[Elecraft] Soldering temperature of KPA100, KAT100

[Tom Hammond]

Hi Ed:

>New to the list, building K2 S/N 3548. I'm about 2/3 of the way done
>with the basic K2, and will be building the KPA100 and KAT100 shortly.
>The KPA100 indicates that the soldering tip temperature should be 800
>which is different from the 700 specified for the K2-do most builders
>agree with this? Obviously, a high wattage iron is needed for the power
>transistors and that is not part of my question.  Also, what tip size is
>the best for the KPA100? Looking at the pad size, it looks like it
>should be the same as the K2, but advice is welcome.
>
>I guess the same questions arise for the KAT100. Using components rated
>for higher current and voltage makes me wonder if I need the higher tip
>temperature for that build as well.

Obviously, personal optinion follows: (e.g. possibly worth what you might 
have paid to download it, but YMMV)

A 700F temp for soldering the power transistors is just fine, AS LONG as 
you can MAINTAIN that temp DURING the soldering operation. That's the 
problem, and generally the reason one might want to use an 800F tip, 
especially if not using a temp-controlled iron. Using a smaller tip, or a 
non-temp-controlled  iron. the tip will give up its heat during the initial 
heating process, and may not be able to adequately replace that heat 
without excessive 'dwell time on the copper to be soldered. This can lead 
to possible damage of the PC board or the copper.

Use of a high-mass, e.g. physically larg(er), tip will make things a bit 
easier as well... something to 'hold' the temp during soldering.

Although I have a good T/C soldering station (Hakko 936-12), I also use a 
high(er) mass tip (larger/wider tip) when it comes to soldering power 
transistors onto large expanses of copper. I'll also often set the tip temp 
a bit higher, say around 750F.

For general PC board soldering, I use a tip width that's about 80%-90% the 
width of the PC board pad. This allows me to pretty well cover the pad with 
the tip (to accelerate heat transfer), while still leaving a bit of 'safety 
room' for not dragging molten solder onto a nearby pad or land.

If you have an old soldering GUN, it will work well for those times when 
you need to solder power transistors, or other large areas of copper. Just 
be careful about the tip temperature... you can control the tip temp a bit 
by 'modulating' the application of heat via the use of the soldering gun's 
ON/OFF trigger. The important thing is to get a clean application of solder 
while NOT overheating things to the point that you risk damaging the 
adhesive holding the copper to the PC board and causing the copper to 'lift'.