Joe G Malley@MACDERMID
11/29/99 11:11 AM
Hi Brian,

Sorry for the delayed response but I was away from all things electronic
over the Thankgiving holidays.

The disadvantages to pulse plating technology tend to be mainly confined to
equipment issues.  For example:

-  Periodic pulse reverse rectifiers are more expensive than traditional DC
units.  This impacts the initial cost but the time to payback can be short
because of the increased productivity that is possible.
-  Some DC tank configurations are not suitable for pulse plating and will
require tank modifications.  We have to be concerned with inductance when
we pulse plate so bussing and cable connections are important.  Also the
distance form the rectifier to the plating tank will have some limitations.

The advantages to using a PPR process can be substantial:

-  Reduced plating time (increased production capacity) because of more
uniform throwing power.  The benefit of PPR becomes more pronounced as the
board thickness and aspect ratio increases.
-  Much improved throwing power on microvias.
-  Some improvements can be made with reducing the overplating on isolated
circuit areas

There was some discussion in the group that the rectifiers are difficult to
set up for this process.  I tend to disagree with this as we have certain
standard cycles that work well for specific types of products.  For
example, there may be one cycle for standard work (aspect ratio < 6:1),
another for higher aspect ratios (> 6:1), and one additional cycle for
microvia work.  On the commercially available rectifiers these cycles can
be pre-programmed allowing you to just call up the proper menu item for
your panel type.  It's as simple as that.

In regards to your question about a 15:1 aspect ratio the throwing power
you would get would also depend on the panel thickness.  The additive
system used would also have influence your results.  To give an example
from the system with which we are familiar, for a 3.2mm (0.125") thick
panel with an 0.2mm (0.008") hole you could expect to get about 60 - 70%
throw when plating at 3.5 ASD (32ASF).  Plating at a lower current density
would improve this number.

If you want additional information you can contact me directly at the
E-mail below.

Joe Malley
Research Manager
MacDermid Inc.
(203) 575-7921  phone
(203) 575-7916  fax
[log in to unmask]  E-mail





brian carlson <[log in to unmask]> on 11/24/99 11:18:55 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
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cc:    (bcc: Joe G Malley/MacDermid/MACDERMID/US)

Subject:  [TN] Pulse plating




Technet,

   Can someone give me an insight on benefits or possible disadvantages to
pulse plating. I am interested to hear some stories of what happens to the
Cu thickness in the hole wall when aspects ratios increase to 15:1. Any
feedback is welcome.

Rgds,
Brian



Brian Carlson
Technical Support Engineer
Yamamoto Mfg. (USA), Inc.

(408)944-8368 (Office)
(800)514-6246 (Pager)
(408)944-1361 (Fax)

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