Environmental Sensor Bond-Wire Capacitance for Deposit Detection

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Solution Overview

Problem

Pressure sensors are susceptible to errors due to fluid contact, leading to inaccurate pressure readings, and existing self-test methods for sensors do not effectively detect and mitigate material deposits such as liquid droplets or salt crusts.

Innovation Solution

An environmental sensor with a MEMS element and an ASIC element connected by bond wires, utilizing an evaluation circuit to determine parasitic capacitance between the bond wires to detect material deposits, allowing for self-testing and potential countermeasures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If pressure sensors are exposed to the external environment to enable measurement, then measurement functionality is achieved, but fluid contact causes offsets in pressure readings

Engineering Contradiction:

Improvemeasurement functionalityVSAvoidpressure reading accuracy

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces a MEMS element as an intermediary between the external environment and the pressure sensing mechanism. This MEMS element is sealed within a protective housing, allowing it to sense pressure changes through fluid transmission while preventing direct contact between the sensing elements and environmental fluids that would cause offsets and reliability issues.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If existing self-test methods are used to check sensor functionality, then basic operational status is verified, but material deposits such as liquid droplets or salt crusts are not detected

Engineering Contradiction:

Improveself-test capabilityVSAvoiddeposit detection capability

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent replaces traditional mechanical self-test methods with an electrical measurement approach. By measuring the electrical capacitance between the MEMS element and the sensor housing, the system can detect the presence of material deposits that alter the electrical field, providing a more sensitive and precise detection capability than mechanical methods alone.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If additional detection components are added to detect material deposits, then detection capability is improved, but device complexity increases

Engineering Contradiction:

Improvedeposit detection capabilityVSAvoidsensor structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes the MEMS element and sensor housing serve multiple functions: they act as both the pressure sensing components and the capacitive detection elements for deposit detection. By utilizing the existing electrical structure for dual purposes, the patent avoids adding separate detection components, thereby maintaining reliability while controlling device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Ease of operation

If bond wires are used to electrically connect MEMS element and ASIC element, then electrical connection is achieved, but parasitic capacitance between bond wires creates detection interference

Engineering Contradiction:

Improveelectrical connectivityVSAvoidcapacitance measurement accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent converts the harmful effect of parasitic capacitance in bond wires into a useful detection signal. By measuring the total capacitance between the MEMS element and housing, the system captures both the intended capacitance and the parasitic capacitance from bond wires. The parasitic capacitance serves as a consistent baseline that helps identify when material deposits alter the electrical characteristics.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

Enables accurate detection of material deposits on the sensor, preventing functional impairment and allowing for timely replacement or cleaning, thus maintaining sensor integrity and accuracy.

Implementation Method 1

an evaluation circuit configured to determine and evaluate a parasitic capacitance between the at least two bond wires connected to pads of the MEMS element in order to detect material deposition on the environmental sensor

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

This exploits a changing permittivity at the environmental sensor due to the material deposit, which can be accompanied by a change in the parasitic capacitance

Methodology Applied

Scientific EffectDielectric constant change: Dielectric

Data Source

PatentEP4490482B1Environmental sensor and method of operating an environmental sensor

Publication Date: 2025.10.01 ROBERT BOSCH GMBH

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AI summary

The invention relates to an environment sensor (100), comprising: - a MEMS element (10); - an ASIC element (20) electrically connected to the MEMS element (10) by means of at least two bonding wires (2a, 2b), wherein the ASIC element (20) has an evaluation circuit (40, 50, 60) which is designed to determine and evaluate a parasitic capacitance (Cp) between the at least two bonding wires (2a, 2b) connected to pads (3a, 3b) of the MEMS element (10) in order to detect a material deposit on the environment sensor (100).