[hpsdr] Resoldering the ADC on Mercury

[Graham / KE9H]

Todd:

Are you really sure you have a problem?

That is a very expensive board, and you don't want to hurt it,
particularly if it is working OK.  Just because the IC and the back
side heat pad are hot to the touch, and you can't hold your fingers
on them more than two seconds does not mean that you have
a problem.  It just means that they are above 128 degrees F.

I would not do anything to the board without temperature
data.

Just because the through-hole is open at the top (back-side heat pad)
of the PC board, does not mean that you have a soldering
problem.  Reflow soldering is NOT intended to fill the through
holes.  In fact if all of the through holes were filled, it is indicative
of a soldering problem (unless the board went through a special
process intended to fill the holes.)

If you have an inspection microscope, look at the bottom
of each through hole (down by the heat pad at the IC, and yes
they are small holes.)  If the hole is not filled, but there is a
meniscus  at the bottom of each hole, then the reflow soldering
process did its job, and you do not have a soldering problem.

If you want to fill the through holes to increase heat flow to
the back side heat pad, then you will need a temperature controlled
soldering iron.  I would personally recommend that you not
go above about 660 deg F., use a good flux, good tin-lead
eutectic solder, and limit your working time to 30 seconds or so
to not start cooking the board.

But my real advise is to not do anything unless you are sure
you have a problem.  Those ICs are designed to live longer than
you will, running at temperatures that you consider hot to the touch.

--- Graham / KE9H

==


Todd Mondragon wrote:
> Hi all,
>   
> I seem to have one of the Mercury boards with soldering issues on the 
> ADC heatpad.
> 11 of the 34 holes show no solder flow at all (most are around the 
> edges with 2 in the middle of the pad). I have not hooked it up yet to 
> check the temperature but I suspect this may be enough of a sign that 
> I'd want to reflow the ADC heat pad anyway.
>
> What would be the best method to make sure I've got a good contact 
> between the board and chip and that I have have all the heat pipes 
> soldered through, those holes are pretty small! Unfortunately all I 
> have at my disposal for this work is a pencil iron.
>
> Or is the experience of the group such that there shouldn't be a 
> problem and that I should not worry about it?
>
> BTW - This is no reflection on the folks at TAPR or anyone else, I 
> completely understand this is an experimenters kit and have no problem 
> fixing any issues I may encounter on my own. The folks at TAPR and the 
> people who designed and made this equipment possible are tops in my book.
>
> 73!
>
> Todd M0GLO
>

 1239208629.0