Re: gEDA-user: QFN soldering

[Rick Collins <gnuarm.2006@xxxxxxxxx>]

There are a number of different QFN package styles.  Some have pads 
only on the bottom, others have pads that wrap around the up the side 
a bit.  These tend to be easier to hand solder since you have a place 
to contact with the solder iron.  Sounds like yours don't have that 
plus they have a thermal pad on the bottom.  If the thermal pad isn't 
required for an electrical connection, and you don't need to use the 
full power capability of the package, you can likely live without 
soldering the thermal pad for a prototype.   But check the data sheet 
carefully.  Sometimes they require you to provide an electrical 
connection.  Is this a power supply devices?  Those are the ones that 
are most demanding I've found.

The assembly houses use a hot air tool.  It heats up the entire part 
and everything in the immediate area such as the board.  The solder 
flows, the part settles down onto the board and all is good.

Rick


At 09:46 PM 9/12/2010, you wrote:
> does anyone have experience with this package?  I want to know if they
> are hard to work with.  The exposed pad underneath is a problem for hand
> soldering - but maybe could be left unsoldered for prototypes.  Maybe
> just place some solder paste under there ?  If the pcb pads are long
> enough, is it feasible to solder to the edge of the chip instead of
> getting it underneath the device?
>
> thanks
>
> gene
>
>
>
> _______________________________________________
> geda-user mailing list
> geda-user@xxxxxxxxxxxxxx
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