MEMS Leadframe Shielding Against EMI RFI
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Solution Overview
Problem
MEMS devices in leadframe chip scale packages are susceptible to electromagnetic interference (EMI) and radio frequency interference (RFI) due to the small output signals and the susceptibility of wire bonds connecting MEMS devices to integrated circuits, which can corrupt the desired signal, especially in high-frequency environments like automobiles.
Innovation Solution
A conductive plate is integrated as a Faraday cage within the molding material to form an electrical node that attracts and routes EMI and RFI away from the signal path, coupled with a conductive paddle to provide a grounding path, thereby reducing interference and protecting the signal between the MEMS device and the integrated circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonds are used to connect MEMS device to integrated circuit, then electrical connection is achieved, but electromagnetic interference and radio frequency interference corrupt the signal
Solution Approach 1:
A conductive plate is introduced as an intermediary element between the wire bond and the integrated circuit input pad. This plate acts as a mediator that intercepts electromagnetic and radio frequency interference before it can reach the sensitive signal path, while allowing the desired signal to pass through to the integrated circuit
Solution Approach 2:
The conductive plate converts harmful electromagnetic interference into a beneficial shielding effect. By positioning the conductive plate to attract and redirect EMI and RFI away from the signal path, the harmful interference is transformed into a protective mechanism that actually improves signal integrity
2Object-affected harmful factors
If conductive plate is added for EMI shielding, then interference protection is improved, but device complexity increases
Solution Approach 1:
The conductive plate is merged with the existing leadframe structure by attaching it to the conductive paddle. This integration approach combines the shielding function with the existing mechanical support structure, avoiding the need for separate complex shielding assemblies and minimizing additional components
Solution Approach 2:
The conductive plate serves multiple functions simultaneously: it provides EMI shielding, acts as a structural support element within the molding cavity, and creates a defined electrical node. This multi-functionality reduces the need for additional components and simplifies the overall package design
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 effectively reduces EMI and RFI interference, ensuring the integrity of the signal path between the MEMS device and the integrated circuit, enhancing noise performance and maintaining signal quality even in high-frequency environments.
Implementation Method 1
The mechanism includes a conductive paddle and a separate conductive plate that form an electrical node. The conductive plate and the conductive paddle act as a faraday cage reducing electro-magnetic interference from reaching the input pad, wirebond, and/or the output pad.
Data Source
AI summary
A lead frame packaged electronic chip. The packaged electronic chip includes a MEMS device, an integrated circuit and a wire bond electrically coupling the MEMS device and the integrated circuit. The packaged electronic chip is encased in a molding material. The packaged electronic chip further includes a mechanism that shields the wire bond and the input/output pads that couple the MEMS device and the integrated circuit from electromagnetic and radio frequency interference.