[Elecraft] [K3] - mods and solder

[Gary Hvizdak]

At 0315 EST on Wednesday April 2nd 2008 David Ferrington (M0XDF) wrote ...

... I KNOW some of you know a lot about solder. ...

--

Hi Dave,

    Your 60/40 solder could possibly result in what are referred to as 
"cold" or "disturbed" solder joints.  If I were you I'd only use that stuff
for non-electrical hobby projects such as leaded glass, and jewelry.

    For best results I would suggest eutectic solder which is an alloy 
composed of 63% tin and 37% lead.  In addition to it's having a lower 
melting point, it also transitions pretty much instantly from a liquid to a 
solid, without any intervening "plastic" state.

    In addition your .048" solder is much to thick for SMD work.  I suggest 
something in the neighborhood of 0.020", plus or minus 0.005".  (You need to

match your solder size to your task, being careful that the solder isn't too

fine as this could result the flux burning off before it does its job, which

is to clean the surfaces to be soldered of any oxidation.)

    Regarding the flux, your best bet is a mildly activated rosin core flux.

FYI, here mildly activated is a reference to the temperature at which the 
rosin melts (so that it can do it's job).

    DO NOT USE WATER SOLUBLE FLUX AS YOU WILL VOID THE WARRANTY OF WHATEVER 
IT TOUCHES!  WATER SOLUBLE FLUX IS HIGHLY CORROSIVE AND HYDROSCOPIC.  NEVER 
EVER USE IT WITH INSULATED WIRE (ESPECIALLY STRANDED) AS IT WILL WICK UP 
UNDER THE INSULATION WHERE IT CAN'T BE COMPLETELY REMOVED.  OVER TIME IT 
WILL EAT RIGHT THROUGH THE WIRE!

    SIMILARLY DO NOT USE ACID CORE SOLDER!

    No-clean fluxes are okay, but they have a higher activation temperature 
and you should have some experience with them before using them on something

as expensive as the K3.  The advantage of no clean fluxes is that they only 
leave about 3% of the residue left by a traditional rosin flux.

    BTW, I won't even go into the subject of whether or not to remove the 
flux and how to go about doing that.  If you are interested you can see my 
previous post on this subject in the archives here ... 
http://mailman.qth.net/pipermail/elecraft/2005-November/049886.html 

73,
Gary  KI4GGX

P.S.  I don't know a lot about solder, but I work with someone who does!