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Thermal/Mechanical Specifications and Design Guidelines 27
Independent Loading Mechanism (ILM)
4 Independent Loading
Mechanism (ILM)
The ILM has two critical functions: deliver the force to seat the processor onto the
socket contacts and distribute the resulting compressive load evenly through the socket
solder joints.
The mechanical design of the ILM is integral to the overall functionality of the LGA1155
socket. Intel performs detailed studies on integration of processor package, socket and
ILM as a system. These studies directly impact the design of the ILM. The Intel
reference ILM will be “build to print” from Intel controlled drawings. Intel recommends
using the Intel Reference ILM. Custom non-Intel ILM designs do not benefit from Intel's
detailed studies and may not incorporate critical design parameters.
Note: There is a single ILM design for the LGA1155 socket and LGA1156 socket.
4.1 Design Concept
The ILM consists of two assemblies that will be procured as a set from the enabled
vendors. These two components are ILM assembly and back plate. To secure the two
assemblies, two types of fasteners are required a pair (2) of standard 6-32 thread
screws and a custom 6-32 thread shoulder screw. The reference design incorporates a
T-20 Torx head fastener. The Torx head fastener was chosen to ensure end users do not
inadvertently remove the ILM assembly and for consistency with the LGA1366 socket
ILM. The Torx head fastener is also less susceptible to driver slippage. Once assembled
the ILM is not required to be removed to install / remove the motherboard from a
chassis.
4.1.1 ILM Assembly Design Overview
The ILM assembly consists of 4 major pieces: ILM cover, load lever, load plate and the
hinge frame assembly.
All of the pieces in the ILM assembly except the hinge frame and the screws used to
attach the back plate are fabricated from stainless steel. The hinge frame is plated. The
frame provides the hinge locations for the load lever and load plate. An insulator is pre-
applied to the bottom surface of the hinge frame.
The ILM assembly design ensures that once assembled to the back plate the only
features touching the board are the shoulder screw and the insulated hinge frame
assembly. The nominal gap of the load plate to the board is ~1 mm.
When closed the load plate applies two point loads onto the IHS at the “dimpled”
features shown in Figure 4-1. The reaction force from closing the load plate is
transmitted to the hinge frame assembly and through the fasteners to the back plate.
Some of the load is passed through the socket body to the board inducing a slight
compression on the solder joints.
A pin 1 indicator will be marked on the ILM assembly.