Finishing Touches in Routing

•         If you have thin tracks (<25 thou) then it’s nice to add a “chamfer” to any “T” junctions, thus eliminating any 90 degree angles. This makes the track more physically robust, and prevents any potential manufacturing etching problems. But most importantly, it looks nice.
• Check that you have any required mounting holes on the board. Keep mounting holes well clear of any components or tracks. Allow room for any washers and screws.

• Minimise the number of hole sizes. Extra hole sizes cost you money, as the manufacturer will charge you based on not only the number of holes in your boards, but the number of different hole sizes you have. It takes time for the very high speed drill to spin down, change drill bits, and then spin up again. Check with your manufacturer for these costs, but you can’t go wrong by minimising the number of hole sizes.

• Double check for correct hole sizes on all your components. Nothing is more annoying than getting your perfectly laid out board back from the manufacturer, only to find that a component won’t fit in the holes! This is a very common problem, don’t get caught out.

• Ensure that all your vias are identical, with the same pad and hole sizes. Remember your pad to hole ratio. Errors here can cause “breakouts” in your via pad, where the hole, if shifted slightly can be outside of your pad. With plated through holes this is not always fatal, but without a complete annular ring around your hole, your via will be mechanically unreliable.

• Check that there is adequate physical distance between all your components. Watch out for components with exposed metal that can make electrical contact with other components, or exposed tracks and pads.

• Change your display to “draft” mode, which will display all your tracks and pads as outlines. This will allow you to see your board “warts and all”, and will show up any tracks that are tacked on or not ending on pad centers.

• If you wish, add “teardrops” to all your pads and vias. A teardrop is a nice “smoothing out” of the junction between the track and the pad, not surprisingly, shaped like a teardrop. This gives a more robust and reliable track to pad interface, better than the almost right angle between a standard track and pad. Don’t add teardrops manually though, it’s a waste of time. But if your program supports automatic teardrop placement, feel free to use it.