Thank you Roger for bringing up the topic of solution and  part agitation. 
You are right, it is an area I should have addressed  in my last posting to 
make it more complete.
 
There are 2 main paths to improve mass transfer and get  solution into a 
high aspect ratio hole; chemical and mechanical.
 
Chemical is based on diffusion as ions are removed by plating  more ions 
will migrate to the diluted area by diffusion; of course the rate of  
diffusion has to match the rate of plating and hence plating longer at lower ASF  
will always improve Cu thickness distribution in the hole.
 
Mechanical is based on solution agitation and part agitation,  solution 
agitation is accomplished by air sparging or the use of e-ductors. The  design 
and layout of e-ductors have to be optimized to support mass transport  thru 
the hole. Part agitation is thru hole or knife edge, both improve mass  
transport; thru hole is more commonly used.
 

Best Regards  
George Milad
Nat'l Accts Mgr for Technology
Uyemura International  corp
516 901 3874






In a message dated 3/5/2012 6:26:36 P.M. Eastern Standard Time,  
[log in to unmask] writes:

George,

Apologies.  I don't want to be disagreeable but  you're overlooking the
transport dynamics of getting fresh electrolyte in  the hole.  In the 
process
you're making a "high-throw" bath seem much  more important than it really 
is
in the grand scheme.

If, for  instance, the cathodes were more numerous, perhaps cup shaped and
arrayed  on a conventional plating rack then I get it on "high throw" but
when it  comes to circuit boards, especially those with small holes?  Find
the  way to get the solution moving better through those holes and you  
don't
have to worry as much about maintaining a high-throw  system.

Sincerely,

Roger Mouton

EIMC - Advanced Plating  Technologies



Best  Regards 
George Milad
Nat'l Accts Mgr for Technology
Uyemura  International corp
516 901  3874




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