PCB design tips

Here are some tips for circuit board design:

Design in Package Flexibility into Your Next PCB tells that to err is human: to order the wrong component foot print is just part of engineering – it happens to us all who work with hardware. David Cook has a solution that could save your bacon. He shows you how to design multiple footprints into your board to avoid the most common mistakes such as voltage regulators with different pin-outs than expected.

PCB Design Patterns web page has a few tricks and tips that from prototype to production PCBs to provide flexibility on parts, easier assembly, and faster circuit testing. It shows that PCB layouts featuring a few extra holes and a little bit more copper can increase flexibility, speed installation, and improve reliability of your printed circuit boards. You can find following tips: Flexible Voltage Regulator Layout, Choice of Trimmer Potentiometers, Choice of Capacitors, Error-Free Part Insertion, Button Choice, Faster and More Reliable Soldering of Through-Hole Parts, Solder Mask Issue, Copper Fill to Reduce Heat and Increase Efficiency, Wire Loop for Test Probe Hook and Traces.

Here is one example: Universal layout for three-pin linear voltage regulators that can cover practically all TO-220 and TO-92 packages regulators.

Universal layout for three-pin linear voltage regulators


1 Comment

  1. Tomi Engdahl says:

    Engineering correct-by-design PCBs

    As both chip and board complexities continue to spiral upwards, so do the number of challenges faced by designers. The proliferation of multi-Gbps differential signals, for example, brings with it the need for tightly length-matched routing and restrictions on the use of vias. Extensive simulation to characterize these busses, including long bit streams to validate performance down to very low bit error rate (BER levels), is necessary to ensure adequate system margins. This requirement is no longer unique to high-speed serial links, but has now spread to single-ended, parallel links like DDR4. PCBs have to be tested for signal integrity, power integrity, and radiated emissions, in order to ensure that the design works correctly before the first prototype is even built.

    As such, designing a modern, high-speed PCB is a pretty daunting task. It requires high levels of expertise in a number of different areas. Infusing that expertise into the design process, however, can be made more practical through the use of rules-based verification.

    Concurrent Verification During Layout
    Every design requires that a set of constraints be developed during each phase of the project.
    Floorplanning constraints are essential for a number of reasons involving several disciplines. For example, certain components may need to be placed close together to ensure timing margins are met or loss budgets are not exceeded. If terminations are used on a signal, these termination components need to be placed close to a driver or receiver to be effective. Decoupling capacitors need to be placed as close to an IC as possible to limit the inductance between the capacitor and the power pins of the IC. Mechanical constraints on placement, including placement interferences or heating concerns, must also be considered when doing floorplanning.

    As critical nets are routed, they must conform to requirements set by the electrical constraints. They must not exceed maximum length limits. Signals often have to be tightly length-matched to other signals. They must not be routed with an excessive number of vias. They must be routed with certain widths and above solid reference planes so as to maintain a consistent characteristic impedance. They must not be routed too close together to alleviate crosstalk concerns.

    Similarly, care must be taken when routing power nets. There must be adequate metal to supply all the current-carrying needs of the ICs. Planes adjacent to high-speed routing need to be solid and continuous.

    In order to meet schedule constraints, complex printed circuit boards need to be designed right the first time. Validating that the PCB meets all of the electrical design requirements is a huge undertaking.


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