[hpsdr] [Fwd: Re: Flux sources? Some other ideas..]

[Philip Covington]

On 8/19/06, John Nordlund <jnordlund at earthlink.net> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Phil,
>
> We were using Kester products at that time, though I could not tell you
> what the product number was.  The unused solder did however make
> wonderful 45 caliber roundball for my muzzle loader.  I was invited to
> remove about 45 1lb rolls from the plant after the changeover.  That is
> a lot of 45 caliber ball..
>
> I will add to this that I haven't used any water based products since
> then, and they may be much better now that when the concept was
> relatively new.  As a company, Audio International changed to the 'no
> clean' chemistry and never looked back.  shortly after the change, they
> sold off the $40k+ stainless steel 'dishwasher' that had been purchased
> to clean up the boards from the production area.
>
> Another issue we discovered that contributed to the high return rates at
> the time was that some of the components would trap water and/or flux
> residues inside their structure.  The water flux contained a small
> amount of hydrochloric acid in it's formula, and when that got inside
> switch contact assemblies that had a tiny vent hole the acid would
> dissolve the gold plating and then rapidly eat the copper conductors
> leaving a switch contact that was either shorted by metal chloride
> crystals or permanently opened by removing the connecting metal traces.
> Since the majority of our products are switch modules this presented a
> really serious problem to our quality program.
>
> I was working as a production technician when the water flux was first
> brought in for trials and the problem I encountered was that the flux
> would boil before the alloy would flow and the boiling action would
> interfere with the flow properties of the alloy.  When the alloy arrived
> at proper flow temperatures the flux had boiled away from the joint
> leaving a dull dry finish on the component terminations and solder
> lands.  it was very easy at that point to wind up with a 'cold' joint as
> there would be an oxide layer over the metal surfaces that interfered
> with the flow of the alloy.
>
> A few months later as an inspector in the quality department I was
> examining these same issues under a microscope and all of the production
> techs were having trouble creating clean solder joints consistently in
> hand built assemblies.  Soldering done in the reflow oven did perform
> better, but there we did experience a larger number of components that
> were displaced from their proper locations, requiring manual rework to
> correct.  It is my belief that this was caused by the boiling of the
> flux during the passage through the reflow oven.
>
> After changing to the No Clean flux chemistry the soldering problem
> issues  virtually ceased to occur.  Now as the data analyst writing
> reports on the returned items it is a very rare event when I have a
> soldering related failure on items built after the change to No Clean
> flux.  One of our largest customers has a very interesting warranty
> agreement with us that starts the 5 year term of coverage at the time
> the aircraft is certified and delivered to the purchaser.  Due to this
> arrangement I am still seeing items from time to time that have
> experienced failures directly traceable to the water based flux
> 'experiment' of 2001-2002.
>
> For those people who are familiar with rosin flux soldering I would
> still recommend the No Clean products, as the flux viscosity and
> activity are almost identical to the rosin flux products, especially at
> soldering temperatures.  The No Clean flux does not tend to burn and
> darken like rosin flux unless the iron temperature is set way too high.
>
> This is of course my own experience and opinion with the water based
> flux.  Your experience may be (and I hope is) different.
> These opinions do not represent the official position on my employer.
>
> 73 de AD5FU - John in Little Rock

Hi John,

Thanks for the very interesting information.  I remember talking to a
manufacturer who tried water soluble process back about the time
period you were talking about.  They did not have good experiences
either.  They do say that now the products are a lot better.  They
were not using Kester's stuff back then, that's why I asked.

Phil N8VB

73 de Phil N8VB

 1156039483.0