<<I would like to read your conclusion and test results on why a
tilted rack is not recommended. After I read your conclusions I will
give you some input on my experience in working with Toppan, Niigata
Prefactuure, Japan and Hitachi Chemical, Shimodate Ibaraki, Japan. >>
<<One Japanese process that I am truly impressed with is how the above
fab shops focus a majority of the copper plating in electroless (more)
and then electrolytic (less) versus the states which are less
electroless (time consuming) and more electrolytic.>>
<<Thomas John Gulley
PCB Project Engineer
[log in to unmask]>>
Thomas:
Two of the tests that I have conducted drove that point home to me:
The first included varying degrees of rack agitation in the catalyst
bath. It was very clear that more agitation was worse. That is,
coverage in the holes by the catalyst wasn't as good (measured by
backlight) when the agitation was higher (it was not extreme). The
catalyst is known to have a weak physical bond to the surface, via the
wetting agent "conditioner" and more agitation will interfere with the
adhesion of the catalyst on the hole wall.
The second test used a tilted rack versus a standard vertical rack.
The pieces processed in the tilted rack had very obvious voids upon
inspection after the deposition process.
I would like to see the test data that you know of. I think that it
would have to be very strong data for me to consider trying again.
MB
______________________________ Reply Separator _________________________________
Subject: Re: Electroless plating
Author: [log in to unmask] at HALSIC_CCSMTP
Date: 11/15/95 8:45 AM
That could be a long wish list!
Whatever you but, I would want to see processing data on the features
that will be included. For instance, I personally wouldn't want to
see the tilted racks, due to some testing that I have conducted in the
past (DATA!). Remember also, that there are two ways to tilt them:
off of vertical (z axis) and off of the y axis. The tilted racks
create faster solution movement through the holes which can cause
problems (IMHO) with the catalyst deposit step.
You definitely want to have vibration on the chemical steps. The key
is the copper bath, followed by catalyst and conditioners. Include
good rinsing too.
Get a control system that allows random process loading using varying
cycles. Today's high Tg laminates require special processing in the
permanganate desmear (you ARE including desmear in the line, aren't
you?).
Also, get a top notch electroless copper chemistry supplier and tie
them into the loop on equipment selection and specification. The best
equipment won't help much unless the chemistry is good.
The equipment suppliers should have good processing data these days,
but they don't always have it. It is hard choosing who to buy from.
You MUST see some similar equipment in operation at other shops and
talk to the users & installers before you buy.
Matt Byrne
Hadco, Owego
[log in to unmask]
(BTW: Why is it that I can't see who writes messages on this system?
I get the impression that other users can see the writers' addresses,
even when they don't sign the work (90% of the time). The only
address I generally see is "[log in to unmask]" Is it the same for
others?)
______________________________ Reply Separator _________________________________
Subject: Electroless plating
Author: [log in to unmask] at SMTPLINK-HADCO
Date: 11/7/95 1:34 PM
My company will be installing a new computer controlled vertical electroless
line soon. We believe that we have, with the help of our equipment and
chemistry suppliers, configured it to have all the features necessary to
acheive small hole coverage ( 7-8 to 1 aspect ratio): tilted racks,
vibrators, automatic chemistry replenishment for appropriate tanks. Does
anyone have other suggestions for optimizing this process? a "perfect"
electroless line wish list? Thanks for any input.
Lyle Anderson
Lundahl Astro Circuits
Logan, Utah
801-753-4700
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