Ceramic Substrate Pressure Sensor Assembly Solder Mounting

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Solution Overview

Problem

Existing pressure sensor assemblies fail to reliably measure fluid pressure in harsh environments due to limitations in adhesive properties, thermal expansion mismatches, and inaccuracy at high and low temperatures and pressures.

Innovation Solution

A pressure sensor assembly using a ceramic substrate and a solder layer with a silicon chip diaphragm and electrical sensing elements, where the sensor die is mounted via a solder layer engaging both the die and substrate metallization layers, providing improved adhesion and thermal expansion matching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If RTV silicone rubber is used to attach the sensor die to the substrate, then the assembly process is simplified, but the adhesive fails at high pressures (greater than 200 psi) and deteriorates in harsh chemical environments

Engineering Contradiction:

Improveassembly process simplicityVSAvoidadhesive performance at high pressure and chemical resistance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the material parameters by transitioning from RTV silicone rubber to a cured epoxy adhesive with superior mechanical and chemical properties. The epoxy adhesive maintains structural integrity at pressures exceeding 200 psi and resists deterioration from harsh chemicals including fuels, oils, and refrigerants, while still enabling a simplified assembly process.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite material system consisting of the cured epoxy adhesive that combines both mechanical strength for high-pressure applications and chemical resistance for harsh environments. This composite material integrates multiple functional properties that neither RTV silicone rubber alone could provide.

Inventive Principle:

Principle #40Composite materials

2Strength

If a metal substrate is used to provide structural support, then the mechanical strength is sufficient, but the CTE mismatch with the silicon pressure sensor die causes high thermo-mechanical stresses at extreme temperatures

Engineering Contradiction:

Improvesubstrate mechanical supportVSAvoidmeasurement accuracy at extreme temperatures

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent changes the thermal parameter by selecting a substrate material with a coefficient of thermal expansion (CTE) that closely matches that of silicon. This CTE matching minimizes thermo-mechanical stresses during temperature cycling between -40°C and 150°C, preventing measurement errors such as thermal hysteresis and zero-offset drift while maintaining adequate mechanical strength.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If the pressure sensor die is exposed to harsh chemicals through ports in the substrate, then the measurement function is maintained, but the chemicals impinge on the bottom side of the die causing deterioration

Engineering Contradiction:

Improvepressure measurement capabilityVSAvoidchemical exposure to sensor die

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary protective layer or coating on the bottom side of the pressure sensor die that is chemically resistant to harsh environments. This intermediary layer allows pressure transmission while protecting the silicon die from direct chemical impingement, maintaining measurement precision while eliminating chemical deterioration.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 pressure measurement in harsh conditions, including high pressures up to 1500 psi and temperatures from -40°C to 150°C, with reduced thermo-mechanical stresses and enhanced durability against corrosive fluids.

Implementation Method 1

The sensor die is mounted to the ceramic substrate via a solder layer that engages the ceramic substrate and the second side of the sensor die

Methodology Applied

Scientific EffectSoldering: Soldering

Implementation Method 2

The silicon chip has a diaphragm configured to be exposed to a working fluid. The sensor die includes one or more electrical sensing elements mounted on the diaphragm and configured to measure a pressure of the working fluid

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Data Source

PatentUS10781094B2Pressure sensor assembly mounted to a ceramic substrate

Publication Date: 2020.09.22 TE CONNECTIVITY SOLUTIONS GMBH

AI summary

A pressure sensor assembly includes a sensor die and a ceramic substrate. The sensor die has a first side and a second side that is opposite to the first side. The sensor die includes a silicon chip that has a diaphragm configured to be exposed to a working fluid. The sensor die includes one or more electrical sensing elements mounted on the diaphragm and configured to measure a pressure of the working fluid. The sensor die is mounted to the ceramic substrate via a solder layer that engages the ceramic substrate and the second side of the sensor die.