RE: Started building my K2 have a few ?

[Matt Palmer-4]

A metcal 037 tip is 700 deg F. I'm using some kester 60/40 solder I had
laying about(pocketpak), not sure of actual part number. In regards to my
plating question, from a commercial production standpoint, if gold plating
is too thick on a part, it tends to cause cracking in a solder joint in
later life. Under JSTD001 gold platings above a certain thickness are
supposed to be filed/sanded down to alleviate this problem. Usually at least
in my place of business we do not know of problems with plating until it is
too late. I was just curious if there were any other  'crafters out there
that have had issues with the gold plated connectors, if not I don't plan on
worrying about it, I have not had the opportunity to look at the joints
under a scope, however just the fact that capillary action failed to pull
solder thru the vias and wet the top of the board gave me a bad initial
feeling
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[AJSOENKE]

Gold plated surfaces are tricky to solder. They are excellent to get  wetting
and a superior solder job, but gold is a metal that will dissolve in  solder
as well as many other metals. That is why platers use a nickel flash over  
copper to plate gold that won't dissolve into the copper. In space applications  
this is a problem over time and in weightless environments. OK so what this  
means to you is if you play with the solder too long or prolong applying heat,  
the gold may actually dissolve somewhat exposing a less desirable surface.
You  need to work hot and fast with good solder.  Personally, I prefer 60/40  
over 63/37 eutectic solder because it provides a little temperature range  
between solidus and liquidus, commonly referred to a paste stage that relaxes  the
dexterity of the operator a little. You do have to hold the parts steady a  
little longer as it cools so you don't fracture the alloy while it cools. For  
this reason some ops may prefer the 63/37.  The thickness of gold varies  
depending on application. 50 u inch is often used on connector pins for  
lubrication in the contact zone, so you will likely have 50 u inch in the solder  cup -
unless they are VERY expensive connectors.
For corrosion resistance and solder wetting, 15 u inch is usually  
adequate... JSTD 001D Class 3. . .are you planning on launching it (couldn't  help
myself there  ;p)
 
Of course, now you'll need to regale us with some fine photos.
 
73 es hop to work u soon AL, WA6VNN



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