Ian, please see below
> --- In [EMAIL PROTECTED], "Ian Wilson" > <[EMAIL PROTECTED]> wrote: > On 02:05 PM 8/10/2002 -0700, JaMi Smith said: > snip > Chemistry is not one dimensional. Agreed > . . . It takes longer to etch a few > microns > off a large area of copper than it does a small area. Granted, but not monumentially as everyone would imply. > . . . Balanced > copper as > being discussed is a general even density across the design. It has > been a > standard desire by almost all board houses I have spoken to over the > last > 20 years that I have been doing boards. > While I will agree that almost all board houses request a balanced copper design, they almost unanomously do so for other reasons, and not this reason. In over 35 years of doing boards I cannot remember ever having had one board house bring up this issue in the context now being argued. > We have a company in this country that does very high end work. The > do > their etch on 2 micron copper plated boards (plasma plating is one of > their > first steps). This very fine layer means very tight edge control and > under > etch etc (they will do 2 mil tracks as a special and padsless-vias I > think). When issues such as line width, edge control, undercut, etc., are important in a design, they must be specifically specified, and then your board house will get into working out the details with you, but in the absence of specific stated requirements, nothing that we have discussed would go beyond standard tolerancing issues, and create a problem of the magnatude that everyone is implying. > > I refer you to their capability page: > http://www.lintek.com.au/boa.htm > > Note the text "(Tolerance on track widths is +- 0.008mm or better > depending > on the design and uniformity of copper distribution.)" > Please note that they state "uniformity of copper distribution", which in most instances means the uniformity of copper thickness across the surface of the board, which is at least as big a problem as the one that we are discussing. JaMi * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 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/proteledaforum@techservinc.com * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
