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Component placement and its importance

VVRD

Placing components on the board is one of the major steps in the complete cycle of board production, starting from schematic design until the physical board goes into the product or system. Component placement plays a major role in PCB functioning. Factors like the physical size of the board, board stackup, routing, EMC/EMI, high-frequency components, heat dissipation, minimizing current loops, ESD, decoupling factors, etc. decide component placement. It is good to have all components in their positions before you start routing. Consultation with mechanical engineers or system-integration engineers about the placement of input and output connectors is also a good practice.

Draw a floorplan for the board or divide the board into blocks or sections like the processor and memory sections, the power supply section, the Ethernet section, and the analog and digital sections. Initially, you just need to know whether you can fit all components on the board. Place the components so that routing will be easy and efficient. Components like processors, memories (DDRs), and microcontrollers need to be placed close to each other. Crystal oscillators, beads, and decoupling or bypass capacitors should be placed close to the microcontroller pins. Bulk-decoupling capacitors and a reverse-voltage protection circuit need to be placed near the input voltage of the board to avoid external voltage surges. While placing power supplies (converters), follow the guidelines that are given in the datasheet. Align the components in the same direction to make routing and soldering easy. Placing heat-generating components away from each other or from sensitive components can prevent heat accumulation and minimize temperature rise.

With increasing component density and small form factors, how do you challenge yourself in component placement? What are the best practices you follow?

  • avant

    I agree. I place the components by schematic page, and group components per the schematic. I can then move the components in each group according to the rats-nest for best trace routing. The schematic needs to be reviewed while placing. I've worked with some designers that never look at the schematic - big mistake. Highlighting busses and matched length groups is very helpful. I design high-density solid state drives. When the number of pins on a device exceeds a certain number, the rats-nest is only pin to pin, not nearest conductor. This is a huge issue I wish was fixed. It's very time consuming not seeing the rats on the ends of traces.

  • VVRD
    in reply to avant

    Hi Avant,

    Can you let us know which version and hotfix you're using and after how many pins you're getting the rats nest issue?

    Thank you.

  • avant
    in reply to VVRD

    Allegro Designer 17.2 070. I can't recall the pin number limit that causes rats to be only pin-to-pin. We use some devices that have 575 pins.

  • VVRD
    in reply to avant

    Hello avant,

    To debug this further it requires data exchange , we will contact you through another channel.

    Best Regards,

    VVRD

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