A blast of hot air

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.

Revised by Martin Oldfield on 14 Oct 2013, original version 14 Oct 2013.
Contact: Martin Oldfield, ex-atelier@mjoldfield.com
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