Shielded Encapsulating Structure for MEMS Devices
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Solution Overview
Problem
Existing MEMS microphone packages face high manufacturing costs and dimensional constraints due to the need for through vias, which also lead to incomplete Faraday shielding and limited cavity height, especially in hermetically sealed pressure sensors.
Innovation Solution
A shielded encapsulating structure and manufacturing method that uses conductive columnar elements or continuous conductive structures to connect the substrate's ground plane with the cap, eliminating the need for through vias and allowing for complete Faraday shielding while maintaining accessibility and mechanical protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through vias are used to connect the cap's metal layer with the substrate's ground plane, then electrical shielding (Faraday cage) is achieved, but manufacturing cost increases and side wall thickness is constrained
Solution Approach 1:
The patent extracts the electrical connection function from the side walls and relocates it to the cap's bottom surface. By forming contact pads directly on the cap's inner surface and using conductive adhesive to connect these pads to the substrate's ground plane, the design eliminates the need for through vias in the side walls, thereby reducing manufacturing complexity and cost while maintaining effective electrical shielding.
Solution Approach 2:
The patent transitions the electrical connection from a vertical through-wall path to a horizontal contact pad arrangement on the cap's bottom surface. This dimensional shift allows the connection to be made at the interface between the cap and substrate rather than penetrating through the side walls, freeing up side wall thickness requirements and simplifying the manufacturing process.
2Reliability
If through vias are formed in side walls, then electrical connection is established, but minimum side wall thickness is required which limits cavity height
Solution Approach 1:
The patent removes the electrical connection requirement from the side wall structure entirely. By placing contact pads on the cap's bottom surface and using conductive adhesive for the ground plane connection, the design allows side walls to be optimized purely for mechanical support and shielding, enabling greater cavity height without compromising electrical connection integrity.
3Ease of manufacture
If conductive through vias are formed at certain distances from each other, then manufacturing is simplified, but portions of side walls remain unshielded creating incomplete Faraday cage
Solution Approach 1:
The patent extracts the electrical connection function from the side walls and places it on the cap's bottom surface. This eliminates the need to compromise shielding completeness for manufacturing simplicity, as the side walls can now be fully continuous and conductive without requiring spaced vias, achieving both complete Faraday shielding and manufacturing ease.
Solution Approach 2:
The patent merges the electrical connection function with the cap's bottom surface structure by forming contact pads directly on it. This integration allows the cap to serve both as the shielding barrier and as the electrical connection point, eliminating the need for separate via structures and enabling complete side wall shielding.
4Ease of manufacture
If a planar cap with metal layer is used, then manufacturing is simplified, but complete Faraday shielding cannot be achieved without through vias
Solution Approach 1:
The patent extracts the electrical connection requirement from the side walls and implements it through contact pads on the cap's bottom surface connected via conductive adhesive. This approach maintains the simplicity of planar cap manufacturing while achieving complete Faraday shielding, as the side walls can be fully continuous without needing through vias.
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 reduces production costs, enables complete Faraday shielding, and increases the internal cavity volume, making it suitable for various MEMS devices, including microphones, while maintaining mechanical protection and accessibility.
Implementation Method 1
the package operates according to the known principle of the Faraday cage... To complete formation of a Faraday cage, the metal layer of the cap is electrically connected to the ground plane of the substrate
Data Source
AI summary
One or more embodiments are directed to encapsulating structure comprising: a substrate having a first surface and housing at least one conductive pad, which extends facing the first surface and is configured for being electrically coupled to a conduction terminal at a reference voltage; a cover member, set at a distance from and facing the first surface of the substrate; and housing walls, which extend between the substrate and the cover member. The substrate, the cover member, and the housing walls define a cavity, which is internal to the encapsulating structure and houses the conductive pad. Moreover present inside the cavity is at least one electrically conductive structure, which extends between, and in electrical contact with, the cover member and the conductive pad for connecting the cover member electrically to the conduction terminal.