In a message dated 2/12/01 8:07:09 AM, [log in to unmask] writes: JAMES: If immersion tin does whisker, wouldn't exposed traces (not solder pads) be a concern even after assembly? ROBERT: In my experiences tin "whiskering" of nonporous immersion white tin (IWT) ceases to be a theoretical possibility after assembly, as the greater mass of the solder alloy provided at assembly displaces the IWT. You can't find the IWT after proper assembly -- including pad edges -- as the matte nature of the IWT promotes whole-pad wetting (unlike OSP). JAMES: Is whisker growth a function of the environment or just time? ROBERT: In the case of IWT (versus electroplated tin), "whiskering" exists only as a theoretical possibility. Search the TechNet archives (and anywhere else); I assure you that you'll find not a single complaint about nonporous immersion white tin whiskering, irrespective of time or environment. JAMES: Could the tin in the immersion tin process be alloyed (with a small percent of something else) to prevent whisker growth? ROBERT: Whether you assemble with tin/lead, tin/silver, tin/bismuth or tin kryptonite, the IWT is alloyed by a large percentage of something else upon assembly. You've got a greater likelihood that the tin from your assembly solder will "whisker", but I'll leave that aspect to the abundant solder experts. - Robert Lazzara --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------