We have many customers who routinely use 50 micron dry film solder
mask. We are even supplying some customers 25 micron dry film solder
mask. The limiting factor is circuit height. Traditional pattern plating will
often produce high conductors requiring additional mask thickness. In
Japan the reason dry film mask works so well is for the most part they
are panel plating with conductor heights usually not exceeding 50-60
microns.

The other thing to consider is application of the dry film solder mask. We
have new applications that allow the mask to conform to circuitry more
efficiently than traditional dry film solder mask. A 50 micron film can
encapsulate what formally required a 100 micron dry film solder mask.

Bob Metcalf
Morton Electronic Materials

>>> Goldman, Patricia J. <[log in to unmask]> 10/30/96 11:24am >>>

Now, maybe I'm wrong here, but I do believe that 50 microns = 2 mils. 
That  doesn't seem very thin to me....  The problem I believe with
extremely thin  dry films is usually pinholes and some sort of  difficulty
with the carrier. 
 The other problem with a dry film solder mask is getting conformity over 
relatively high traces with a very thin film.  You may hear from some df 
solder mask people on this one.

There were some recent lengthy discussions on plugging vias.  Best go
to the  web site and browse on that subject.

Patty
 ----------
From: TechNet-request
To: TechNet
Subject: Relative issues concerning the tenting of vias
Date: Monday, October 28, 1996 11:12PM

As the industry heads towards a point where surface mount technology
and dense circuit topologies are the norm it becomes imperative to revisit
the issue of to tent or not to tent.
With liquid photoimageable solder masks still being an unreliable means of
providing a uniformly conformal coating over copper features, is dry film
the answer?  Have strides been made of late in this technology which
allay the inherent problems of process control, media thickness, and
contamination due to oily residue buildup and its subsequent promise of
sundry other problems such as delimitation?  Has MIL SPEC 2000 (is rev
C out yet?) acquiesced in the use of either the dry film or lpi tenting of
vias as an acceptable practice?
I have seen boards produced in the orient with dry film thicknesses as
small as 50 microns.  Are these available in the US or is their use
shunned as being too thin?  The suppliers I have spoken with cite
minimum thicknesses in the >1 mil range.  This lays bare other problems,
such as potential tomb stoning while providing the opposite benefit of
creating a solder well around SMT lands.  The latter stated benefit is of
dubious value if paste stencils and application coupled with fine tuned
temperature control bogs down production and outweighs the reliability
bonus, if any.
It is a confusing issue and all the literature I can find seems to be horribly
out of date (the latest being an excerpt from PC FAB magazine dated
1991.  I am reasonably certain things have progressed since then, but
where is the data?
If you have any insights into this well masked dilemma, I for one could
stand the relief. [log in to unmask]

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.       
*
***************************************************************************

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.       
*
***************************************************************************



***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************