Epoxy Compound Moisture Diffusion Kinetics during Reflow
Epoxy compound moisture absorption generates critical steam pressures during lead-free reflow, demanding strict MSL dry-pack handling to prevent internal delamination.
Leadframe Adhesion
Mechanical Bond
Structural integrity of microelectronic packages depends on the strength of the interface between the internal metal frame and the plastic molding compound. This mechanical interface strength is leadframe adhesion, which prevents the separation of the encapsulation material from the internal conductor. It ensures the package remains intact during thermal cycling.
The quality of the interface determines the long-term reliability of the device.
Delamination Threat
Weak bonding at the metal-plastic interface allows moisture to accumulate along the internal leads. During reflow soldering, this trapped moisture vaporizes and creates high pressure that can separate the molding compound from the metal. This separation is called delamination, which can break the internal wire bonds and cause electrical failure.
This mechanical risk is heightened when using lead-free soldering profiles.
Surface Treatment
Metal frames are subjected to chemical etching or oxidation to roughen the surface and increase mechanical interlocking. This surface treatment is completed before the encapsulation step. Copper leadframes are often coated with specialized metal layers to improve bond strength.
These treated surfaces resist separation under high thermal stresses.
Assessment Metric
Adhesion strength is evaluated using pull testing or acoustic microscopy to check the bonded interfaces. Acoustic microscopy reveals any internal gaps or delamination areas without damaging the package. Standard shear testing provides a numerical force value required to separate the molding compound from the metal frame.
These quality metrics are analyzed to qualify new molding compounds and leadframe alloys. High-precision testing systems apply controlled forces to ensure that production samples meet or exceed minimum shear thresholds.