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
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