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PCB Layout and RF Shielding Affect Signal Integrity

Many high-speed electronic circuits generate noise and interference that can cause a wide range of problems for end users, from device failure to misreading data. This interference takes the form of radio-frequency interference (RFI) and electromagnetic interference (EMI). The problem is made worse when PCB layout and rf shielding pcb aren’t considered early on in the design process.

Fortunately, good PCB layout techniques can help minimize both EMI and signal integrity (SI) problems in addition to using appropriate RF shielding. EMI/RFI concerns tend to be different from SI problems, with the former typically involving noise generated by high-threat signals that radiate off component leads and packages while the latter is usually a result of power supply voltage tolerances.

In both cases, the best approach to preventing these issues is to identify and treat critical traces. That’s because most of the sources of interference are found on just a few of the PCB tracks, which means treating those specific lines is much more effective than applying treatment to every trace on a board. This is particularly important when a trace has to travel through a large area, which increases the chances of unintended coupling between adjacent metallic elements that will impact the circuit’s performance.

To avoid this, RF shielding manufacturers can use special conductive epoxy to prevent metal-to-metal contact during the installation process, or they can utilize aluminum, a highly conductor that also happens to be very inexpensive. These conductive materials can help reduce the overall cost of RF shielding by eliminating the need for costly EMI/RFI suppression components such as grounding, filtering and the like.

How PCB Layout and RF Shielding Affect Signal Integrity

The best RF shields are created from metal alloys that combine copper and other elements to provide both good electrical conductivity and adequate mechanical strength. Brass is a common material because it provides the benefits of copper without compromising on mechanical properties. Brass is also a cost-effective choice because it can be fabricated into a variety of different shapes and sizes and is easily mountable using a wide variety of methods including soldering, adhesives and snap fit.

When it comes to the RF shielding assembly itself, the most important factors are the shape and thickness of the material along with its ability to withstand expected environmental conditions. RF shields are often manufactured by drawing the metal, a process that yields a robust and seamless shield frame that can withstand handling and transportation. These RF shields are then fitted with a snap-on cover to complete the enclosure.

RF shields can be formed in many different ways, and the Masach process is one of the most advanced and sophisticated. This unique technique allows the creation of a shield frame that can accommodate the various heights and X-Y dimensions of the various PCB components. It can also feature a variety of openings, including tabs for pick and place machines and “mouse holes” in specific positions to allow PCB traces to pass through the enclosure. The system can even cut out specific openings to accommodate custom component profiles and unique configurations.

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