It was at ASAT, the comparably sized contract package supplier, that Marcos developed an early Tape Ball Grid Array package, was convinced of its superior thermal, mechanical and electrical performance advantages and became frustrated at the very slow TBGA market penetration. Enter Tom Di Stefano In the same, early 1990s timeframe, Dr. Tom Di Stefano, Tessera founder, was introducing that company's µBGA CSP. An essential stress-reducing element was the S-bend flex "circuit" that served as lead and substrate-then single point bonded to the die, now gang bonded. The Tessera package's present wafer-level fabrication technique uses the flex substrate for low resistance redistribution from die pads. The advances in flex-based BGA and CSP constructions, reflected in lower cost and higher throughput, are typical of products that have passed through early stage development and are heading for the mainstream. One important advance, however, has been very slow in arriving: two-metal substrates to improve high-speed transmission and impedance control, as well as routing capability. Now with 2000 here, developments on that front are coming fast and furious. The table summarizes and characterizes some of the two-metal substrate developers and developments. It is the IC package sales potential that motivates so many players-a phenomenon typical of young markets with high potential. It's too early to predict which vendors and formats will survive. For those that do, by 2002, over 10 billion DRAMs, SRAMs, and ASICs will be in the leadcount sweet spots of flex-substrate packages.
As the table shows, eight U.S.-based companies are expanding production rapidly (along with at least three Japanese companies). It is interesting to note the different market models. Gould and Rogers are strictly materials producers, selling to flex circuit as well as IC substrate fabricators. All the companies are vertically integrated from metallization through circuitization. Honeywell Electronic Materials (formerly ASTI) and Tessera have both recently partnered with Korean companies, Samsung and LG Electronics, respectively, for large volume production in Korea. Sheldahl, with a $75 million production capacity, is looking for an Asian partner. IFT, Innovex and 3M have no present plans to partner. Rogers-Mitsui Chemical casts polyimide on copper foil. All others use sputtering and vacuum deposition techniques.
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
