Re-Evaluating Radiated Emissions and Exposure for Potted Transmitter Housings
Encapsulating transmitters alters dielectric loading, detuning antennas and shifting RF exposure boundaries, demanding re-evaluation of emissions and SAR compliance.
Thermal Curing
Meaning
Heat exposure triggers chemical crosslinking to transform soft polymers into rigid structural solids. The application of thermal curing is used for epoxy adhesives, protective coatings and dielectric resins. This process accelerates the reaction between the base resin and the catalyst to achieve full mechanical strength.
Kinetic Reaction
Energy provided by the oven or heat lamp overcomes the activation barrier of the chemical system. During thermal curing, the viscosity of the resin drops initially before increasing rapidly as the network forms. The time required for this transition is a function of the peak temperature and the chemistry of the material.
Overheating can lead to degradation while underheating results in a soft or tacky finish.
Temperature Profile
Ramp rates and soak times are specified by the material supplier to minimize internal stress. A typical thermal curing cycle includes a ramp up phase, a hold period at the peak temperature and a controlled cooling phase. Rapid cooling can induce cracks in the material or cause delamination from the substrate.
Monitoring the actual temperature of the part is necessary because the air temperature in the oven may differ. Thermocouples attached to the assembly provide the data needed to validate the process.
Structural Integrity
Final hardness and adhesion levels are determined by the completeness of the cure. Successful thermal curing provides the resistance to solvents and mechanical loads required for field operation. Testing through differential scanning calorimetry verifies that the reaction has reached the desired state.
The resulting solid provides a stable environment for the integrated electronic components.