Introduction
Excessive heat on a printed circuit board can be caused by poor design, incorrect selection of parts and materials, incorrect component placement, and inefficient thermal management.
The resulting high temperatures can negatively affect functions, components and the board itself. In many applications, the effect of high temperature is negligible, but in high-performance designs it can be significant.
Therefore, proper thermal management is an important aspect of electrical engineering. An integrated approach to thermal management touches everything from the component level all the way down to the physical board system and operating environment.
The increasing density of components in today’s electronic circuits can cause thermal problems. Additionally, PCB design flaws and ineffective cooling techniques can lead to unacceptably high temperatures.
Incorrect Component Placement
Some high-power equipment requires a location with proper airflow, either natural or forced, to transfer heat away. Therefore, these should be placed in a location with vents or good airflow.
Without proper airflow and heat dissipation, the PCB will retain most of the heat, which will cause the temperature to gradually increase, resulting in poor circuit performance or damage. Also, keep in mind that sensitive components will be thermally stressed if placed near components that emit a lot of heat.
High-power components, such as power transistors, can create hot spots on the PCB. But with proper heat dissipation and natural or forced cooling, the temperature can be kept within a safe range.
Environmental and External Thermal Factors
When a PCB is used in an area with extreme temperatures, components can be thermally stressed if the conditions in the target environment are not considered during the design process.
Manufacturers provide specifications that apply over a range of temperatures.
For example, resistance values are typically used for a temperature of 20°C. It is important to remember that the parameters of components such as resistors, capacitors and semiconductors change with temperature.
Additionally, manufacturers often provide thermal derating curves to specify safe power or current relative to changes in parameters such as ambient temperature or airflow.
Wrong Choice of Components and Materials
Failure to follow recommended guidelines during component selection can lead to thermal issues. It is important to study the datasheet and consider all relevant information related to power dissipation, thermal resistance, temperature limits and cooling techniques.
Also, make sure you choose the right power rating for your application. An easy mistake to make is to reuse the same resistor (probably because the corresponding component is already in your CAD library), although some applications may require a higher power rating. Do a quick power calculation for your resistors and make sure the ratings are significantly higher than the maximum expected dissipation.
Another important issue is the choice of PCB dielectric material. The printed circuit board itself must be able to withstand worst-case thermal conditions.
Poor PCB Design and Manufacturing
Poor layout and manufacturing processes can cause PCB thermal problems. Improper soldering can hinder heat dissipation, while insufficient trace width or copper area can cause temperature rise issues.
In Conclusion
To prevent thermal problems, designers must reduce heat dissipation and use additional removal techniques when free cooling is insufficient. A thermally optimized design requires attention to component specifications, PCB layout, PCB dielectric materials, and environmental conditions.
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