Thermal Bond Line; Solder Joint Protection; Figure 10. Intel (G)Mch Clip Lateral Retention Tab Feature - Intel 845PE Thermal Design Manual

Generic Thermal Attach / Mechanical Solution
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Figure 10. Intel (G)MCH Clip Lateral Retention Tab Feature
4.2

Thermal Bond Line

The thickness of the bond line between the heatsink and die is critical to thermal performance of
the TIM. The bond line thickness is dependent on the pressure between the heatsink and the die.
The clip retention mechanism is used to generate the pressure required to ensure thermal
performance (see Table 7). The generic clip frame and lever design generates more than 50-psi
pressure.
4.3

Solder Joint Protection

The solder joints between the package and the motherboard are susceptible to damage under
mechanical shock conditions depending on the mass and proximity of the processor heatsink.
Other elements (e.g., motherboard bending rigidity and the size and distribution of other mass
components on the motherboard) can also affect solder joint susceptibility to damage.
The generic clip design uses mechanical preload on the package to protect the solder joint
against damage under mechanical shock. The design features a rotating cam (see Figure 11) that
generates substantial preload between the heatsink and package. The cam has a levered handle
that provides a mechanical advantage during installation.
The preload serves to compress the solder ball array between the package and motherboard. The
compression in the solder balls delays the onset of tensile load under critical shock conditions,
and the magnitude of maximum tensile load is thereby reduced. In this manner, the critical
solder balls are protected from tensile loading that may cause damage to the solder joint.
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Insert clip tab between
fins to provide lateral
retention
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Intel 845GE / 845PE Chipset (G)MCH Thermal Design Guide
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clip_lat_ret_tab