Does anyone have experience designing cases to resist damage from ESD? My keyboard just died and several others with the same board are reporting the same or similar failures.
The outside shielding of the USB port has components to trap and dissipate ESD. The case is anodized aluminum. Some PCB pads were covered with Kapton tape in an attempt to inhibit the observed failures but my unit died even with those pads covered.
Any suggestions how to iterate the design in order to resist damage from ESD? or what to try next to protect remaining units? Iām assuming the components around the USB port are effective at dissipating ESD and focused instead on the case design?
Designing cases to resist damage from Electrostatic Discharge (ESD) is critical for electronic devices like keyboards, as ESD can cause immediate or latent failures. Here are several suggestions to improve ESD resistance in your design, particularly focusing on the case and PCB design:
Enhanced ESD Protection Components: Ensure the components around the USB port, such as TVS diodes (Transient Voltage Suppressors), are adequately rated for the expected ESD events. These components should be placed as close as possible to the point where ESD can enter the circuit, in this case, the USB port.
Grounding: Improve the grounding of the case. Anodized aluminum is non-conductive, which might inhibit a good electrical connection between the case and the ground. You could design the case to have non-anodized areas where the case makes contact with the PCB grounding points or use conductive gaskets or coatings that connect the case to the PCB ground.
PCB Design: Revisit the PCB layout to enhance its ESD immunity. This includes:
Placing ESD protection components at every interface that could be exposed to ESD.
Implementing proper grounding techniques, such as using a ground plane and ensuring that the ground paths are short and direct.
Avoiding running sensitive traces near the edges of the PCB where they are more exposed to ESD.
Kapton Tape: While Kapton tape can provide some level of insulation, it might not be sufficient for high ESD events. Consider using conformal coatings on the PCB to provide better protection against ESD.
ESD Testing and Standards: If possible, conduct ESD testing based on standards like IEC 61000-4-2 to understand the susceptibility of your design to ESD and to validate the effectiveness of your ESD protection measures.
Faraday Cage Design: Consider designing the case to act as a Faraday cage, which can help in containing and diverting the ESD around the sensitive components. This might involve ensuring that there are no gaps in the case through which ESD could penetrate and making sure that the case is properly grounded.
Internal Shielding: In addition to the case design, consider adding internal shields or barriers around sensitive components or areas of the PCB. This could be in the form of metallic shields soldered to the ground or conductive foam/paint.
Connectors and Cables: Ensure that the connectors and cables used are also rated for good ESD protection. Sometimes, the weak link in the chain could be the cable or connector, not just the device itself.
User Interface Elements: For areas that users frequently touch, such as buttons or switches, consider additional local ESD protection. This could be in the form of ESD suppressors or capacitors that can absorb and divert the ESD away from sensitive circuits.
By focusing on these areas, you can enhance the ESD resilience of your design. It may also be beneficial to consult with an ESD expert or a specialized firm that can provide insights specific to your design and use case.
