Tim is 100% correct. With over 40 years experience of
cleaning/contamination studies in electronics, I would say that I have
seen many failures due to inadequate cleaning. Spreading contaminants by
spot cleaning residues (especially with oxygenated hydrocarbons, such as
alcohols, ethers or esters) is much more likely to create new failure
mechanisms than doing nothing.
In any case, "no-clean" pastes are formulated specifically NOT to be
cleaned but whose residues are sufficiently benign as to not require
removal for some applications. If you must clean, use a paste whose
chemistry is designed for easy cleaning but whose residues may be more
dangerous if left uncleaned.
If you have a petrol (gasoline) engine in your car, do you put in diesel
fuel? Use the product adequate for the job.
All you are doing is creating a stick to break over your own back.
Brian
Tim Jensen wrote:
> My belief is that spot cleaning of flux residues is risky endeavor with
> respect to reliability. I would always recommend either not cleaning at all
> (using no-clean materials) or cleaning the entire board.
>
> With spot cleaning, how do you ensure that the residue is completely removed
> from the board? It may dissolve the residue, but once the solvent
> evaporates, the residue will be re-deposited on the board. In addition, I
> have seen a number of cases in which partially cleaned no-clean residues are
> much less reliable than when not cleaned at all. The reason for this is
> that often the no-clean residue has some activator still entrapped in the
> rosin/resin remaining on the board. If the solvent does not completely
> remove the residue, but does remove the rosin portion, it could leave behind
> some acids that could negatively impact reliability.
>
>
> Best Regards,
>
> Tim Jensen
>
> -----Original Message-----
> From: Leadfree [mailto:[log in to unmask]] On Behalf Of Fabrice Pires
> Sent: Friday, June 22, 2007 12:18 PM
> To: [log in to unmask]
> Subject: [LF] RE [LF] Flux removing
>
> Hello Yannick,
>
> For touch-up cleaning hydrocarbonated solvents are generally recommended.
> They evaporate sufficient slowly to allow the cleaning but also fast
> enough compared to water-based solutions for correct cycle time. They also
> don't need rinsing generally necessary with water-based solutions. They can
> be used on SAC or SnCu finishes without reactions.
> If necessary you can contact me for precise product names.
>
> Best Regards
>
> **********************************
> Fabrice PIRES
> Electronic Products Application
>
> AVANTEC
> Soldering and cleaning solutions manufacturer
>
> Rue des Coulons BP 27
> Cour de la Gare de Marchandises Phone : +33 (0) 1 49 83 53
> 73
> 94363 BRY SUR MARNE Fax : +33 (0) 1 48 81
> 24 40
> FRANCE
> e-mail : [log in to unmask]
> ***************************************************************************
>
>
>
>
> Yannick Brisson
> <[log in to unmask]>
> Envoyé par : A
> Leadfree [log in to unmask]
> <[log in to unmask] cc
> >
> Objet
> [LF] Flux removing
> 22/06/2007 17:45
>
>
> Veuillez répondre
> à
> "(Leadfree
> Electronics
> Assembly Forum)"
> <[log in to unmask]
> >; Veuillez
> répondre à
> Yannick Brisson
> <[log in to unmask]>
>
>
>
>
>
>
> Hi,
>
> I wanted to know your input on what kind of product is good to
> clean flux residues when you touch up some board, we use SAC305 and SN100C
> wich is no-clean paste.
>
> Thank you
>
> Yannick
>
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