Silicon Sensor Die Packaging Stress Decay Mechanics
Packaging stress decay in silicon sensor dies causes continuous zero-point drift that requires thermal preconditioning bakes to stabilize long-term offset accuracy.
Post Mold Shrinkage
Volumetric Reduction
Molded plastic parts continue to change their shape and size for a period after they are removed from the manufacturing tool. The post mold shrinkage describes the contraction that occurs as the polymer cools and the molecular chains settle into a permanent configuration. This reduction in volume can apply substantial pressure to any components that are encapsulated within the plastic.
Curing Reaction
Continued chemical bonding within the resin matrix contributes to the tightening of the material over hours or days. Even after the part is solid to the touch, the internal structure is still evolving as the remaining monomers react. This process is often accelerated by a post-cure bake to ensure the part reaches its final size before assembly.
Internal Tension
Uneven cooling can lead to warping. Precise mold design is necessary to minimize these effects.
Manufacturing Offset
Designers must calculate the expected amount of contraction and adjust the dimensions of the mold accordingly. If the shrinkage is not properly managed, the final part may not fit the other components in the assembly or may fail to meet the required tolerances. Measuring a sample from each batch ensures that the process remains within the specified limits and that the internal stress levels do not compromise the integrity of the encapsulated electronics.