On 02:05 PM 8/10/2002 -0700, JaMi Smith said: >what are you saying and meaning when you speak of "unbalanced copper". > >first - to my knowledge we are not talking about 1/2 oz on one side and 1 oz >on the other side, which is does in fact cause uneven etching problems, but >that was not stated in the original post that I responded to, nd as far as I >know this is not the topic of this discussion. > >secondly - we are not talking about the "warpage" issue which I specifically >excluded. > >all that taken into consideration, given the proper circulation of the >etchant (which includes removal of the etched copper now in solution), >copper is copper, and etchant is etchant, and a specific etchant will remove >a specific thickness of copper in a given period of time, irrespective of >whether we are talking about a 1/4 sqiare inch area or a 10 square inch >area.
Jami, Chemistry is not one dimensional. It takes longer to etch a few microns off a large area of copper than it does a small area. 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. 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). 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.)" If you want to continue the discussion I suggest you make contact with a number of PCB makers and speak to their process engineers first. Ian Wilson * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 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 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
