Precision Bandgap Thermal Stress Error Reduction across Surface Mount Packages
Mitigate bandgap thermal stress errors using compliant leaded packages, PCB isolation slots, polyimide die buffers, and stabilized factory calibration.
Post-Assembly Relaxation
Stress Recovery
A gradual decrease in internal mechanical stresses occurs within an integrated circuit package after the high-temperature molding and soldering processes are complete. This post-assembly relaxation slowly shifts the physical pressure exerted on the enclosed silicon chip.
Physical Origin
Viscoelastic behavior of the plastic mold compound and the substrate material drives the slowly evolving tension over time. As the polymer chains realign at room temperature, the compressive force applied to the silicon die diminishes. This structural stabilization takes place over several days or weeks depending on the material composition and storage conditions.
Measurement Influence
Piezoresistive effects cause the electrical parameters of sensitive analog components to drift during this stabilization phase. A precision voltage reference might exhibit a small offset shift that appears as long-term instability if tested too soon after assembly. Calibration routines should therefore be delayed until this primary drift has finished.
Mitigation Strategy
Baking the assembled packages at high temperatures accelerates the relief of built-in mechanical stress before final calibration occurs. This thermal conditioning, often called burn-in or stabilization baking, ensures that the post-assembly relaxation is largely completed before the device parameters are trimmed. Testing after this bake results in a highly stable device that will not experience excessive drift during storage or early field operation.