[Elecraft] Source of poor solder joints?

[Tom Hammond]

Hi Keith:

In my limited experience, most poorly soldered joints come from:
  (not necessarily in order of importance)

  1) applying to little heat,
  2) applying ample heat, but not for long enough to allow the
     solder to 'flow' properly,
  3) applying too little solder

If ample heat was properly applied, AND for an adequate length of time,
merely removing the tip of the iron from the soldered joint should
leave more than ample residual heat to allow the joint to properly
solidify.

I've seen 'newbie' builders 'peck' at the joint being soldered with
their soldering iron tip, rather than leaving it in one spot long
enough for the heat to be transferred to the pad wire and solder.
They'll 'warm' up the joint... melt a bit of solder onto the tip of
the iron and then 'dab' at the joint, instead of applying enough for
the solder to FLOW onto and throughout the components of the connection.
This is most often evidenced by looking at the joint thru a magnifier.
You can readily see that 1) the solder never 'flowed' in and around the
joint, 2) often there's NO SOLDER inside the plated-thru hole at all,
just a small 'blob' on one side of the PC board pad, and possible a bit
on the wire lead.

'Cold joints' resulting from the builder's having accidently moved the
component lead after the heat's been removed are much less frequent
than poorly soldered joints from the two above causes.

Take yer time, folks... this is NOT a race... apply the heat long enough
that the solder will flow smoothly, AND apply at least enough that the
solder flows down and INTO the hole of the plated-thru connection.

73,

Tom Hammond    N0SS

At 07:45 AM 11/22/2006, Darwin, Keith wrote:
>Looks like poor soldering joints is the #1 problem with rigs we build.
>While building my KSB2 I was wondering about and came up with an idea.
>
>I wonder if many poor solder joints occur because of the lead moving as
>the soldering tip is removed.  In the case of an IC, while I'm applying
>heat, I'm pushing against the chip's lead.  When I remove the soldering
>iron, the lead is going to spring back just a bit (i.e. move) as the
>solder connection is cooling.  Could this be a major contributor to poor
>solder joints?