Single-Chip Pressure Sensor Backside Exposure Design
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Solution Overview
Problem
Existing pressure sensor systems for harsh industrial environments, such as automotive engines, face challenges with large footprint, complex manufacturing, sensitivity of interconnections, and inaccurate temperature measurements due to protective gels acting as thermal barriers.
Innovation Solution
A single-chip pressure sensor system with integrated temperature sensing and signal processing, using a backside exposure design and film-assisted plastic transfer molding, which reduces assembly costs, enhances component robustness, and eliminates the need for external temperature references.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective gels are used to protect bond pads, then protection of interconnections is improved, but temperature measurement accuracy deteriorates due to thermal barrier
Solution Approach 1:
The sensor is divided into two separate chips: a pressure sensing chip and a signal processing IC. This segmentation eliminates the need for protective gels between the pressure sensing area and the IC, as they are separately packaged. The temperature sensor on the pressure chip can now directly measure media temperature without gel interference, while the IC handles signal processing in a protected environment.
Solution Approach 2:
A new intermediary element - a temperature sensor - is introduced on the pressure sensing chip to directly measure the media temperature. This temperature measurement serves as a mediator to compensate for pressure measurements, allowing accurate pressure readings even when protective gels are used elsewhere in the system, without letting the gels block thermal contact for temperature sensing.
2Ease of operation
If front side exposed pressure sensor design is used, then pressure sensing capability is achieved, but device footprint increases and manufacturing complexity increases
Solution Approach 1:
The patent inverts the conventional front-side exposed design to a back-side exposed configuration. The pressure sensing membrane is located on the back side of the chip, allowing the front side to be fully utilized for bonding and interconnections. This inversion enables a more compact integration of the pressure sensor with the signal processing IC, reducing the overall device footprint while maintaining pressure sensing capability.
Solution Approach 2:
The pressure sensing function and signal processing function are merged into a single integrated package. The pressure sensor chip is directly bonded to the IC chip, combining what were previously separate components into one compact unit. This merging eliminates the need for separate mounting spaces and reduces the overall footprint compared to discrete front-side exposed sensors.
3Device complexity
If 2 chip concept is used with direct bonding, then integration is improved, but calibration costs increase and space requirements increase
Solution Approach 1:
The two chips are pre-bonded together in a controlled manufacturing environment before final assembly. The pressure sensor chip and IC chip are bonded together with precise alignment of bonding pads and interconnections beforehand. This preliminary bonding action ensures proper thermal and electrical contact is established during manufacturing, enabling accurate calibration to be performed once during production rather than requiring expensive field calibration.
4Reliability
If protective gels and noble metal metallization are used, then interconnection protection is improved, but cost increases and harsh media resistance remains insufficient
Solution Approach 1:
The vulnerable interconnections are extracted from the harsh media environment by separating the pressure sensing chip from the signal processing IC. The IC with its sensitive bond pads is housed in a protected package that does not directly expose interconnections to harsh media. Only the robust pressure sensing membrane is exposed to the media, while the IC remains in a controlled environment, eliminating the need for protective gels and noble metal metallization.
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 solution provides accurate, compact, and cost-effective pressure and temperature sensing with reduced electromagnetic interference, faster temperature readouts, and lower calibration costs, while eliminating the thermal barrier effect of protective gels.
Implementation Method 1
piezo resistors
Implementation Method 2
temperature sensor signal conditioning is located next to the temperature sensor on the same IC
Data Source
AI summary
A pressure sensor system comprising a pressure sensor chip is disclosed. The pressure sensor chip comprises a sensing side where pressure sensing is performed and one or more interconnections where electrical connections are made at the other side of the chip. The pressure sensor comprising an integrated circuit (1) forming a substrate, the substrate comprising a membrane shaped portion adapted for being exposed to the pressure, the integrated circuit (1) comprising both pressure signal sensing components and pressure signal processing components.