Pressure Sensor Assembly with Direct Metallic Contacts
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Solution Overview
Problem
Conventional pressure sensors face limitations in accuracy and long-term stability due to the use of intermediate elements like oil and glass paste, which also restrict their temperature range and material choices for electrical contacts, leading to high contact resistance and mechanical weaknesses.
Innovation Solution
A method for manufacturing pressure sensors that integrates the assembly and protection of the micromechanical structure in a single phase, using a support substrate with a deformable membrane and conductive materials like ultra-doped polysilicon, Au, Ag, Ni, Pt, TiW, Cu, Pd, Al, Ti, TiN, and integrating the support into a package using the flip-chip technique with thermocompression, avoiding additional elements and ensuring direct metallic contacts with negligible resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oil and glass paste are used as intermediate elements for electrical contacts, then the micromechanical structure can be protected and assembled, but contact resistance increases and long-term stability deteriorates
Solution Approach 1:
The patent removes the intermediate elements (oil and glass paste) from the electrical contact path entirely. Direct metallic contacts are established between the conductive material deposited on the support substrate and the strain gauges on the membrane, eliminating the sources of high contact resistance and instability.
Solution Approach 2:
A conductive material layer serves as the intermediary between the support substrate and the strain gauges. This conductive layer is deposited in a single step covering both surfaces, providing low-resistance electrical contact while maintaining mechanical integrity, replacing the problematic oil and glass paste intermediaries.
2Ease of manufacture
If glass paste is used for electrical connections, then assembly can be achieved, but contact resistance becomes significant and changes over time under temperature effects
Solution Approach 1:
The patent changes the material parameter from glass paste to a conductive material with superior electrical properties. The conductive material maintains stable contact resistance across temperature ranges, eliminating the time-dependent resistance changes that occur with glass paste under thermal effects.
3Reliability
If electric wires are used for connections, then electrical contacts can be established, but the structure is weakened
Solution Approach 1:
The patent merges the electrical connection function with the structural support function. The conductive material is deposited as an integral part of the support substrate assembly process, creating a unified structure where the support substrate and electrical contacts form a single integrated component, eliminating separate wire connections that would compromise structural integrity.
4Reliability
If encapsulation is implemented at wafer level, then protection is achieved, but material choice for electrical contacts is limited
Solution Approach 1:
The patent performs the conductive material deposition as a preliminary action during the wafer-level encapsulation process itself, before final packaging. This allows a wide range of conductive materials to be selected and deposited while the structure is still in fabricable form, maintaining material versatility despite the integrated encapsulation approach.
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 enhances the quality of assembly, reduces contact resistance, and allows for higher temperature operation without material limitations, improving the accuracy and stability of the pressure sensors while eliminating the need for additional materials that could introduce mechanical constraints.
Implementation Method 1
deposition in a single step of at least one conductive material on the upper surface of the support and in the side recesses of the support
Implementation Method 2
the support substrate being arranged above the deformable membrane... the assembly consisting of an anodic seal
Implementation Method 3
the integration of the support to the case is carried out by a thermocompression process; the thermocompression process is implemented with a temperature of between 250° C. and 500° C., typically 320° C. with a pressure of between 10 MPa and 200 MPa, typically 50 MPa
Data Source
Figure 1a~1c
Figure 1d
Figure 2a~2b
AI summary
The invention relates to a method for producing a pressure sensor, comprising the following steps: assembling a support substrate with a deformable membrane on which strain gauges have been deposited, wherein the deformable membrane comprises a thinned area at the centre thereof, the support substrate is disposed on top of the deformable membrane, the support substrate comprises an upper surface and a lower surface in contact with the deformable membrane, and the support substrate also comprises lateral recesses arranged on top of the strain gauges and a central recess arranged on top of the thinned area of the membrane, so as to obtain a micromechanical structure; and, once the assembly has been obtained, depositing, in a single step, at least one conductive material on the upper surface of the support and in the lateral recesses of the support, said conductive material extending into the recesses in order to be in contact with the strain gauges so as to form electrical contacts in contact with the strain gauges.