MEMS Microphone Bonding Pad Corrosion Protection
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Solution Overview
Problem
MEMS microphone chips face corrosion issues due to aluminum bonding pads during the packaging process, particularly in high temperature and humidity environments, which affects the reliability of the device.
Innovation Solution
A protection layer, such as TiN, is applied fully around the sidewall and partially on top of the metal bonding pads to prevent corrosion, while allowing bonding wires to connect securely, and a sealant like glob top is applied locally to protect the bonding pads and wire ends without compromising the microphone's functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aluminum bonding pads are used in MEMS microphone chips, then the packaging process can be simplified and manufacturing cost reduced, but the bonding pads suffer corrosion in high temperature and humidity environments
Solution Approach 1:
The patent applies composite material structure by combining aluminum bonding pad with protective coatings (such as TiN, Au, or other corrosion-resistant materials). The bonding pad consists of multiple layers where the aluminum provides electrical conductivity and the protective coating layer provides corrosion resistance, creating a composite structure that achieves both electrical functionality and environmental stability.
Solution Approach 2:
The patent changes the material parameters of the bonding pad by introducing protective coating layers with different chemical and physical properties. The coating layers have lower reactivity with corrosive environments compared to aluminum, thereby changing the chemical stability parameter while maintaining electrical conductivity through proper material selection and thickness control.
2Reliability
If protection layers are applied around bonding pads to prevent corrosion, then corrosion resistance is improved, but the device structure becomes more complex
Solution Approach 1:
The patent applies protection layers selectively only around the bonding pads where corrosion resistance is needed, rather than coating the entire chip. This localized approach provides corrosion protection at critical areas while minimizing the addition of structural complexity and maintaining simplicity in non-critical regions of the device.
Solution Approach 2:
The protection layers are applied to the bonding pads during the fabrication process before the packaging stage. This preliminary protection is integrated into the chip manufacturing flow, so the corrosion resistance is built-in before the chip is packaged, avoiding additional complexity in the packaging process itself.
3Reliability
If sealant structures are applied to cover bonding pads and wire ends, then corrosion protection is enhanced, but the manufacturing process becomes more time-consuming
Solution Approach 1:
The patent combines the application of protection layers and sealant structures into integrated manufacturing steps. The protective coatings are deposited as part of the chip fabrication process, and sealant application is merged with the wire bonding process, allowing multiple protective functions to be achieved in combined operations rather than separate sequential steps.
Solution Approach 2:
The protection layers are applied in advance during chip fabrication before packaging, and sealant structures are applied during the wire bonding process itself. These preliminary actions ensure that corrosion protection is established before the chip enters the packaging stage, reducing the need for additional time-consuming protective measures during packaging.
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 protection layer effectively shields the aluminum bonding pads from corrosion, enhancing the reliability and longevity of MEMS microphones in harsh environments by preventing rust-like damage and ensuring stable electrical connections.
Implementation Method 1
A protection layer fully enclosing a sidewall of the metal pad and also partially disposed on a top of the metal pad
Implementation Method 2
A bonding wire is connected between the first bonding pad and the second bonding pad
Implementation Method 3
A sealant structure is locally covering on the first bonding pad and an end portion of the bonding wire on the first bonding pad
Data Source
AI summary
A package structure of MEMS microphone is provided. The MEMS microphone includes a MEMS microphone chip disposed on a circuit board. The MEMS microphone chip comprises a first bonding pad, including a metal pad on a top of the MEMS microphone chip; and a protection layer fully enclosing a sidewall of the metal pad and also partially disposed on a top of the metal pad. A circuit chip is disposed on the circuit board, wherein the circuit chip comprises a second bonding pad. A bonding wire is connected between the first bonding pad and the second bonding pad.