What Adhesive to Encapsulate Internal Circuits of Hall Position Sensors? Focus on Bonding to PA66 Housing, Terminal Sealing and Oil-Resistant Service Conditions

For encapsulation of internal circuits in automotive Hall position sensors, insulation potting adhesives with appropriate flowability, interfacial adhesion and medium resistance shall be selected according to the actual structure of engineering plastic housings such as PA66, metal terminals and PCBs. Special priority shall be given to verifying sealing continuity at the terminal feed-through positions. If the sensor is exposed to oil for long-term operation or subjected to thermal cycling, room-temperature waterproofing and initial adhesion tests alone cannot prove encapsulation reliability. Hall position sensors detect magnetic field changes via Hall elements, and work with magnets and signal processing circuits to measure position, angle or motion status. Widely used in automotive actuators, industrial motors and other position feedback systems, a typical sensor assembly consists of a Hall chip, PCB, metal connecting terminals and an engineering plastic housing. The main functions of encapsulation adhesive are to protect internal circuits, fix partial structures and mitigate ingress of external media. Nevertheless, sensors often feature complex zones such as terminal roots, housing corners and PCB peripheries. Continuous protective coverage in these critical areas matters more than simply coating the entire cavity surface. Why Special Attention Is Required for Terminal Feed-Through Zones in Hall Sensor Encapsulation Material and structural discrepancies exist between metal terminals and plastic housings. Even if terminals are fixed by insert moulding or other processes, the surrounding interfacial area requires careful evaluation. When the sensor undergoes temperature fluctuation, metal terminals and engineering plastics exhibit different thermal expansion behaviours, subjecting the adjacent interface to repeated deformation. Discontinuous adhesive coverage or insufficient bonding to the substrate in this zone compromises long-term sealing performance. Therefore, sealing design at terminal roots cannot rely solely on the nominal temperature range of the potting material. Validation shall combine terminal geometry, housing structure and actual thermal cycling conditions. For sensors with…