Close shave: consortia to standardize on Tin Whisker test. (Around The World / Manufacturing).

TOKYO -- Calling the work "important for implementation of lead-free technology," a group of national consortia are taking steps to develop a standard test protocol for tin whiskers. The test method would predict the susceptibility of component terminals to the growth of tin whiskers, and that methodology must be accepted worldwide, say the National Electronics Manufacturing Initiative (nemi.org), Soldertec of Tin Technology Ltd. (leadfree.org) and the Japan Electronics and Information Technology Industries Association (jeita.org.jp).

At a joint meeting held May 15, in Tokyo, consortia representatives agreed to form a joint team to study tin whisker growth mechanisms, a known source of electrical shorts.

The phenomenon of tin whiskers occurs through the recrystallization of tin into long, usually single crystal, filaments; the filaments can bridge two tin-plated terminals. Not every product lot (or plating bath) grows whiskers, however, and the basic mechanism for growth is not understood.

At the May 15 meeting, the organizations agreed to several test conditions:

* High temperature/humidity condition test: 60[degrees]C, 93 (+2/-3) %RH.

* Thermal cycling: 85[degrees]C for the high temperature, -40[degrees]C or -55[degrees]C for the low temperature; dwell time, heating and cooling rates to be determined.

* Ambient conditions: 20 to 25[degrees]C for room temperature, or 15 to 35[degrees]C, to be determined.

Work remains to establish the exact test protocol, although these conditions have been agreed to and identified as the basis for a full protocol of whisker test conditions, the groups said. The team will propose a test method to the International Electrotechnical Commission (iec.ch) by 2004.