How to ensure the high and low temperature EMC stability of I/O modules

To ensure stable EMC performance of I/O modules under extreme high and low temperatures, it is crucial to monitor component parameter drift and material property changes. Many passive components, such as capacitors, inductors, and ferrite beads, exhibit temperature-dependent parameter variations, especially ceramic capacitors. During design, components with stable temperature characteristics should be selected, such as X7R or X5R capacitors, or filter topologies with minimal temperature-dependent characteristics. At high and low temperatures, the conductive pads of the shielded housing may harden or shrink, leading to increased contact impedance and decreased shielding effectiveness. Wide-temperature-range conductive rubber or metal springs should be used.

The dielectric constant of the PCB board also changes with temperature, potentially affecting the integrity of high-speed signals. Temperature compensation should be implemented for temperature-sensitive analog front-ends in circuit design. Power modules must operate stably at extreme temperatures without generating additional noise. During testing, EMC testing under high and low temperature cycling is necessary. A common practice is to first place the module in a high/low temperature chamber to achieve thermal equilibrium, then quickly transfer it to a test site for rapid EMC testing, or remotely monitor radiated emissions within a temperature chamber. Ensure that EMC performance meets requirements across the entire operating temperature range.