We had a similar scenario where previously run lots that were good all of a sudden started exhibiting solderballs. The root cause was the soldermask wasn't properly cured and when the solder paste was deposited, it went under the mask and "solderballed" out during the reflow process. We were able to attribute this to a specific date code of the boards and return them to the board supplier. Jan Pelchat Benchmark Electronics Hudson Division ______________________________ Reply Separator _________________________________ Subject: Re: [TN] [Fwd: Solder-ball] Author: "Stephen R. Gregory" <[log in to unmask]> at 0UTG0ING Date: 11/10/98 4:11 PM In a message dated 11/10/98 11:30:36 AM Pacific Standard Time, briankoo@AQS- INC.COM writes: << Dear Technet users, I am experiencing some solder balls on some of PCBs' that we are assemblying now. We set the temperature according to recommended thermal profile based on Supermole which we are using to set first time processing board. Certain times, we do not see any solder balls for same PCB, but we are seeing solderballs that we ran last night. Mostly, balls are appear near capacitor location. We are contract manufacturer in San Jose. Please respond to my email. Thank you. Brian Koo >> Hello there Brian! Don't that kinda' stuff make ya' crazy? Set something up one day and it's running fine, come back in the next and everything goes to hell in a hand- basket! Makes ya' wonder sometimes don't it? Well, if you've been running this board before without any solderball problems, tells me that your stencil is okay, and if you've plotted the board with a supermole and the setpoints are the same on your oven as the settings when you plotted it, tells me that your profile is okay too. You didn't change paste either, and I'm assuming that nothing with the board has changed either...(just going down my list of variables here). About the only other variables that I can think of that might have an affect whether or not you'll solderball is: 1. Print deposition - Nobody's changed the squeegee blades on you have they? Going from plastic to metal squeegees you'll find that you print thicker paste...you don't have that scoop-out anymore. How about the wipe during the print stroke? Has that changed? If in the beginning the printer was set-up giving you a clean wipe and then the next set-up you maybe didn't have so clean a wipe might give you enough additional volume to cause a solderball or two. 2. You said that it was occuring on the capacitors, did the capacitor change? Maybe what had happened was that the capacitor reel ran out and the new reel changed to a thicker one on swing shift, which would cause the placement force to be greater than it was with the old ones. You might be on the razors edge as far as the volume of solder paste being printed and not get any solder balling, but when the paste gets squished out off the pads from too much placement force that'll give you solderballs too. This one's a "toughie"...to have something be running good for you and then go wacko is always a pain. Something has changed in between the time it was running good for you and now. It's just finding out what.... Hope this helps, -Steve Gregory- ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################