Characterization of a PCB Based Pressure Sensor and Its Joining Methods for the Metal Membrane

Area of Science:

• Materials Science
• Sensor Technology
• Mechanical Engineering

Background:

• Essential quality features for pressure sensors include accuracy, measurement range, operating temperature, and long-term stability.
• Capacitive pressure sensors are widely used but require optimization for demanding applications.
• The joining process significantly impacts sensor performance and reliability.

Purpose of the Study:

• To optimize the quality features of a capacitive pressure sensor with a 10-bar measurement range.
• To evaluate and compare different joining methods for sensor assembly.
• To assess the impact of joining techniques on sensor accuracy, stability, and cost.

Main Methods:

• Fabrication of a capacitive pressure sensor with a metal membrane connected to a PCB and digital readout.
• Comparative analysis of four joining techniques: transient liquid phase (TLP) bonding, reactive joining, silver sintering, and electric resistance welding.
• Characterization using measurement of characteristic curves, long-term stability tests at maximum pressure, and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) for joint quality assessment.

Main Results:

• Transient liquid phase (TLP) bonding and silver sintering demonstrated the smallest measurement errors.
• Electric resistance welding and silver sintering exhibited no statistically significant long-term drift.
• Reactive joining and silver sintering were found to be the most cost-effective in terms of equipment.
• Electric resistance welding presented favorable conditions for mass production due to low material costs and short process times.

Conclusions:

• The choice of joining method critically influences the performance and suitability of capacitive pressure sensors for specific applications.
• TLP bonding and sintering are recommended for applications prioritizing high accuracy.
• Welding and sintering are suitable for applications requiring high long-term stability.
• Electric resistance welding offers a cost-effective and efficient solution for mass production of pressure sensors.