Take me off distribution. You have the wrong Michael Patterson -----Original Message----- From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Denny Cantwell Sent: Monday, September 13, 2004 12:53 PM To: [log in to unmask] Subject: Re: [IPC-600-6012] Etchback Question Tino et el, There was a study conducted by Dwayne Poteet of Texas Instruments (and his crew) regarding the reliability of "etchback (positive)", smear removal only, and "negative etchback"---back in 1982 when the committee's were working on MIL-P-55110, MIL-P-50884, MIL-STD-275 and MIL-STD-2118. The studies may not be available after all of this time, but from memory, all of the conditions listed passed the <10% max increase in resistance when subjected to Thermal Shock per IPC-TM-650 Method 2.6.7.2 for 100 cycles. The "negative etchback" of .0005"(0.013mm) allowance was also established at that time. The thought process was that if the copper interface was clean enough to etch negatively from the "as-drilled" condition, it was also clean enough to electroplate reliably. These values were in all of the above referenced specs and continued in MIL-PRF-55110F (PAGE 11) PARA A.3.6.5, A.3.6.5.1, A.3.6.5.1.1, and A.3.6.5.2 plus the others that I don't have on hand. If, as you state, that the end customer is a military org., then the parts produced had to have had coupons on the panels. If you propose to the customer, or the military end user, that the "D-portion" of the coupon be subjected to Thermal Shock per above for 100 minimum cycles, or 400 cycles, or even to destruction, then you should be able to establish a "reliability-factor" that will satisfy everyone. The "functionality" of the device would thus be established independently of a "visual" determination of where and how much etchback is present in the "A/B" coupons used for microsectioning. Regards, Dennis J. Cantwell Q.A. Mgr./R & D Liaison Printed Circuits, Inc. 1200 West 96th Street Minneapolis, MN 55431-2699 952-888-7900 [log in to unmask] -----Original Message----- From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Constantino J. Gonzalez Sent: Monday, September 13, 2004 11:59 AM To: [log in to unmask] Subject: [IPC-600-6012] Etchback Question Hello help.... My question is, do you have any knowledge of any studies having been performed regarding reliability of ethchback vs. non, or low etchback on innerconnect joints of polyimide PWBs? My customer is asupplier for an aerospace company, and the issue is that they recently have found through microsection analysis that some boards they have already installed in a vehicle are suspect, with regards to etchback. I am looking for supporting documentation to disposition the boards. Our requirement is for etchback per 6012 CL III, but I don't believe they are necessarily un-usable. The sections are otherwise structurally sound, no post or plating sep, 1oz and greater conductors, etc. As always, I appreciate any info you might be able to pass on. Regards, Tino Gonzalez