RF Absorber Layer Stack for Heat Dissipation and Channel Isolation

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Solution Overview

Problem

In radio frequency devices, such as radar systems, increased power loss and interference between signal channels lead to heat buildup and reduced signal isolation, necessitating enhanced heat removal and improved isolation methods.

Innovation Solution

A device comprising a radio frequency chip, a heat sink, and a layer stack that includes a radio frequency absorber material with a high relative permittivity and loss tangent, or a mold compound material with specific electromagnetic properties, arranged between the chip and the heat sink to mitigate crosstalk and facilitate efficient heat dissipation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If functions are packed into components with small packages, then device integration is improved, but heat removal becomes insufficient and signal isolation deteriorates

Engineering Contradiction:

Improvedevice integrationVSAvoidheat removal

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

A thermal interface material layer is introduced between the radio frequency chip and the heat sink to improve thermal coupling. This intermediary layer with specific thermal conductivity (0.1-5 W/mK) and thickness (1-100 μm) enables more effective heat transfer from the chip to the heat sink, resolving the heat removal insufficiency in compact packages

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If functions are packed into components with small packages, then device integration is improved, but signal isolation between radar signal channels deteriorates

Engineering Contradiction:

Improvedevice integrationVSAvoidinterference between radar signal channels

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

A lossy material layer with high loss tangent (0.1-1.0) and relative permittivity (3-10) is introduced between the radio frequency chip and the heat sink. This intermediary layer absorbs electromagnetic energy and reduces crosstalk between adjacent radar signal channels, maintaining signal isolation in compact packages

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The lossy material layer's electromagnetic parameters (loss tangent and relative permittivity) are specifically optimized to create signal attenuation. By controlling the thickness (1-100 μm) and material properties, the design achieves signal isolation through parameter optimization rather than increased physical distance

Inventive Principle:

Principle #35Parameter changes

3Object-generated harmful factors

If a lossy material layer is added between the radio frequency chip and heat sink, then signal isolation is improved, but thermal coupling may deteriorate

Engineering Contradiction:

Improvecrosstalk between radar signal channelsVSAvoidthermal coupling

Core Design Contradiction:

Object-generated harmful factorsVSTemperature

Solution Approach 1:

The interface between the radio frequency chip and heat sink is segmented into two distinct functional layers: a thermal interface material layer for heat transfer and a lossy material layer for signal isolation. This segmentation allows each layer to be optimized independently - the thermal interface material with high thermal conductivity for heat removal, and the lossy material with high loss tangent for crosstalk reduction

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the interface structure are assigned different material properties: the thermal interface material region is optimized for thermal conductivity (0.1-5 W/mK), while the lossy material region is optimized for electromagnetic loss (loss tangent 0.1-1.0). This local quality differentiation enables simultaneous achievement of thermal coupling and signal isolation

Inventive Principle:

Principle #3Local quality

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 solution effectively reduces crosstalk between radio frequency channels and enhances thermal and electrical performance by using the absorber or mold compound materials to manage heat and signal interference, improving the overall efficiency and reliability of radio frequency devices.

Implementation Method 1

A radio frequency absorber material arranged between the radio frequency chip and the heat sink. A relative permittivity of the radio frequency absorber material is greater than 3, and a loss tangent of the radio frequency absorber material is greater than 0.2

Methodology Applied

Scientific EffectDielectric loss: Dielectric

Implementation Method 2

a thermal interface material, and a metal layer arranged between the first material and the thermal interface material

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS20240030092A1Radio frequency devices including radio frequency absorbent features

Publication Date: 2024.01.25 INFINEON TECHNOLOGIES AG

AI summary

A device includes a radio frequency chip and a heat sink arranged over the radio frequency chip. The device further includes a layer stack arranged between the radio frequency chip and the heat sink. The layer stack includes a first layer including a first material, a thermal interface material, and a metal layer arranged between the first material and the thermal interface material.