Soldering a DFN package

I soldered some leads to a MCP1624 boost converter in 0.5mm pitch DFN for prototyping.

This is very tricky with such a small package. My method was to tin the pads and the leads, with the solder on the leads extending past the pad area. I then positioned them carefully using adhesive putty to hold everything in place, fluxed everything, and reflowed the solder by touching the tinned part of the leads one at a time by touching them with a soldering iron. I inspected it with a cheap hand-microscope and had to redo a few connections because of shorts. I didn't connect anything to the thermal pad because I'm not going to put much load on this chip. I later discovered this chip is also available in SOT-23 which would have been much easier to solder.

The connection are very fragile, so as soon as they were all in place I covered them with hot glue. Hot glue can be repeatedly melted, so you can add a single blob of glue and reflow it with a hot air gun. This is an easy way to evenly apply glue to all sides of the wires

I added some 0.1" headers for breadboarding and some perf board for reinforcement. I set up the circuit as described in the datasheet. I used a tantalum output capacitor instead of the recommended ceramic, and a substantially larger inductor (22uH instead of the recommended 4.7uH) because of component availability. Unfortunately the circuit did not work. I'm not sure if the problem is the component substitutions, the breadboard, or if I somehow damaged the chip. The nominal frequency is 500KHz which is low enough that I think it should be possible to get it working on a breadboard. I might try again with an etched PCB and correct components later.

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