Hi,
Based on our thermal cycle testing, generally flash plating does not
improve reliability. Improperly applied, however, it can significantly
reduce reliability. The problem appears to be that this is an extra
process step that is usually not needed and can, like any other process
step, be screwed up.
If the flash plating is a normal part of the process, by that I mean it
is a planned part of the process flow, a process that has been
engineered, and is monitored and maintained as such, it may work well.
We see some companies using a panel plating step in conjunction with
pattern plating to improve line resolution through imaging and etching,
or in conjunction with microvia processing. On cross section this may
look like a copper flash but it is a engineer process step done for a
specific reason and tends to be reliable.
If the flash is a band aid, a second process step, possibly to prevent
voids, it usually is a reliability liability. Frequently we see a copper
flash that includes a second electroless plating step and we find that
this is usually a bad idea, from a reliability point of view.
I notice that some companies in Japan have a double plating step where
the first electrolytic plate is a micro-throw (high throw) bath followed
by a macro-throw (leveling) bath. This double plating process, with two
different electrolytic brightener systems is usually reliable. Most
companies that produce reliable PWBs do not include flash plating, they
do it once, they do it right and in the process save time and money and
have improved reliability to boot. Companies that just run the board
down the line twice, or stop plating leaving the boards in a bath (while
they check thickness for example), tend to produce boards that are less
reliable based on thermal cycle testing.
One failure mode for flash plating is cracks that originate at a glass
fiber and proceeds through the flash then up and down between the flash
and the next electrolytic plating then out through the barrel of the
PTH. This failure mode is usually associated with low cycles to failure.
Sincerely,
Paul Reid
Program Coordinator
PWB Interconnect Solutions Inc.
235 Stafford Rd., West, Unit 103
Nepean, Ontario
Canada, K2H 9C1
613 596 4244 ext. 229
Skype paul_reid_pwb
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Uppina Nagaraj
Sent: November 2, 2010 12:16 AM
To: [log in to unmask]
Subject: [TN] Query on Copper plating
Hi All,
We have a low build electroless Copper plating for Through Hole
metalization, which's giving around 0.5 to 0.6microns of Copper.
The subsequent processes are pattern image printing followed by
pattern plating (electrolytic copper plating).
One of our customer has a requirement to do flash Copper plating
(electro plating) of around 8 to 10 microns, immediately after
electroless Copper plating, prior to pattern image printing.
I want some inputs on the above.....
Is there a distinct advantage on PTH reliability by having
8-10microns of electroplated copper immediately after
electroless Copper plating.
Will having additional flash plating have better Thermal
stress & Thermal Shock performance.
Thanks!
U.Nagaraj
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