I'm almost certain that the failure mechanism for this defect is the formation of gas bubbles during the electrolytic plating process, at the edge of the plating resist to clearance for the pad. The bubble prevents the complete tin plating of the exposed pad which when etched gets through to the substrate, hence the "perfect" circle formations that you see. To minimize the formation of the gas, is to ensure that the plating CD (current density) is correct for the process and area of board to be plated, and that suitable agitation/vibration is employed to jar these bubbles free. Colin McVean Production Manager Artetch Circuits Limited Tel: 01903 725365 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Matthew Lamkin Sent: 05 April 2005 08:29 To: [log in to unmask] Subject: Re: [TN] Strange marks on PTH pads... What causes them/how are they made? -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Judy Brown Sent: Monday, April 04, 2005 11:09 PM To: [log in to unmask] Subject: Re: [TN] Strange marks on PTH pads... They are commonly called mousebites. Yes I would reject them, especially if these pads are intended to have a fillet to the component lead, for less than minimum annular ring. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Stephen Gregory Sent: Monday, April 04, 2005 2:10 PM To: [log in to unmask] Subject: [TN] Strange marks on PTH pads... Hey All! Well, my Monday is just about to wind down... One of my Receiving Inspectors called me back to look at some fabs we just got in that had some strange looking marks on the PTH pads. They almost look like some sort of probe marks, but I would think that they would be pretty much in the same place if a fab was to have to be tested multiple times for whatever reason. You can see what I'm looking at. Go to: http://www.stevezeva.homestead.com and look at "Annular Ring 1-3". The marks are on the topside of the fab only, and they are at random places on the fabs. Anybody ever seen anything like this before? Would you accept them? If not, what would you reject them for? Kind regards, -Steve Gregory- Senior Process Engineer LaBarge Incorporated Tulsa, Oklahoma (918) 459-2285 (918) 459-2350 FAX __________________________________________________________________ This message may contain information that is privileged and confidential to LaBarge, Inc. It is for use only by the individual or entity named above. If you are not the intended recipient, you may not copy, use or deliver this message to anyone. 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