[sdiy] Hand soldering TQFP packages

[Peter Ullrich]

Hallo!

> > Anyone tried hand-soldering these 0.5mm pitch SMT packages?
> 
> I've done the AVR QFP packages until I blue in the face, they're a doddle.
> I did solder an FPGA (XC2S200-6PQ208)  and that took me an AGE to get 
> 'right' on my fes2 board (http://fpga.f2g.net) I've no idea what the pitch 
> was on that, but it looked like there was around 5 pins for every 2 of the 
> AVR..

This part has a 0.5mm pitch...

I should forward you a hint from a collegue of our prototype laboratory
that works very fine:

You only need a normal (not SMD) soldering iron - but also a SMD one can be 
used.
The important part is a special flux paste: RMA 04-HV (Stannol and other 
companies have it).

- First you have´fix the IC on two edges (no matter if you connect some pins 
together!) - just be sure to fix the part on the right place.

- Then put a the flux paste on all end of the pins (the end of the pins and the 
rest of the copper needs the paste). 

- Take your soldering iron (temperature a little bit higher than normal - 380 
degrees celcius are ok) and start from one corner (but not one of the two 
corner where you fixed the part!) and deliver enough solder and move with 
constant speed over all pins on that side to the end of the row.
The fluc paste garantees that the solder can flow under the pins AND that the 
excessive solder flows back to the soldering iron and so to the next pins. When 
the soldering iron leaves the pin there is normally no bridge between pins and 
you get very nice soldering joints!

With this method my collegue soldes a 208pin 0.5mm part in about 3 minutes 
including optical control and maybe one or solder wick corrections.

I also tested this method by myself and it works fine!
The flux paste is not cheap but worth every cent!
You can buy it f.e. from RS-components...

I hope that helps you soldering your chips.

Ciao
Peter

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                               Ing. Peter Ullrich   
	               Hardware & Software Developer  /  Electronic Musician
                               Private Homepage: http://www.ullrich.at.tt
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