New findings in the occurrence of false-healing in plastic encapsulated microcircuits using scanning acoustic microscopy

"False-healing" refers to the occasionally observed reduction of delamination in plastic encapsulated microcircuits, In previous studies, "false-healing" was reported only at the leadframe-plastic interface. It was thought that the chemical contaminants present in the flux enter the package and form corrosive products which fill up the internal air gaps. This paper reports on some new findings in the occurrence of false-healing in plastic packages using scanning acoustic microscopy. This study found that false-healing also occurs in instances where there was no exposure to corrosive media. Additionally, false healing was observed at the die-plastic interface, where chemical contaminants could not reach. Alternate explanations for this phenomenon are suggested and its impact on damage assessment of plastic encapsulated microcircuits is discussed.