A bit OT but anyone soldered a QFN package to a pcb, and how?

I've seen a couple of videos but would like to hear personal experience s.

Oh, and if you don't know and can't be asked googling, these are tiny surface mount ICs, and I mean tiny.

Yes
Not a easy task

My DIY version is to tin both PCB and IC.
Plenty of flux, then heat with hot air using a hot air pencil.

My hot air source has heat control and a 4mm nozzle.

To check this method get a scrap PCB an practice with any of the components.

And make your life easier and use 60/40 tin lead and not the new unleaded crap.

its feasible if you have a very fine soldering iron and magnifying gear.

You get sockets for QFN's but they aren't cheap, you can also get QFN to DIP adapters to so that you can have a few goes on the QFN without messing up your PCB if you make a mistake.

Bear in mind some QFN's have a pad underneath that can need soldering although it is often only for thermal/mechanical reasons so can be skipped in less demanding situations

It is very easy to bridge the pads when soldering so get some ‘solder wick’ to help you if you do make a bridge when soldering.

I’m assuming there is no equivalent package with leads like a TQFP available? Most automakers avoid QFN packages and prefer QFP for vibration and thermal reasons. typically QFN are used in cost and space sensitive applications like phones and toys as it is one of the cheapest ways of packaging a chip and the area can be kept reasonably low vs the die area.


[Edited on 2/2/19 by DanP]

Flux is your friend here, and I mean proper SMD flux rather than something from your plumbing kit. Some very fine solder, or solder paste will also be needed, along with a fine tip on your iron.

With plenty of flux the solder doesn't tend to form bridges easily, so you can drag the end of the iron down the side of the IC to create pretty neat solder joints.

Done it loads and in different ways, what tools do you have?

Yes, done numerous times. Very fine soldering iron and smt solder paste.

I do need glasses now to do them now though...must be an age thing! lol.

Ian

Solder paste and a lot of flux and hot air rework gun.

Hmm, seems to be easier than I expected, I've got solder paste as well as some pcbs to convert to DIL package on the way, and digital thermometer. . I don't have hot air gun (I do have a small gas soldering iron) so am looking at the oven or griddle method with solder paste, just need to get the special flux.

One things that's been puzzling me is how low can the smd device be kept at the temperatures required for the solder to melt, can't seem to find that in the spec. Sheet.

[Edited on 2/2/19 by 02GF74]

It’s the reflow profile you need, it’s more for the QFN package than the device itself.

An example: http://infocenter.nordicsemi.com/pdf/nan_400-08.pdf