A number of projects I have been working on have outgrown the breadboard phase, and I have been learning how to do PCB layout. My first tiny project (a cable adapter) went smoothly, but as I have been ramping into more complex designs, things have gotten much hairier.
As a second project, I was trying to assemble a high-performance LED driver (roughly the "typical design" presented here), but every layout I create in that direction leans towards some jabba-the-hut style amalgamation of parts.
What I am trying to understand is what is the typical flow that a (skillful) EE undertakes that results in a well-designed board? I included the above link as a specific example to talk strategy around, but I would like to know more about general approach that people use to tackle PCB layouts. Books/links/suggestions all welcome.
Thanks!
Answer
1st check the reference design for layout coupling , isolation and grounding requirements.
Then try to fit on 1 layer with wire jumps, using all SMT and power/ ground fills and beefy driver tracks, then 2layer if necessary for low density boards. Add extra pads for spare chips, caps, polyfuses, connectors, test points.
A pro layout designer for logic may use orthogonal signal layers with separate power ground layers and understand the impact on signal skew, track impedance and ground topology for analog and digital.
A good Test Engineer with define the requires for test nets, testability, and all the DFT specifications. A good Process Engineer knows the IPC pad requirements for wave and reflow are different and how to design the solder mask and component orientation deign rules. A component Engineer knows how to reduce costs on component selection which impacts layout. A mechanical engineer understands the stress on solder joints from warp , shadow effects of big near little parts and an industrial engineer also understands how the ground fill affects reflow thermal profiles and instrument designers will understand how to construct differential pairs with guarding, and signal decoupling from high current switched power tracks. An RF engineer knows how to specify copper geometry with layout. A good cost/quality engineer will know how to choose feature specs from all suppliers under consideration.
A great PCB designer knows all of this and more. You can start with reading about DFM, DFT, DFC,or DFX and borrowing IPC stds from somewhere. ($$$)
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