I thought SAC use ramp-to-spike...not ramp-soak-spike...may be just silly me...jk -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Jason Gregory Sent: Thursday, October 13, 2005 5:05 PM To: [log in to unmask] Subject: Re: [TN] SAC reflow profile and flux vaporization Leo, I use a different mfr. of SAC305 but I stay in the 60-90 sec for the 150-170c part of the profile. It works great for me. 160 seems very excessive. Also, the 365 sec from ambient to reflow is long too. I stay with 4-4.5 min. (10 zone, 14 in. zone lengths at 32 ipm). If we find voiding at the 5DX, I slow to 31 or 30. Are they using ramp-to-spike or ramp-soak-spike? Jason Gregory Manufacturing Engineer Innova Electronics (281)653-5593 (281)653-5594 fax (281)212-0844 cell [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Leo Higgins Sent: Thursday, October 13, 2005 3:51 PM To: [log in to unmask] Subject: [TN] SAC reflow profile and flux vaporization Hello, I have a case where a customer may be running an inappropriate reflow profile for surface mounting on a board with and OSP pad finish. The time/temp features of the profile push up against every min or max in the recommended IPC reflow profile for SAC. The surface mount solder is Sn-3Ag-0.5Cu (Senju 705). The time from 150-200C is 160 seconds (seems way too long). The time from RT to peak is 365 sec. Time above 220C is 57 seconds. The solder shows wetting to the leadless contact on the package and to the board, but temp cycle life is much less than normal. Solder joint cross-sections show a atypically grainy structure and some show microvoids dispersed across the joint. Looks to me like the flux was vaporized before liquidus was reached, resulting in poor coalescence of solder particles, further aggravated by a low peak temp of 234-235C. The discussions about good SAC wetting on OSP needing 235-237C from Steve at ClearCube add further concerns. The solder joints were somewhat hour-glassed in cross-section so virtually all failures occurred through the waist of the solder joint, so the impact of poor wetting was not seen, but is not doubted. I think there are a number of possible problems with this profile. Any comments? Specifically do you think the 160 sec. from 150-200C could have vaporized most of the flux? Best regards, Leo Director of Applications Engineering ASAT, Inc. 3755 Capital of Texas Highway, Suite 100 Austin, Texas 78704 ph 512-383-4593 fx 512-383-1590 [log in to unmask] www.asat.com The information contained in this electronic message is CUSTOMER/SUPPLIER PRIVILEGED AND CONFIDENTIAL INFORMATION intended only for the use of the individual or entity named above. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution and copying of this communication is strictly prohibited. If you have received this communication in error, please immediately notify the sender by electronic mail. 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