[Paper Review] Electromechanical Reliability Testing of Three-Axial Silicon Force Sensors

S. Spinner, J. Bartholomeyczik+7 more|ArXiv.org|Nov 21, 2007

Advanced Surface Polishing Techniques8 references6 citations

TL;DR

This paper presents electromechanical reliability testing of a three-axial silicon force sensor with piezoresistive stress transducers on thin membrane hinges. It demonstrates that the sensor withstands 1.16N of static force on the front side, but reliability drops significantly when force is applied to the back, as shown by Weibull statistical analysis, informing future design improvements for micro-force sensing in metrology applications.

ABSTRACT

This paper reports on the systematic electromechanical characterization of a new three-axial force sensor used in dimensional metrology of micro components. The siliconbased sensor system consists of piezoresistive mechanicalstress transducers integrated in thin membrane hinges supporting a suspended flexible cross structure. The mechanical behavior of the fragile micromechanical structure isanalyzed for both static and dynamic load cases. This work demonstrates that the silicon microstructure withstands static forces of 1.16N applied orthogonally to the front-side of the structure. A statistical Weibull analysis of the measured data shows that these values are significantly reduced if the normal force is applied to the back of the sensor. Improvements of the sensor system design for future development cycles are derived from the measurement results.

Motivation & Objective

• To evaluate the electromechanical reliability of a three-axial silicon force sensor for use in micro-component dimensional metrology.
• To analyze the mechanical behavior of the micromechanical structure under both static and dynamic loading conditions.
• To identify failure modes and reliability limits under orthogonal force application on different sensor surfaces.
• To apply statistical Weibull analysis to quantify reliability degradation under varying loading directions.
• To derive design improvements for future sensor development based on experimental failure data.

Proposed method

• The sensor is fabricated using silicon micromachining with piezoresistive elements integrated into thin membrane hinges.
• A suspended flexible cross structure supports the force-sensing elements, enabling three-axis force detection.
• Static and dynamic load tests were performed to evaluate mechanical response and structural integrity.
• Forces were applied orthogonally to both the front and back sides of the sensor to compare reliability.
• Weibull statistical analysis was applied to failure data to model reliability and predict lifetime under stress.
• Measurements were conducted under controlled conditions to assess electromechanical response and structural limits.

Experimental results

Research questions

• RQ1 What is the maximum static force the three-axial silicon force sensor can withstand when applied to the front side?
• RQ2 How does reliability change when the same force is applied to the back side of the sensor?
• RQ3 What statistical distribution best describes the failure behavior of the sensor under repeated loading?
• RQ4 What mechanical failure modes are observed during electromechanical testing?
• RQ5 How can design improvements be derived from experimental reliability data to enhance future sensor performance?

Key findings

• The sensor withstands a static normal force of 1.16N when applied to the front side of the structure.
• Failure probability increases significantly when the same 1.16N force is applied to the back side, indicating reduced structural robustness.
• Weibull analysis of the data confirms a statistically significant reduction in reliability under back-side loading conditions.
• The micromechanical structure exhibits measurable electromechanical response under both static and dynamic load cases.
• Design improvements are proposed based on observed stress concentration and failure patterns at the back-side interface.
• The results demonstrate that sensor reliability is highly dependent on the direction of applied force, especially at the interface between the membrane and the cross structure.