Dear All, I have seen a few SMT chip resistors images showing a layer of solder between the component termination and the PCB pad (the termination and the pad don't seem to touch at any point). I wonder why this is possible (the suraface tension and the chip weight should force the chip to come into contact with the pad)? Is it because 1) bubbles trapped between pad and component, 2)uneven termination and pad creating contact points, 3)solder trapped under chip, 4)needle-like intermetallics form during reflow, 5) flux residual, etc etc. I am sure somebody out there has a convinving answer! Regards, Hua BTW: Solder fillets of these resistors all have concave shape. --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------