User's Manual

24 603 Hardware Specifications, REV 2
Preliminary—Subject to Change without Notice
Notes: 1. Junction-to-ambient thermal resistance is based on measurements on single-sided printed circuit
boards per SEMI (Semiconductor Equipment and Materials International) G38-87 in natural
convection.
2. Junction-to-case thermal resistance is based on measurements using a cold plate per
SEMI G30-88 with the exception that the cold plate temperature is used for the case temperature.
The vendors who supply heat sinks are Aavid Engineering, IERC, Thermalloy, and Wakefield Engineering.
Any of these vendors can supply heat sinks with sufficient thermal performance.
1.7.6 Thermal Management Information for the IBM Package
This section provides a thermal management example for the 603; this example is based on a typical desktop
configuration using a 240-lead, 32 mm x 32 mm, IBM C4-CQFP package. The heat sink used for this data
is a pinfin configuration from Thermalloy, part number 2338, and a flat aluminum plate with dimensions of
24 mm x 24 mm and 1.5 mm thickness.
1.7.6.1 Thermal Characteristics for the IBM C4-CQFP Package
The thermal characteristics for a C4-CQFP package are as follows:
Thermal resistance (junction to heat sink) = R
θjs
or θ
js
= 1.1°C/Watt (junction to heat sink)
1.7.6.2 Thermal Management Example
The following example is based on a typical desktop configuration using an IBM C4-CQFP package. The
heat sink used for this data is a pinfin heat sink #2338 attached to the C4-CQFP package with 2-stage epoxy.
The junction temperature can be calculated from the junction to ambient thermal resistance, as follows:
Junction temperature = T
j
= T
a
+ R
θja
* P
or
T
j
= T
a
+ (R
θjs
+ R
sa
) * P
Where:
T
a
is the ambient temperature in the vicinity of the device
R
θja
is the junction-to-ambient thermal resistance
R
θjs
is the junction-to-heat sink thermal resistance
R
sa
is the heat sink-to-ambient thermal resistance
P is the power dissipated by the device
Note: R
θjs
includes the resistance of a typical layer of thermal compound. If a lower conductivity material
is used, its thermal resistance must be included.
In this environment, it can be assumed that all the heat is dissipated to the ambient through the heat sink, so
the junction-to-ambient thermal resistance is the sum of the resistances from the junction to the heat sink
and from the heat sink to the ambient.
Note that verification of external thermal resistance and case temperature should be performed for each
application. Thermal resistance can vary considerably due to many factors including degree of air
turbulence.