Chip Assembly Heat Spreader Layout for CTE Stress Relief

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Solution Overview

Problem

The coefficient of thermal expansion (CTE) mismatch between heat distribution devices and other components in chip assemblies leads to stress and mechanical failures due to temperature changes during manufacture or use.

Innovation Solution

A microelectronic device assembly is designed with a substrate, microelectronic elements, a stiffener element with a higher CTE, and a heat distribution device with a lower CTE, where the stiffener element extends around the microelectronic elements and the heat distribution device is bonded to the rear surface of the microelectronic elements using a thermal interface material.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a one piece heat distribution device comprised of a single thermally conductive material is used to cool microelectronic elements, then thermal management effectiveness is improved, but CTE mismatch stress and mechanical failure risk increase due to differential expansion between the heat distribution device, substrate, and chip

Engineering Contradiction:

Improvethermal management effectivenessVSAvoidmechanical failure risk

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The heat distribution device is divided into two separate components: a heat distribution device that contacts the microelectronic element and a stiffener element that contacts the substrate. This segmentation allows each component to be optimized for its specific function and material properties, resolving the CTE mismatch issue by preventing direct mechanical coupling between mismatched components.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stiffener element acts as an intermediary component between the substrate and the heat distribution device. It provides mechanical support and distributes stress without being directly bonded to both the substrate and heat distribution device, thereby mediating the CTE mismatch and preventing warpage and mechanical failure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If a single material is used for the heat distribution device, then manufacturing simplicity is maintained, but the ability to optimize both thermal conductivity and CTE matching is limited

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidmaterial optimization capability

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

Dividing the heat distribution device into two separate components enables each component to be manufactured from optimally suited materials. The heat distribution device can use high thermal conductivity materials while the stiffener element can use materials with appropriate mechanical properties and CTE characteristics, achieving material optimization without compromising manufacturing feasibility.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration effectively manages thermal expansion, reduces stress, and enhances thermal conductivity, thereby improving the reliability and performance of chip assemblies.

Implementation Method 1

The coefficient of thermal expansion (CTE) mismatch between the heat distribution device and other components in the chip assembly can stress the assembly when any one of these components expands at a different rate than other components due to temperature changes

Methodology Applied

Scientific EffectCoefficient of thermal expansion (CTE): Thermal Expansion

Implementation Method 2

a heat distribution device joined to the plurality of chips using a thermal interface material ('TIM')

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

heat distribution devices can be utilized within a microelectronic assembly to aid in the reduction of heat generated by microelectronic elements

Methodology Applied

Scientific EffectHeat distribution: Conduction (thermal)

Data Source

PatentUS12243802B2Methods and heat distribution devices for thermal management of chip assemblies

Publication Date: 2025.03.04 GOOGLE LLC

AI summary

A method of manufacturing a chip assembly comprises joining an in-process unit to a printed circuit board; reflowing a bonding material disposed between and electrically connecting the in-process unit with the printed circuit board, the bonding material having a first reflow temperature; and then joining a heat distribution device to the plurality of semiconductor chips using a thermal interface material (“TIM”) having a second reflow temperature that is lower than the first reflow temperature. The in-process unit further comprises a substrate having an active surface, a passive surface, and contacts exposed at the active surface; an interposer electrically connected to the substrate; a plurality of semiconductor chips overlying the substrate and electrically connected to the substrate through the interposer, and a stiffener overlying the substrate and having an aperture extending therethrough, the plurality of semiconductor chips being positioned within the aperture.