Steve- Then is it electroless gold? Even if it is, I'm not seeing how you'd make gold slivers with it, but it can plate out on top of dielectrics if not controlled properly--so I could see independent particles which could drastically reduce breakdown voltage, but not slivers which could bridge a significant gap. Wayne -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Kelly Sent: Thursday, August 09, 2007 8:41 AM To: [log in to unmask] Subject: Re: [TN] Failed Flex Circuit Assembly Hi Wayne, The circuit is not pattern plated with gold - the gold plating is done after the kapton covercoats are laminated on. Regards Steve Kelly Steve Kelly PFC Flexible Circuits Limited PH: (416) 750-8433 Fax: (416) 750-0016 Cell: (416) 577-8433 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer Sent: Thursday, August 09, 2007 12:02 AM To: [log in to unmask] Subject: Re: [TN] Failed Flex Circuit Assembly Hi Steve! Sounds like your circuit may be pattern plated with the electroplated gold. This is a common way to get the slivers: The copper etchant undercuts the gold--actually, I've seen it eat the nickel a whole lot faster than eating the copper! If these are flaking off, you've got a fairly high voltage stress, so imagining a short isn't difficult. If the circuit is indeed pattern plated, then it's usually possible to either re-design with shorting features to plate the nickel and gold after solder masking or switch to electroless processes. But that, of course, is only speculation. I fully appreciate your frustration at not being able to replicate the problem. Wayne Thayer ________________________________ From: TechNet on behalf of Steve Kelly Sent: Wed 8/8/2007 5:05 PM To: [log in to unmask] Subject: [TN] Failed Flex Circuit Assembly Fellow Technetters, We have a problem with a field failure on a flex circuit we manufacture. This explanation is going to take a while so please bear with me. The flex problem area is between two wire bondable gold pads. The wire bond pads are approx. .008 wide with .006 between the pads. The stack from the top down is 50-75 microinches of soft gold, 150 microinches electroplated nickel, .0007 RA copper. .002 kapton, .0005 adhesive, .0005 kapton. After electroplating, the edge of the flex circuit where the wire bond pads are is die cut. We have noticed some slivers coming off from the die cutting (look like gold). The flex is electrically tested twice before shipment (test voltage is 250V). The flex then goes for die attach. After die attach another electrical test is performed. It then goes to the end customer who assembles it into the final box and does another electrical test. The box is then purged with nitrogen then sealed. After 5 months in the field (benign office environment) some channels on the die failed. Maximum voltage in the field is 190 volts. Our theory is that one of these slivers somehow propagated over between the wire bond pads and over time caused the short. And to make matters more complex when the flex cable assembly was removed from the box it worked. We have done SEM and EDS and do have some evidence of copper between the pads but the questions are a) can we grow some kind of whisker in this environment to cause this short b) why are only able to detect copper (no nickel or gold) c) anyone ever seen this before. Thanks in advance. Regards Steve Kelly Steve Kelly (416) 750-8433 (work) (416) 750-0016 (fax) (416) 577-8433 (cell) --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 15.0 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 15.0 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 15.0 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 -----------------------------------------------------