Understanding Smart Sensors - Nomads.usp

234 Understanding Smart SensorsChip-and-wire Flip-chip TAB(a) (b) (c)Figure 10.3 Bare die mounting techniques for MCMs.Figure 10.4 Dual-chip custom plastic package. (Courtesy of Motorola, Inc.)10.3.4 Ball Grid Array PackagingBall grid array (BGA) packages are among the newer semiconductor packagesthat may also have potential for multichip smart sensors. An overmolded padarray carrier (OMPAC) package is one of the new developments in semiconductorpackaging. 1 It is also known as solder bump array (SBA), pad array carrier(PAC), and land grid array (LGA). Each technique relies on a blind solderjoint for direct attachment of a leadless chip carrier to a printed circuit board[8]. As shown in Figure 10.5, the OMPAC has solder bumps attached to thecopper foil pad on an epoxy glass substrate. The die in the plastic molded packageis attached by gold wire bonds. Thermal vias run between solder bumps to1. OMPAC is a trademark of Motorola, Inc.