While the concept of the PCB has certain fundamentals in its design that have remained unchanged for a long time, a technology that affects PCBs have changed rapidly over the last few decades.
One issue that remains constant is the issue of PCB temperature.
The physical shape of a PCB is made up of traces, holes, layers, through holes, and solder masks. Each of these things can be affected by PCB temperature.
A snowball effect of problems can occur if PCB temperatures rise linearly. If unchecked, this will negatively affect the performance of the PCB.
This article will provide an overview of the design of high-temperature boards and how temperatures can be micromanaged.
1、Causes of High PCB Temperature
The first step in micromanaging anything is to detect the source of the micromanagement needed. PCB temperature is no exception to this, and since PCBs use heat to function, it is first necessary to determine the cause of the PCB's high temperature.
High PCB temperature can lead to performance issues. When currents are too strong throughout a PCB, temperatures will rise.
There are three telltale signs of this anomaly.
It is the first sign that temperatures in a PCB are rising too high. One thing to remember here is that heat generated by a component is directly proportional to the load current that flows through said component.
In this particular case, component dissipation occurs when one component of the PCB is not generating the kind of power it usually generates. It causes other components to generate more power than usual in an attempt to balance out the dissipating component.
If the current that travels through a resistor is inconsistent, for example, the capacitor and other major circuit board components will carry a larger charge than usual to compensate.
One of the most common things that provide power to a component is the heat sink. Heat sink components are also known as through-hole components.
These components generate heat by dissipating heat in the air. The heat sink makes this possible, and one way that you can micromanage PCB temperatures here is to see if the heat sink is soldered correctly.
If another component on the PCB is interfering with through holes or heat sinks, this will cause the other components to work overtime to generate more heat than necessary.
SMD stands for “surface mount device.” It is connected to a PCB just like a through hole component is, and allows currents to travel smoother among the through hole and heat sink components.
As far as maintaining PCB temperatures is concerned, one of the most common issues that one can encounter pertains to the position of the through hole components on the PCB relative to the SMD components.
If they are too far away, it might take too long for the power to travel to and from these components. It can result in the components staying cool for too long, which will cause other components to overheat. If they are too close to each other, the temperature will be unusually high.
A lot of this information comes from WellPCB, an organization that specializes in exploring new ways to micromanage PCB temperatures.
2、PCB Temperature Transfer Channels
A common thing about temperature is that they are never static. Temperatures generally never stay the same. It is aware of this, as well as multiple channels of PCB temperature transmission.
Temperature is affected in many ways, and one of the ways that you can micromanage both the general temperature in your PCB as well as the components of the PCB is to not only know about these channels but also what components of the PCB utilize which channel.
When people are referring to thermal energy in the form of electromagnetic waves, they are talking about radiation. Radiating heat is usually generated passively, meaning that you cannot get directly lower or increase temperature by radiation.
Radiant heat has an almost negligible effect on PCB temperature. At the same time, it is also the channel that you should probably worry about the most. It is because PCB temperatures are also affected by thermal energy.
When it comes to temperature, nothing is truly negligible. Think of what would happen if an airplane were to move just one degree off course. If this happens, it will land in a different location than planned no matter how short the distance could be.
PCB temperatures operate the same way. If a PCB needs to be at a temperature of 30 degrees Celsius to operate optimally but stays at 32 degrees for a very long time, the results will not be desirable.
While there is no way to micromanage radiating heat directly, it is possible to micromanage radiating heat indirectly. Being in an environment with consistent temperature when building and manufacturing PCBs is one way to do this.
Convection takes place when heat is transferred to fluids or air. Unlike radiation, convection is completely direct and has a very strong effect on overall PCB temperature.
The most popular example of convection is when cooking something. After all, nearly all ovens are convection ovens. Heat from the oven is transferred to the air, and that is what allows it to heat things.
“Cooking” also takes place when it comes to PCB materials, and just like it is important to know your temperatures when preparing food in a kitchen, it is also important to know your temperatures when heating PCB materials.
The most direct form of temperature transfer channel is conduction. In conduction, heat is transferred between a heat source and a heat sink.
The strongest example of this is when lightning strikes something metallic or fluid. In these examples, the heat source is the lightning, and the heat sink is the fluid material or the metallic material.
It knows what components of your PCB function as heat sources and which components of the PCB function as heat sinks are a good way to determine when it is a good idea to determine what kinds of currents which components can withstand.
3、PCB Temperature Tolerance
PCB manufacturers also have trouble with overheating components in PCBs because they simply have not taken the time to learn what kinds of temperatures material can withstand.
Just knowing this and making a list is something that every manufacturer should do. Keeping a list on hand displaying how hot each material can get is very useful and in many cases, necessary.
For example, the panels of a PCB contain a material called FR-4, which can withstand temperatures up to 90 to 110 degrees Celsius. Therefore, when preparing a PCB with FR-4 materials, you should be aware of any currents that involve this material that could exceed 110 degrees Celsius.
Knowing what kinds of temperatures the panels of the PCBs you plan to manufacture is one of the most important aspects of micromanaging the temperature of a PCB, but also one of the most overlooked.
4、How to Measure PCB Temperature
It is extremely important to understand what kinds of temperatures your PCB panel materials can withstand. It is also very important to know how heat is transferred among the components of the PCB.
Knowing these things will help you micromanage your overall PCB temperature. Another thing that is good to know is how to measure PCB temperature.
Measuring, in this case, does not mean checking the environmental temperatures that are displayed. It instead refers to measuring how the temperature increases and decreases. Knowing these processes is one of the most accurate methods of measuring overall PCB temperature.
There are a few things that you need to identify before measuring PCB temperature this way. These are the main heat source and the temperature sensor. It is how most of the heat is generated and where most currents take place.
The next thing to do is to find the GND pin of the heat source. It is usually connected to the substrate of the heat source.
After doing this, you can measure PCB temperature by doing these three things:
Using a common ground plane between the temperature sensor and the heat source.
You are connecting the GND pins of all temperature sensors to the ground plane of the heat source.
You are keeping the temperature sensor and heat source reasonably close to each other on the PCB.
Doing this will allow you to accurately and consistently track the global temperature of the PCB as well as the main heat source.
5、Results Caused By Excessive PCB Temperature
Knowing how to measure PCB temperatures accurately and adequately is one thing. But what happens when the components and materials of a PCB get too hot?
Excessive temperatures will destroy the integrity of the layer.
What happens when something gets unusually hot or cold? They expand and contract, respectively.
PCBs are no different. The layers of the PCB are sensitive to temperatures. If they are not micromanaged, excessive temperatures will warp the length, width, and thickness of any PCB layer.
Going back to the example of convection in chapter 2, this is similar to leaving food in the microwave for too long, causing the food item inside to explode.
A similar thing happens to PCB layers if they are overheated.
Thermal energy expands most substances, altering them.
Substances expand when heated too much, Altering their shape in some way.
Circuit materials are not exempt from this. High temperatures can and will change the shape of the transition lines in these circuit materials. When this happens, it will change the dimensions of the circuit materials themselves.
It will result in straight losses, distortion, and frequency shifts in circuit materials.
Materials expand at different rates.
Materials in a PCB will not only expand when around high temperatures, but they will also expand at different rates.
The surface of a PCB is made up of either dielectric layers or conductive metal layers. These layers expand to different limits at different speeds. These differences are not just separate from dielectric and conductive. No dielectric or conductive layer is created equal.
One of the most common mistakes any PCB manufacturer can make is confusing these two layers. Make sure to take the time to know which layer you are working with.
Board soldering requires different temperatures.
Welding and soldering is a necessary skill for anybody who wishes to produce, test, and manufacture PCBs.
It knows what kind of temperatures to work with when welding and soldering is something that anybody in a PCB manufacturing firm needs to know, even if they are not directly involved in the welding and soldering of any materials.
6、 Choosing the Right PCB Materials
Another way to micromanage and properly set temperatures for PCBs is to choose the proper materials for the plates. Choosing the wrong materials will make it much more difficult than it should be to micromanage these temperatures.
The most common material for a PCB plate is called FR-4. Anybody who is just starting in PCB manufacturing or who wants to minimize risks should choose this material. A common thread about FR-4 materials is that they can resist temperatures well.
Two other materials are not as common as FR-4, and these are polyimide and RF. While these two do not resist temperatures as well as FR-4, they do have other properties that FR-4 materials do not have.
This list will provide most of the information that you’ll need regarding these materials in regards to their specific temperature capacities.
You can view the entire list here: https://bayareacircuits.com/material-library/
7、Methods of Reducing PCB Temperature
Finally, it is time to explore ways to reduce PCB temperatures. These can be applied to any material of any PCB.
Parts, materials, and components of PCBs all generate heat. A proper heat sink will dissipate this heat, allowing for heat to be micromanaged.
Nearly every electronic device contains a fan, but many do not understand what the purpose of it is.
Whether it is part of a fully completed electronic device or part of a PCB manufacturing device, the purpose of a cooling fan is to allow hot air out of the device while letting cool air into it.
Thicker plates require more power to reach high temperatures.
Plate thickness is one of the more confusing issues that manufacturers face when dealing with PCB temperatures.
While it does take more power for thicker plates to reach higher temperatures, the wider a plate is, the less it resists. It can slow the temperature. This anomaly allows yet another method of controlling PCB temperatures.
Heat pipe integration considerations
What is the main purpose of any given pipe? It is to organize the flow of any given substance.
It is also true when it comes to micromanaging PCB temperature, as liquids involved in PCB production can absorb heat, evaporate, then condense back to liquid.
This kind of process allows you to continue working with whatever materials and components you need to work with while at the same time micromanaging the temperatures involved automatically.
8、Conclusion and Summary
If you possess an acute attention to detail and are well informed, it is not difficult to understand the causes and solutions surrounding PCB temperature. Additional information can be found with WellPCB’s article archives as well.
There are many things to learn when it comes to micromanaging PCB temperatures, and the key to doing this is to be patient and consistent. Mastering the art of managing PCB temperatures takes time, and guides like this are designed to save a lot of it.
WellPCB has been specializing in the PCB manufacturing field for some time. We are committed to not only providing information for other PCB manufacturers, but also providing the best materials, components, and services for both.