Nancy, Flux of some sort is almost always needed to make a reliable soldered
connection. We have found that the flux in the core of the solder (R or RMA)
at 2 to 3 % is more than adequate and we "strongly" discourage the use of
liquid flux except for tinning of wires and occasional touch-up. All
unvolitized flux is useless and wasteful and worse than that it adds costs
to clean it up and dispose of the residues. (Assuming that you are hand
soldering of course.)
Ron Dieselberg
-----Original Message-----
From: Nancy M. H. Holloway [mailto:[log in to unmask]]
Sent: Wednesday, January 05, 2000 09:56
To: [log in to unmask]
Subject: Re: [TN] cleaning flex circuits
To all,
Nothing makes a beautiful joint like flux! I have to admit, that during
my high reliability soldering training, we were discouraged against using
flux when soldering, but it makes all the difference in world as to how
well the solder wets and flows.
Nancy
At 04:26 PM 1/4/00 -0800, Carey Pico wrote:
>To all
>
>I've been keeping out of this discussion. But one thing I don't get... why
>isn't the board industry looking at a fluxless process?
>
>Carey
>
>-----Original Message-----
>From: Kelly M. Schriver <[log in to unmask]>
>To: [log in to unmask] <[log in to unmask]>
>Date: Tuesday, January 04, 2000 2:52 PM
>Subject: Re: [TN] cleaning flex circuits
>
>
>>Hi Nancy -
>>
>>To begin with, the cleaning media is driven by the particular flux you are
>>using. This, in turn, will drive the issue of what equipment you may be
>>able to use for the process. I have had good success removing RMA
residues
>>from flex circuits with quite a number of blended solvents in vapor
>>degreasers and conveyorized spray systems. Size of the flex assembly must
>>obviously be considered - there are a number of suppliers who can provide
>>cleaning baskets to restrain small flexes for processing thru conveyorized
>>cleaning systems. Manual cleaning would not be my first choice if I were
>>dealing with a high reliability article, particularly if it were to be
>>conformal coated.
>>
>>Another possibility might be one of the saponifiers, in either a heated
>bath
>>or a "dishwasher" type system.
>>
>>If you are not currently using a low residue ("no clean") flux, might that
>>be a possibility? If this is a consideration, and you plan to conformal
>>coat or use adhesives on the assembly, be sure to verify full
compatibility
>>of the flux residues and the specific coating material you intend to use
>>before proceeding.
>>
>>Contact me directly if I can be of assistance.
>>
>>Regards - Kelly
>>
>>
>>
>>
>>-----Original Message-----
>>From: Nancy M. H. Holloway <[log in to unmask]>
>>To: [log in to unmask] <[log in to unmask]>
>>Date: Tuesday, January 04, 2000 10:57 AM
>>Subject: [TN] cleaning flex circuits
>>
>>
>>>TechNet,
>>>
>>> What is the best technique to clean flux off of a polyimide flex
>circuit
>>>after population? Thus far, we have been cleaning the flex circuits with
>>>alcohol but it is time consuming and tedious. We use a machine to clean
>>>rigid boards, but I am hesitant to use it for our flex circuits. How are
>>>you all cleaning your soldered flexible printed circuit boards.
>>>
>>> Thanks,
>>> Nancy
>>>
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