PCX745BVZFU350LE Atmel, PCX745BVZFU350LE Datasheet - Page 18

• Manufacturer Part Number: PCX745BVZFU350LE
• Description: IC MPU 32BIT 350MHZ 255PBGA
• Manufacturer: Atmel

Specifications of PCX745BVZFU350LE

• Processor Type: PowerPC 32-Bit RISC
• Speed: 350MHz
• Voltage: 2V
• Mounting Type: Surface Mount
• Package / Case: 255-PBGA
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Features: -

18
PC755/745
Table 6-3.
The board designer can choose between several types of heat sinks to place on the PC755.
There are several commercially-available heat sinks for the PC755 provided by the following
vendors.
For the exposed-die packaging technology, shown in
on page
Figure 6-1
mounted to a printed-circuit board.
Heat generated on the active side of the chip is conducted through the silicon, then through the
heat sink attach material (or thermal interface material), and finally to the heat sink where it is
removed by forced-air convection.
Since the silicon thermal resistance is quite small, for a first-order analysis, the temperature drop
in the silicon may be neglected. Thus, the heat sink attach material and the heat sink conduc-
tion/convective thermal resistances are the dominant terms.
Figure 6-1.
Note the internal versus external package resistance.
Characteristic
Junction to board thermal resistance
• The die junction-to-case (or top-of-die for exposed silicon) thermal resistance
• The die junction-to-ball thermal resistance
16, the intrinsic conduction thermal resistance paths are as follows:
External Resistance
External Resistance
Internal Resistance
depicts the primary heat transfer path for a package with an attached heat sink
Package Thermal Characteristics for CI-CGA
C4 Package with Head Sink Mounted to a Printed-circuit Board
Printed ± Circuit Board
Heat Sink
Radiation
Radiation
Symbol
Rθ
JB
Convection
Convection
“Recommended Operating Conditions
PC755 CI-CGA
Thermal Interface Material
Package/Leads
Die Junction
Die/Package
Value
8.42
2138G–HIREL–05/06
°
Unit
C/W
(1)
”