Soldering 0.4mm pitch QFN 48 chip

Question

I have this QFN 48 chip which has the following design :

As it can be observed, the pitch is 0.4mm. It seems like the conventional QFN adapters won't fit because the conventional ones has the pitch of 0.5mm.

I should have read thoroughly before buying it. Do you have any suggestion to help me use this chip?

The chip is just a little small for the QFN adapter, so I tried soldering it anyway but it doesn't work.

The chips is 6mm x 6mm but the QFN is 6.07mm x 6.07mm. I have three different kinds of QFN48 adapters but they have the same design in terms of size.

For your information, I don't have the hot air gun.... would that be a problem?

Answer 1

You need to be sure that you have the correct adapter board for your IC. "Close" just isn't good enough! The problem is not the overall dimensions, but the difference in pin pitch.

It looks like my usual sources don't make a breakout board for 0.4mm QFNs. Here is one for your IC from ProtoAdvantage. I haven't used that company's products, so I can't recommend them.

Regardless, I couldn't solder a 0.4mm QFN (with exposed pad) without either hot air or a reflow oven. And I've done a lot of soldering!

If you still want to try soldering, your simplest solution might be to actually make your own breakout board. Companies like OSHPark will produce PCBs very inexpensively, although you might have to wait a week or two.

Answer 2

I should have read thoroughly before buying it. Do you have any suggestion to help me use this chip?

Yes, if your soldering by hand, it helps to have a length for the solder pad that is longer than the l (little l) by a factor of 2 so that the pad extends out past the pin and you can hit it with the soldering iron. Or if you put a blob of solder on the iron it has something to attach to to heat the entire pad. I have soldered QFN's with only an iron, be sure to use lots of flux. The center pad may be problematic if using only an iron however, if your desiging your own board, a via on the thermal pad can help solder it from the bottom of the board.

If your using a hot air gun the pad length is not as critical.

Either way there are plenty of videos that can give you a good idea of how to do this.