Lid Reservoir Structure for Liquid TIM Pumping-Out Prevention

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Solution Overview

Problem

Conventional lidded flip chip packages face challenges in using liquid thermal interface materials (TIM) due to pumping-out issues during thermal cycling, leading to incomplete gap filling and potential electrical damage, which limits their thermal performance and reliability.

Innovation Solution

A heat-dissipating object with a reservoir structure, including a seal ring and connecting hole, is designed to accommodate a liquid TIM, allowing it to expand and contract while maintaining a sealed gap and reservoir system, ensuring consistent thermal performance and preventing electrical issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a liquid metal TIM is used in a conventional lidded flip chip package, then thermal conductivity and surface wetting capability are significantly improved, but the TIM is pumped out during thermal cycling due to volume changes

Engineering Contradiction:

Improvethermal reliabilityVSAvoidTIM pumping out

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The lid is designed to perform multiple functions: it serves as both the heat-dissipating component and contains an integrated reservoir structure that compensates for TIM volume changes during thermal cycling, preventing TIM pumping out

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The reservoir structure is nested within the lid body, creating a compact design where the reservoir cavity is integrated into the lid's internal structure, allowing the lid to contain both the sealing function and the TIM compensation function

Inventive Principle:

Principle #7Nested doll (Nesting)

2Manufacturing precision

If a liquid metal TIM is used to fill the gap between flip chip and lid, then gap filling capability is improved, but electrical conductivity causes potential damage when TIM pumps out

Engineering Contradiction:

Improvegap filling capabilityVSAvoidelectrical damage

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The electrical conductivity of liquid metal TIM, which is normally a harmful factor when TIM pumps out causing electrical damage, is converted into a beneficial feature by ensuring complete gap filling maintains proper electrical isolation while the reservoir prevents pumping out

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Adaptability or versatility

If the gap volume changes during thermal cycling, then thermal expansion is accommodated, but the liquid TIM is pumped out due to volume variation

Engineering Contradiction:

Improvethermal expansion accommodationVSAvoidTIM volume loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of substance

Solution Approach 1:

The reservoir structure compensates for TIM volume changes by allowing TIM to expand into the reservoir cavity when heated and contract back into the sealed gap when cooled, maintaining constant TIM presence in the functional gap area

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The reservoir structure adds a third dimension (vertical cavity within the lid) to accommodate TIM volume changes, transforming the one-dimensional gap filling problem into a three-dimensional volume management solution

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

The reservoir structure effectively prevents liquid TIM from being pumped out, maintaining a consistent thermal interface and enhancing the thermal performance and reliability of the lidded flip chip package by ensuring the liquid TIM remains in place, even under varying temperatures.

Implementation Method 1

the seal ring is an elastic-type ring mounted on the bottom surface of the base plate

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

when the package is under a thermal cycling test or in its long term of application, the volume of the gap between the flip chip and the lid varies with temperature due to the warpage of the flip chip

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

a thermal interface material (TIM) is usually used to fill the gap between the flip chip and a heat-dissipating object, like a lid or a heat sink for transferring the heat from one to the other

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS11507017B2Package aspect of heat-dissipating lid and reservoir structure for liquid thermal interfacing materials

Publication Date: 2022.11.22 IC CHIP COOLING TECHNOLOGIES LLC

AI summary

The disclosure describes a heat-dissipating object having a reservoir structure so that a reservoir system can be formed in an electronic device, allowing for a liquid TIM in the gap between the heat-dissipating object and the heat-generating object of the electronic device. The reservoir structure comprises a seal ring, a connecting hole and a reservoir which is a space for taking in a liquid material and releasing it again when needed. As a specific case of the heat-dissipating object and the electronic device, a lid having a reservoir structure and a lidded flip chip package based on the lid are particularly described in details of the embodiments of the present invention.