[Elecraft] [POSSIBLE SPAM] Re: Cleaning solder flux
Dr. William J. Schmidt
bill at wjschmidt.com
Sun Jan 2 10:10:59 EST 2022
During my under-graduate and graduate school careers, I worked at Honeywell's circuit board fabrication shop for about a year and a half. We had two machines in the shop that dealt with flux: a reflow machine and a parts set machine. The reflow machine was used to reflow the solder after plating so that it looked shiny. The board was emersed in a 601-type flux, heated to about 425F, cooled down, and then scrubbed (brushed) with Isopropanol alcohol three times (stages) with a water rinse and force-air dried (all automagically). The solder was beautiful and shiny at the end of this process. The parts-setting machine was similar... the whole (pre-reflowed) board was fluxed, the parts set, heated, and then cleaned. All fluxes come off with Isopropanol alcohol (remember IPA is polar like water and works that way).
Fluxes come in various forms... some are more corrosive and some not... so you should follow the directions (right off the website). Rosin can remain on a board, but also can be problematic because it can collect debris (dust and other unwanted materials) because its plastic (flows at room temperature) sticky. Many of the water-soluble fluxes are more acidic, and will tarnish the solder joints if not removed.
On the subject of using water on electrical components... most components (particularly if they might be mil spec) are made for water emersion (NOT ALL!). In my office lab we routinely clean circuit boards by scrubbing them with just water and force-drying them. Works fine. About a decade ago, I used to buy up surplus AM/ broadcast band transmitters for repurposing to other countries (mainly south America) for the Christian broadcasting markets. Once back at my shop, the first stop was a good through power washing in the driveway (paper and other water damaged goods removed of course) followed by a good drying (leaf blower). Works fine!
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email: bill at wjschmidt.com
-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of edauer at aya.yale.edu
Sent: Saturday, January 1, 2022 10:36 PM
To: 'Mark Goldberg' <marklgoldberg at gmail.com>
Cc: elecraft at mailman.qth.net
Subject: [POSSIBLE SPAM] Re: [Elecraft] Cleaning solder flux
Yes, that makes sense; though my focus was on Elecraft’s boards in their traditional kits. For my very limited purpose the replies have told me enough and I am grateful for them all.
I am reminded nonetheless of a trope that’s popular in the kind of work I do, or did: “If all the economists in the world were laid end to end, they would still not reach a conclusion.”
There’s a similar quote by Dorothy Parker, but I’ll leave that one for off-line.
Ted, KN1CBR
From: Mark Goldberg <marklgoldberg at gmail.com>
Sent: Saturday, January 1, 2022 9:24 PM
To: edauer at aya.yale.edu
Cc: Elecraft Mailing List <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] Cleaning solder flux
There is no clear consensus because there are many different fluxes, different use cases and different environmental conditions that the products will be expected to be used in. It would be useful to find out what the manufacturer of the particular flux used says to do. That is not sufficient, as the product requirements then come into play. If you really want to go off the deep end, get copies of IPC-A-610 and J-STD-001, which define how electronic assemblies should be built and inspected. Unfortunately, unless you have access through work or academia, they cost money. They also reference many other documents for specific aspects.
73,
Mark
W7MLG
On Sat, Jan 1, 2022 at 7:56 PM <edauer at aya.yale.edu <mailto:edauer at aya.yale.edu> > wrote:
My thanks to the many who replied. The answer to my question - whether there is a consensus about how (or whether) to remove solder flux from PCBs
- is a clear no, there is no consensus.
But I learned a lot. Tnx to all,
Ted, KN1CBR
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