Sensor Assembly Fluid-Isolated Bond Pads
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Solution Overview
Problem
Many sensors are prone to corrosion or damage when their electric bond pads are exposed to the sensed fluid, leading to a need for a robust design that protects these pads while allowing fluid delivery to the sensor device.
Innovation Solution
The design includes a substrate with a flow channel and bond pads on one side, a housing for fluid inlet and outlet, and a sense die with bond pads that are bump bonded and isolated from the fluid using an adhesive or non-conductive material to prevent corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bond pads are exposed to fluid for sensor operation, then fluid delivery to sensor device is enabled, but bond pads become corroded or damaged
Solution Approach 1:
The sensor device is segmented into distinct functional zones: a sensing area exposed to fluid and a bonding area protected from fluid. The substrate includes a flow channel that directs fluid away from the bond pads, physically separating the fluid delivery path from the electrical connection region. This segmentation allows the bond pads to remain protected while the sensing elements perform their function in contact with the fluid.
Solution Approach 2:
An intermediate structure (such as a protective coating or barrier layer) is introduced between the bond pads and the fluid environment. This intermediary layer allows electrical connections to be maintained while preventing direct contact between the bond pads and corrosive fluid, thus protecting the bond pads from damage while enabling sensor operation.
2Reliability
If bond pads are protected from fluid, then corrosion resistance is improved, but fluid delivery path becomes more complex
Solution Approach 1:
The protective function and fluid delivery function are merged into a single integrated substrate structure. The substrate simultaneously serves as the mechanical support, the fluid conduit, and the protective barrier for the bond pads. By combining these functions into one component rather than adding separate protective elements, the overall device complexity is minimized while achieving both fluid delivery and corrosion protection.
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 configuration effectively protects the bond pads from fluid exposure, ensuring the sensor's reliability and accuracy by reducing the risk of corrosion and damage, while allowing fluid flow for sensing applications.
Implementation Method 1
an adhesive or other material may be disposed between the sensing side of the sense die and the second side of the substrate. The adhesive or other material may help isolate the plurality of bond pads on the sensing side of the sense die from the fluid in the flow channel
Data Source
AI summary
A sensor may include a substrate defining a flow channel that extends through the substrate, and a plurality of bond pads on the substrate. A first housing may be disposed along the substrate and may permit at least some fluid to flow from a fluid inlet to a fluid outlet along at least part of the flow channel. A second housing may be disposed along the substrate. A sense die may be disposed between the second housing and the substrate and may include a sensing side facing the substrate with a sense element in registration with the flow channel and a plurality of bond pads on the sensing side that are in registration with, and bump bonded to, the plurality of bond pads on the substrate. An adhesive or other material may be disposed between the sensing side of the sense die and the substrate.