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Rework and Repair Costs Affect RF Shielding on PCBs

RF shielding is vital to protect against disruptive interference from high-threat signals. From smartphones and laptops to critical medical equipment like MRI machines and pacemakers, electronics need effective EMI/RFI shielding to avoid signal loss, malfunction or performance degradation. The ideal solution is a combination of PCB level EMI suppression techniques including grounding, filtering and proper circuit board layout to minimize the loop area. However, RF signals still radiate from component leads and packages and so an additional layer of attenuation is often required. That’s where PCB level EMI shielding cans come in.

Designed to fit over individual components or a whole flex PCB, shields are available in a variety of sizes, shapes and mounting types – adhesive, snap-fit, solder, or surface mount. Depending on the product and design, they can provide a range of attenuation to meet EMC-related regulatory standards for different operating frequencies.

Shielding materials vary in terms of electrical conductivity, thermal stability and mechanical properties as well as cost. Copper and its alloys are a common choice for EMI/RFI shielding due to their conductivity, which reduces electromagnetic interference. However, if the material is exposed to moisture it may be subject to corrosion or oxidation, which can lower its performance. To address this, it’s often plated with tin or nickel silver, which improves its longevity and solderability while providing excellent attenuation.

How Rework and Repair Costs Affect RF Shielding on PCBs

In addition to determining the type of shield, it’s important to determine how the circuit will be used. Some applications require shielding that’s thin enough to not interfere with a signal’s transmission path while others are more demanding and require shielding with very high attenuation. For instance, an RF shield designed for an automotive or aerospace application will need to be durable and able to withstand a great deal of vibration.

Another factor in determining the appropriate thickness of a shield is its maximum bend capacity. A shield that’s too thick will limit a flex PCB’s minimum bend capability, which can lead to mechanical failure and other problems. To ensure that the shielding is up to scratch, it’s essential to test its performance with a number of bending cycles to make sure that it can withstand a dynamic operating environment.

During production, it’s inevitable that some PCBs won’t pass quality inspections and will need to be reworked or repaired. This can be costly, especially if the PCBs are part of a just-in-time manufacturing system and can’t be remade quickly. Fortunately, there are environmentally conscious options for disposing of and repairing reworked PCBs that can help mitigate these costs. In addition, the cost of rework and repair can also be offset by recouping some of the bare board cost from the reused parts. The key is to design and manufacture a PCB with minimal defects in the first place to avoid expensive rework and remanufacturing. This can be achieved through careful design and engineering, including consideration of rf shielding pcb requirements at the earliest possible stages of the design process.

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