Another interesting aspect of the ED process is that the number of steps
can be significantly reduced compare to traditional and it can be
automatised .. 
One could do Electroless + panel plating + ED resist coating on the same
line without touching the boards. This could mean significant reduction in
the number of steps as well as shorting the production cycle. Also, one
might want to do innerlayers with ED, and disgard all the dry film
laminators etc.. -> leading to less equipment needed etc.. 

As per Patricia information, you could be concerned with non-plated holes..
and you right. Experience showed us that regular exposing machines could
expose inside of holes if necessary in working on one side and using
aluminium reflectif material on the other side. 

Generally speaking, UV exposure is a key issue and good equipment is
necessary as exposure time is important as well as even exposure over the
entire surface.

Regards

Roland

----------
> From: Goldman, Patricia J. <[log in to unmask]>
> To: TechNet <[log in to unmask]>; yuanl <[log in to unmask]>
> Subject: RE: What is ED?
> Date: lundi, 2. juin 1997 17:20
> 
> 
> ED stands for "electro-deposited" and they were most likely talking about

> electrophoretic photoresist.  ED photoresists are deposited onto a
(usually) 
> copper surface using an electric current, much like electroplating. 
There 
> are both anodic and cathodic systems (where the copper surface acts as 
> either the anode or cathode), and both positive-acting and
negative-acting 
> (imaging) formulations.
> 
> An advantage to these types of resists is the ability to conformally coat

> all of the copper surfaces, including hole walls and other 3-dimensional 
> features.  The resists are generally coated to a thickness of 0.2-0.3
mils 
> (after drying), so it is clear that very fine feature definition is 
> possible.  The best applications appear to be 1) very fine feature 
> innerlayers with vias, 2) as a final etch resist after panel copper
plate, 
> and 3) on 3-D circuit boards, and 4) other, probably non-PWB
applications. 
>  On the other hand, these resists are not suitable for full copper
plating, 
> as the copper would overplate over the thin resist.
> 
> While it is true that ED resists have had some failures, there have also 
> been success stories, and there is new technology available that works
very 
> well.  The most interest in the market place has been for a
positive-acting 
> system, because small vias can be coated but do not need to be imaged in 
> order to remain protected during subsequent etching (or plating) steps. 
>  This eliminates the concern of getting enough UV energy in high aspect 
> ratio holes to insure cross-linking (hardening) of the resist, since 
> positive resists are already cross-linked and "un-crosslink" during UV 
> exposure.
> 
> I hope this helps your understanding.
> 
> Patty Goldman
> PPG Industries, Inc.
> (yes, we supply this type of photoresist)
>  ----------
> From: yuanl
> To: TechNet
> Subject: What is ED?
> Date: Friday, May 30, 1997 11:50AM
> 
> 
> 
>   Sometime ago, a PCB manufacturer gave a presentation and talked about
"ED" 
> 
>   technology while unfortunately I was not present. People in the
>   presentation are still not clear what ED is and asked for my help. I am

> not
>   a PCB expert either. I tried to find something on the net w/o luck.
> 
>   Is ED a new resist technology? What are the conventional technologies?
>   Could someone on the net offer some insights or some references?
> 
>   Yuan Li
>   Exabyte
> 
>
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