Semiconductor Assembly Dummy Fill Thermal Spreading Resistance

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Solution Overview

Problem

In semiconductor devices, particularly in stacked IC configurations, the thermal design is compromised due to high thermal spreading resistance caused by the interface between the primary IC die and stacked dice, leading to poor heat dissipation and increased junction-to-package thermal resistance.

Innovation Solution

The implementation of dummy fills with high thermal conductivity, such as silicon or metallic materials, adjacent to the secondary IC dice, which thermally couple the primary IC die to a heat extraction element, reducing thermal spreading resistance by providing a direct thermal conduction path and alleviating the interface resistance between the secondary IC dice and the heat extraction element.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If stacked IC dice are mounted on the backside of the primary IC die, then the interconnection bottleneck is addressed and device functionality is improved, but thermal spreading resistance increases and heat dissipation deteriorates

Engineering Contradiction:

Improvedevice functionalityVSAvoidthermal spreading resistance

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

A dummy fill structure is introduced as an intermediary thermal conduction path between the primary IC die and the heat sink. This dummy fill acts as a mediator that provides an additional thermal pathway, reducing the thermal spreading resistance at the interface between the stacked dice and the heat extraction element.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The thermal conduction path is segmented into multiple pathways: one through the stacked dice and another through the dummy fill. This segmentation allows heat to be conducted through parallel paths, reducing the overall thermal spreading resistance and improving heat dissipation efficiency.

Inventive Principle:

Principle #1Segmentation

2Temperature

If the heat sink base area is increased to reduce spreading resistance, then thermal performance improves, but the device area占用 increases and compactness is reduced

Engineering Contradiction:

Improvespreading resistanceVSAvoidheat sink base area

Core Design Contradiction:

TemperatureVSArea of stationary object

Solution Approach 1:

The solution moves from a two-dimensional heat sink base area expansion to a three-dimensional vertical stacking configuration. By utilizing the vertical dimension for thermal conduction through the dummy fill and stacked dice, the heat sink can maintain a smaller base area while achieving effective heat dissipation through the vertical thermal pathway.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of manufacture

If thermal paste is used to attach the heat sink, then ease of assembly is improved, but thermal contact resistance increases and heat dissipation efficiency is reduced

Engineering Contradiction:

Improveassembly easeVSAvoidthermal contact resistance

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The thermal conductivity parameter of the bonding material is significantly improved by replacing conventional thermal paste with a bonding material that has higher thermal conductivity. This parameter change reduces thermal contact resistance while maintaining the ease of assembly through bonding processes.

Inventive Principle:

Principle #35Parameter changes

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 reduces thermal spreading resistance, enhancing heat dissipation and improving the thermal design of stacked ICs by providing a more efficient path for heat extraction, thereby lowering junction-to-package thermal resistance.

Implementation Method 1

At least one dummy fill each includes a top surface and a bottom surface. The bottom surface of each of the at least one dummy fill is mounted to the first surface of the first IC die adjacent the at least one additional IC die. A mounting surface is configured for thermal contact with a heat extraction element.

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

Methodology Applied

Scientific EffectThermal spreading resistance reduction: Conduction (thermal)

Data Source

PatentUS8299590B2Semiconductor assembly having reduced thermal spreading resistance and methods of making same

Publication Date: 2012.10.30 XILINX INC

AI summary

Semiconductor assemblies having reduced thermal spreading resistance and methods of making the same are described. In an example, a semiconductor device includes a primary integrated circuit (IC) die and at least one secondary IC die mounted on the primary IC die. A heat extraction element includes a base mounted to the semiconductor device such that each of the at least one secondary IC die is between the primary IC die and the heat extraction element. At least one dummy fill is adjacent the at least one secondary IC die, and each thermally couples the primary IC die to the heat extraction element.