Miniature Pressure Sensor with Stress Isolation Pedestal
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Solution Overview
Problem
Current pressure sensors in the automotive industry face challenges in achieving high accuracy while being compact in size, particularly in height and diameter, and in minimizing stress transfer to the sense element.
Innovation Solution
A miniature pressure sensor design featuring a cup-shaped housing with a doped monocrystalline silicon die bonded to a borosilicate glass pedestal on a metallic substrate, using leaded glass or bismaleimide resin for attachment, and incorporating radial flanges and an elastomeric O-ring to minimize stress and temperature-related issues, along with a flexible circuit for assembly access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional pressure sensor designs are used, then manufacturing experience and acceptance are achieved, but size reduction particularly in height and diameter is limited
Solution Approach 1:
The sensor is divided into distinct functional segments: a sense element for pressure detection, a pedestal structure for mechanical support, and a housing for environmental protection. This segmentation allows each component to be optimized independently for miniaturization while maintaining manufacturing reliability through standardized assembly procedures.
Solution Approach 2:
The design implements nested structures where the sense element is positioned within a pedestal cavity, which is itself housed within a protective housing. The pedestal structure nests the sense element securely, allowing compact vertical stacking that reduces overall sensor height and diameter while maintaining structural integrity for automotive manufacturing.
2Volume of moving object
If sensor size is reduced, then compactness is achieved, but stress transfer to the sense element increases
Solution Approach 1:
The pedestal structure serves as an intermediary element between the sense element and the external mounting environment. It absorbs and isolates mechanical stresses from mounting and temperature variations, preventing direct stress transfer to the sensitive pressure sensing element while enabling compact sensor dimensions.
Solution Approach 2:
The sensor employs composite material construction with the pedestal made from stress-resistant material and the sense element made from pressure-sensitive material. This composite approach allows the pedestal to mechanically support the compact structure while the sense element maintains high sensitivity, resolving the conflict between size reduction and stress protection.
3Temperature
If material CTE matching is optimized, then temperature stress is minimized, but material selection and manufacturing complexity increases
Solution Approach 1:
The design optimizes the thermal expansion parameter by selecting materials for the pedestal and sense element with closely matched coefficients of thermal expansion (CTEs). This parameter matching minimizes differential thermal expansion and associated stresses during temperature cycling, while the standardized material selections keep manufacturing complexity manageable.
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
The solution enables the creation of a compact pressure sensor with reduced size and cost, effectively minimizing stress transfer and maintaining high accuracy for pressure measurements up to 1000 psi, while ensuring reliable operation over a wide temperature range.
Implementation Method 1
all chosen to have closely matching coefficients of thermal expansion, hereinafter referred to as CTEs, and configured to minimize transfer of mounting and temperature stresses to the sense element
Implementation Method 2
incorporates a doped monocrystalline silicon die as the sense element
Data Source
AI summary
A high pressure, miniature pressure sensor has a cup-shaped housing having an open end closed by a metal substrate. A raised stress isolation pedestal portion is formed on the substrate that receives a stress isolation glass pedestal element and in turn a silicon pressure sense element, all having closely matched CTEs to minimize temperature induced stresses. A fluid passageway is formed through the substrate and glass pedestal and an O-ring is placed around the passageway on the lower side of the substrate. A flexible circuit having a slit tail formed with two lobes for receipt respectively in the housing and on the substrate allows easy access of a solder iron during assembly. Mounting flanges extend from the substrate to facilitate mounting of sensor and minimize transfer of mounting stresses to the sense element.