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Fri, 17 Nov 95 17:01:05 EST
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     <<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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