======== Original Message ======== Sender: [log in to unmask] Received: from simon.ipc.org (IPC.ORG [168.113.24.64]) by arl-img-5.compuserve.com (8.6.10/5.950515) id UAA09081; Wed, 8 May 1996 20:06:27 -0400 Received: from ipc.org by simon.ipc.org via SMTP (940816.SGI.8.6.9/940406.SGI) id TAA10790; Wed, 8 May 1996 19:05:24 -0700 Resent-Date: Wed, 8 May 1996 19:05:24 -0700 Received: by ipc.org (Smail3.1.28.1 #2) id m0uHFyK-0000FrC; Wed, 8 May 96 15:36 CDT Resent-Sender: [log in to unmask] Old-Return-Path: <[log in to unmask]> From: [log in to unmask] Date: Wed, 8 May 1996 16:42:40 -0400 Message-ID: <[log in to unmask]> To: [log in to unmask] Subject: Fab:Re: Breakout at innerconnect Resent-Message-ID: <"QtwGI.0.SvD.DNGan"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/3953 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask] Eugenio We all have had for many years a gut feeling that breakouts at the internal connection between the hole and the conductor is bad/bad/bad. IPC-RB-276 restricts the breakout at this point on Class 3 but is silent on Class 1 and 2. We who have manufactured boards know that in the complex board unless the lands are elongated or pear shaped the likelyhood of breakout at these points are not infrequent. I have done failure-cause on many that did have via breakouts at the interconnect and have not seen a failure related to the interconnect that occurred at a breakout unless other holes without breakout exhibited the same failure mode. Their does not seem to be a published analysis on the subject where a good DOE was done and statisically evaluated. Most testing that I am aware of appears to be random short quick-looks and move on. I have heard that in some recent evaluations by the post separation group that the innerconnects that did not have an annular ring (landless vias) were better than those that did. The Military Specification MIL-P-55110 does not allow breakout at the innerconnect; however, the coupon called for testing this on the internal layer does not have internal connections at the holes; therefore, is not directly evaluated but is secondarily determined by annular ring measurement. . The landless via is being increasing used with good results and will probably be the way of the future. If any of the other subsribers have though on breakouts at internal interconnects please log on. Phil Hinton [log in to unmask] ======== Fwd by: Tony King / N ======== Phil, When we as manufacturers finally look at where we have come, what the various specifications require to build "acceptable" product and where the future technology seems to be going, we wonder how in the world we got here. Its another case of "you cant get here from there", or so it seems. We have specifications arise which REQUIRE etchback to guarantee product integrity for example, but gradually it is realized that desmear works just as well, after all you dont need to build a tank to drive down the street, a car works just as well. The controversy over pink ring, aesthetics or defective. How much product was scrapped over the years on the possibility that pink ring was a defect or indicator of a possible process problem... We now look at the driving force to reduce pad size to free valuable design real estate yet maintain the same annular ring specifications imposed on previous designs. Padless vias ??? Is it now time to step back and look at our "progress" over the years ??? Look back to multi wire product, a system of manufacture used for years and still in use where thin wire is laminated into multiple layers and then drilled. Landless vias... how far have we come and where are we going... Tony King Elexsys International 603-886-0066