FD-FBGA Reduces Mount Space
01/01/2000
San Jose, Calif. - A new small-footprint array package called the Face-Down Fine Pitch Ball Grid Array (FD-FBGA), intended for wireless and computer assemblies, measures only 6.4 x 10.10 mm. At a maximum elevation of 1 mm and weighing only 0.11 g with a 0.65 mm ball pitch, it is said to require 75 percent less mounting area and volume than the ubiquitous thin small-outline package.
Developed by Fujitsu Microelectronics Inc., the FD-FBGA`s face-down configuration is constructed with a single-layer, 0.16 mm-thick FR-4 substrate and is attached to a chip via a resin (biphenyl epoxy) post. The substrate features a single trace on its bottom side, which is covered by solder resist. There is no through hole; the substrate opening for wire bonding is less than 1.0 mm. A special characteristic enables a fan-in and fan-out wiring configuration as die size dictates. Lastly, a new interposer molding technology accompanies the development: It permits mold resin to flow through a gap between the die and the interposer, covering the die`s entire surface and side.
Although the FD-FBGA features a higher thermal resistance - 60°C/W for the 60-pin unit vs. 30°C/W for the 54-pin TSOP - its face-down configuration exposing the die reportedly enables it to manage thermal performance via direct attachment of a heat sink to the package.
The package will be made available in several versions. A 60-pin FD-FBGA is suited for SDRAMs, an 85-pin for 128 Mb DDR-SDRAMs and a 74-pin version for 72 Mb RDRAMs (Rambus) will enable a transfer rate of 800 MHz.
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The FD-FBGA`s package structure. The face-down configuration by compensation for its small size improves thermal performance.