ENIG ground plane?  is that for a heat sink  attach?  or thermal  
ground as well?  If the it is physical contact, you have problem.   
check smoothness of the splash area and clamp force defined at  
assembly level,  that allow any solder to be deformed and compliant  
to the matting surface.  Lead free solder is very strong, not like  
Lead solder. Chances are, you can't do it, unless some what hammer  
it.   If it is using electrical contact, such as Ag paste, thermal  
pads, etc.  depend upon what it is used, you may or may not impact  
design intend (for example, there are evenly distributed thermal vias  
for uniform heat distribution, it may or may not cause non- 
uniformity).  If it is physical contact, such as key pads, No.  any  
solder splash is not allowed (visual inspection 20X - stereo  
microscope , validated using anything you want - including SEM/EDX,  
including flux residue, finger print, etc. etc.), anything will cause  
intermittent... It all depend upon your application and voltage (key  
pad, voltage is low, more sensitive to change contact resistance).   
Of course, if ENIG intend to be as corrosion protector, such as  
exposed to corrosive environment, your splash just not meet the  
design intend.  -  your build instruction should all spell out with  
acceptable process parameter.  If you inherited prior product, that  
without splash, you would need to find out what changed...(usually  
the qual unit is done without any issues, move from proto to MFG, it  
is always someone what "relax the spec".  your proto engineer should  
nail  it  all  down (if proto can do it with smaller,usually inferior  
tooling, why not large scale, better generation of  tooling?) in   
build instruction.  my 1.4 cents.
   jk
On Mar 22, 2017, at 4:54 PM, Gumpert, Ben wrote:

> Dick,
>
> Solder where it's not supposed to be should be considered  
> contamination and whether or not it affects form, fit, or function  
> isn't always clear on an assembly or drawing - you probably need to  
> know how the surface will be used.
>
> I like to see criteria on the drawing stating what is allowed, or  
> to define any critical regions (i.e. contact areas) that may be  
> restricted from solder splashes.
>
> Ben
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Richard Krug
> Sent: Tuesday, March 21, 2017 1:36 PM
> To: [log in to unmask]
> Subject: EXTERNAL: [TN] Solder "Splash" on ENIG Gold - Is this a  
> defect?
>
> We occasionally get solder "splash" on exposed ground plane areas  
> with an ENIG finish.  The "splash" is occasionally really splash  
> from a selective wave process.  More frequently solder fines from  
> solder paste, either from reflow spatter or from tooling / gloved  
> hand transfer is the source of "splash".   "Splash" sites are  
> typically no larger than ~0.5mm diameter.
>
> Are these defects per J-STD-001, class 3,  or IPC-A-610, class 3?
>
> Dick Krug, CSSBB, CSMTPE
> Lead Process Engineer
> Sparton Brooksville, LLC
> 30167 Power Line Road
> Brooksville, FL  34602-8299
> (352) 540-4012
> [log in to unmask]