Matthew, Are these capacitors being wave or reflow soldered? Assume wave soldered if assembly dept is asking for reduction in pad width. Some have found that reduced pad widths are better for their process. Check out http://www.kemet.com/kemet/web/homepage/kechome.nsf/vapubfilesname/F3102Fce.PDF/$file/F3102Fce.PDF . (I hope the link works.) Here a mfgr has a pad width for wave soldering at about 70% of the width for reflow soldering. Also, if wave soldering, is the dwell time too long in the wave? Preheat cycle too short? Parts along board edges or near connectors perpendicular to board surface? Rough handling? Same type of part failing each time? Here's a question for everybody: IPC-SM-782A has reduced width pad geometries for resistors, but not capacitors. Back in unused portion of brain a memory keeps saying that the no-rev version of SM-782 had reduced width for res-s and caps. Anybody care to comment? Any reason for the change (if it really was so)? Roger M. Stoops, C.I.D., PCB Designer Trimble Engineering and Construction Division 5475 Kellenburger Rd. Dayton, OH 45424-1099 USA Ph: +01 937.233.8921 or +01 937.233.4574 ext 288 Fax: +01 937.233.7511 Matthew Lamkin <matthew.lamkin@PROTEC-FIRE-DETECTI To: [log in to unmask] ON.PLC.UK> cc: Sent by: DesignerCouncil Subject: [DC] Capacitor pad reduction ? <[log in to unmask]> 08/27/01 10:09 AM Please respond to "(Designers Council Forum)"; Please respond to Matthew Lamkin Hello everyone, I wonder if I can tap into your experience of cracking of ceramic capacitors. I have a situation where the shop floor are having problems with cracked capacitors, due to several possible causes. However, the blame for the problem is being thrown at design with an instruction to reduce the width of the pads (1206/0805/0603 caps only) to be less than the width of the component. Now there are many documents out there advocating using the IPC SM-782-A pads, and many that advocate reducing the pads. However, I have the IPC specs which give me actual dimensions to follow whereas the documents that advocate reduced pad widths do not. Can anyone give me some advice on what size these pads should be when reduced to prevent MLCC cracking? Can anyone supply a URL of a document that gives any good information on this? I have many documents from AVX/SYFER etc on the subject but they do not quote any figures on reducing the width. Thankyou - Matthew Lamkin Protec Fire Detection PLC. England, U.K., Planet Earth. P.S. Come on Steve, I'm timing you now, to see how long it takes until you quote a website....he, he.... --------------------------------------------------------------------------------- DesignerCouncil 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 DesignerCouncil. To set a vacation stop for delivery of DesignerCouncil send: SET DesignerCouncil 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 --------------------------------------------------------------------------------- --------------------------------------------------------------------------------- DesignerCouncil 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 DesignerCouncil. To set a vacation stop for delivery of DesignerCouncil send: SET DesignerCouncil 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 ---------------------------------------------------------------------------------