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March 2004

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Subject:
From:
"Dehoyos, Ramon" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 31 Mar 2004 09:34:12 -0800
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        Once the resin, rosin or other type of solder oxide  barrier coating material is hydrogenized it turns white and it is hard to remove ( leaving it on for a long time or baking boards without cleaning them before hand ).  The white residue sometimes diffuses into the porous parts. One of the ways is to mechanically remove it with a brush.  The forum consensus from previous posting is that if a board is going to be coated it needs to be cleaned to remove dust, oils, flux etc.
         Some one correct me if I am wrong, it is my understanding that no clean flux cleaning agents after becoming activated and removing the oxides from the leads,  barrels and pads they become inert. That is why they are no clean. It does not mean that the remaining rosin will stick to the coating. On the contrary. CC will only lay over the top of it.
        Regards,
        Ramon


> -----Original Message-----
> From: Brian Ellis [SMTP:[log in to unmask]]
> Sent: Wednesday, March 31, 2004 9:55 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] White residue
>
> Doug's answer is 100% correct, you can, BUT ... should you? There is no
> cut and dried answer. This has already been discussed n* times on this
> forum and you would get far more info by searching through the archives
> than we could summarise in a short answer here. In brief, though not as
> brief as Doug, only YOU can answer the question, yourself, after
> conducting extensive tests and qualifying both your processes and
> materials. If you don't wish to do this, the best recommendation is
> don't coat on top of residues of any nature.
>
> Brian
>
> * where n is a large integer.
>
> Somtawin Pornpottanamas wrote:
>
> > Has anyone ever seen white contaminate ( like a crystal) on assembly
> > boards , between IC lead? I found white residue on  some board after
> > reflow . I try to clean by used IPA, flux removal solvent and also DI
> > water. But could not remove it. I also found that after we used the
> > solvent to clean, the white residue increase more.
> >
> > Our process used no clean . What is this residue?  What type of solvent
> > that should be use to clean flux residue when we have to rework or
> > Dedug?
> >
> >
> >
> > Thanks & Regards,
> >
> >
> >
> > Somtawin Pornpottanamas
> >
> > Material Engineer
> >
> > Kimball Electronics (Thailand)
> >
> > Tel. 038-401566  ext. 211
> >
> > Fax. 038-495029
> >
> >
> >
> >
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