Have you ever wondered what a PCB is? A printed circuit board (PCB) is an electronic component used to connect various electrical devices. Copper conductors make electrical connections between components on a printed circuit board (PCB) (electronic assembly). The printed circuit board provides mechanical support for the electronic components, leaving space for the device in the housing. When designing a printed circuit board, the manufacturing process, the integrated circuit package, and the structure of the bare circuit board must be considered.

What is the highest temperature a PCB can withstand?

The material used for the PCB determines how much heat it can withstand. While some materials are less reliable in terms of withstanding high temperatures, the materials with the best thermal properties can provide reliable protection against the effects of high temperatures. The glass transition temperature (TG) indicator shows this resistance.

For example, FR-4 has a TG of about 135 degrees Celsius. Therefore, if a PCB can withstand a maximum temperature of 150 degrees Celsius, it is usually used to mark a high-temperature PCB Boards made of materials with poor heat resistance can only operate safely at considerably lower temperatures. At the same time, some high-temperature PCBs may be able to withstand higher heat.

Why Do PCBs Get Hot?

Poor design, inappropriate parts, material selection, incorrect component placement, and poor thermal management can all cause your printed circuit board (PCB) to overheat. The resulting high temperatures can compromise the overall performance of the board, components, and temperature. In many applications, the effects of high temperatures may be negligible, but it can significantly affect high-performance designs. Listed below are some of the reasons why your PCB may be getting hot:

Improper Component Placement
Some high-power devices need to be placed in an area with proper airflow (natural or forced). Therefore, PCB manufacturers should place these devices in areas with vents or adequate airflow. If ventilation and heat dissipation are inadequate, the PCB will retain much of the heat, which will gradually increase the temperature and may cause circuit operation failure or damage. Also, keep in mind that placing delicate components next to heat-generating components can subject them to thermal stress.

Environmental Factors
When making a high-temperature PCB, you must consider environmental conditions: the conditions required by the PCB and the external conditions. Some PCBs can work optimally and efficiently under certain conditions. However, when these conditions are deviated from, the performance of the PCB is negatively affected.

Improper Component and Material Selection
Before using any PCB, you must study the guidelines set by the manufacturer. When working with high temperature PCBs, people often overestimate the capabilities of PCBs because of their name. Lack of knowledge when picking components for a PCB can cause the circuit to behave abnormally and cause it to heat up.

Poor PCB Manufacturing and Design
The design and manufacturing of PCBs covers everything from the number of connectors to the materials used. Lack of knowledge about high temperature PCBs can lead to a lack of cohesion and can cause the PCB to overheat and, in some cases, not only stop working but burn out.

Why is it important to manage the heat of high-temperature PCBs?

The significant difference between a PCB that can withstand heat and one that does not perform well at high temperatures is that PCBs that can handle heat effectively need to go through a higher level of thermal management. When objects are heated, they expand. The problem with a high temperature PCB is that it contains many connectors.

These connectors contain components that are added to the PCB. When the PCB heats up, these connectors expand and, therefore, the corresponding components can fall out as the connection loosens. The goal of thermal management is to ensure that these components do not expand or cool down quickly. Otherwise, there may be damage to the circuit and changes in the composition of the materials used.

Understanding the importance of thermal management is that it can play a role in selecting PCB materials. You can manipulate materials to withstand high temperatures. Temperature on a PCB can be affected by oxidation. Most PCB assemblers severely underestimate this, if you can micromanage the temperature, then oxidation can too.

Most PCBs have a copper laminate on top of the dielectric material. It prevents oxidation from occurring when the temperature rises. If the dielectric material is worn or not covered by the copper laminate, the dielectric material will oxidize faster due to the heating process. Understanding how to manage heat can also help manage the heat of materials and components.

Use of Coefficient of Thermal Expansion and Its Strategies for Heat Dissipation in High Temperature PCBs

We cannot avoid thermal expansion of PCB components and materials at high temperatures. However, thermal expansion can be measured. Using the Coefficient of Thermal Expansion, also known as CTE. We can calculate the thermal expansion rate of PCB materials and components from CTE. The Celsius temperature scale gives the coefficient of thermal expansion in parts per million. It is valuable to know the exact calculation of these parts per million.

However, the following summary about CTE is equally valuable. Ideally, your CTE calculations for the board’s dielectric layer would result in the same estimate for the laminated copper. In this approach, the two don’t move apart, but rather expand together. As the two pull against each other, certain board areas may get too hot. Doing so will help you modify your PCB materials and components to withstand higher temperatures.

Thermal Management in High-Temperature PCBs

When designing high-temperature PCBs, special precautions must be taken to ensure they function properly in harsh environments. Using materials optimized for thermal conductivity, such as “thick copper” boards, is one of the most popular strategies. As the name implies, these materials increase current-carrying capacity while reducing electrical losses, reducing heat generation, and enhancing heat dissipation. Thick copper PCBs can help reduce costs by reducing overall size and the number of heat sinks required. However, this raises the question of whether the spreading of heat in thicker copper configurations reduces overall thermal resistance.

Thermal adhesives can reduce the need for thermally conductive silicone insulators or gap fillers, which are used to separate devices from heat sinks, and can replace mechanical attachments such as clips and screws. Other material issues to look out for are chemical resistance, reduced smoke and ash generation, and flame retardancy. These properties make glass epoxies very useful, such as FR4 standard materials. In addition, they have resistivity and reduce heat dissipation. Some well-known examples include IS410, IS420, and G200.

Cooling the PCB
In configurations where a lot of heat is generated, techniques to passively dissipate PCB heat are not enough. It is your responsibility as the creator to include the following evaporation features:

Arrays are surface mounted, ideally with nearby holes located under the heat source. Simple through-holes (in-pad) and filled and capped through-holes are two different types of thermal vias. To generate heat directly, place the latter next to the thermal pad of the LED.
Heatsinks are usually open and help spread the heat over a larger area of ​​the component.
Heat pipes are ideal for high temperature applications in the aerospace industry. Imagine a heat pipe surrounding the heat source of the PCB that can bend without breaking.
Thermal grease adhesive or pads: They provide a thermally conductive path for components to release heat.
Considerations for cooling fans include size, noise levels, friction, cost, and more.
Enclosure-Based Design
The primary goal of enclosure-based thermal design is to maximize airflow. It makes sense to consider the design of the enclosure last, since it is installed last during the assembly process. However, you can improve the following aspects by building the electrical enclosure at the same time as the internal “guts”:

Cost-Effectiveness
Lead Time
Quality
Industries that require delicate or external devices, such as the telecommunications industry, must carefully consider enclosure design. Create an open electronic enclosure that allows air to flow in and out to reduce the possibility of component damage. For confined environments, you can choose forced air dissipation methods, such as surface-mounted fans. Designs that anticipate high heat levels may require multiple fans to keep the electronics safe. Finally, choose a surface finish that will not absorb heat when the enclosure is exposed to sunlight.

The PCB design industry is one of the world’s leading industries. As the world develops, the importance of the PCB industry seems likely to continue to grow for the foreseeable future. Learning how to manage and track the heat of PCBs is essential to gaining widespread potential in related markets and achieving high-temperature PCBs.