Sunday, April 28, 2013

Reflow Soldering!

The boards I ordered recently arrived and it was time for assembly. Because I am designing for minimal cost, I had to hand solder the accelerometer and gyroscope. Both were QFN packages so I couldn't simply use a soldering iron for the job. Instead I needed to learn how to use soldering paste and do basic reflow.

The boards from SeeedStudio.

So I talked to a couple people and they suggested hot air rework. The problem was I didn't have a hot air rework station and didn't feel like shelling out $100 for one. So when I went to Fry's electronics to buy some soldering paste, I saw a $14 personal skillet and I remembered this great tutorial from SparkFun. They found that a skillet is a fitting alternative to a toaster oven and in some ways works better. I decided to give it a try and I wasn't disappointed.

The skillet from Fry's. Only $13.99!
Cooking up some electronics!

The most difficult part of the process was applying the soldering paste since I didn't have a stencil or syringe. Instead I used my pair of tweezers to "paint" it on the pads which I wouldn't recommend. It worked, but it was tedious and messy. (I have since ordered a syringe). After adding the parts to the board, I simply laid it on the skillet and watched as the parts reflowed and slid into place. Everything seemed to reflow fine save a one or two solder bridges which were easily fixed with a soldering wick.

The board after reflow. You can see some small solder bridges.

One disadvantage of the skillet method (and toaster?) is that you can only reflow one side. This meant that I designed my board with all of the reflow parts on top so I could hand solder the bottom. This wasn't too hard as I only really had to solder the microcontroller which is pretty easy with the help of soldering braid.
The hand-soldered bottom of the board.

The end result looked great and I was really pleased with skillet reflow. It was fast, cheap, and easy to do! Check out my next post where I will show how I tested the boards.

The finished product.

1 comment:

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