Hey - thanks for the insights!  I will keep my eyes open for the 15-20
oz copper jobs.



Jeffrey Bush
Director, Quality Assurance and Technical Support

                          76 Technology Drive - POB 1890
                             Brattleboro, Vermont 05302-1890
                                Tel. 802.257.4571.21 Fax. 802.257.0011
                                    [log in to unmask]
                              http://www.vtcircuits.com	



-----Original Message-----
From: r Tarzwell [mailto:[log in to unmask]] 
Sent: Monday, April 26, 2004 12:07 PM
To: [log in to unmask]
Subject: Re: [TN] Stack-up for 2 layer, 3oz. copper board


Hi Jeffrey but the bussines of heavy copper is definatly not lab stuff
at present there are 9-10 shops world wide doing about 22-30 million in
heavy copper and many more just starting, the etch factor in this type
of design with the very thin base copper is  nothing,  as your only
etching off the 1/8 -1/4 oz base copper the etcher is set at high speed
and run through.therefore the line resolution is a factor of dry film
resolution and plating factors. But the accuracy of 16 mils of dry film
would blow your socks off. And  it is correct the holes need to be
drilled bigger to allow for the extra plating, The 3 oz of plating in
the hole is very strong and the board can withstnd 10-20 solder cycles
and many thermal cycles. Typicaly 3 oz is not considerd heavy copper it
starts at 5-6 oz and goes to typicaly 15-20 oz . stripping is not to bad
with a pre dip in KOH. start to think way more outside the box , heavy
copper rules. robert Tarzwell

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