RF MEMS Switch Thermal Management via Landing Posts
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Solution Overview
Problem
MEMS switches experience excessive temperature rise when handling high electrical power applications, leading to reduced device lifetime and altered operational characteristics due to resistive heating and thermal expansion.
Innovation Solution
The implementation of electrical landing posts that provide both a parallel electrical path and a thermal path to reduce heat in the MEMS plate, comprising a substrate with electrodes, insulating layers, and a switching element with conductive and insulating portions that contact the posts to manage current flow and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high electrical power is applied across the MEMS switch, then the switching capability is improved, but temperature rise in the MEMS portion increases leading to reduced device lifetime
Solution Approach 1:
The patent segments the electrical current path by introducing separate landing electrodes that are electrically connected to the substrate, creating parallel current paths. This segmentation reduces current density in the MEMS plate and provides dedicated thermal dissipation paths, thereby reducing temperature rise while maintaining high power handling capability
Solution Approach 2:
The patent introduces landing electrodes as intermediary elements between the MEMS plate and the substrate. These landing electrodes serve as mediators that provide both electrical connection and thermal dissipation pathways, reducing the thermal load on the MEMS plate while maintaining electrical functionality
2Power
If high electrical power is applied across the MEMS switch, then the switching capability is improved, but resistive heating causes temperature rise that modifies device operation
Solution Approach 1:
The patent segments the electrical current path by introducing separate landing electrodes that are electrically connected to the substrate, creating parallel current paths. This segmentation reduces current density in the MEMS plate and provides dedicated thermal dissipation paths, thereby reducing temperature rise while maintaining high power handling capability
Solution Approach 2:
The patent converts the harmful resistive heating effect into a beneficial thermal dissipation mechanism by providing dedicated thermal paths through the landing electrodes to the substrate. The heat generated in the MEMS plate is rapidly conducted away through these thermal paths, preventing unwanted temperature rise and maintaining stable device operation
3Ease of operation
If the MEMS plate contacts the actuation electrode directly, then electrical contact is achieved, but stiction and thermal expansion cause changes in switching voltages
Solution Approach 1:
The patent segments the contact interface by introducing separate landing electrodes for electrical contact and thermal management. This segmentation allows the MEMS plate to make reliable electrical contact while the thermal paths through the landing electrodes prevent thermal expansion, maintaining stable switching voltages
Solution Approach 2:
The patent introduces landing electrodes as intermediary elements between the MEMS plate and the substrate. These landing electrodes serve as mediators that provide both electrical connection and thermal dissipation pathways, reducing the thermal load on the MEMS plate while maintaining electrical functionality
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 solution effectively limits temperature rise in MEMS switches during high power operations, enhancing device reliability and maintaining consistent switching voltages by reducing current through the most resistive leg portions and providing an additional thermal path for heat dissipation.
Implementation Method 1
Electrical landing posts can be positioned to provide a parallel electrical path while also providing a thermal path to reduce heat in the plate
Implementation Method 2
The plate of the MEMS device moves by applying a voltage to an actuation electrode. Once the electrode voltage reaches a certain voltage oftentimes referred to as a snap-in voltage, the plate moves towards the electrode
Implementation Method 3
high electrical powers applied across the switch can cause current flows through the free standing MEMS device. These currents can cause resistive heating resulting in a temperature rise in the MEMS portion
Implementation Method 4
The heating could cause unwanted thermal expansion leading to changes in the switching voltages
Data Source
Figure 1~2B
Figure 3A~3B
Figure 3C~3D
AI summary
The present disclosure generally relates to a mechanism for making a MEMS switch that can switch large electrical powers. Extra landing electrodes are employed that provide added electrical contact along the MEMS device so that when in contact current and heat are removed from the MEMS structure close to the hottest points.