Inverted Ground Plane RF MEMS Package Design
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Solution Overview
Problem
Existing RF MEMS packages require structural modifications to integrate a MEMS device without an integrated ground plane, which is difficult and time-consuming, especially when using materials like quartz and silicon.
Innovation Solution
A radio frequency (RF) microelectromechanical systems (MEMS) package with an inverted or flipped ground plane design that forms a RF transmission line by coupling a secondary substrate with a ground plane to the MEMS device, eliminating the need for through-vias in the MEMS substrate and allowing RF signal propagation without altering the MEMS device or its mounting substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an integrated ground plane is added to the MEMS device substrate, then RF signal transmission is enabled, but the manufacturing process becomes complex and time-consuming requiring through-substrate vias
Solution Approach 1:
The ground plane functionality is segmented from the MEMS device substrate and placed on a separate secondary substrate. This allows the MEMS device to maintain its original simple structure while the ground plane exists independently on another substrate, eliminating the need for through-substrate vias in the MEMS substrate.
Solution Approach 2:
A secondary substrate acts as an intermediary carrier for the ground plane, positioned adjacent to the MEMS device substrate. This intermediary structure enables RF signal transmission without requiring direct integration or through-substrate modifications to the original MEMS device substrate.
2Reliability
If through-vias are formed in quartz or silicon substrates to integrate ground plane, then RF transmission line is formed, but manufacturing difficulty and time increase significantly
Solution Approach 1:
The ground plane integration process is extracted from the MEMS device substrate manufacturing flow. Instead of forming through-vias in the difficult-to-process quartz or silicon substrates, the ground plane is created separately on a secondary substrate that is then positioned adjacent to the MEMS device, eliminating the need for complex through-substrate via formation.
Solution Approach 2:
Instead of integrating the ground plane into the MEMS substrate by forming vias through it, the approach is inverted: the ground plane is placed on a separate secondary substrate adjacent to the MEMS device. This reverses the traditional integration approach and avoids the manufacturing difficulties of processing through-vias in hard materials.
3Reliability
If ground plane is positioned on the opposite surface of the mounting substrate, then RF signal propagation is enabled, but additional vias and grounding structures are required increasing device complexity
Solution Approach 1:
The ground plane is positioned in a different spatial dimension - adjacent to the MEMS device substrate rather than on its opposite surface. This lateral positioning eliminates the need for vertical through-substrate vias and complex grounding structures, simplifying the overall device architecture while maintaining RF signal propagation capability.
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 reduces signal losses and enables the use of a wider range of materials for package manufacture, while allowing for higher density signal lines and improved RF signal propagation without the need for substrate modifications, particularly beneficial for challenging materials like quartz and silicon.
Implementation Method 1
Conductive signal line 14 and ground plane 18 interact with each other to create an electromagnetic wave that travels through dielectric substrate 12 to create a RF signal
Implementation Method 2
dielectric substrate 12 having a conductive signal line 14 positioned on a top surface 16 of the dielectric substrate 12
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A RF MEMS package includes a MEMS die assembly having a signal line (46) formed on a top surface of a first mounting substrate (42), the signal line comprising a MEMS device (48) selectively electrically coupling a first portion of the signal line to a second portion of the signal line, and two pairs of ground pads (52, 54, 56, 58) formed on the top surface of the first mounting substrate adjacent respective portions of the signal line. The pairs of ground pads are positioned adjacent respective sides of the MEMS device. A ground assembly (43) is electrically coupled to the pairs of ground pads and includes a second mounting substrate and a ground region (62) formed on a surface of the second mounting substrate. The ground region faces the top surface of the first mounting substrate and is electrically coupled to the pairs of ground pads. A cavity is formed between the ground region and the signal line.