1)  Historically, the "red" or "brown" oxide were developed in part to use
on polyimide materials, since the very long crystalline structure of the
"black" oxide leads to fracturing because of lap shear stress induced
when the panel cools after the relatively high laminationand post-bake
temperatures used with polyimide.  The only real difference between
"red" oxide and "black" oxide is in the concentrations of the caustic and
oxidizer; the actual chemicals are the same.  A reduced oxide also works
just fine for polyimide, as long as you are using a reduced "red" or
"brown" oxide formulation.

2)  Despite what an earlier posting has said, although permanganate
(when used in conjunction with a sweller, either a butyl-caustic or a
pyrol-type) works VERY well for conventional polyimide, the MDA-free
polyimides are not attacked very well by a permanganate process.  If
etchback is required, it will be almost mandatory to use a plasma.  It is
common to follow plasma with permanganate to get the surface
microroughening that plasma has difficulty in providing.

3)  SEMs will be required to verify roughening of the resin.  Once again,
topography will be a real challenge if using MDA-free polyimide.

Fred J.

>>> Deron Pirie <[log in to unmask]> 05/25/98 09:08am >>>
        can anyone help me please, i have some questions concerning
polyimide pcbs :-

1/ what type of inner layer oxidation is recommended / suitable for
polyimide e.g. black, brown, red, reduced etc. ?

2/ what type of hole desmear is recommended / suitable for polyimide ?

3/ we have produced some trial pcbs and are getting slight hole wall
pullaway - any ideas as to what might be causing this ?

best regards, deron pirie.

Deron Pirie
Irlandus Circuits Ltd.

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