How to Strategically Select PCB Materials for Low-temperature Applications?

Printed circuit boards (PCBs) are a vital part of electronic devices, providing a physical foundation and enabling electrical connections and subsequent functioning. Their performance, reliability, and longevity are crucial for the devices they power. However, various factors can compromise their performance, with temperature being a significant one. In environments with low temperatures, it's essential to use materials that can maintain their functionality and reliability. This is because low temperatures can significantly alter the physical properties of materials, leading to brittleness, reduced flexibility, and changes in electrical conductivity. So, which are the best PCB materials for low-temperature applications and how to select the right materials for such environments? This post provides detailed answers to these questions.
 
Top Materials for Low-temperature Applications
Here is a list of PCB materials best suited for low-temperature applications.

• Polyimide: This high-performance plastic is recognized for its thermal stability, making it an excellent choice for PCBs operating in low-temperature environments. Polyimide retains its electrical and mechanical properties at low temperatures. Additionally, it can resist thermal expansion, which is crucial for maintaining the circuit’s integrity. This material is ideal for applications in aerospace, military, and other high-reliability industrial sectors, where electronic systems must withstand extreme conditions without compromising performance.
• FR-4: This is the most commonly used PCB material, composed of woven fiberglass cloth and an epoxy resin binder. While FR-4 is primarily suited for normal environmental conditions, it can be modified with specific additives to enhance its performance in low-temperature environments. These modifications improve its thermal and mechanical properties, allowing the material to maintain stability and enable the circuit to function effectively.
• Teflon (PTFE): This is another widely used material used for low-temperature PCBs. PTFE, commonly known by the brand name, has exceptional thermal resistance and low dielectric constant, crucial for maintaining signal integrity in electronic circuits. Teflon has low thermal expansion and remains stable at low temperatures.
• Ceramic-filled Laminates: These laminates combine the properties of PTFE with the added benefits of ceramic fillers. This combination provides excellent dimensional stability and reduced thermal expansion, while enhancing the mechanical properties of the material. These laminates also offer stable dielectric properties, crucial for maintaining signal integrity in RF applications. They find uses in space and satellite technology, where low temperature and high reliability are required for mission-critical components.
• Rogers Materials: Rogers Corporation's RO3000® and RO4000® series cater to low-temperature PCBs. The RO3000® series, made of ceramic-filled PTFE composites, offers low dielectric constant and loss, ensuring stable electrical performance across a wide temperature range, ideal for high-frequency applications like microwave and millimeter-wave circuits in aerospace and defense. The RO4000® series features a unique thermoset hydrocarbon resin system, combining ease of processing with excellent electrical properties, making it essential for automotive radar and ADAS due to its balanced performance and cost-efficiency. Both series maintain excellent dimensional stability, low thermal expansion, and reliable signal integrity, ensuring efficient circuit boards in high-performance applications.

 
Considerations for Low-Temperature PCB Design
Designing PCBs for low-temperature environments requires attention to detail and careful consideration of materials, designing techniques, and components. Here are some key considerations.

• Materials: It is important to consider materials that maintain their mechanical and electrical properties at low temperatures. For instance, FR-4 with specific low-temperature ratings or PTFE-based laminates are commonly used for low-temperature environments.
• Solder and Solder Mask: Use a solder with a low melting point to avoid cracking. The solder mask should be flexible and adhere well at low temperatures.
• Components: Selected components must operate within the intended temperature range without performance degradation. Also, consider the Coefficient of Thermal Expansion (CTE) of components and substrates. Mismatched CTEs can lead to mechanical stress and potential failure.
• Design Techniques: Ensure thermal management, signal integrity, and conformal coating characteristics in the required temperature range.
• Mechanical Considerations: Ensure the PCB can handle thermal cycling without excessive mechanical stress. Use connectors and interconnects designed for low-temperature operation to prevent issues like brittleness or poor contact.
• Testing and Validations: Perform thorough environmental testing, including thermal cycling and shock testing, to validate the PCB design under low-temperature conditions. Perform reliability analysis to predict and mitigate potential failure modes at low temperatures.

 
Masking your PCBs with the right materials and considering their operational environment is as essential as their design, fabrication, and assembly processes. If you are an OEM that manufactures electrical and electromechanical devices, ensure your PCB manufacturer and assembling partner has the capabilities and adequate experience to understand your requirements. For those newbies who need clarification on PCB design, materials, and processes, seek a full-service manufacturer offering end-to-end services. Twisted Traces stands ahead in the competition. Over the years, the company has provided PCB designing, fabrication, and assembly services using advanced materials, ensuring the highest quality. Get in touch with their expert team to know more about their services.