How to Select Potting Materials for Server Power Supplies amid Rising Power Density

When selecting potting materials for server power supplies, thermal conductivity alone should not be the sole consideration. With the continuous increase in power density of AI servers, power supply modules, high‑frequency transformers, inductors, PFC and DC‑DC modules are subjected to rising temperature rise, vibration and electrical stress. A suitable potting material must strike a balance among thermal conductivity, electrical insulation, stress resistance, flame retardancy, flowability and production cycle time. Improper material selection may lead to incomplete filling, excessive bubbles, cracking upon curing, component stress‑induced damage and unstable heat dissipation performance. 1. Why Do Server Power Supplies Require Potting? Server power supplies integrate a large number of power devices and magnetic components, operating continuously under high‑load, frequent start‑stop and persistent heat‑generation conditions. Potting materials generally deliver the following functions: It should be noted that potting does not mean fully filling the entire power‑supply module. High‑frequency transformers, inductors and auxiliary power supplies are suitable for potting. Between power semiconductors and heat sinks, thermal gels, thermal greases or other thermal interface materials are more applicable. 2. Do Not Rely Solely on Thermal Conductivity for Material Selection 2.1 Actual Thermal Resistance Outweighs Nominal Thermal Conductivity High nominal thermal conductivity does not guarantee superior practical heat dissipation. Whether a stable thermal conduction path can be formed after potting depends on multiple factors: For server power supplies, temperature‑rise tests on actual modules are recommended, instead of merely comparing W/m·K values from product datasheets. 2.2 Flowability Determines Potting Feasibility Fine winding gaps commonly exist inside high‑frequency transformers and inductors. Excessively high material viscosity prevents sufficient penetration into gaps among coils, bobbins and magnetic cores, resulting in bubbles or unfilled areas. Therefore, key points to verify during selection: High‑thermal‑conductivity materials contain abundant thermal fillers. Higher thermal conductivity is usually accompanied by increased viscosity and density. A balance between…