PCB Layout Lessons Learnt

Buy yourself a PCB Ruler

For half the price of a cup of coffee you can buy a PCB Ruler on eBay (This one from the seller thepenking). This will enable you to visualise the size of tracks, pad, vias/holes and to check them against your components before committing the design to manufacture.

Check the component footprint

Hmm, not much room for this salvaged (2.5mmx1.2mm) resistor on an 0603 component pad, just as well I put a full PTH pad pair on the board as well.

Check the pad sizes

To make room to get your soldering iron on the pad use the right pad size !

Standard PTH Header pads are small

As you can see, on the image to the left, the shoulders of standard PTH (Pin Through Hole) solder pads are half the thickness of the prototype boards that I use. This makes them very difficult to hand solder as it is difficult to get the iron in contact with both the component lead and pad shoulder at the same time.

This is not an error but is done deliberately to allow space for a standard width track (0.25mm) to be routed between any pair of pins.

But for my level of micro-soldering competency I would prefer the larger pad and to route tracks around headers and PTH components.

I think I will have to develop some of my own component footprint models....

Soldering to a Ground Plane

A second problem with the headers having small shoulders is that you have very little contact area with which to heat up the large mass of copper that is the ground plane. This makes soldering header ground pins with a small headed soldering iron very difficult. I may need to consider using pre-heat with the air gun or even isolating the ground pins from the ground plane and soldering to a separate ground via.

PCB Mounting Holes

On the first set of boards I had made up I did not have any board mounting holes! They were there on the early versions of the PCB, but when I decided to start again from scratch, as I could not clear the Net errors from EasyPCB, I simply forgot to put them back in as they are not shown on the schematic. Stupid Boy!

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