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34 Intel
®
855GME and Intel
®
852GME Thermal Design Guide for Embedded Applications
Thermal/Mechanical Applications
8.2 Mechanical Loading
The pressure applied to the surface of the 855GME or 852GME MCH package should not exceed
100 psi.
If the pressure on the surface of the chipset MCH package is exceeded, problems may arise. The
solder ball joints between the package and the motherboard may be subjected to fractures that
could result in a loss or degradation of electrical signals from the chipset MCH. Also, the die may
be exposed to warpage or, at unusually high levels of stress, cracking.
If a large compressive load is applied to the die surface precautions should be taken to help
alleviate some of the load. One manner of doing this is to provide some backing support for the
motherboard directly underneath the chipset MCH. Standoffs can be used between the motherboard
and the chassis to add rigidity to the motherboard under the chipset MCH and reduce the amount of
board flexure under large loads.
8.3 Thermal and Mechanical Reliability
Recommendations for thermal mechanical reliability testing are shown in Table 5. These should be
considered as general guidelines. The user should define validation testing requirements based on
anticipated use conditions.
Table 5. Reliability Validation
Test
(1)
Requirement Pass/Fail Criteria
(2)
Mechanical Shock
• Quantity: three drops for + and – directions in each
of three perpendicular axes (i.e., total of 18 drops).
• Profile: 50 G trapezoidal waveform, 11 ms duration,
170 in/s minimum velocity change.
• Setup: Mount sample board on test fixture
Visual Check and Electrical
Functional Test
Random Vibration
• Duration: 10 min/axis, three axes
• Frequency Range: 5 Hz to 500 Hz
• Power Spectral Density (PSD) Profile: 3.13 G RMS
Visual Check and Electrical
Functional Test
Power Cycling (for
active solutions)
• 7500 on/off cycles with each cycle specified as 3
minutes on, 2 minutes off at 70 °C
Visual Check
Thermal Cycling
• -5 °C to +70 °C, 500 cycles Visual Check
Humidity
• 85% relative humidity, 55 °C, 1000 hours Visual Check
NOTES:The above tests should be performed on a sample size of at least 12 assemblies from 3 different lots
of material.
Additional Pass/Fail Criteria may be added at the discretion of the user.