Lourdes,
From my experience with polyimide it can sure smear. Although, thanks to its higher Tg, the problem is not as severe as for FR-4 but it exists.
I've seen polyimide resin smear even on boards drilled with perfectly new drills.
Standard permanganate desmear can get rid of this smear in a similar manner as in FR-4.

Now, post separation is more complicated (and troubles many of us, manufacturers).
Post separation basically occurs as a result of faulty connection between the innerlayer and the PTH. It can be a result of either poor surface preparation or problem with the electroless. 
"Poor surface preparation" can, of course, mean many things - 
 - conditioner: some of the cleaner/conditioners are "film-forming" and over-conditioning can lead you to a situation where there is a weak interface between the innerlayer and the electroless copper.
- The activator (palladium, for example) can cause over-conditioning, too. Since these "layers" (conditioner film, activator...) between the hole wall and the electroless copper are supposed to be as thin as possible, the condition of "over-conditioning" is when there is an excess of material under the electroless. On the other hand - too small amount of these conditioner agents (under-conditioning) can result in poor copper coverage on the surface.

Another important factor (although I am in some debate over it with a colleague of mine) is the stresses induced on the PTH because of poor mechanical properties of the electroplated copper. 
Low ductility copper will do one of two things during the high z-expansion that happens at elevated temperatures:
- thin copper will result in corner/barrel cracking as a means of stress relief.
- Thick copper will separate from the hole wall, as the hole wall moves by thermal expansion.

It is important that the ductility of plated copper be >15%.


Good luck,
Yehuda Weisz



    ************************************* 
    *          Yehuda E. Weisz              
    *  e-mail: [log in to unmask]
    *  Tel: 972-3-6342045                    
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-----Original Message-----
From:   Lourdes Mertens [SMTP:[log in to unmask]]
Sent:    17 ôáøåàø, 1998 17:40
To:     [log in to unmask]
Subject:        [TN] Polyimide and BT material

1. Does Polyimide and BT laminate material smear?
2. What are the critical processes to watch out for when using polyimide
and BT materials to safeguard against post separation?

TIA,
Lourdes M.


--
Lourdes

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