Semiconductor Package Metal Thermal Interface for IC Die Heat Dissipation

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Solution Overview

Problem

Conventional thermal interface materials (TIM) used in semiconductor chip packages face issues with thermal bottleneck and poor adhesion, leading to inefficient heat dissipation from integrated circuit (IC) dies, which can damage the IC or reduce overall chip performance.

Innovation Solution

A printed circuit board assembly with a metal thermal interface layer comprising a backside metal layer in direct contact with the IC die and a solder paste conformally printed on it, mounted on an array of copper thermal pads with slits filled with solder paste, providing improved heat transfer and adhesion to a heat spreading structure like a heat sink.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional thermal interface material (TIM) is used between IC die and heat spreading structure, then the assembly is simple to manufacture, but thermal bottleneck occurs and adhesion is poor

Engineering Contradiction:

Improvethermal interface qualityVSAvoidinterface structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent removes the conventional TIM layer from the thermal interface and replaces it with a metalized interface structure consisting of a backside metal layer on the IC die and a solder paste layer, directly eliminating the thermal bottleneck caused by TIM while maintaining manufacturing simplicity

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent employs a composite thermal interface structure combining a metal backside layer (e.g., gold, copper, or aluminum) with a solder paste layer, creating a multi-material interface that provides both excellent thermal conductivity and strong adhesion to the heat spreading structure

Inventive Principle:

Principle #40Composite materials

2Temperature

If conventional TIM is used for heat dissipation, then the process is simple, but thermal resistance is high and heat transfer efficiency is poor

Engineering Contradiction:

Improveheat dissipation efficiencyVSAvoidmanufacturing process simplicity

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent fundamentally changes the thermal conductivity parameter of the interface material by replacing TIM (with low thermal conductivity) with a metal backside layer and solder paste combination (with high thermal conductivity), thereby dramatically improving heat transfer efficiency while maintaining ease of manufacture through standard metal deposition and solder printing processes

Inventive Principle:

Principle #35Parameter changes

3Reliability

If TIM is applied on the contact surface, then adhesion is provided, but thermal bottleneck occurs and contact resistance is high

Engineering Contradiction:

Improveadhesion strengthVSAvoidthermal energy loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent creates a composite interface structure where the metal backside layer provides excellent thermal conductivity to eliminate thermal bottleneck, while the solder paste layer provides strong mechanical adhesion to the heat spreading structure, simultaneously achieving both low thermal resistance and high adhesion strength

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent replaces the mechanical/adhesive bonding mechanism of TIM with a metallurgical bonding mechanism using solder paste, which provides both superior thermal conductivity and strong mechanical attachment, eliminating the thermal bottleneck while maintaining or improving adhesion

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enhances heat dissipation efficiency and adhesion, allowing for rapid heat transfer from the IC die to the heat spreading structure, significantly improving thermal performance and reducing thermal resistance.

Implementation Method 1

the metal thermal interface layer comprises a backside metal layer that is in direct contact with the backside of the IC die... providing improved heat transfer and adhesion to a heat spreading structure... allowing for rapid heat transfer from the IC die to the heat spreading structure

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a solder paste conformally printed on the backside metal layer... providing improved heat transfer and adhesion to a heat spreading structure

Methodology Applied

Scientific EffectSoldering: Soldering

Data Source

PatentEP3690935B1Semiconductor package having improved thermal interface between semiconductor die and heat spreading structure

Publication Date: 2025.01.08 MEDIATEK INC

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AI summary

A semiconductor package (1) includes a base (10) having an upper surface (10a) and a lower surface (10b) opposite to the upper surface (10a). An antenna array structure (11) is embedded at the upper surface (10a) of the base (10). An IC die (20) is mounted on the lower surface (10b) of the base (10) in a flip-chip manner so that a backside of the IC die (20) is available for heat dissipation. Solder ball pads (118, 120) are disposed on the lower surface (10b) of the base (10) and arranged around the IC die (20). The semiconductor package (1) further includes a metal thermal interface layer (30) having a backside metal layer (310) that is in direct contact with the backside of the IC die (20), and a solder paste (320) conformally printed on the backside metal layer (310).