A simple recipe
A while ago I bought an Atten 858D+1 rework station from a seller on Amazon.
Here are a few notes on using it:
- I applied Qualitek 619D paste2 to the board with a compressed-air dispenser though a 23 gauge needle. This is a Sn62/Pb36/Ag2 no-clean (ROL0) paste, with 86% metal content.
- I didn’t apply any extra flux: the only flux I’ve got on hand is in a pen and applying that before the paste stopped the paste sticking to the pads.
- For 0805 parts I put a dab on each pad, for a 16-pin LFCSP3 package, I put a sausage along the rows of pads, and a couple more in the centre tab.
- I set the temperature on the 858D+ to 275̣°C, the air-flow to a medium setting and used the medium nozzle. In most cases the solder melted quite quickly and surface tension pulled the parts into place.
- The surface tension pulled the LFCSP chip close the board, squeezing out some of the solder into blobs on the side of the chip: they were easy to remove with braid.
I’m not saying that this is the best way to proceed, merely that it worked for me.
Failures
I had a couple of problems:
- If the air was too fierce or too close to the part, or the nozzle too small, the part tended to blow away from the right location. Small deviations are fine: surface tension pulled the parts back; larger movements become a problem if the part moves to the next pad.
- On occasion, the paste ‛popped’, sometimes blowing the part off the board. I think it might indicate the the paste has absorbed water, which boiled, but I’m really not sure.
References
- 1. http://www.atten.eu/atten-858d-smd-rework-reflow-station.html
- 2. http://www.somersetsolders.com/product.php/392/218/leaded_solder_paste_syringe_qualitek_619d
- 3. http://www.analog.com/static/imported-files/packages/PKG_PDF/LFCSP(CP)/CP_16_17.pdf