Yes - I think in the lab this is OK but copper over 5 oz is not commmon.
A good rule for thumb we use that the circuit pattern lines and spaces
are 3x the conductor thickness minimum to ensure proper line resolution
and management of etch factor - a 1:1 etch factor with a .0056"
conductor thickness requires a fair line size to start. I can see the
real trick to the .003"/.003" technology with 4 oz copper would
stripping the resist. Also the base adhesion of a line that is taller
than wide is a challenge.  My hat is off to those of you working with
this type of technology!      



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: robert Tarzwell [mailto:[log in to unmask]] 
Sent: Monday, April 26, 2004 9:47 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Mask over Tin/Lead...


HI Jeffry  but you can manufacture much better line resoultion then 15
mils in 3 oz of plated copper , using the method I stated even 3/3 is
possible, through my research we found thick dry film up to 20 mils,
produced almost as good a line resolution as thin 1.5 mil dry film did,
in fact I made many boards for IBM with 20 oz of plated copper at 10/10
technology. we started with thin base copper and in fact did not use a
tin protective  layer but just a quick etch as the 1/8 oz base copper
etched very quickly with no damage to the plated copper. The exposure
and developing is not tricky but does require a  bit of the "out of the
box" additude. robert Tarzwell  megadawn.com

---------------------------------------------------
Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for
additional information, or contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------