Backside Heat Conduction in SAW Substrates to Reduce Thermal Drift
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Solution Overview
Problem
Microelectronic components, particularly those with low thermal conductivity like SAW components, face self-heating issues that lead to mechanical stresses, premature fatigue, and changes in properties, affecting frequency stability and signal transmission.
Innovation Solution
A heat conducting agent with a higher thermal conductivity than the substrate is applied to the backside, structuring the substrate to reduce layer thickness in specific areas, allowing heat to be efficiently routed through the substrate and dissipated via metallic connecting means to a carrier, which includes heat sinks for effective thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a substrate with low thermal conductivity is used for SAW components, then the component can maintain its acoustic wave properties, but self-heating occurs leading to mechanical stresses and frequency drift
Solution Approach 1:
A heat conducting agent layer is introduced as an intermediary between the substrate and the component structures. This layer has higher thermal conductivity than the substrate material, acting as a thermal mediator that efficiently transports heat away from the active areas without interfering with the acoustic wave propagation in the substrate.
Solution Approach 2:
The heat conduction path is extended into the vertical dimension by applying the heat conducting agent layer on the substrate surface. This creates an additional thermal conduction dimension perpendicular to the substrate plane, allowing heat to be conducted away more efficiently without affecting the horizontal acoustic wave propagation.
2Loss of energy
If the substrate layer thickness is reduced in structured areas, then the heat path length is shortened improving heat dissipation, but the mechanical strength may be compromised
Solution Approach 1:
The substrate is structured with locally reduced thickness only in specific areas where heat dissipation is needed, while other areas maintain their original thickness to preserve mechanical strength. This local modification allows optimized heat conduction paths without compromising overall structural integrity.
Solution Approach 2:
The substrate structure combines regions of different thicknesses to create a composite structure that optimizes both thermal and mechanical properties. The thinner regions provide efficient heat conduction paths while the thicker regions maintain mechanical strength and structural stability.
3Temperature
If additional heat conducting layers are added to improve thermal dissipation, then heat dissipation efficiency increases, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of adding complex multi-layer structures, the solution changes the thermal conductivity parameter of the existing substrate by applying a heat conducting agent layer. This parameter change approach achieves improved heat dissipation with minimal additional structural complexity.
Solution Approach 2:
The heat conducting agent layer is applied as a simple, easily manufacturable coating that can be integrated into existing production processes. This approach uses a relatively simple material layer rather than complex permanent structural modifications, reducing manufacturing complexity.
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 approach significantly reduces thermal drift, extends component lifespan, and improves reliability by minimizing heat path length and enhancing thermal dissipation, thus maintaining frequency stability and signal transmission accuracy.
Implementation Method 1
uses a heat conducting agent applied to the back of the component substrate, which has a significantly higher coefficient of thermal conductivity than that substrate has
Data Source
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AI summary
In the case of a component with component structures that generate heat loss on an active side of the substrate, it is proposed to apply a heat conductor on the rear face of the component substrate, said rear face having a second coefficient of thermal conductivity αLS that is substantially higher than the first coefficient of thermal conductivity αS of the substrate. The heat dissipation then occurs across the heat conductor and across connecting means that connect the substrate to a carrier.