HTCC Exhaust Sensor Platinum Circuit Trimming

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Solution Overview

Problem

Existing exhaust gas temperature sensors face accuracy issues due to glass ink becoming permeable at high temperatures, allowing contaminants to reach the resistive thermal device and drift the resistance-temperature relationship, while substitutes like alumina ink face shrinkage mismatches.

Innovation Solution

The implementation of high temperature co-fired ceramic (HTCC) technology, where a green ceramic substrate with a printed platinum ink circuit is trimmed to a predetermined resistance, laminated with a polyester sheet, and fired, eliminating the need for glass ink and maintaining accuracy at high temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If glass ink is used to seal the alumina cover plate to the substrate, then the RTD is protected from exhaust gas compounds at low temperatures, but at high temperatures the glass becomes permeable allowing contaminants to reach the RTD and cause drift

Engineering Contradiction:

Improveprotection from exhaust gas compoundsVSAvoidpermeability at high temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent changes the material parameter from glass ink to alumina ink, which has different thermal properties. Alumina ink maintains its sealing properties at high temperatures where glass ink becomes permeable, thus resolving the contradiction between low-temperature protection and high-temperature stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite sealing approach by combining alumina ink with the alumina substrate and cover plate, creating a thermally stable composite structure that maintains integrity at high temperatures unlike the glass ink alone.

Inventive Principle:

Principle #40Composite materials

2Temperature

If alumina ink is used as a substitute for glass ink, then high temperature stability is improved, but shrinkage mismatch occurs during firing

Engineering Contradiction:

Improvehigh temperature stabilityVSAvoidshrinkage mismatch

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent modifies the alumina ink formulation to match the shrinkage characteristics of the alumina substrate and cover plate during the firing process. This parameter adjustment eliminates the shrinkage mismatch problem while maintaining the high-temperature stability benefits of alumina.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If the RTD is directly exposed to exhaust gas for temperature sensing, then measurement accuracy is maintained, but compounds in the exhaust gas alter the resistance and cause drift

Engineering Contradiction:

Improvetemperature sensing accuracyVSAvoidexhaust gas compound contamination

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent introduces alumina ink as an intermediary sealing material between the exhaust gas environment and the RTD. This intermediary provides a barrier that prevents direct contact with harmful exhaust gas compounds while allowing thermal energy to reach the RTD for accurate temperature sensing.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Ease of manufacture

If glass ink is used to form the seal, then ease of manufacture is improved, but the seal becomes soft and permeable at high temperatures allowing contaminants to reach the RTD

Engineering Contradiction:

Improvesealing process simplicityVSAvoidseal integrity at high temperature

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the sealing material from glass ink to alumina ink, which has superior high-temperature stability. Although alumina ink may require more sophisticated application processes, the formulation is optimized to match substrate shrinkage, maintaining ease of manufacture while dramatically improving seal integrity at high temperatures.

Inventive Principle:

Principle #35Parameter changes

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 approach significantly reduces resistance changes, ensuring accurate resistance-temperature correlation and maintaining sensor accuracy even at extreme temperatures, with a six-hour hold at 1450°C providing stable resistance.

Implementation Method 1

RTD 12 changes resistance based on the exhaust gas temperature

Methodology Applied

Scientific EffectResistive thermal device (RTD) effect: Thermo-resistive Effect

Implementation Method 2

Alumina cover 16 blocks the exhaust gas compounds from reaching RTD 12

Methodology Applied

Scientific EffectPhysical containment: Physical Containment

Implementation Method 3

At high enough temperatures, glass 18 becomes permeable. The exhaust gas compounds may then diffuse through glass 18 to RTD 12

Methodology Applied

Scientific EffectThermal permeability and diffusion: Diffusion

Implementation Method 4

In order for alumina to be impermeable, it must first be sintered

Methodology Applied

Scientific EffectSintering with shrinkage matching: Sintering

Data Source

PatentUS8162536B2Combined sensor

Publication Date: 2012.04.24 BORGWARNER US TECHNOLOGIES LLC

AI summary

A method of manufacturing an exhaust temperature sensor is disclosed. It includes forming a green ceramic substrate; and printing an electrical circuit on the green ceramic substrate. The method then contemplates trimming the electrical circuit to a predetermined resistance prior to firing the green ceramic. Finally, the method contemplates firing the green ceramic substrate with the electrical circuit thereon.