Problem statement

This project evaluates the compression of two thermal interface material (TIM) layers in a stacked processor assembly:

1. A thin die bondline TIM between the processor die and the copper heat spreader.
2. A thicker spreader TIM between the copper heat spreader and aluminum.

Although the two TIMs carry the same approximately 4 lbf compressive load, their contact areas are significantly different:

Interfaces	Contact area	Initial BLT	Target BLT
Processor die / copper spreader	0.300 in²	0.010 in	0.005 in
Copper spreader / aluminum	1.400 in²	0.040 in	0.025 in

The copper-spreader interface has approximately 4.67 times the area of the die interface. Because average pressure is determined by

[ P = \frac{F}{A}, ]

the same 4 lbf assembly load produces substantially different average pressures:

• Die interface: approximately 13.33 psi
• Copper-spreader interface: approximately 2.86 psi

The engineering problem is to determine whether the applied assembly load can compress both TIM layers from their initial bondline thicknesses to their target thicknesses without causing unacceptable squeeze-out, insufficient contact, or excessive material displacement.

This model therefore quantifies:

• The average pressure applied to each TIM interface.
• The change in bondline thickness and compressed TIM volume.
• The volume of material displaced as each interface reaches its target thickness.
• The sensitivity of interface pressure to changes in assembly force.
• The geometric squeeze-out implied by an approximate conservation-of-volume assumption.

The model does not assume that pressure alone guarantees the target bondline thickness. Actual TIM compression depends on material-specific behavior, including stiffness, flow characteristics, temperature, loading rate, surface condition, and manufacturing tolerances. Experimental compression data or fixture testing is required to confirm that the selected TIM materials achieve the intended bondlines.

Model scope

This model calculates average interface pressure, compression geometry, TIM volume displacement, and idealized squeeze-out under an approximate volume-conservation assumption.

It does not predict final bondline thickness from applied force unless material-specific compression data or experimental measurements are supplied.

Results should be validated using a controlled compression fixture before being used for production design decisions.

Baseline configuration

Interface	Material	Area	Initial BLT	Target BLT	Average pressure
Die	GEL 8010	0.300 in²	0.010 in	0.005 in	13.33 psi
Copper spreader	GEL 75	1.400 in²	0.040 in	0.025 in	2.86 psi

Applied load: 4 lbf

Baseline assumptions

• No load bypass
• Same resultant force through both interfaces
• Flat and parallel contact surfaces
• Approximately incompressible TIM for geometric volume calculations
• Static and centered applied load
• Average pressure rather than local pressure distribution

Example output

Average interface pressure

Pressure sensitivity to clamp force

Initial and target bondline thickness

Retained and displaced TIM volume

Sharing statement

This repository contains a Jupyter-based TIM compression and squeeze-out model for the current die and copper-spreader stack. It calculates average pressure, compression geometry, displaced volume, and force sensitivity.

The current version is a geometric model. Material-specific pressure-to-bondline behavior still requires experimental validation.