Hi Gary and others, Gary Moman wrote:
See http://www.labx.com/v2/adsearch/Detail3.CFM?adnumb=200978 for a used SZ40 or perhaps something else like it. You're kidding yourself if you try to do it without something like this.
I have soldered few QFN's without magnification, possible but tiresome. Usually I use table mounted magnifier with illumination light. Makes life easier. I also would confirm that good light source or even several adjustable ones, is a must.
The hardest part is getting good wetting directly under the pin.
Hot air soldering iron and good solder paste help there.
When looking through the eyepiece, the smallest tip you can get usually covers a pin on either side of the one you are attacking, but a little tilt on the iron will let you contact only the desired pin. It will just look like everything is going to be one big blob when you pull it back.
I usually use rather large, but spoon shaped tip, (with JBC soldering station), really makes soldering easy (hint: surface tension).
Most of my 430 pad placements seem to end up with more pad under the chip than I want. I think it is mostly due to the way the pins are spec'd.
Refer to (soon to be released) IPC-7351 for those problems :) PCBLibraries.com also has a rather nifty IPC-7351 calculator. Indrek -- Indrek Rebane | Borthwick-Pignon Electronics Engineer | Tartu Science Park Phone: (+372) 7 302 641 | Riia 185, 51014 Tartu Fax: (+372) 7 383 041 | Estonia ind...@bps.co.ee | www.bps.co.ee
