Dale, is your package a face down chip cavity?  you might have  
problem in reliability if "all kind of flux" was not qualed with your  
new observation of "penetrating into a chip package... - once got in,  
it is difficult to get out.  my 2 cents.  may be your process temp is  
out of parts spec - at least 20 C (just a guess).
              jk
On Feb 11, 2015, at 5:42 PM, David Hillman wrote:

> Hi Dale -for either our tin/lead soldering processes (20+ years of  
> data) or
> our lead-free processes (5 years of data), I have never seen the  
> phenomena
> you detailed. I have seen several instances of package cracking and  
> process
> materials penetrating the package due to MSL ("popcorning") issues  
> but no
> incursion into the package with normal soldering processes that was  
> not MSL
> related.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> On Wed, Feb 11, 2015 at 4:25 PM, Dale Ritzen <[log in to unmask]>  
> wrote:
>
>> Hello Technetters,
>> Has anyone ever experienced issues with solder paste flux (or  
>> potentially
>> flux from cored wire solder or wave solder or selective solder  
>> processes)
>> penetrating into a chip package during reflow or cleaning or  
>> whatever? One
>> of our customers has asked about it and I know of no incidents  
>> like this.
>> Their question applies to all types of flux in general. But, I  
>> thought
>> someone out there may have run across this in their travels.
>>
>> I'm trying to figure out just how that could possibly happen with  
>> all the
>> package retooling for the higher temperature RoHS processes, but I  
>> will
>> rely on your vast experience and knowledge to provide the right  
>> answers.
>>
>> I am waiting for all the "It depends..." answers to start rolling in!
>>
>> Thank you in advance,
>> Dale Ritzen, ASQ CQA
>> Quality Manager / ISO Management representative
>> _____________________________
>> Austin Manufacturing Services
>>
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