Pressure Sensor Rounded Corners Prevent Crack Formation
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Solution Overview
Problem
Conventional pressure sensors with resin-molded cases and soft protective materials face issues with bubble formation due to cracks at the corners, leading to variations in pressure transmission and sensor characteristics.
Innovation Solution
The pressure sensor design incorporates rounded corners with a curvature radius of 0.5 mm or more and a two-layer protective material structure, where the first protective material contacts the corner and the second, softer material covers the sensing chip, with a dam portion to prevent air entry through cracks and ensure effective pressure transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the case is formed by molding resin, then the case can be easily manufactured, but cracks are likely to occur at corners where stress concentrates
Solution Approach 1:
The corner of the case is formed with a rounded shape having a curvature radius of 0.5 mm or more, eliminating the stress concentration that occurs at sharp corners during resin molding. This curvature modification prevents crack initiation while maintaining the ease of injection molding manufacturing process.
2Reliability
If air enters through cracks in the case, then bubbles are produced in the protective material, but this causes variation in pressure transmission characteristics
Solution Approach 1:
By rounding the corner with a curvature radius of 0.5 mm or more, the case structure prevents crack formation that would otherwise allow air to penetrate into the protective material. This eliminates bubble generation and maintains consistent pressure transmission characteristics to the sensing chip.
3Reliability
If the corner radius is increased to prevent cracks, then stress concentration is reduced, but the case size increases
Solution Approach 1:
The corner curvature radius is optimized to 0.5 mm or more, which is sufficient to prevent stress concentration and crack formation during resin molding while minimizing the increase in overall case dimensions. This parameter optimization balances reliability improvement with compact design requirements.
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 effectively prevents crack formation and bubble production, maintaining sensor accuracy and reliability by reducing stress concentration and air entry, thus stabilizing pressure transmission and detection functionality.
Implementation Method 1
small cracks, such as a micro crack K shown in FIG. 8, may be caused when the case 10 is molded. Such a crack K is likely to be caused at a corner 18a where stress particularly tends to be concentrated in the case 10.
Implementation Method 2
a protective material 40, such as a soft gel, that serves as a pressure transmission medium
Data Source
AI summary
A pressure sensor is provided, which includes a case, a sensing chip located in the case for detecting pressure, and a protective material for covering and protecting the sensing chip in the case. Corners of the case, which are in contact with the protective material are each formed into a rounded shape. A curvature radius of each of the corners is adapted to be 0.5 mm or more.