I have found mouse bites on inner layers related to contaminated circuits. I am assuming you are talking about a "print and etch" application. I also assume the mousebite is circular and are on the edge of traces. I also assume that there are no full opens involved. The mouse-bites look like the edge of a circle or of a bubble. If these assumptions are wrong please disregard the following. One type of mousebite occurs typically by a droplet that contaminates a small area of the copper before resist lamination. The resist does not properly bond to the base copper at that spot and areas were the image bisects the contaminate will have very slight degree of resist lifting during developing or etching. The enchant undercuts the resist and the classic circular mousebite appears. Another type of mouse bite is cause by contamination on the resit laminated boards before or after developing. If a droplet of stripping or developing solution lands on the surface of the resist it can slowly attack the resist causing it to swell and lift off the copper. Look for the mousebites before developing, etching and again before stripping the resist. They will typically be a lighter color, circular and of correct size. The size of the circle may be an indicator of the source of the contaminat. The condition of lifted resist may indicate the cause of the lifting. New developing solutions may cause the "foot" of the resist to be weaker allowing this condition to occur. Check the break point, temperature and the ph of the developer solution. The same applies for the etcher check; the break point, pH and temp. Eliminate the source of contamination. Cleaning and drying of the laminate before resist lamination needs to be reviewed. I had a pumice scrubber once that sprayed a very fine mist that contaminated cleaned boards that were drying near by and produced random mousebites. Note: New developer solutions may attack resist also but I would expect that the defects include wide line width reduction and opens. A picture would be useful. PR -----Original Message----- From: Franklin D Asbell [mailto:[log in to unmask]] Sent: Friday, March 28, 2003 9:55 AM To: [log in to unmask] Subject: [TN] Mousebites on innerlayers What would cause 'mousebite' appearing defects along the edges of innerlayers? We've started seeing them on one lot, about 75% of 30 layers. There are about 5 or 6 on an 16X21 size layer, extending across the trace almost to 90% plus... Any thoughts would be appreciated. Franklin --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------