Can someone describe the mechanism by which the Palladium metal or Palladium 
Sulfide in these alternatives to electroless is dissolved by the etcher? 
 Looking at the Handbook of Chemistry it says Palladium is only soluble in 
Aqua regia(nitric hydrochloric mix) or hot nitric acid.  Is there a 
solubility in ammonicial etchant which Coombs says contains Ammonium 
Hydroxide, ammoniun chloride, copper ions, NaClO2, NaHCO3?  Or is it removed 
by the stripping solution?  I have trouble with that scenario as I can't 
come up with a plausible mechanism of reaction there either.
 My printed circuit board  who uses one of these Palladium type alternatives 
to electroless says not to worry it is removed in the normal board 
fabrication process and wants to put all critically dimensioned holes in at 
first drill to hold tolerances.

Previous TechNet correspondance:

The problem of conductive material remaining in the non pth holes on direct 
plate systems does not exist for carbon because all conductivity is 
eliminated

in the dry film stripper after plating. As long as the holes can be tented
both sides they can be drilled with the pth holes. Palladium systems would 
be the same as electroless copper and the palladium layer would be removed 
in the etching process.

Paul Gould
[log in to unmask]

> Just a word of warning, there have been several TechNet  e mails about 
this > first drill approach being dangerous if an alternative to electroless 
copper

> system is in use and any circuitry does not have a clearance around the > 
nonplated hole as the alternatives do leave the hole with a unremoved > 
conductive layer that can result in leakage.  Reportedly it is not like the 
> electroless where you can remove all the plating.
>  ----------
> From: [log in to unmask]
> To: [log in to unmask]
> Subject: Re: MISC: drill files 1 or 2
> Date: Wednesday, September 25, 1996 1:59PM
> >      Since the effort is made to drill as many of the holes in the
>      primary drill operation as possible, we prefer that the drill
>      be sent as one file to reduce the number of steps in the
>      CAM operation. Non-plated holes are only drilled in a
>      secondary operation if they cannot be tented in the imaging
>      plating operation.
>         Don Bloye
>      PC World
> > > ______________________________ Reply Separator
> _________________________________
> Subject: MISC: drill files 1 or 2
> Author:  [log in to unmask] at INET
> Date:    9/25/96 2:04 PM
> > > Hi - :)
>    What is prefered from the fabricators point of view:
>    One drill files containing both plated and non-plated holes?
>                            or
> Two drill files one plated the other non-plated?
>    Reasons?
>        ---------------------------
> John Laur
> Rockwell Automation
> Allen-Bradley Co Inc.               1201 South Second Street
> Milwaukee, WI 53204
> +1 414 382 2162 (fax)
> +1 414 382 2393 (phone)
>    [log in to unmask]
>  ---------------------------
 

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