What is a PCB Pressure Sensor & How Does it Work?

PCBs have traditionally been designed to enhance the functionality of various electronic devices. However, the capabilities of PCBs can be further extended when integrated with pressure sensors. In this article, we will explore the role of PCB pressure sensors, what they are, and how they function.

Understanding Pressure Sensors

A pressure sensor, by definition, is designed to detect various parameters such as turbulence, dynamic pressure fluctuations, and pulsations, typically in high-static pressure environments. Given this capability, pressure sensors have found their way into circuit boards used for high-end applications, particularly in industries like automotive electronics.

Impact of Pressure Sensors on PCB Performance:

Now that we understand how pressure sensors operate independently, let’s delve into their relevance to Printed Circuit Boards (PCBs). The primary function of a pressure sensor within a circuit board is to act as a transmitter, converting excess pressure into an analog electrical signal. This conversion helps in balancing the performance of the circuit board, especially when it comes to measuring small pressure fluctuations in high-static pressure environments.

Measurement Principles

To optimize the use of PCB pressure sensors, it’s essential to consider the different principles and methods used to measure their performance. Two common measurement methods include piezoresistive and capacitive effects, with piezoresistive effects being the more popular and the focus of this article.

Piezoresistive Effect:

The piezoresistive effect primarily measures dynamic changes in the circuit board’s temperature. However, it may not be the best option for scenarios involving static pressure sensitivity. Piezoresistive transducers are used to harness the piezoresistive effect’s capabilities and facilitate the conversion of electrical charges generated by certain solid materials into the required energy.

Types of PCB Pressure Sensors

To fully grasp the significance of these sensors, it’s essential to explore the different types available. The choice of sensor type depends on the intended application. Here are some common types:

1. Mountable PCB Pressure Sensors: These sensors are designed for use with Printed Circuit Boards (PCBs) that primarily employ Surface Mount Technology (SMT) for component placement.
2. Hazardous Area Pressure Sensors: These are specifically designed for areas of PCBs that contain more hazardous components or are prone to hazards.
3. Combined Pressure and Temperature Transducers: Ideal for applications or devices requiring both pressure and temperature measurements, these sensors offer versatility.
4. Pressure Transducers: Focusing solely on pressure measurement, these sensors are suitable for applications where pressure is the critical parameter.
5. Pressure Switches: These sensors are designed to activate or deactivate based on a certain pressure threshold, making them useful in various control systems.

Applications of PCB Pressure Sensors

When selecting a PCB pressure sensor, it’s crucial to consider the intended use case. While common applications include the marine and automotive industries, these sensors have relevance in other fields as well. Here are some ideal use cases:

• Aviation Applications: Pressure sensors play a vital role in aviation for altitude and airspeed measurement.
• Pneumatic and Hydraulic Systems: These sensors are used to monitor pressure in pneumatic and hydraulic systems, ensuring optimal performance.
• Gas Turbines: In the energy sector, pressure sensors are employed to monitor gas turbine performance and efficiency.
• Combustion Dynamics: Pressure sensors help in combustion analysis, ensuring efficient and clean combustion processes.
• Blast and Ballistics: In defense applications, these sensors are used to monitor blast pressures and ballistics.
• Hydro-Turbines: Pressure sensors play a critical role in hydroelectric power generation, ensuring efficient energy conversion.

Characteristics of PCB Pressure Sensors

PCB pressure sensors are specialized components with distinctive characteristics that enable them to function effectively within various applications. These characteristics are key to their optimal performance. Here are the primary characteristics of PCB pressure sensors:

Solid Construction

PCB pressure sensors are engineered with rugged and solid-state construction. This robust build ensures that these sensors can be seamlessly integrated into circuit boards without compromising their structural integrity. The solid construction enhances their durability, making them suitable for deployment in demanding environments, where reliability is essential.

Excellent Pressure Measurement

One of the core attributes of PCB pressure sensors is their exceptional ability to measure pressure accurately. These sensors can detect and quantify even the smallest changes in pressure, ensuring precision in their measurements. This capability is particularly valuable in applications where precise pressure monitoring is critical. PCB pressure sensors excel at measuring pressure fluctuations, pulsations, and dynamic pressure changes, even in high-static pressure environments.

Fast Timing

Timing is crucial in many applications that utilize PCB pressure sensors. These sensors offer rapid response times, typically in the microsecond range. This swift response time enables them to capture and report pressure variations with exceptional speed and accuracy. Whether monitoring dynamic pressure fluctuations or capturing real-time data, the fast timing of PCB pressure sensors ensures that critical information is available promptly.

In summary, PCB pressure sensors possess a combination of characteristics that make them highly effective in a wide range of applications. Their solid construction guarantees durability, while their excellent pressure measurement capabilities ensure accurate and reliable data. Additionally, their fast timing allows for real-time monitoring and rapid response to pressure changes. These attributes collectively contribute to the versatility and reliability of PCB pressure sensors in various industries and use cases.

Advantages of Piezoresistive Transducers

Since piezoresistive transducers constitute the functionality of PCB pressure sensors, it’s essential to understand their advantages:

• Flexibility: Piezoresistive transducers are flexible and available in various sizes and shapes, making them suitable for diverse applications.
• Self-Generating Capabilities: These transducers can generate voltage when exposed to specific energy sources, eliminating the need for an external power source.
• Frequency Response: Piezoresistive transducers offer a high-frequency response, enabling rapid parameter shifts in the transducers.
• Accessibility: They are easy to handle due to their large measuring range and small dimensions.

The Relationship Between PCB Pressure Sensors and Metal Membranes

In the realm of PCB pressure sensors, metal membranes, particularly stainless steel variants, have emerged as indispensable components that significantly enhance sensor performance. These metal membranes serve as vital interfaces between the sensor and the circuit board, facilitating optimal functionality. Let’s delve into the intricacies of this symbiotic relationship.

Connection Methods

The fusion of metal membranes with Printed Circuit Boards (PCBs) involves the utilization of diverse connection methods, each carefully chosen to suit specific requirements. These connection processes play a pivotal role in ensuring the reliability and temperature resistance of the overall sensor assembly. Here is an overview of these connection methods:

1. Silver Sintering: Silver sintering operates on the principle of diffusion and is employed when the temperature resistance requirement is high, reaching up to 200˚C. This method involves the interconnection of the metal membrane to the PCB. During the process, a substantial pressure of up to 40 megapascals (MPa) is applied to the materials, enhancing the bonding process. Silver sintering offers advantages such as reduced total surface energy and serves as a superior alternative to conventional high-melting soldering techniques.
2. Transient Liquid Phase (TLP) Bonding: TLP bonding relies on diffusion processes to create intermetallic phases. It finds application in microelectronic packaging for high-temperature scenarios. What sets it apart is the relatively high melting point of the connecting alloy, surpassing the bonding process’s temperature. This characteristic ensures the durability of the connection.
3. Electric Resistance Welding: Electric resistance welding involves the fusion and connection of two metal components. To achieve optimal results in PCB pressure sensor applications, it is essential to fine-tune process parameters, including time and current. This optimization minimizes the risk of damaging the circuit board during the welding process, ensuring a reliable connection.
4. Reactive Joining: Reactive joining is another method used to establish a connection between the metal membrane and the PCB, regulating the pressure sensor’s operation. This process relies on an exothermal reaction that generates the required heat. Once heat is generated, a multilayer metal known as the Reactive Foil (RF) is placed or stacked between the two layers of solder, facilitating the soldering procedure.

Alternative to MEMS Pressure Sensors

The integration of metal membranes with capacitive pressure sensors offers a compelling alternative to the conventional use of Microelectromechanical Systems (MEMS) pressure sensors. While MEMS sensors excel in measuring low and absolute pressures, they do have limitations, especially in scenarios involving higher pressures and specific applications. Here’s how metal membranes with capacitive pressure sensors provide a viable alternative:

1. Measurement Range: MEMS pressure sensors are renowned for their ability to measure low and absolute pressures with precision. However, they often fall short when it comes to measuring higher pressures. Metal membranes with capacitive pressure sensors fill this gap by excelling in applications demanding accurate measurements at elevated pressure levels.
2. Specialized Applications: Certain applications, such as those requiring exposure to silicone gel or transmission fluid, may not be suitable for MEMS pressure sensors. Metal membranes, with their robust design and flexibility, offer an ideal solution for such specialized scenarios.

In conclusion, the integration of metal membranes, particularly stainless steel variants, with capacitive pressure sensors enhances the functionality of PCB pressure sensors. These membranes serve as crucial interfaces, and the choice of connection method plays a pivotal role in ensuring reliability and temperature resistance. Furthermore, metal membranes with capacitive pressure sensors offer a viable alternative to MEMS pressure sensors, particularly in applications involving higher pressures and specific environmental conditions.

Conclusion

The integration of capacitive pressure sensors with metal membranes into Printed Circuit Boards (PCBs) offers several advantages, including simplified housing requirements and cost savings. To harness these benefits effectively and optimize the use of PCB pressure sensors in high-pressure environments and applications, it is essential to have a comprehensive understanding of their principles, types, applications, and advantages.

PCB pressure sensors play a pivotal role in various industries and applications, where the accurate measurement of pressure fluctuations and dynamic changes is critical. Their solid construction, excellent pressure measurement capabilities, and fast timing make them invaluable components for real-time pressure monitoring and data acquisition.

By choosing the right type of PCB pressure sensor and understanding its principles, manufacturers and engineers can ensure that their electronic systems perform optimally in high-pressure scenarios. Whether used in aviation, pneumatic and hydraulic systems, gas turbines, or other applications, PCB pressure sensors provide the precision and reliability required to meet industry standards and customer expectations.

In conclusion, PCB pressure sensors are versatile components that enhance the performance and functionality of electronic systems in high-pressure environments. Their ability to accurately measure pressure changes, coupled with their durability and rapid response times, makes them indispensable tools for engineers and manufacturers seeking to achieve precision and efficiency in their applications.