intermediate process should not use no-clean flux... it should use  

low residue or no residue flux... if they used no clean flux, you  

need to clean it before put on assembly (your part of parts qual  

should including amount  of flux residue allowable on the part).  On  

the other hand, what you can do on the assembly level, when you got  

such a part...you need to use strong (corrosive  possibly) flux/paste  

and clean the assembly after if you have to (stuck with the parts or  

vendor).  IMHO.

good luck.

jk

On Aug 24, 2017, at 2:11 PM, Steven Kelly wrote:



> Hi All,

> I have a new hi-density BGA connector I am trying to assemble. When  

> the supplier makes the connector they "solder balls onto the  

> pin" (lead free). We see dried flux on the balls and when we solder  

> the connector we are getting a few joints with head in pillow. The  

> connector manufacturer says the dried flux is not an issue - is  

> this true? Thanks. Steve Kelly