Does AP 9121 necessarily mean Dupont pyralux material? I saw on the dupont datasheet that you could order this material As ED but my fabricator assures me that they used RA material. My fabricator says he can remove the coverlay with a CO2 laser. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Chuck Brummer Sent: Friday, May 15, 2009 10:17 AM To: [log in to unmask] Subject: Re: [TN] FLEX question Guys, AP 9121 1 ox copper is not automatically RA, we purchase it as ED all the time. Even then it should not be that sensitive. Plating plays a big roll in the propensity to crack. You can open up the polyimide by Plasma etching but there are draw-backs to that and you probably don't have a plasma etcher. There are several wet etch methods as well but unless you have a pretty good tech for this type of thing I suggest you stay with either the dremmel tool or sand blasting using aluminum oxide and the pen type system. I know of two, both made here in the San Fernando Valley. If you are looking for cracks look for ripples in the traces. We have found cracks next to stress in the copper that can look like waves. more later, Chuck Brummer 3M Manufacturing Engineer 8357 Canoga Ave. Canoga Park, CA 91304-2605 (818) 734-4930 Werner Engelmaier /* <[log in to unmask]> Sent by: TechNet <[log in to unmask]> 05/14/2009 06:29 PM Please respond to TechNet E-Mail Forum <[log in to unmask]>; Please respond to [log in to unmask] To [log in to unmask] cc Subject Re: [TN] FLEX question Hi John, Unfortunately, you do not give us an adequate picture of the situation. Missing: 1) 2-mil core thickness, the critical dimension is 1/2 of core plus 2x1.4 mils=2.4 mils [not exactly small]; 2) bend radius, approximately .35 inches could be an average with minimum much smaller depending on who and how the bend is made; 3) fracture location is not clear, open is about in the middle of the flexible section?does that mean half-way between the stiffener and the connector? 4) any cracks in the 17-mil wide traces? 5) While you say the CU is rolled annealed, have you confirmed the anealing?if not annealed the ductility in the rolling direction will be significantly larger than X-rolling direction?you can tell be etched x-sections showing needle-like grains in the rolling direction; Obvious: 1) Crack propagation being roughly equal, the 8-mil trace will show an open first; 2) if not fully annealed, rolled Cu direction should be along flexed leg. Werner -----Original Message----- From: John Foster <[log in to unmask]> To: [log in to unmask] Sent: Thu, 14 May 2009 8:52 pm Subject: [TN] FLEX question I was hoping I could get some input on a problem we are having with a flex circuit. I have a 2 layer flex circuit that is shaped like a L. one leg is about 5 inches long the other leg is about 4 inches long At the corner of the L is a stiffener on both sides. The stiffener extends into both L sections a very small amount about=2 0.3 inches. Both ends of the flex have Omnetics connectors which are designed to be soldered onto flex circuits. The A28300 series. Some of the traces are 17 mils wide and some are 8 mils wide. The traces are spaced fairly evenly across the flex and are spaced like the omnetics connector which means you can't see through the circuit as the traces overlap from side to side. One section of the L flexs the other section is stationary. The bend radius for the flexible section is approximately .35 inches ( I am not positive of this number and will find out tomorrow but I know it is far more the 6X of the thickness). The flex is constructed as follows The core is AP-9121 with 1 oz copper on both sides. The coverlays are LF-0110 The adhesive for the stiffener is LF-0200 And the stiffeners are .028 FR-4 The edges of the stiffeners are beaded with emerson & cummings ecobond. I have spoken with the fabricator and they assure me that the copper is roll annealed and not electro deposited. The flex circuit has failed after less than 1000 cycles. The cycles are very slow and maybe 10 or 20 per day. The current going through the traces is very low on the order of 10 mA. We have had two circuits fail and they both have failed on the 8 mil traces. I have scraped the coverlay off of the flex and have concluded that the open is about in the middle of the flexible section but I can't see it. I would have expected to see an open at the=2 0end of the coverlay as I have seen this before. We have been potting the connectors to move the stress point from the omnetics connector pins to further down the flex past the end of the coverlay. I have a couple of questions. 1. Is there a way to remove the coverlay without using mechanical means I fear that I could screw up the sample by scraping it with a razor. 2. Does this surprise anyone that it would fail this soon with a bend radius that I know is large and only a 2 mil core? The flex has been removed many times from the system and reinstalled and I am still having a hard time convincing people that flex circuits must be treated with care. i.e. can't be laid on benches and smashed. Tomorrow I will get to get into the system and see the mechanicals but the mechys assure me that at no time is the flex stretched to the point of pulling the bend radius down. I soldered a wire onto the connector and ran a needle up and down the scraped flex and it sure seems as though it opens about in the middle of the flexible section. Anyway any input will be appreciated Thank you --------------------------------------------------- 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 Techn et 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 -----------------------------------------------------