers into the epoxy market.
Meanwhile, assemblers want a reworkable epoxy for removing and replacing a flawed multichip module rather than discarding a circuit board.
These findings were drawn from interviews at the March 1-5 Nepcon West conference and exhibition in Anaheim. End products include disk drives, cellular telephones, pagers, laptop computers and digital cameras and camcorders.
On one material front, development of chip-scale packages provides an opportunity for U.S. encapsulant makers to capture a share of a market that Japanese companies have dominated for many years, Michael Warner said. He is vice president of product development for Tessera Inc., a San Jose, Calif., independent technology developer with licenses issued to 18 integrated-circuit assemblers.
Silicone dominates as an encapsulation material now for Tessera's proprietary microball grid array, but outgassing concerns are driving researchers to find a flexible epoxy as an alternative.
End users are anxious for replacements and have tried a number of materials unsuccessfully, Warner said.
He estimates the industry will make a minimum of 200 million chip-scale packages this year, up sixfold over 1997, and that it will exceed a billion annually in the near future, Warner said.
Tessera believes its micro BGA may suit the industry's needs better than other chip-scale packages.
``Having a standard package available in quantities leads the designers to be comfortable with adopting a new technology,'' Warner said, noting that cellular phone makers are switching to micro BGAs from the existing thin-small-outline-package technology, known as TSOP. ``A micro BGA is about a quarter of area of a TSOP and about 10-15 percent of total volume.''
Currently, Tessera uses a strip handler of stainless steel but seeks a different material. Researchers want a plastic replacement that is dimensionally stable and inexpensive, he said.
``All semiconductor manufacturers are shrinking dies for either performance or cost,'' said Steve Anderson, senior vice president of corporate product marketing in Chandler, Ariz., for Amkor Electronics Inc. ``Cost is the big factor this year.''
Smaller dies mean that interconnect densities get tighter, leading to the use of polyimide tape as a carrier onto which adhesives and metal are attached to build a circuit board, Anderson said. At one of its South Korean factories, Amkor is ramping up production of a new flexible BGA to meet the demand from makers of micro devices.
While polyimide is used now, cheaper plastics probably will appear, Anderson said.
Electronics assemblers must increase productivity levels as time to market becomes more important, said Ken Gilleo, technology director in Cranston, R.I., for Alpha Metals Inc., a unit of Cookson Group plc. Alpha Metals is a solder supplier that is new to polymers.
Developing reworkable epoxy blends is important, said Gilleo, a polymer chemist. If rework is needed, a manufacturer needs a way to remove higher-value dies rather than discard the entire board.
Suppliers ``have to figure out how to make them reworkable,'' he said, suggesting a search for ``a magic unzipping at a particular temperature.'' Some day, the industry may use thermoplastics, but no forecast is available.
Gilleo noted that newer catalysts activating seasoned epoxies can make dramatic reductions in processing times and meet high-volume demands of makers of cell phones and other devices.
Alpha has put color into its epoxies to create ``a dramatic color change'' reflecting thermal changes.
``Everyone in the industry is striving to make an epoxy [that is] more stable,'' said Ross Berntson, manager of technical services with Utica, N.Y.-based Indium Corp. of America.
``The key is to make the epoxy stable at room temperature over a long period of time,'' he said. Much experimentation is taking place, he said, and the next generation of conductive epoxies may permit open working time of three to four hours and cure time of less than 10 minutes.
In Nepcon's Technology Advancement Center, RRA Technical Services organized four complete, state-of-the-art assembly lines in which more than 80 manufacturers showcased materials, equipment and processes.