Mold Compound and Copper Wire Selection for Quad-Flat Packages with High Density Leadframe in Automotive Applications

Abstract

The amount of electronics within vehicles continue to increase with the drive towards autonomous driving and green vehicles through improved engine controls and hybrid or full electric vehicles. Engine control units require electronic components which are located very close to the engine, and thus must operate within a high temperature ambient environment, at least meeting AEC Grade 1 or Grade 0 requirements. This paper reviews the bill of material selection for quad-flat package (QFP), in particularly, mold compound and copper wire, with high density leadframes. Palladium coated copper wire (PCC) is the current preferred wire of choice due to the improved manufacturability. Although PCC wire is susceptible to galvanic corrosion due to the presence of sulfur in the molding compound, the level of corrosion is minimal and impact is cosmetic only. Wire sweep is a major factor in the mold compound selection, especially for high density leadframes. Wire sweep percentage differs greatly from row to row, and mold compound type contributes significantly for a robust process on high density leadframes. Furthermore, on large body sized QFPs, package warpage is another main consideration in the selection of mold compound type as warpage directly impacts the lead co-planarity. It is shown that additional heat treatment post assembly, such as during burn-in, may contribute significantly towards warpage degradation. As such, it is necessary to select the molding compound with sufficiently low warpage through repeated heat treatment on the package. Lastly, the selected mold compound needs to meet the delamination requirements as per AEC-Q006 for copper wire interconnects.