Lead-free commercially close, but likelihood only 18%

08/01/2002

Several presentations at Semitool's Peaks in Packaging 2002 conference focused on the industry's readiness with lead-free bumping technology for wafer-level packaging, where the current choice is between electrochemically deposited near-eutectic SnAg, SnCu, and SnAgCu.

The overall conference message, however, was that widespread, long-term industry adoption — which is being driven by environmental concerns about lead on one hand and by lead-originating alpha particles on the IC performance side — seems to be of low probability. Postponed from 2001, the conference was held June 6-8 in White Fish, MT.

Bioh Kim, a process development engineer at Semitool, Kalispel, MT, said, "We have demonstrated good uniformity and repeatability on all processes, achieving fine-grained, dendrite-free morphology. Further, our deposition rates are high; we have observed good reflow results with smooth surfaces, no voids, and a moderate melting point. This technology could be commercial within a year."

The key industry drivers, however, seem to be reshaping. David Goosen, business development superintendent at Teck Cominco, says, "We are delivering ultralow alpha — <0.002 counts/cm²/hr — that originates at the 0.2-0.4 level right out of our Polaris mine in Cornwallis Island, NWT, Canada." While ultra-low alpha lead may not be low enough if wafer-level bumping is eventually adopted for high-volume DRAM, memory designs could also play a factor in reducing memory sensitivity to alpha emissions.

On the environmental side, analyst Neil Moskowitz of Prismark Partners, LLC, Cold Spring Harbor, NY, says, "The probability of sustainable long-term lead-free electronics being adopted is only 18%, and for lead-free, high-end electronics, it's only 1.4%. While lead-free is popular today, recycling will likely become the dominant solution." Lead-free manufacturing legislation is pending with key countries worldwide, particularly in Japan and Europe, but Moskowitz believes that countries over time will adopt a recycling exemption. In addition, exemptions may include high-lead bumps and lead inside packages.

Prismark recommends that companies involved in lead-free solder implementation invest defensively in ongoing lead-free developments. Further, Moskowitz encourages all levels of the industry to recognize the benefits of recycling over lead-free.

"Recycling is a more comprehensive solution than lead-free because it includes other toxic substances, reduces waste volume, and reduces reliance on raw materials supply. Recycling and reclamation will happen anyway, so why go lead-free also? In a free democratic society, legislation reflects the will of the people. The informed will prefer recycling."

Confirming the view of other manufacturers at the conference, Darrel Frear, manager of RF and power packaging technology development at Motorola, Tempe, AZ, said, "For us, the drive for lead-free is not political or environmental — it is cost. Electronics is only the sixth largest use of lead, at about 0.6%." From reliability survey work managed by Frear, Motorola is ready with SnCu lead-free technology. "From our work we know that lead-free materials form intermetallics at a slower rate, whiskers are a potential problem, and accelerated testing is still something of a 'black art,' but lead-free use with flip-chip will be driven by issues such as improvement in flip-chip reliability," he suggests. —P.B.