Cap Isolation for Differential Pressure Sensor Bond Pads
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Solution Overview
Problem
Differential pressure sensors face reliability issues due to exposure of bond pads to corrosive media, leading to long-term failures and increased production costs from inadequate media isolation, which compromises accuracy and efficiency.
Innovation Solution
A differential pressure sensor design featuring a cap that isolates die bond pads from harsh media, allowing media to pass through while routing electrical signals under the cap, using die attach materials and piezoresistive elements on a thin silicon diaphragm to measure pressure without exposing bond pads to the media.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If differential pressure sensors expose bond pads to media for pressure sensing, then pressure measurement function is achieved, but reliability deteriorates due to media corrosion
Solution Approach 1:
The sensor is divided into separate functional zones: a media-exposed pressure sensing area and a media-isolated electrical connection area. The bond pads are segmented from the media path, allowing pressure sensing while protecting electrical connections from corrosive media.
Solution Approach 2:
A media isolation structure acts as an intermediary barrier between the corrosive media and the bond pads. This intermediary protects the bond pads from direct media contact while maintaining the pressure sensing function through the diaphragm.
2Object-affected harmful factors
If additional hardware is added for media isolation, then media compatibility improves, but manufacturing cost increases
Solution Approach 1:
The media isolation function is merged with the existing sensor housing and diaphragm structure. Rather than adding separate isolation components, the design integrates media protection into the fundamental sensor architecture, reducing additional manufacturing costs.
Solution Approach 2:
The diaphragm and housing structures serve multiple functions: they provide both pressure sensing capability and media isolation protection. This multi-functionality eliminates the need for separate isolation hardware, reducing manufacturing complexity and cost.
3Ease of operation
If bond pads are exposed for wire bonding, then electrical connection is achieved, but long-term reliability deteriorates due to media exposure
Solution Approach 1:
The electrical connection area is segmented from the media-exposed area. Bond pads remain accessible for wire bonding through isolation structures that prevent media contact, maintaining both accessibility and long-term reliability.
Solution Approach 2:
Isolation structures serve as intermediaries that allow electrical connections to be made while preventing media from reaching the bond pads. This enables reliable wire bonding without compromising long-term sensor reliability.
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 design enhances the reliability and accuracy of differential pressure sensing while maintaining a low production cost by preventing media exposure to bond pads, ensuring robust and efficient media isolation.
Implementation Method 1
The stress can be measured by piezoresistive elements formed in the silicon diaphragm. The measured stress can be calculated to measure the pressure of the fluid media.
Implementation Method 2
The cap can isolate the die bond pads from the harsh media and route the electrical signals under the cap.
Data Source
AI summary
A differential pressure sensor includes two pressure ports for allowing media to pass into contact with both the top and bottom sides of the diaphragm. A silicon pressure sensor die can be attached between the pressure ports using die attach materials for sensing a differential pressure between the media to evaluate media differential pressure. A cap with an opening can be placed on topside of a diaphragm formed in the silicon pressure die. The silicon pressure die can include die bond pads that can be electrically connected to the diaphragm to output electrical signals. The cap can seal the die bond pads from the harsh media and route the electrical signals therein. Media can pass through the opening in the cap such that a media path to the top of the diaphragm is not exposed to the die bond pads of the silicon pressure die to ensure long-term sensor reliability.