MPC7457 datasheet(60/68 Pages) FREESCALE

60 / 68 page

MPC7457 RISC Microprocessor Hardware Specifications, Rev. 5

Freescale Semiconductor

System Design Information

temperature—airflow, board population (local heat flux of adjacent components), heat sink efficiency, heat sink

attach, heat sink placement, next-level interconnect technology, system air temperature rise, altitude, etc.

Due to the complexity and the many variations of system-level boundary conditions for today's microelectronic

equipment, the combined effects of the heat transfer mechanisms (radiation, convection, and conduction) may vary

widely. For these reasons, we recommend using conjugate heat transfer models for the board, as well as system-level

designs.

For system thermal modeling, the MPC7447 and MPC7457 thermal model is shown in Figure 28. Four volumes will

be used to represent this device. Two of the volumes, solder ball, and air and substrate, are modeled using the

package outline size of the package. The other two, die, and bump and underfill, have the same size as the die. The

silicon die should be modeled 9.64 × 11.0 × 0.74 mm with the heat source applied as a uniform source at the bottom

of the volume. The bump and underfill layer is modeled as 9.64 × 11.0 × 0.69 mm (or as a collapsed volume) with

orthotropic material properties: 0.6 W/(m • K) in the xy-plane and 2 W/(m • K) in the direction of the z-axis. The

substrate volume is 25 × 25 × 1.2 mm (MPC7447) or 29 × 29 × 1.2 mm (MPC7457), and this volume has

18 W/(m • K) isotropic conductivity. The solder ball and air layer is modeled with the same horizontal dimensions

as the substrate and is 0.9 mm thick. It can also be modeled as a collapsed volume using orthotropic material

properties: 0.034 W/(m • K) in the xy-plane direction and 3.8 W/(m • K) in the direction of the z-axis.

Figure 30. Recommended Thermal Model of MPC7447 and MPC7457

Bump and Underfill

Die

Substrate

Solder and Air

Die

Substrate

Side View of Model (Not to Scale)

Top View of Model (Not to Scale)

Conductivity

Value

Unit

Bump and Underfill

0.6

W/(m • K)

0.6

Substrate

k18

Solder Ball and Air

0.034

3.8

MPC7457 датащи(PDF) 60 Page - Freescale Semiconductor, Inc