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32 DESIGN007 MAGAZINE I NOVEMBER 2023 sure. Instead, take the time needed to establish a well-defined and measurable set of design goals. Include the project stakeholders, get buy in, and then execute. Three Design your PCB power delivery system (PDS) Your PCB power delivery system (power planes/structures) should be based on your power distribution requirements and not a coincidence of layout. is means that your PDS design should take place before settling on a board stackup. A typical PDS is composed of discrete capacitors, power plane capaci- tance, and on-chip capacitance. Determining the amount of plane capacitance needed for a specific design should involve the use of a simulator such as HyperLynx, ADS, or HFSS. Designing an appropriate PDS for your board design is easy to say, much harder to do, and very much worth your time. Improper or poorly implemented PDS designs are nearly impossible to recover from without a costly board respin. Fr Know your drill holes A PCB can play host to many types of drill holes for various reasons. A few examples are vias, mounting holes, tooling holes, and press fit holes. Vias come in many forms, but they tend to be some type of plated hole that is typi- cally used for signal, ground, or power transi- tions from one PCB layer to another. Vias can also be used for thermal conduction between PCB layers. It is important to understand that mechanical engineers typically regard mount- ing and tooling holes as two very different types of holes that serve entirely different purposes. Mounting holes can be plated or non-plated and provide a clearance/loose fit for the PCB so that it may be attached to some other struc- ture. Tooling holes are designed and manufac- tured to a tight tolerance so they can provide a transition fit needed for precise alignment of a PCB in an assembly or test fixture. PCBs use interference fit holes for press fit connec- tors. e connector/PCB mating pins interfere slightly with the holes on the PCB, requiring force to be applied to the connector during the mating process instead of soldering the pins to the PCB itself. Knowing the types of drill holes used on your PCB and their purposes allows designers to effectively communicate their purposes to other stakeholders in a project. Five Coordinate your design with your fabricator e last thing you want to hear from a PCB fabricator is that they are no-bidding your design because it is not compatible with their capabilities. It is perfectly reasonable to include your PCB fabricator in your design reviews. Making sure that your design fits within the manufacturing capabilities of your fabricator is a primary objective, not an "on the side" proj- ect. Furthermore, your PCBs built for produc- tion should be well within fabricator's range of capabilities and should not be pushing their edges so that your yields (major PCB cost driver) are not driven by process variations. S Consult with the group or company assembling your boards It is best to know what practical limitations your assembly process imposes on your design instead of finding out post assembly. Not all pick-and-place machines are created equal. Accuracy of small component placement can vary greatly between different pick-and-place machines. Manually removing assembled boards from panels can damage shock-sen- sitive components. e risks associated with