Electrode Assembly with Inclined Substrate for pH Sensor
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Solution Overview
Problem
Existing pH sensors with ISFET chips face challenges in preventing air bubbles from accumulating and blocking measurements when immersed in liquid, due to the design of the through-hole and sealing materials used.
Innovation Solution
The electrode assembly features a substrate with a through-hole that is shallow and inclined, allowing air bubbles to be easily displaced, eliminating the need for a lead and sealing materials, and the substrate is attached at an angle to the body, ensuring the sensor chip and wiring are closely connected for efficient signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sealing materials are placed around the ISFET chip to insulate the lead, then electrical insulation is improved, but air bubbles accumulate in the deeper hole blocking measurement
Solution Approach 1:
The patent removes the lead and sealing material components entirely by adopting a flat plate configuration where the ISFET chip is mounted directly on the substrate back surface with wire bonding for electrical connection. This eliminates the deep hole and sealing material that caused air bubble accumulation, while maintaining electrical insulation through the substrate structure itself.
Solution Approach 2:
Instead of insulating the lead from the outside, the patent inverts the approach by making the substrate itself the insulating structure. The ISFET chip is mounted on the back surface with the substrate providing natural electrical insulation, eliminating the need for separate sealing materials and leads that created the air bubble problem.
2Length of stationary object
If the ISFET chip is attached on the back surface of the substrate to decrease thickness, then sensor thickness is reduced, but air bubbles still accumulate in the through-hole
Solution Approach 1:
The patent removes the through-hole structure entirely by mounting the ISFET chip on the back surface of the substrate. This extraction of the deep hole eliminates the air bubble accumulation problem while maintaining the thin profile through direct mounting and wire bonding connections.
3Ease of operation
If a lead is used to take out the output signal from the ISFET chip, then electrical connection is achieved, but sealing material is required increasing device complexity
Solution Approach 1:
The patent removes the lead and sealing material by using wire bonding technology to connect the ISFET chip directly to the substrate. This extraction eliminates the need for deep holes and sealing materials, simplifying the device structure while maintaining electrical connectivity for signal output.
Solution Approach 2:
The patent replaces the mechanical lead-and-sealing-material system with a wire bonding electrical connection system. This substitution eliminates the need for physical insulation barriers and deep mounting holes, reducing device complexity while achieving the same signal output function.
Data Source
AI summary
The electrode assembly is provided with: a rod-like body 1 that extends along a predetermined axis; a substrate that is formed with a through-hole penetrating between a front surface and a back surface and attached to a fore end part of the body; and a sensor chip for electrochemical measurement, which is attached on the back surface of the substrate such that a sensing part is exposed outside from the through-hole, wherein: on the back surface of the substrate, a wiring for obtaining an output signal from the ISFET chip is formed, and the sensor chip is attached to the wiring directly or closely; and the substrate is attached with being inclined with respect to the predetermined axis of the body, and thereby the front surface of the substrate forms at least a part of a fore end surface that is inclined with respect to the predetermined axis.