Have you ever wondered what a PCB is? A Printed Circuit Board(PCB) is an electronic component used to connect various electric devices. Copper conductors make electrical connections between parts on a printed circuit board (PCB), an electronic assembly. Electronic components are mechanically supported by printed circuit boards, allowing space for a device in an enclosure. The manufacturing procedure, integrated circuit packaging, and the bare circuit board’s structure must all be considered while designing a printed circuit board.
What is the maximum temperature that a PCB can withstand?
The materials a PCB is made of determine how much heat it can withstand. While certain materials are less trustworthy at withstanding high temperatures, those with the best thermal qualities offer reliable protection against the effects of high heat. The glass transition temperature (TG) metric shows this resistance. For instance, the TG of FR-4 is around 135 degrees Celsius. So, if a PCB can resist a maximum temperature of 150 degrees Celsius, it is often used in marking the high-temperature PCBs. Boards made from materials with less heat resistance will only be able to operate safely at considerably lower temperatures. At the same time, some high-temperature PCBs may be able to survive even higher heat.
Why do PCBs heat up?
Unsatisfactory design, inappropriate parts, material selection, erroneous component arrangement, and ineffective heat management can all contribute to excessive heat on printed circuit boards (PCBs). High temperatures that result harm the board’s overall performance, components, and temperature. In many applications, the impact of high temperatures may be insignificant, but it can significantly impact high-performance designs. Some of the reasons listed below are why your PCB might be heating up:
- Placing components incorrectly
Some high-power devices need to be placed in areas with the proper airflow, natural or forced. So the PCB manufacturers should place these in areas with vents or sufficient airflow. The PCB will retain the majority of the heat in the absence of adequate ventilation and heat evacuation, which will gradually raise the temperature and could cause faulty circuit operation or damage. Additionally, keep in mind that placing delicate components next to heat-emitting ones will subject them to thermal stress.
- Environmental factors
When making a high-temperature PCB, you must consider your environmental conditions: the ones required by your PCB and the external conditions. Some PCBs efficiently work optimally under certain conditions. Yet, when one deviates from them, it negatively affects the PCB’s performance.
- Wrong component and material selection
You must study the guidelines set by the manufacturer before using any PCB. When using a high-temperature PCB, people often overestimate the capabilities of the PCB due to its name. The lack of knowledge when picking up components for your PCB can lead to irregularities in the circuit and cause it to heat up.
- Poor PCB manufacturing and design
The design and manufacturing of the PCB encompass all from the number of connectors to the material used. Lack of knowledge of how a high-temperature PCB results in a lack of cohesion and can cause a PCB to heat up and, in some instances, not only stop functioning but also burn up.
Why is it important to manage heat for a high-temperature PCB?
The significant difference between PCBs that can take the heat and the ones that do not fare well under high temperatures is that the ones that handle heat efficiently are the ones that undergo a higher level of heat management. When objects are heated, they expand. The problem with a high-temperature PCB is that it holds a lot of connectors. These connectors contain the elements added to the PCB. When PCBs heats up, these connectors expand, and due to this, the corresponding parts fall off as their connections come loose. The goal of managing heat is to ensure that these parts do not expand or cool rapidly. It can cause damage to the circuit as well as cause change in the composition of the materials used.
The importance of knowing heat management is that it allows for a levy when picking the material for the PCB. You can manipulate the material to withstand high levels of heat. Temperatures on PCBs may be affected by oxidation. The bulk of PCB assemblers grossly undervalue this, and if you can control the temperature through micromanagement, so can oxidation.
Most PCBs have copper laminate on top of dielectric materials. It stops oxidation from happening as temperatures rise. The dielectric materials will oxidize considerably more quickly due to the heating process if the worn or dielectric material does not cover the copper laminate. Knowing how to manage heat is also helpful in managing the heat of the material and the components.
The coefficient of thermal expansion usage and its strategies to target the heat of a high-temperature PCB
We can’t avoid the thermal expansion that occurs when PCB components and materials endure increased temperatures. Thermal expansion, however, can be measured. The coefficient of thermal expansion is utilized (also known as CTE). We can calculate the thermal expansion rate for PCB materials and components through CTE. The Celsius temperature scale is the coefficient of thermal expansion given in parts per million. There is value in being aware of the precise computations for these parts per million. The following generalization about CTE is equally valuable, though. Your CTE calculations for the dielectric layers of your circuit board ideally lead to identical estimates for the laminated copper. In this approach, rather than pulling apart, both expand together. Some board areas can become too hot when these two pull against one another. Doing this will support your efforts to modify the PCB materials and components to withstand greater temperatures.
- Managing heat in a high-temperature PCB
While designing high-temperature PCBs, special precautions must be taken to guarantee them to function under harsh circumstances. Using materials optimized for thermal conductivity, such as “heavy copper” boards, is one of the most popular tactics. In keeping with their name, these materials increase current carrying capacity while lowering electrical loss, reducing heat generation, and enhancing heat dissipation. By lowering the overall size and the number of heat sinks required, heavy copper PCBs can help reduce costs. Yet, it brings the question of whether heat spreading in a thicker copper configuration reduces the overall thermal resistance to debate.
Thermal adhesives can reduce the requirement for thermally conductive silicon insulators or gap fillers that separate a device from a heat sink and can replace mechanical attachments like clips and screws. Other material concerns to keep in mind are chemical resistance, reduced smoke and ash generation, and flame resistance. These characteristics have made glass epoxy resins useful, such as FR4 standard materials. Moreover, they also offer electrical resistivity and reduced heat dissipation. Some well-known examples include IS410, IS420, and G200.
- Cooling a PCB
Techniques for passively dissipating PCB heat are insufficient in a configuration that generates a lot of heat. You, the creator, are responsible for including evaporating features like:
- Arrays, ideally close-by holes positioned beneath a heat source, are surface-mounted. Simple vias (in-pad) and filled & capped vias are the two different thermal vias. To generate heat directly, place the latter right next to an LED’s thermal solder pad.
- Heat sinks typically in the open assist in spreading the heat across a greater area for the component.
- Heat pipes are excellent for high-temperature uses in the aerospace and aviation industries. Think of heat pipes that enclose the PCB’s heat source and can bend without breaking.
- Thermal grease adhesives, or pads: These give the component a thermally conductive channel for releasing heat.
- Considerations for cooling fans include size, noise level, friction, cost, etc.
- Enclosure based design
The main goal of enclosure-based thermal design is to maximize airflow. It makes sense to consider the housing’s design last because it is installed at the end during assembly. However, you can improve the following aspects by constructing your electrical casing at the same time as the “guts” inside:
- Lead period
Industries that require delicate or outside equipment, like telecommunications, must considerably consider enclosure design. Create an open electronic enclosure that allows air to enter and exit to reduce the likelihood that your components may deteriorate. You may choose forced-air dissipation methods for confined environments, such as surface-mounted fans. To keep the electronics safe, designs with high predicted heat levels may require numerous fans. Finally, pick a surface treatment that won’t absorb heat if the enclosure is exposed to sunlight.
The PCB designing industry is one of the leading industries in the world. With the world evolving, this increase in the significance of the PCB industry appears to continue in the foreseeable future. Learning how to manage and track the heat of a PCB is crucial to gain extensive potential in the relative market and getting high-temperature PCBs. So what are you waiting for? Brush up on these PCB designing skills and rule the world while discovering an interesting new hobby.