Thursday, May 29, 2014

Hot air reflow? Yes!

I finished a couple of TinyBlinkys this evening. I had made them over the weekend and discovered that I was out of the correct kind of tactile button for them. So I placed an order with DigiKey and they arrived today. I had already gone so far down the process of placing components that I decided at the time to reflow all of the components except for the button, so when I came back to them today all that was necessary was to paste and reflow the buttons themselves.

Rather than stick them in the oven, I decided to just use my hot air rework station to melt the paste on just the buttons.

That worked just fine, but then my daughter asked if I could make her a blinky with alternating white and blue LEDs. So since I had everything out, I said "sure!"

So I pasted and placed one. I was about to get up and run it out to the garage to stick it in the reflow oven, but then I realized that I had the hot air gun going.... why not?

Long story short, it worked beautifully. Not only that, but it was really neat to watch the paste grey, then contract in on itself and ball on top of the pads and "suck in" the part (the surface tension and pad geometry conspire to center most parts).

For such a small board (1 inch in diameter), it was probably quicker to do it this way than in the oven. Anything much larger, and the oven probably wins. But faster or not, it's pretty cool to watch.

If you want to try it yourself, set your air station to 250°C and set the airflow to around "medium" or so. That should work for traditional (non-RoHS) tin-lead solder paste.

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