SEMICON West Technical Talks

09/01/2002

SEMICON WEST REPORT

BY JULIA GOLDSTEIN

The technical sessions began with the presentation of the IEEE/CPMT Electronics Manufacturing Technology Award to Scott Kulicke of K&S for his "commitment and dedication" and "outstanding leadership and service." Kulicke is donating the cash award back to IEEE.

Keynote speaker Richard Dasher (Stanford University) spoke on photonics-electronics (P-E) integration and how it relates to four semiconductor industry trends: increasing outsourcing, increasing focus on chip design for competitive advantage, polarization into large and small firms with mid-size companies being squeezed out, and a market driven by consumer applications.

Dasher suggested that "radical new technologies" such as P-E integration favor either large, vertically integrated companies or start-ups spun off from research groups at universities or national laboratories. Optical component makers are focused on current products, not P-E integration. Driving applications most likely will not be consumer products because the requirements for high reliability at low cost cannot be met. Optical network applications are a possibility, but current market conditions are poor.

Dasher suggested that new markets, such as security applications using sensors, might end up being the drivers. He said, "If you have a technology, it will find an application." Trends to watch are technology transfer from corporate R&D into product development at large firms, people from the chip industry getting involved in P-E integration, and a drive toward standard platforms and packaging for photonics. Dasher also warned that standards should be driven by products, not technology.

The best paper award for the flip chip session went to Hing Chan of ST Assembly and Test Services for his talk, "Material and Process Considerations for Reliable Overmolded Flip Chip PBGAs." The packages in this work were built on very thin organic substrates, with the die underfilled and then overmolded to minimize handling damage. Results of environmental testing in an autoclave showed that an alumina-filled underfill material performed better than a silica-filled, higher modulus material or unfilled, low modulus underfills. Because the modulus of the alumina-filled underfill most closely matched that of the overmolding compound, stresses were reduced. A package using the optimum underfill has been qualified.

Ning-Cheng Lee, Ph.D., (Indium Corp.) discussed the benefits of screen printing solder paste instead of using preformed solder balls for bumping CSP and BGA packages. Solder ball cost per bump is fixed as sphere size changes because yield decreases for smaller balls. With paste, cost per bump decreases with sphere diameter, making it cost-effective for sizes less than 30 mils. Screen printing also is less expensive than electroplating. It has not been used much, however, because of bridging problems caused by solder slump.