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?