Lid Pocket Structure for Liquid Metal TIM Bleed-Out Control

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Solution Overview

Problem

Liquid metal thermal interface materials (TIM) tend to bleed out from the area between the heat sink and the semiconductor die during attachment, reducing their effectiveness in heat transfer.

Innovation Solution

A cover or lid structure with vertical walls forming a pocket around the semiconductor device is used to contain the liquid metal TIM, ensuring it remains in place and maintains effective heat transfer by routing excess material along the walls within the pocket.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If liquid metal TIM is used to increase thermal conductivity, then heat transfer efficiency is improved, but TIM bleeds out from the attachment area during heat sink attachment

Engineering Contradiction:

Improveheat transfer efficiencyVSAvoidTIM distribution stability

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The heat sink is segmented into a body and a separate lid structure with vertical walls that form a pocket. This segmentation allows the lid to contain the liquid metal TIM within the pocket during attachment, preventing bleed-out while maintaining thermal conductivity benefits.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The lid structure with vertical walls acts as an intermediary between the TIM and the heat sink body. It controls TIM distribution by containing excess material within the pocket formed by its walls, ensuring proper TIM placement without direct contact between the heat sink body and TIM during attachment.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If more liquid metal TIM is applied to ensure coverage, then thermal contact is improved, but excess TIM bleeds out and reduces effectiveness

Engineering Contradiction:

Improvethermal contact reliabilityVSAvoidTIM loss

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The lid structure segments the TIM application area by creating a pocket with vertical walls. This allows excess TIM to be contained within the pocket rather than spreading uncontrollably, ensuring sufficient TIM coverage for reliable thermal contact while preventing material loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The vertical walls of the lid structure add a vertical dimension to TIM containment. By routing excess TIM along the vertical walls within the pocket, the structure prevents lateral spread and bleed-out, maintaining TIM where it is most effective for heat transfer.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Manufacturing precision

If a lid structure with vertical walls is added to contain TIM, then TIM distribution is controlled, but device complexity increases

Engineering Contradiction:

ImproveTIM distribution controlVSAvoidheat sink structure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The lid structure merges multiple functions into a single component: it provides structural support for the heat sink, forms the pocket containing walls for TIM control, and acts as a barrier to prevent TIM bleed-out. This integration reduces the need for separate TIM containment features.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The lid structure serves multiple purposes: it is part of the heat sink assembly providing structural integrity, creates the pocket that controls TIM distribution, and prevents TIM loss during attachment. This multi-functionality justifies the added structural element by delivering multiple benefits from a single addition.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution effectively prevents TIM bleed-out, ensuring consistent and enhanced thermal conductivity between the semiconductor die and heat sink, thereby improving heat dissipation and reducing the risk of delamination.

Implementation Method 1

A TIM is disposed between the heat sink and a surface of the semiconductor die to assist with the transfer of heat between the semiconductor die and heat sink

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

A cover or lid structure with vertical walls forming a pocket around the semiconductor device is used to contain the liquid metal TIM

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Data Source

PatentUS20240371719A1Semiconductor Device and Method of Controlling Distribution of Liquid Metal TIM Using Lid Structure

Publication Date: 2024.11.07 STATS CHIPPAC LTD

AI summary

A semiconductor device has an electrical component and a heat sink disposed over the electrical component. The heat sink has a cover with a wall extending from the cover forming a pocket around a perimeter of the electrical component. The heat sink also has a horizontal step, and a riser extending from the horizontal step to the cover. The wall extends from the cover to form the pocket. A TIM is disposed between the cover and a surface of the electrical component. The TIM can be liquid metal. The heat sink is pressed onto the TIM under force and heat to distribute the TIM between the cover and surface of the electrical component. The TIM remains contained within the pocket by the wall. The wall or cover can have a vent hole. The TIM may extend over a side surface of the electrical component.