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USB Li-ion battery charger

USB Li-ion battery charger

This is a charger for lithium ion batteries which takes its power from the USB port of a computer. It uses the MCP73861 or MCP73863 Li-ion battery charger chip manufactured by Microchip.
The circuit board is a piece of single sided copper clad board. A hole is cut inside it so that it will accommodate the integrated circuit.

The MCP73861 or MCP73863 (they are similiar, with only slight differences which do not affect the circuit connections) is available in a small leadless package.

The difficulty? There are no leads to solder to. The advantage? There are no leads to break!

The ic is placed so that its connection side (the side with solder pads) lines up with the copper side of the board and it is then fixed in position with epoxy or some such glue.


The area around the ic is tinned and the solder pads joined to the board with bits of wire.

I find it helpful to flatten the wire with pliers before soldering, so that it stays in position without any tendency to roll about. Some of the leads go to the same node and these are conveniently placed together.

After the leads have all been soldered, the space in between the leads are cut out to form islands and the other components are soldered to these islands of copper.

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