Guy, I'm assuming you are talking about rework. (why else would you use a micro stencil?). The complaint with flux only seems to center around loosing the additional solder volume. However, with BGA's, you do not need to flatten the pads; just make them level. HASL boards work fine for BGA's, so why not leave the BGA site "HASL"ed. That way, the 2.5 mils of solder people complain is missing by not using solder paste will still be there. This leveling can be done with a flat bar iron. (You have to touch the pads with an iron anyway. Just get rid of the braided copper wick.) Since the balls are eutectic, the collapse will take care of minor pad height differences. (Don't try this with high temp solder balls). Personally, I have found that the resulting standoff on a BGA varies significantly on any given BGA, especially PBGA. So any difference the 2.5 mils of solder would contribute gets lost in the noise. BTW, I did do a case study comparing "flux only" attached BGA's at rework against "solder paste" attached BGA's and temp cycled the parts and found no significant difference. Kind Regards Ryan Grant Advanced Technology Engineer MCMS (208) 898-1145 [log in to unmask] > -----Original Message----- > From: Guy Ramsey [SMTP:[log in to unmask]] > Sent: Friday, September 07, 2001 11:26 AM > To: [log in to unmask] > Subject: [TN] Paste verses tacky flux > > Anyone out there with data, case study, anecdotal evidence, strong > opinions, relative to installation of PBGA components (with eutectic > solder balls of course) using micro stencil and solder paste verses tacky > flux. > > Guy Ramsey > Senior Lab Technician / Instructor > > > E-Mail: [log in to unmask] <mailto:[log in to unmask]> > Ph: (610) 362-1200 x107 > Fax: (610) 362-1290 > > --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------