Designing PCBs With Surface Mount Components

Summary: all the design tools work well.

This describes the tools I used and a constantly-evolving personal style.

I’ve used the free-as-in-beer DesignSparkPCB commercial product from RS running in wine. I didn’t choose Eagle because of its irritating limitations (size, pins etc). I didn’t try KiCAD, and have no opinion about it.

Also see my techniques for making and assembling homebrew PCBs, and reference material.

Schematic and Layout

DesignSparkPCB provides:

  • a large library of components via RS. In reality the RS library was missing several components I needed, but I’ve found it very easy to create components (both schematic and PCB). Hence the RS library hasn’t been as beneficial as I originally thought
  • decent schematic and PCB layout editors, with forward/backward changes
  • reasonable design rule checking, although manufacturers tend to produce DRCs for Eagle, which have to be manually translated

I originally ran DesignSparkPCB in WinXP, but now run it under wine-1.4 in xubuntu 12.04. Less than once a day it crashes, which is acceptable. N.B. I haven’t tried the 3D modelling, because that’s uninteresting.

designSparkPCB

DesignSparkPCB Layout

Sanity Check

To check the gerbers, I use

gerblook

GerbLook Front View

Personal Style

I made the component pads longer than specified in the data sheets in order that hand soldering might be easier, but:

  • for the non-leaded components such as 0805 resistors it might mean that too much solder paste sets up thermal stresses; in future I will be less pessimistic
  • for leaded components, particularly the FMC connector, the slot in the paste stencil was larger than necessary and may have contributed to the stencilling problem mentioned below. On the other hand it helped with the “Schmartboard technique”. In future I will make them shorter, but still longer than the minimum

I spaced the components by 1mm on all sides, so that I could get an iron to all of the pads. That was unnecessarily pessimistic for 0805, 0603 and IC components – I would use 0.5mm in future, provided that they aren’t in the “shadow” of tall components.

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