Re: gEDA-user: OT: soldering QFN packages with exposed bottom pad?

[Stefan Salewski <mail@xxxxxxxxxxxx>]

On Mon, 2009-04-27 at 22:55 -0500, Bill Gatliff wrote:
> Guys:
> 
> 
> Got any recommendations for how to hand-solder a QFN package that has an 
> exposed bottom pad?  At the moment, all I have is a soldering iron.
> 
> Do you think I could just put a plated-through via underneath the pad, 
> and then flow solder through that from the back side?
> 
> 
> b.g.
> 

Hello,

I will have the same problem soon, when the layout of my DSO board is
finished. Your suggestion "plated-through via underneath the pad" should
work (indeed is does, some people did it). I am not sure if I should
make a large hole so that the tip of the soldering fits in it, or only a
smaller, which I may fill with a piece of copper wire to conduct heat.
The problem is to control/see when the solder flows -- to prevent
heating to long. And one problem may be that too much solder may flow in
making connections to other pins. And of course fixing the device at the
right position is difficult when soldering from the backside.

For cheap, small PCB boards heating the whole PCB with a heating plate
may be fine, but I do not like to do this with my expensive board.

I think I will have to do some experiments...

Best regards

Stefan Salewski
 



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