Nicolas, If the paste looks good after printing and has not bridged or smeared after the parts are placed, the paste may be 'hot slumping' inside the reflow oven. You can test this by printing a board and then placing it into an oven at 100 deg C. for about 10 minutes. If the paste moves significantly, you have bad solder paste. Jim Kittel -----Original Message----- From: Nicolas Ortiz [mailto:[log in to unmask]] Sent: Tuesday, February 06, 2001 7:45 AM To: [log in to unmask] Subject: Re: [TN] QFP144 solder bridging Stencil is OK. No changes in design. Trevor Goddard To: [log in to unmask] <tgoddard@XLT cc: EK.COM> Subject: Re: [TN] QFP144 solder bridging Sent by: TechNet <[log in to unmask] ORG> 02/06/01 06:03 AM Please respond to "TechNet E-Mail Forum."; Please respond to Trevor Goddard Nicolas I have a couple of questions for you. Is this a new board or a new Rev of an existing product? Did you review the stencil design or did you actually have the stencil measured? I got caught one time when I was given a new Rev of an existing product. We had a couple of QFPs .20mm and a .50mm pitch that were shorting out like crazy, which was never a problem on the previous Rev. I questioned the guys that ordered the stencil and the layout guys about what specs the stencil was ordered to and if there had been a footprint changed. The answers to my questions was that nothing had changed, but I could still not fix the problem with process changes. Finally we were able to get the stencil measured and the pad sizes measured and found out that the apertures on some components were 100% of the pad size and another was a tiny bit bigger than pad size. My guess is, if nothing has changed in your manufacturing process i.e.. screen printing parameters, reflow profile and your placement is good than something may have changed in the design side. Trevor -----Original Message----- From: Nicolas Ortiz [mailto:[log in to unmask]] Sent: Monday, February 05, 2001 3:45 PM To: [log in to unmask] Subject: [TN] QFP144 solder bridging Currently we are experiencing solder bridging on a 0.5mm pitch, LQFP, 144 leads. I already reviewed the stencil design, screen printer parameters and reflow profile. Everything is OK. We have HASL boards. Our current process outputs 38 dpmo's. My concern is if I reduce more the apertures, I have the risk to have solder open or insufficient solder, instead of bridging. Does anybody has some input? What dpmo's do you have? ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------- ----- ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------- ----- ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------