Why Temperature Resistance Alone Is Not Enough for Pressure Sensor Potting: High-Temperature Performance, Low CTE and Low Stress Must Be Evaluated Together

The potting of pressure sensors should not be judged merely by the “maximum temperature resistance in °C”. Long-term reliability is actually determined by CTE, modulus of the cured compound, substrate matching, thermal conductivity requirements and stress induced by temperature cycling. Especially for assemblies combining aluminum housing, ceramic, PCB and sensing die, the fact that an adhesive can cure at high temperatures does not guarantee reliability after long-term thermal cycling. Pressure Sensor Potting 1. Why Are Pressure Sensors Particularly Vulnerable to Thermal Stress? First: Thermal expansion of internal materials is inconsistent. A pressure sensor may incorporate multiple components: These components expand to different extents as temperature rises. If the potting adhesive features high thermal expansion and high stiffness, thermal deformation will be converted into mechanical stress. Second: Pressure sensors require not only protection but also stable measurement performance. General electronic modules mainly focus on basic functionality. For sensors, extra concerns arise: Will the encapsulation affect the sensitive structure and output stability? Therefore, “harder equals better” is not a universal rule. 2. What Do Temperature Resistance, Tg, CTE and Modulus Respectively Address? Parameter Core Question to Answer Risks of Improper Selection Operating Temperature Whether the adhesive can withstand the service temperature long-term Aging, performance degradation Tg Whether the material state changes drastically upon temperature rise Variation of modulus and dimensional stability CTE How significantly the adhesive expands and contracts with temperature Interfacial stress, cracking, delamination Modulus / Hardness How much stress the adhesive transfers to components Stress damage to sensing die and solder joints Thermal Conductivity Whether heat can be dissipated efficiently Local overheating Adhesion Whether interfacial bonding remains intact after thermal cycling Delamination, water ingress To sum up: Temperature resistance answers whether the adhesive can survive at a given temperature; CTE and modulus determine whether temperature fluctuations will damage the assembly…