AVR-Chat

> 
> I was considering getting a 1/64" tip for an iron, but now I think 
> that something slightly wider (chisel tip shape) may be better 
> for "drag soldering".
> 
> I still have not found a good reference on the technique of drag 
> soldering?  I t seems as if the technique is to make a blob of 
> solder and drag it across all the pads on one side of the chip.  I 
> guess the solder mask prevents bridging?  I would have thought that 
> all the pins would just get shorted together in one big glom of 
> solder....
> 
> -Tony

The thermal mass of the iron tip & the flux are both important. This is 
why the minihoof and blade tips are used.  The concave in the mini-hoof 
will tend to draw the solder back to the tip, the sheer mass of the 
blade will also draw solder away from the joint. The flux will provide 
the thermal bridge and combination of the two will cause the joint to 
draw enough solder to form a joint but no more.

As you work along the chip with the 'blob' you will see it wet out and 
bridge pins at the leading edge while'snapping' away from pins at the 
trailing edge, leaving a good joint.

Be careful at the last few pins along each side as it is easy to leave a 
bridge on these.

The thing with magnification is that it gives you a very good idea of 
the subtlties what is happening so that you can refine your technique 
and later work with lower magnification.


-- 
Cheers

Don