Folded Lead-Frame MEMS Packaging for EMI Shielding
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Solution Overview
Problem
Current MEMS device packaging methods are costly and inefficient, failing to provide adequate acoustic chambers and electromagnetic interference shielding while being unsuitable for devices with movable structures, and often require expensive materials and complex assembly processes.
Innovation Solution
A cost-effective lead-frame packaging method that incorporates pre-molded plastic cavities and metallic sidewalls for electromagnetic interference shielding, with folded metal leads forming surface mounting pads and an inlet hole for external signal entry, creating an enclosed cavity for MEMS devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional lead-frame packaging with plastic molding is used, then manufacturing cost is reduced, but acoustic chamber sufficiency deteriorates
Solution Approach 1:
The package is divided into distinct functional regions: a molded cavity portion providing the acoustic chamber, and a folded lead-frame portion providing EMI shielding and electrical connections. This segmentation allows each part to optimize its specific function while maintaining overall cost-effectiveness.
Solution Approach 2:
The MEMS device is nested within the molded cavity, which is itself nested within the folded lead-frame structure. This nested arrangement creates the acoustic chamber at the core while using the lead-frame folds to provide external shielding and connections.
2Object-affected harmful factors
If flexible printed circuit boards are used, then EMI shielding is improved, but manufacturing cost and assembly complexity deteriorate
Solution Approach 1:
The lead-frame structure serves multiple functions simultaneously: it provides EMI shielding through its folded metal portions, electrical connections through its conductive paths, and structural support for the MEMS device. This multi-functionality eliminates the need for separate FPCB components.
Solution Approach 2:
The lead-frame structure is designed to be self-sufficient, providing all necessary functions (shielding, connection, support) within a single integrated component that is already part of the packaging process, eliminating the need for additional assembly steps required by FPCB-based solutions.
3Device complexity
If packages with insufficient acoustic chambers are used, then manufacturing simplicity is improved, but device performance deteriorates
Solution Approach 1:
The molded cavity is pre-formed during the molding process to create the acoustic chamber with appropriate volume and geometry. This preliminary formation of the acoustic chamber ensures sufficient space for diaphragm movement before the device is assembled into the final package structure.
Data Source
AI summary
The MEMS package comprises a first and a second pre-molded lead-frame substrate, at least one of them having a cavity formed by plastic sidewalls along its periphery. The first and second pre-molded lead-frame substrates are interconnected with metal leads. At least one MEMS device is attached to one of the substrates. The first pre-molded lead-frame substrate is folded over and joined to the second pre-molded lead-frame substrate to house the at least one MEMS device. In one embodiment, the first pre-molded lead-frame substrate has metal leads extending outside of sidewalls of the cavities. The extended metal leads are folded over the top of the second pre-molded lead-frame substrate to form surface mounting pads. In some embodiments, extended metal leads are folded along the sidewalls and connected to ground for electromagnetic interference (EMI) shielding.