An IC packaging technology developed by Advanced Interconnect Technologies (AIT) offers functionality comparable to fine-pitch ball-grid arrays (BGAs), but at lower cost. It will debut in two upcoming product series—the Very Thin Fine Pitch Quad Flat Packages-No Leads (VFQFP-N) and the Very-Very-Fine Pitch Quad Flat Packages-No Leads (WFQFP-N).
I/O pads on the bottom of these packages replace the gull-wing leads found in traditional leadframe-based packages. The resulting QFPs resemble leadless chip carriers, but with no metallization on the sides. Connections to a copper leadframe are made either through wirebonds or flip-chip assembly (see the figure). The latter exploits a pillar bumping interconnect licensed from Advanpack Solutions PTE of Singapore.
AIT's packages reduce IC assembly costs by exploiting a batch-style manufacturing process based on a standardized leadframe and common mold. The process accommodates body sizes from 2 by 2 mm to 15 by 15 mm, die sizes up to 10 mm2, and lead counts up to 80. The packages are more cost-effective than many existing array types because they eliminate expensive BGA substrates and ball-attach tooling.
As an example, consider a 7- by 7-mm QFN versus an equivalent fine-pitch BGA. The BGA's material cost would be about 40% greater than the QFN, its assembly cost would be 13 times as great, and its associated overhead costs would be about 70% more.
Better electrical and thermal performance accompany the cost benefits. Lead inductance is reduced by 75% compared to fine-pitch BGAs. Thermal resistance is 50% less than comparably sized TSSOPs, due to an included, exposed leadframe pad that solders directly to the printed-circuit board. The VFQFP-N and WFQFP-N are slated for third-quarter production this year.
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