1/4 oz. is something that many shops have evaluated or may be using
     for "leading edge" technologies. Some difficult .004/.004" 
     technologies may have better yields utilizing this type of thin foil.
     Pricing-I'm finding that the cost (at this point in time) is much 
     higher. Availability is also an issue. Sometimes we must order large
     amounts to justify the "cut and tool to size" requirements.
     Handling is an issue. Some of it is available with a temporary
     carrier. (Peeled away after lamination) This is far beneficial than
     the loose thin foil.
     These foils are additionally available in 3/8 oz and 1/8 oz.
     Technology....hummm. I believe that with these thin foils that 
     image and develop become the gauging factor. (eg. <.005" technology
     is achievable) Other issues that become apparent are AOI resolution 
     and electrical test. (Electrical test when the parts have extremely
     high IO)
     Peel strength-You can anticipate a peel strength much less than 1/2
     oz. These thin foils have very low profile topology on the treated
     side and naturally yield low peel strengths. Rework/pads lifting off-
     I don't have any idea on that question. Maybe someone else can offer
     more input.
     
     If you would like to discuss further information, please feel free
     to email me direct.
     
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: 1/4 oz cu
Author:  [log in to unmask] at SMTPLINK-HADCO
Date:    12/6/95 10:20 AM


We have traditionally used 1/2 oz cu in our designs and are considering 1/4 
oz on some new designs (density issues).  Are any of you using 1/4 oz?  What 
min trace/clearance are you using.  In rework, do the pads lift off?  Any 
special concerns in manufacture??  Is cost greater/less than 1/2 oz?  Special 
handling problems? Etc etc etc???
     
Any input would be appreciated.
     
thanks
     
gary ...