An Independent Journal Dedicated to the Advancement of Chip - Scale Electronics March - April 2000 Email the editor

Dr. Guna Selvaduray on Lead-Free Manufacturing

Dr. Selvaduray is a Professor in the College of Engineering at San Jose State University. His fields of interest include chemical thermodynamics, microelectronics interconnect and encapsulation, design for the environment and materials characterization. A native of Malaysia, he earned a bachelor's degree in mechanical engineering from the Tokyo Institute of Technology, a master's degree in materials science and engineering from Stanford University, and a doctorate in metallurgy from Stanford. He speaks five languages, including German and Japanese, and has lived and worked in several countries. In 1997, he was awarded the Excellence in Scholarship Award by SJSU's College of Engineering. For the past year, he has also served on the Chip Scale Review Editorial Advisory Board and has helped guide the publication to a leading position in IC packaging journals. Readers may contact him at gunas@email.sjsu.edu or by phone at 408.924.3874.

Dr. Guna Selvaduray

Europe usually trails the U.S. in electronics. What accounts for its lead in the "no-lead" movement?

The U.S. has tended to lag behind Europe in several areas related to conservation and preservation of the environment. While the U.S. has argued that environmental preservation hurts the economy, Europe has been more serious about environmental protection and preservation. In the area of recycling of plastics and materials from automobiles, for example, Europe has also been taking the lead.

This is perhaps due to increased awareness among Europeans that we cannot afford to continue polluting the earth without our descendents paying severe penalties. Additionally, Europeans have much higher population densities, with less land available for permanent disposal and storage of materials that are harmful to the environment.

Another factor may be the lack of industry lobbyists in Europe. In the U.S., legislation is frequently affected by industry lobbyists in Washington, D.C.

Where will the best no-lead solder originate?

Currently, it looks like the most frequently used no-lead solder will originate in Japan. The Japanese have take the most aggressive attitude toward implementing lead-free solders and have really accelerated the timetable.

Once a lead-free solder begins to be employed, superior or not, the electronics industry is likely to be reluctant to make any changes. The behavioral pattern of the industry, thus far, shows that there will be no real effort to carry out a complete and thorough investigation to establish-in an unbiased manner-whether there is one superior no-lead solder or several application-specific no-lead solders.

How quickly can U.S. firms implement lead-free requirements?

The primary question is not "how soon," but rather "how soon can lead-free manufacturing be implemented reliably?" Given that a number of non-U.S. companies are now implementing lead-free assembly conditions, U.S. companies also ought to be able to do the same.

Based on my current understanding of international trends, U.S. companies need to be able to implement lead-free conditions within a year or so. If they can do so on a pilot scale within the next six months, that would be even better.

Are lead-free solder alternatives going to be a "realtime" test of their abilities in the semiconductor industry?

The lead-free alternatives currently being proposed are not "tried and true," and it looks like their use will be a realtime test.

While the opportunity to go about employing lead-free alternatives in a systematic manner still exists, I do not see people doing this; many people seem to be waiting for somebody else to develop the solutions so that they can then implement them. This "wait-and-see" attitude is going to result in a lot of companies ending up doing realtime testing of alternative solders.

Will the elimination of lead-free materials, such as solder, result in higher prices?

I do not think the elimination of lead will result in price increases. The adoption of past initiatives-such as the elimination of ozone-depleting chemicals-has not resulted in price increases. If price increases, as a result of the adoption of lead-free alternatives do take place, this will be due to the lack of a proper development program with the resulting reduction in reliability.

What industry segments are likely to be most concerned about making their equipment run lead-free?

An obvious segment is the group that makes reflow equipment. However, besides equipment, there are a large number of other materials issues that need to be "solved." These issues pertain to all of the other polymeric materials that are employed in assembly and interconnect, and specifically relate to their ability to withstand higher reflow temperatures without degradation.

Many industry organizations have sponsored "lead-free" conferences and proposals, but none seem to have a complete program. Is an industry-wide initiative going to have to wait for government to step in?

The issues and problems related to lead-free solders is symptomatic of what has been happening with electronic materials thus far. While the industry has moved far ahead in the assembly process, these advances have been made with little or no investment in performing the basic research necessary to understand the materials used and the mechanisms at work.

For example, there is no data on diffusivities of atomic species in the 100-300^oC range-at least not in the open literature. I do not think that waiting for the government to legislate lead-free materials and processing will be a very wise thing to do.

The semiconductor assembly and interconnect industries must realize that they need to invest in basic research to maintain their technological lead as the 21st century progresses.

If we don't watch out, the U.S. will become a country that is forced to follow a path defined by others-which is exactly the case with lead-free solders.

Can we be confident in the reliability of new, lead-free solders?

There is no reason to assume that the new lead-free solders will not perform reliably. Pb-Sn solders have demonstrated their share of reliability problems. The fundamental issue is not whether the new lead-free solders are inherently reliable or not, but rather, whether we know and understand how to use these solders so that we are able to design IC packages appropriately.

If a package is designed so that the solder is stressed beyond its UTS, then it is bound to begin failing. This, however, is a design issue and not a materials issue.