High Tg PCBs High Temperature PCB FR4 Materials
Temperature fluctuations have a considerable impact on the quality, reliability, and performance of PCB assemblies. Higher temperature causes the expansion of materials. But, standard materials used for PCBs do not have the desired thermal expansion coefficient. It may lead to micro-cracks due to mechanical stress. Electrical tests cannot always detect these cracks. As a result, the product may experience random failures. So, it has led to the innovation of a high Tg or high temperature PCB. However, the Tg value of every PCB is different depending on its substrate. Let us talk more about high Tg PCB and the materials used for it.
Know About the High Tg PCB
Tg refers to the mechanical property designating a particular transition temperature to every base material (such as glass or polymer). Under this temperature, the material transforms into a rubbery form from a solid, glassy state. Materials exceeding their Tg value do not get melted, but they have structural transformation. However, it is challenging to measure the temperature precisely because the molecular structure of the material and other factors cause variation.
So, a high Tg PCB is a special circuit board capable of enduring higher temperatures. The operating temperature endurable to ordinary PCBs is 120°C. But, these PCBs work only in normal appliances and devices. They are not ideal for high-temperature electronic gadgets. FR-4 material is mainly used for designing the high Tg PCBs.
The minimum Tg value must be 20 to 25°C higher than the standard operating temperature of the particular device. For instance, if your board has a Tg value of around 130°C, the device’s operating temperature must be below 110°C.
The higher Tg value means a better capability to resist moisture and temperature. When the operating temperature has exceeded or reached the Tg value, the board’s structure will undergo transformation. Thus, the board will not work properly. The Tg value has a connection to the board’s structure and dimension.
There are also multilayer PCBs with dense and compact circuits, causing reduced air circulation and higher heat generation. It can cause a problem with the device’s functionality and the hardware’s integrity. So, a high Tg PCB can be the best choice for multilayer boards.
It is advantageous to use high Tg PCBs for various reasons.
Higher Stability
High Tg PCBs have strong mechanical resistance to corrosive chemicals, heat, and moisture. They keep the conditions in a device stable. If you use a high Tg PCB, there will be minimal impact on the hardware due to internal transformations for processes. As a result, the PCB boards have a longer lifespan and reduced risks of short circuits.
High-Power Density Board Design–
The design turns out to be high temperature and withstands the energy.
Unique Features of High Temperature PCB
The most important features of high Tg PCBs are-
- Resistant to Pressure and Temperature-
Many electronic devices have high power density and complex designs. Complex and multilayer circuits produce high heat and increase the temperature. Ordinary PCBs do not have high efficiency to work with those devices. On the contrary, a high Tg PCB is highly resistant to pressure and temperature. As the thermal resistance of the PCB is high, it is suitable for working in extreme temperatures.
- Never Gets De-Shaped Under High Temperature
Due to improved electrical and mechanical properties, high TG PCBs are advantageous. These boards retain their solid shape in high temperatures and heat. Moreover, as their thermal expansion risk is low, they are perfect for complex devices and circuits. Thus, they will not expand under high temperatures.
- Minimal Risks of Chemical Damage–
The robust high Tg circuit boards are resistant to chemical erosions. Chemicals cannot affect them easily. Although these circuit boards are better than standard PCBs, they cost more. So, devices with these advanced PCBs are costly because of their temperature capacity and robustness.
Use Cases of High Tg PCBs
A high Tg PCB is useful in different industries.
Metal Industries
Processing a metal piece involves different steps. For instance, a metal can be shaped to any form based on its purpose. The cutting processes lead to varying temperatures. An increase or decrease in temperature causes instability in a machine’s microcontrollers. The best way to maintain steadiness is to integrate a high Tg PCB.
Engine Controllers
The efficiency of an engine depends on the reliability of the controllers. A high Tg PCB is capable of enduring extreme temperatures caused by long running hours.
A high Tg PCB is also used for
- RFID gateways
- W-Fi boosters
- Low-cost PLC
- Computer hardware
- Telecommunications systems
- Jets and missiles
- Automotive and industrial equipment
- Airplane engines
In most cases, a high Tg PCB has provided a good solution for machines and devices that work in harsh environments.
FR4 Material for High Tg PCB Manufacturing Projects–
FR-4 refers to the fiberglass-reinforced sheets laminated with epoxy. They are used for the high Tg PCB manufacturing processes. However, FR-4 is also a grade for rating epoxy laminated sheets. It represents the sheet’s base quality, which means a range of sheet materials. FR is an abbreviation for the flame retardant properties, whereas the 4 differentiates the class of the material.
Materials that are considered as FR4 have a composite structure. Their basic layer is fiberglass integrated into a sheet. Fiberglass also provides structural stability for FR4. The innermost layer of fiberglass is surrounded by epoxy resin that ensures material rigidity.
FR4 sheets have become popular among professional electrical designers and engineers as the base material for PCBs. Versatility and affordability are the main reasons for choosing FR4 sheets. Besides, they have high dielectric strength and electrical insulation capability. They are lightweight, moisture-resistant, and have good dielectric strength. FR4 materials show excellent performance in any environmental conditions.
Due to these qualities, FR4 is chosen as the best substrate material for manufacturing high Tg circuit boards. When used properly, these properties of FR4 also develop the base for high-quality yet affordable PCBs. So, FR4 is the backbone of your PCB. Manufacturers always consider it while building the circuit board. They laminate the FR4 with single or multiple copper foil layers with adhesive and heat. The copper creates the circuits in the end product and covers the sides based on the board design.
Selecting the FR4 Material for High Tg PCB Manufacturing
The thickness of FR4 sheets varies significantly depending on your project needs. However, it mainly ranges from 10 inches to 3 inches. Board thickness is not an important factor for your PCB design project. Still, you should know some facts before choosing the FR4 board.
If you have a space issue, a thinner board is the right choice. It is also suitable for manufacturing smaller items, such as Bluetooth accessories and USB connectors. These smaller and thinner FR4 PCBs are also preferable to save some space inside the device.
The multilayered board works like a capacitor on layers. The thickness level of the FR4 material makes a difference in the dielectric’s thickness, which affects the capacitance value. It is the main factor for creating high-frequency circuit boards like microwave and RF designs. These designs consider impedance matching as the main component to allow the best board function.
So, FR4 is an essential material for designing high Tg circuit boards. If the product operates at more than 130 degrees Celsius, it is safe to use a high Tg printed circuit board.
