PCB protection type

In the simplest terms, PCB retention can be defined as follows:

A PCB wiring frame is designed by the designer for external components in areas not set up on the circuit board, where copper traces or other circuit board components shall enter or cross. The area can be or contain copper and can be of any shape.

In most cases, retention zones are used to keep certain board areas far enough away from other components to prevent or minimize EMI. However, they are also used to provide spacing for fan-out tracing of surface-mounted components. Examples are processors or FPGas, which are usually PCB evaluation and development boards. Some common reservation types are listed below.

Type of PCB protection

L antenna

Probably, the most common type of reservation is to reserve an area of copper wire around an onboard or connected antenna to prevent EMI from affecting the fidelity of the transmitted or received signal. Reservations may also contain antenna wiring to other circuits.

L parts

It is also common to make room for fan-outs around components (especially EM radiators). This is true for microprocessors, FPgas, AFE and other medium to high pin count components (commonly used for patch packages).

L Plate edge clearance area

Edge clearance is very important in manufacturing. Specifically, panels are split into individual boards during PCB assembly. To do this, enough clearance must be left for wiring or scoring.

L tracking

Sometimes it may be advantageous to define reservation areas around traces. Sometimes used for coplanar grounded transmission lines to achieve controlled impedance.

L drilling

Many plates are installed by screws or bolts. In these cases, it is helpful to define the spacing around the holes. Insufficient spacing can affect assembly, interrupt circuit operation, and even cause circuit board damage. For through-holes, you usually just follow CM’s DFM rules.

L connector

Depending on the connector type in terms of layout and placement, your board design may need to consider two considerations: the footprint of the connector board and the paneling. Usually, the layout of the connector or plug does not include space for external wiring or cable connections. In these cases, maintaining state is important to ensure that the circuit actually performs as expected.

L switch

Another good use of reserve is to provide room to flip or move horizontally mounted switches.

The list above gives some common types and uses for PCB retention. In other cases, however, you may need to define reserved areas. For example, if your design uses components; For example, in operational amplifiers, where there is a large impedance mismatch between input and output, the circuit may be susceptible to feedback current leakage, so it may be necessary to provide the following form of protection: PCB protection ring. Although not classified as a protected area, the protection ring does act as a physical barrier to external components and wiring, and prevents internal current from leaving the area. Now we’re ready to look at how to ensure that reservations do their job.

Stay away from trouble

PCB retention measures are only effective if they actually achieve their objectives. This is to provide isolation in specific areas of the board from any and all external elements. To achieve this, you need to follow these good Keepout guidelines.

PCB retention criterion

L Determine why retention is required

L Determine how much space is needed according to usage

L Use screen printing markers to identify reservation areas

L Ensure that your design document contains retention information

PCB hold is a valuable asset to your board design, ensuring that it performs as expected. By following these guidelines and taking full advantage of them, you can avoid layout conflicts and improve PCBA reliability after deployment.