Progression of damage caused by temperature cycling on a large die in a molded plastic package

Large silicon chips in molded plastic packages suffer physical damage to top-surface regions when subjected to repetitive thermal excursions. It is shown that a delamination between the molding compound and the die surface, progressing inward from a crack in the molding compound at a die corner, can enter an aluminum film through a crack in the passivation glass at an edge, travel through the metal, and exit at the opposite edge. This permits migration of glass and metal inward from corner regions. It is pointed out that reduced susceptibility to this effect may be obtained through the use of tougher metal, thicker passivation glass in lower metal edge corners, and tougher glass. A silicon integrated circuit chip approximately 250*290 mils in a 52-lead PLCC (plastic leaded chip carrier) was used as a test vehicle. Temperature and thermal shock cycling, from as low as -65 degrees C to +150 degrees C and for as many as 2000 cycles was performed.<>