
108 Heat Transfer: Thermal Management of Electronics
Figure 6.11 shows the schematic cross section of a plastic ball grid array (PBGA)
package. The die is mounted on a laminated substrate similar to a printed circuit
board. The connection between the integrated circuit on the die and the solder balls
at the bottom of the substrate is through gold wire bonds and vias in the substrate.
The die and the gold wires are covered by a plastic mold and that is why the package
is called a PBGA.
FIGURE 6.10 (See color insert following page 240.) Bottom sides of a 23 mm × 23 mm
169 ball BGA (a), a 27 mm × 27 mm 256 ball BGA (b), and a 27 mm