PCB DESIGN
Designing a PCB is incredibly detail-oriented and time-consuming, and is almost never done correctly on the first revision. If future groups are considering doing a transformerless inverter project with a PCB, we highly recommend that the PCB is the primary focus of the project, you will almost certainly not have time to do full, adequate simulation, optimization, design, testing and debug for a transformerless inverter topology in the two and a half weeks given to complete this project.
Top signal layer of our PCB
While we were creating our PCB, we found it helpful to draw out the approximate areas we wanted our components to be in, and being sure our board was not bigger than necessary. We used four layers, with a ground plane and power plane in between our top and bottom signal layers. Be sure to use polygons on any relatively high voltage or power traces. If connecting polygons across layers, be sure to use lines of vias between the planes to ensure a good solid connection. Place ground planes on all layers anywhere you do not have other signal lines to help reduce noise, and double check your PCB footprints and pinouts that you added to your chosen CAD libraries one last time before shipping the board.
Bottom signal layer of our PCB
We recommend getting stencils ordered with your PCB, and ordering at minimum two boards and two copies of all critical parts. Stencils make assembly much easier, as you can spread solder paste across the board, place components on the pads with tweezers, and then heat the PCB in a toaster oven or at low heat on a hot plate to reflow the components. Be careful not to overheat your PCB, and do not add through-hole components to your board until after adding all of the surface-mount components.
Three Phase Assembled PCB
After assembly and during test, visually check the board for any shorts or bridges before hooking up any power, and when you initially apply power to your board, use a heatsense camera to see if any portions of the board appear to be shorting and drawing too much heat. A good place to start in debug after you are sure your board is free of shorts is the ground planes and vias, any test points you may have placed on your PCB, and the VDD or power signals going into your chips. If at any point you discover something to be wrong with your board, carefully review your CAD documents, then slice any traces that are wrong with a thin blade or razor. Hack wires can be soldered from pin to pin on components to fix your incorrect connections.
Single Phase PCB with Hack Wires and Discovery Board
