On Tue, 8 Oct 2002 11:18:07 -0700, you wrote: >Some boardhouses may still "dip" or submerge the board into an "etchant >tank", where the board simply sits in the etchant, however, there should be >enough "agitation" or "circulation" of the etchant to prevent what they are >describing from happening.
Nothing you can do will eliminate the problem, just hope to reduce the effects. A lot of copper in one area of the PCB will take longer to etch resulting in over etching (undercutting) in areas with less copper. The board house can't afford to over etch because some tracks will undercut unacceptably (or even completely and fall off the board), under etching risks leaving shorts in the dense areas. You are giving them process control and yield problems seems reasonable they want you to pay extra. Before the etching problem there is a similar problem with plating. Need 100A for the copper on one side of the board and 5A for the other - how do you arrange that? I think the only thing they can do is fiddle around with anode spacing on each side of the board to try to balance it a bit. They can't plate at 100A anyway because it puts too much current through the sparse areas and leaves the tracks with an uneven 'frazzled' appearance. Again you are giving them process control and yield problems and slowing them down. Cheers, Terry. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/[email protected] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
