Raghav
Nothing you have said convinces me, yet, that you have to clean the
boards. If you use a modern "no-clean" flux, this will save you having
to do a meticulous, costly and dangerous operation and will leave very
little residue on the boards and what there is will be hardly visible.
Using IPA alone is not effective and the boards will almost certainly be
less reliable than with using a good "no-clean" process. The "white
residues" you are seeing are almost sure to be ionic or partly so,
because they will contain metallic salts. In addition, IPA is a distinct
fire hazard unless operated in an inert atmosphere (flash point less
than room temperature) and is somewhat toxic (can be absorbed through
the skin).
If I were you, I would scrap your current process as soon as possible
and run qualification tests on selecting a "no-clean" flux from the many
available. If, for any good reason (and I don't really consider that
there is a good cosmetic one), you cannot use "no-clean", then select a
good water-soluble flux, again from the many available, and clean with
water. However, be warned: water-cleaning MUST be done well and proper
qualification of the process is essential.
For further reading: http://www.protonique.com/plcom/files/whycl.htm and
http://www.protonique.com/unepstoc/report/STOC1998ch2.pdf (you may find
other useful references on http://www.protonique.com/unepstoc which is
the official site of the UNEP solvents committee).
Am I correct in thinking you are in Bangalore? If so, I have a colleague
who is a consultant in cleaning technology, stationed in Hyderabad. He
is not specifically into defluxing, although he is quite knowledgeable
in this sub-sector. You may find it more economical to use his services,
rather than do it all yourself.
Brian
PS. I would prefer it if you spelt my name right!!
Raghavendra Bs wrote:
> Hello Brain,
>
> Sorry could not complete the mail.
>
> Now we are facing the cleaning problem in the boards which are processed in
> wave soldering. After wave soldering process, we are cleaning the flux
> residues and this process is taking more time to effectively clean the
> boards with IPA (more time consumed to clean the white patches formed due to
> IPA, which is not good in cosmetic). The PCBA is a communication purpose
> boards (Class B according to IPC). Now we need to try out any other solution
> which is effective in cleaning and should not be harmful for the board. If
> any other information is required, please let me know.
>
> Thanks in advance
>
> Raghav
>
> -----Original Message-----
> From: Raghavendra Bs
> Sent: Sunday, October 27, 2002 2:23 PM
> To: 'Brian Ellis'; TechNet E-Mail Forum.
> Subject: RE: [TN] TechNet
>
> Thanks for the reply Brain,
>
> -----Original Message-----
> From: Brian Ellis [mailto:[log in to unmask]]
> Sent: Sunday, October 27, 2002 12:15 PM
> To: TechNet E-Mail Forum.; Raghavendra Bs
> Subject: Re: [TN] TechNet
>
> Raghav
>
> IPA is not a good solvent for most types of flux residue, because it
> will not dissolve many components. Tell us more about what you are doing
> (soldering methods and parameters, flux type, type of end product,
> degree of reliability needed, conditions of use of end product and so
> on) and we shall be able to help you better.
>
> Brian
>
> Raghavendra Bs wrote:
>
>>Hi,
>>
>>Can any one give some hints on Cleaning of wave soldered PCB's, to remove
>>flux residues on the board. In IPA, white stains are left on the board and
>>cosmetically does not look good. Is there any other solution.
>>
>>Regards
>>Raghav
>>
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