Pressure Sensor Resin Cantilever Thermal Distortion

Solution Overview

Problem

Existing pressure sensors face challenges in maintaining accuracy when detecting physical quantities due to thermal stress-induced distortion, which can be exacerbated by the length of the sensor chip and the distance of the sensing portion from the sealing member, leading to either increased size or inadequate accuracy limitations.

Innovation Solution

A pressure sensor design featuring a sensor chip with a membrane and a piezoelectric element, where the sensor chip is cantilevered by a resin portion, with a fixed end covered by the resin and a free end spaced away, ensuring the shortest separation distance between the membrane and the resin portion is equal to or greater than the sensor chip's width, thereby minimizing distortion from temperature changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the sensor chip is made long to increase distance between sealing member and sensing portion, then thermal stress distortion at sensing portion is reduced, but the size of sensor chip excessively increases

Engineering Contradiction:

Improvedetection accuracyVSAvoidsensor chip length

Core Design Contradiction:

Measurement precisionVSLength of moving object

Solution Approach 1:

The patent applies local quality by creating a thin membrane region at the free end of the sensor chip where the sensing portion is located. This membrane has a smaller thickness than other parts of the chip, allowing it to be more flexible and less susceptible to thermal stress distortion from the sealed fixed end, thereby improving detection accuracy without requiring excessive chip length.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent transitions from considering only the length dimension to incorporating the thickness dimension as a critical parameter. By making the membrane thickness smaller than other parts of the chip, the invention uses the thickness dimension to reduce thermal stress effects, allowing for a more compact overall chip length while maintaining detection accuracy.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Length of moving object

If the sensor chip is made short to reduce size, then manufacturing is easier, but thermal stress distortion reaches the sensing portion causing accuracy decrease

Engineering Contradiction:

Improvesensor chip lengthVSAvoiddetection accuracy

Core Design Contradiction:

Length of moving objectVSMeasurement precision

Solution Approach 1:

The patent applies local quality by creating a thin membrane region at the free end of the sensor chip where the sensing portion is located. This membrane has a smaller thickness than other parts of the chip, allowing it to be more flexible and less susceptible to thermal stress distortion from the sealed fixed end, thereby improving detection accuracy without requiring excessive chip length.

Inventive Principle:

Principle #3Local quality

3Strength

If the membrane thickness is increased to strengthen the sensing portion, then structural strength is improved, but thermal stress distortion is not effectively reduced

Engineering Contradiction:

Improvemembrane strengthVSAvoiddetection accuracy

Core Design Contradiction:

StrengthVSMeasurement precision

Solution Approach 1:

The patent applies local quality by creating a thin membrane region at the free end of the sensor chip where the sensing portion is located. This membrane has a smaller thickness than other parts of the chip, allowing it to be more flexible and less susceptible to thermal stress distortion from the sealed fixed end, thereby improving detection accuracy without requiring excessive chip length.

Inventive Principle:

Principle #3Local quality

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 limits the decrease in accuracy due to thermal stress while preventing the sensor chip from becoming excessively large, maintaining detection precision and durability by specifying the relationship between the separation distance and width to prevent membrane distortion.

Implementation Method 1

a piezoelectric element provided in the membrane

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

When the temperature changes, the sealing member expands or shrinks, and accordingly the sensor chip is distorted by the thermal stress

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10527513B2Pressure sensor with resin portion and membrane having reduced temperature change distortion

Publication Date: 2020.01.07 DENSO CORP

AI summary

A pressure sensor includes a sensor chip and a resin portion. The sensor chip extends in a lengthwise direction and includes a membrane whose length in a thickness direction perpendicular to the lengthwise direction is smaller than another part, and a piezoelectric element provided in the membrane. The sensor chip includes a fixed end that is covered with and fixed to the resin portion, and a free end opposite from the fixed end in the lengthwise direction. The free end is spaced away from the resin portion in the lengthwise direction, and the membrane is located in the free end. A shortest separation distance between the membrane and a part of the resin portion covering the sensor chip is equal to or larger than a length of the sensor chip along a crosswise direction of the sensor chip perpendicular to both the lengthwise direction and the thickness direction.