Hello Technet,

I have performed a solderability test Surface Mount Simulation Test 
according to the J-STD-003C on samples of PCB ENIG finish.
The reflow has been done with vapor phase equipment using Lead free solder 
paste SAC305.
Solder paste was depositied with ministencil for BGAs (1mm pitch) areas 
and manually deposited on other different pads (CHIP 0603,0805, SOT,BTC 
components and others).
The paste in this case was placed with not homogeneous deposition on pad 
area
I know that this manually deposition is not correct, but I didn't have the 
gerber file for stencil. 

The result was that on BGA areas there was a perfect wetting (100%) while 
for some pads of others components I got some areas showing dewetting.
On these pads, the surface of the dewetting area were around 6--8% of the 
pad surface (cumulative percentage divided in 2-4 areas) and in one case 
was around 15% (cumulative, 3-4 areas of the same pad) .

Really I think these results is mainly due to the uncontrolled paste 
deposition considering also that the lead free paste has a high contact 
angle and that it wet less all the surface finishing and not due to poor 
PCB finishing, since I found several pads well wetted. 

Looking to the standard I see that the requirement for the Pass Condition 
is a good wetting for at least 95% of the pad surface area, but there is 
also the statement saying "There shall be no nowetting area or exposed 
base metal within the evaulated area" .
This should mean that, if there is an area of nowetting (exposed base 
metal) the test should be considered Fail also if there is a good wetting 
for more than 95% of the pad area?
In subject case I have a no-wet area of 1.65% I consider this as Pass 
condition.

Does anyone has experience on subject? Or suggestion ?

Thanks in advance.
Francesco 
Francesco Di Maio 
IPC e Formazione
IPC A-600, IPC A-610, IPC 7711/21 Certified IPC Trainer
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