Meaning
Component manufacturing involves the replacement of the thermosetting plastic that protects integrated circuits from environmental stress. An epoxy mold compound substitution occurs when a supplier changes the chemical formulation used to encapsulate a semiconductor die. This material provides mechanical support and moisture protection.
Altering the filler content or the resin base changes the thermal expansion properties of the part.
Material Equivalence
Chemical analysis determines if the new substance matches the performance of the original resin. An epoxy mold compound substitution requires a detailed comparison of glass transition temperatures and moisture absorption rates. Manufacturers verify that the new compound does not introduce corrosive ions.
Matching the coefficient of thermal expansion prevents mechanical stress during temperature cycles.
Qualification Procedure
Testing sequences validate the reliability of the assembly after an epoxy mold compound substitution has been implemented. Stress tests include unbiased highly accelerated stress testing and temperature cycling to ensure the bond wires remain intact. Failure analysis looks for delamination at the interface between the plastic and the lead frame.
A successful qualification proves that the change does not shorten the operating life of the device. Documentation must reflect the specific lot numbers used during the validation.
Thermal Integrity
Heat dissipation characteristics change when the density of the filler material varies. Because the epoxy mold compound substitution affects the thermal resistance from the junction to the case, engineers must re-evaluate the cooling requirements of the system. A compound with lower thermal conductivity leads to higher operating temperatures.
Higher temperatures accelerate the aging of the silicon.
