https://test-devzone.nordicsemi.com/f/nordic-q-a/83342/nrf52840-esd-failure-4kv-body-modelDear All, We are developing a device based around nRF52840 on a rigid-flex custom PCB that is mounted inside an anodized aluminum cube with one face covered with plastic. During certification we failed the 4 kV body model ESD test. The ESD pulse wasen-USTelligent Community 13 Non-ProductionThu, 12 May 2022 15:45:27 GMThttps://test-devzone.nordicsemi.com/thread/367698?ContentTypeID=1Thu, 12 May 2022 15:45:27 GMT137ad170-7792-4731-bb38-c0d22fbe4515:f26e1feb-57c5-4b1e-b709-b502da4859aduser88066<p>Dear ketilja,</p> <p>Thank you for reply, explanation and suggestions. You were right. ESD events slowly melted the pad drivers. We have used ESD protection diodes to protect GPIO lines and serial resistances do further decouple them from nRF. We are now ESD compliant!</p><div style="clear:both;"></div>https://test-devzone.nordicsemi.com/thread/346431?ContentTypeID=1Thu, 06 Jan 2022 11:06:47 GMT137ad170-7792-4731-bb38-c0d22fbe4515:f639ede6-baf1-41e1-bfab-ea81bb424b37ketiljo<p>Tracking ESD events where they enter the design and how they spread on the PCB can be challenging. Decoupling and protection of pins that are exposed are needed. But also consider improving the HV insulation of the PCB. Maybe place a plastic sheet between the PCB and the housing.&nbsp;</p> <p>The ESD event will partly melt the internal structure of the pad driver. You can see different effects of this, but usually a lower than normal resistance to ground.</p><div style="clear:both;"></div>