It seems that finding after the fact cracked ceramic Caps is a chore. The emphasis should be put on avoidance. This subject was talked about before. One of the main avoidance steps is to lay the length of the caps perpendicular to the length of the board. Ramon -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory Sent: Tuesday, June 06, 2006 10:03 AM To: [log in to unmask] Subject: Re: [TN] Finding cracked capacitors, fix the issue Good Morning Werner, You bring up an interesting point about wave soldered capacitors that reminds me of something that I seen on a board long ago. All the passive bottomside pads were thinner than the terminations of the components. Like this: ________________________ | | | | ___________| | | |_________ | | | CAPACITOR | | | | PAD | | | | PAD | |___________| | | |_________| | | | | |___|________________|___| Would this type of layout give a more reliable connection? I've only seen it one time, and I imagine that if it were more reliable, everybody would be doing it by now. But like I said, I've only seen it once and it was probably 10-12 years ago. I wonder if they were experimenting to try and solve a capacitor cracking problem? -Steve Gregory- -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier Sent: Tuesday, June 06, 2006 8:45 AM To: [log in to unmask] Subject: Re: [TN] Finding cracked capacitors, fix the issue Hi Ioan, The keywords are your addition to the Subject Line: "Fix the Issue." Unfortunately, the way chip components are solder-attached to PCBs harks back to the requirements for wave soldering-you need large PCB soldering pads that can be touched by the liquid solder wave for heat and material transfer. The consequence of this are large solder fillets and very thin solder joint gaps between the CC and the PCB. The large solder fillets act like the jaws of a vice both during cooling from the soldering process and during any kind of PCB flexure, thus putting the CCs under a lot of stress; the thin solder gaps provide no compliance for the solder attachment, thus reducing the capability of the SJs to absorb some of the deflection/warpage deformation as well as thermal cyclic loads. The large fillet/thin SJ gap geometry is about as bad an attachment scenario as you can imagine. This is explained in more detail in my Reliability Column in Global SMT & Packaging magazine, "Lead-Free (LF) Wave-Soldering: Can (Should) It Be Eliminated," Global SMT & Packaging, Vol. 5, No. 9, October 2005, pp. 46-50. As I pointed out in my column, the solder attachment geometry can be dramatically improved if one uses reflow rather than wave soldering. This not only essentially eliminates CC cracking, but has a number of other advantages as well, particularly with lead-free soldering. The soldering pads need to be only the size of the termination, eliminating the fillets and increasing the SJ gap between CC and PCB. Werner --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------