Hi Steve! There are a couple of possible causes for having a blue tint on a solder joint and most of them relate to the oxide condition. I have seen various cleaning systems (terpene, soaps, alcohols, etc.) stain the tin/lead oxide surface leaving a non-shiny, cosmetic appearance change - very similar in appearance to a thin oil film oil on water. A second possible cause is surface etching of the solder joint by the cleaning chemistry. I have some wonderful pictures of solder joints on an assembly which underwent a dozen passes (yes a dozen and don't ask why!) through an aqueous cleaning system using soap saponifier - the joints are purple! (we called them "Barney boards"). The multiple cleaning passes resulted in an etching of the tin on the solder fillets leaving a heavy lead oxide - I used SERA testing and microsectioning to verify the oxide changes. The solder joints were very purple and very reliable. There have also been some industry reports/investigations which discuss a visual solder joint appearance change due to overall solder joint surface texture (e.g. when solder joints get rough they look different). Hope this helps. Dave Hillman Rockwell Collins [log in to unmask] --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------