Temperature-cycle-induced chip surface damage in lead-on-chip packages

In lead-on-chip (LOC) packaging technology, the lead fingers are auached directly to the surface of the chip using a double-side adhesive tape. This method of chip attachment naturally leads to concerns about stress on the polyimide coated chip surface. Device failure related to fracture in the passivation layers and the Al-Si metal has been observed in temperature cycle tests. To investigate the effect of material characterization on the surface damage, devices were fabricated with different types of molding compounds, tapes and polyimides. This paper describes the optimum material properties, the assembly process parameters, and the experimental and simulated results of the surface damage. Keywords: surface damage, LOC package, polyimide, tape, mold compound, simulation

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