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

[John Nordlund]

Eric,

As I just noted in a response to Phil, the water based flux products may 
be much better now that they were when my company tried them.

My experience with water based flux does not inspire me to want to use 
them again.  The No Clean products I do recommend are very good for 
people who are familiar with the rosin flux most of us learned to solder 
with.  The flux stays in the joint doing it's job of reducing oxides all 
the way to flow temperatures of the alloy.  The viscosity at temperature 
is the same as rosin flux, and the only difference you would see in 
using it is that it stays water clear to a much higher temperature than 
rosin, and smokes less.

Some of the failures were corrosion related in that the flux contained 
acids that would attack metals if not completely removed from the 
assembly.  I think it is in fact more corrosive than rosin flux, and 
careful cleaning is essential to prevent corrosion failures.  The 
formula of the No Clean products is completely inactive below solder 
flow temperatures and will not cause corrosion if it is left on the board.

I do clean my boards after assembly even with the No Clean flux, but 
only to remove excess flux to prevent it from migrating to areas of the 
assembly where it might interfere with things like switch contacts, 
sockets, and headers where it might insulate the contact surfaces.  
Because the flux is not reactive, I am not concerned if there is a 
slight residue left on the board, so long as it is not enough to flow 
across the board surface.  I use denatured alcohol as a cleanup solvent 
when conditions require it.

This is the inspection standard used in our production processes that 
have been reviewed and approved by the FAA.  The only cleaning required 
is where there is excessive amounts of flux that might migrate or where 
there is other debris such as solder balls trapped in the flux residue 
that could break loose and migrate to other parts of the assembly.

This HPSDR project is probably the best radio I ever expect to own, and 
I want it to be the best it can be.  Give me a print to follow and parts 
and a board to assemble and I can do the assembly labor for just about 
anything except BGA chips.  I have worked with SMD caps that looked like 
grains of sand under the microscope.  I for one will enjoy the assembly 
as much as using the finished product.

These comments are my own experiences and opinions and do not represent 
the official opinions of my employer.

73 de AD5FU - John in Little Rock

Eric Blossom wrote:
> On Sat, Aug 19, 2006 at 03:48:58AM -0500, John Nordlund wrote:
>   
>> Hi all,
>>
>> I thought I might chime in and confuse all of you solder slingers just a 
>> bit.
>>
>> Water based fluxes do work to a point, but there are some other options 
>> you might want to consider.
>>     
>
> Thanks for sharing your "real world" exerience.  It's always good to
> have hard numbers on failure rates ;)
>
> 73, Eric K7GNU
>
>
>   
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