Soldering QFN surface mount devices

[Daniel Kelly \(AKA Jack\)]

Hi,

I need to solder a 3 x 3 (total 9 pin) QFN surface mount device. But I
don't have any of the exotic soldering kit needed for this job. Has anyone
attempted soldering these packages without re-flow kit?

I have two ideas of how this may be possible

1) Manually solder thin wires onto the QFN, one by one. Then connect these
wires to my PCB. The end result will be a "belly-up" QFN package with
little spider-like wire legs connecting it to the PCB.

2) Solder the QFN directly onto my PCB by taking advantage of the tiny leg
that sticks out the side of the chip.

I think technique 1 has a much great chance of success than technique 2.

The chip is just a Lithium Polymer charger chip (from Maxim). It doesn't
use large currents or high frequencies (all the charge current is dealt with
by an external MOSFET).

All sharing of experience is very very much appreciated.

Many thanks,
Jack

PS
Sorry for the cross-posting.

 

[CWatters]

This might be of interest....

http://www.wj.com/pdf/appnotes/AH201_QFN Package Hand_Soldering Application Note.pdf

 

[Daniel Kelly \(AKA Jack\)]

Dear Colin,

Thanks again for your excellent advice... the PDF is very handy.

Thanks,

Jack

 

[Leon Heller]

Hi,

I need to solder a 3 x 3 (total 9 pin) QFN surface mount device. But I
don't have any of the exotic soldering kit needed for this job. Has anyone
attempted soldering these packages without re-flow kit?

I have two ideas of how this may be possible

1) Manually solder thin wires onto the QFN, one by one. Then connect these
wires to my PCB. The end result will be a "belly-up" QFN package with
little spider-like wire legs connecting it to the PCB.

2) Solder the QFN directly onto my PCB by taking advantage of the tiny leg
that sticks out the side of the chip.

I think technique 1 has a much great chance of success than technique 2.

I've managed to solder the ADI ADXL202 which has a similar package onto a
home-made PCB without too many problems. I tinned the pads, used plenty of
flux and held a fine soldering iron tip against the junction between each
contact and the pad. Inspect each joint carefully with a powerful magnifier.

Leon

 

[Robert Lacoste]

Using soldering paste you will have no issue with option 2. Just put some
paste on each pad, position the chip, and then heat each pad one by one
using a standard (but fine pitch) iron until refusion of the paste. Of
course an hot air iron will be far easier...

Cheers,
Robert
www.alciom.com

 

[Antti Lukats]

Hi,

I need to solder a 3 x 3 (total 9 pin) QFN surface mount device. But I
don't have any of the exotic soldering kit needed for this job. Has anyone
attempted soldering these packages without re-flow kit?

http://wiki.openchip.org/index.php/SmdManualSoldering


Antti