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October 2001
Chassis Clearance Considerations For Systems Based On The Pentium® 4 Processor In The 478-pin Package:
Summary:
When integrating a system based on the Intel® Pentium® 4 processor in the 478-pin package, there are chassis clearance considerations to be aware of when selecting either a MicroATX or ATX chassis. Due to a bow or bend in the motherboard, which is inherent to thermal/mechanical solutions designed to place a compressive load on the CPU package and socket, there is potential for interference with the chassis and components or solder leads on the back/underside of the motherboard. Intel recommends customers select chassis which have a minimum effective clearance of 0.250" [6.35mm] between the chassis and motherboard or provide adequate electrical/mechanical insulation (non-conductive material between chassis and motherboard) to protect the motherboard and/or other system components from potential damage.
Details:
For chassis that do not have a minimum effective clearance of 0.250" [6.35mm] under the motherboard, components on the back/underside of the motherboard or solder leads may contact the chassis back plane and possibly cause damage to the motherboard and/or other system components (See Figure 1).
To find the effective clearance between the chassis and the back/underside of the motherboard, you will need to use a caliper or other measuring tool. Use the following formula to calculate the effective clearance:
Effective Clearance under the motherboard = Chassis standoff height (See Figure 2)
- Obstruction height (subtract highest intruding item such as stiffening rib(s), structure support(s), or other conductive mechanical structures underneath the footprint of the motherboard-See Figure 2)
Figure 1. Backside Components with Potential Interference with Chassis
Figure 2. Chassis Standoffs and Raised Ledges
To ensure successful integration and protection of systems based on the Pentium 4 processor in the 478-pin package, it is recommended to select a chassis which has a minimum effective clearance of 0.250" [6.35mm] under the motherboard. For chassis with less than the recommended effective clearance, it is recommended to verify that conductive obstructions in the chassis do not contact the back/underside of the motherboard. If contact between components on the back/underside of the motherboard and chassis is possible, it is recommended to provide adequate electrical/mechanical insulation (non-conductive material) between the motherboard and chassis.
Intel recommends that independent testing be conducted on the specific platform configurations used. OEMs and System Integrators are ultimately responsible for both thermal and mechanical validation of their specific system configuration.
Additional Information:
For more information regarding the bow or bend of motherboards based on the Pentium 4 processor in the 478-pin package, please refer to the document entitled, "Assembling Intel Reference Components for the Pentium 4 Processor in the 478-pin Package".
This applies to:
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