Component Placement Essentials for High Speed PCBs

Overview: As a qualified PCB designer, you must understand the schematic diagram. If necessary, FS Tech recommends that you divide it into more detail according to the function of the circuit, such as analog, digital, high speed, high current, power supply, etc.

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PCB component placement schematic

Component placement considerations
Placement of high-speed equipment
1. High-speed devices are prohibited from being placed on the edge of the PCB. As we all know, high-speed equipment is a relatively sensitive instrument, and the edge of the bare board has different impedance characteristics, which will cause serious damage to the electromagnetic interference machine. It is said that there have been some turnkey PCB manufacturers in the past and this has resulted in radiated EMI from the connectors of the PCB. Therefore, FS Technology generally places sensitive high-speed devices in the center of the bare board, in this way to reduce the adverse effects of EMI. In past manufacturing experience, we believe this is the best approach.

Thermal effect placement strategy
For PCB component placement, thermal effects are a factor that we must consider. When manufacturing high-speed circuit boards, the production equipment will be in a high temperature state due to the influence of the rotational speed. When the temperature of manufacturing equipment reaches a critical point, the pins of PCB components will be damaged. To keep your thermal components cool, develop a sensible placement strategy. In order to deal with this problem, FS Technology will move the components away from the air path of the BGA when installing large components. This method effectively prevents the components from directly facing the hot air flow, so as to achieve the effect of cooling.

PCB Component Mounting Guidelines

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Process for placing components
Prioritize the location of the connector
The size of the PCBA board depends on the product housing, so prior to PCB design, the location of the connector is prioritized. Note: Here is the PCBA board instead of the bare PCB board. There are essential differences between the two. If you don’t know much about this, you can read the article of FS Technology’s PCB vs PCBA.

Chip placement
Place the main functional chips such as microcontrollers, operational amplifiers, drivers, and power chips. These chips are the heart of the entire PCBA, and they determine the functionality of your board. We recommend that you place auxiliary components such as crystals and decoupling capacitors close to the relevant main chip.

Place passive components
Passive components include the following types: series resistors, pull-up resistors, ESD diodes, etc. There are many points to pay attention to when placing passive components. In order to help you to carry out PCB assembly smoothly, FS Technology lists the following points:

Voltage and current levels
Function type (analog, digital, power, high speed)

placed to facilitate the flow of high currents to minimize loops

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Power and GND Distribution

In addition to circuit function, voltage and current levels should also be considered. Circuits with similar VCC and GND should be grouped and placed together as shown in Figure (4). Different functional sections are prioritized and placed. Most critical in order of priority

Wireless Wi-Fi, GPS

digital

motor control

power supply

Place the main components according to the signal flow.
Refer to the circuit schematic when placing components. Identify the main components of the circuit, such as microprocessors, Ethernet chips, memories, etc.

Place these according to the floor plan and use the shortest possible traces between these master chips according to the datasheet guidelines, which makes the signal flow as smooth and unidirectional as possible.

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