Hi, Peter, I was at a seminar earlier this year where BGA's and their solder joints were discussed at some length. The received wisdom is that voids in solder joints are not of themselves a 'defect' unless they break out through the side of the ball. In fact, they make the joint more "flexible" - better able to withstand creep fatigue - so are beneficial, up to a point. What causes them is often outgassing of volatiles in the solder paste flux during the reflow process, though the size and shape of voids increases and changes when there are via-in-pad features as well. About the only way to detect them is by X-ray, and to judge from previous TechNet postings, there are some pretty fancy machines around now that can give you a very much clearer view of the balls than is normally the case ... if you have cash to splash! Peter Duncan Peter Lee <ppwlee@YAHOO To: [log in to unmask] .COM> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Sent by: Aero/ST Group) TechNet Subject: [TN] BGA voids <[log in to unmask] ORG> 11/16/01 04:25 PM Please respond to "TechNet E-Mail Forum." Hello, I am encountering voids after reflow on several micro BGAs on one PCA product. The voids that I $B!G (Bve observed (with Xray) contribute to as high as 60-70% of the joint area. My reflow profile was designed by running a sample board with dummy components and thermalcouples attached right at the joint. I also inspected the PCB lands and didn $B!G (Bt see any via on pad. Does anyone know the possible reasons for voids formation in BGA (micro) reflow? In general, in step by step how would one trouble shoot such a defect? Rgds, Peter [This e-mail is confidential and may also be privileged. If you are not the intended recipient, please delete it and notify us immediately; you should not copy or use it for any purpose, nor disclose its contents to any other person. Thank you.] --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------