PCB thermal management has long been considered secondary to signal integrity. However, we’re now seeing a greater, more dramatic evolution of power densities in transistors. Consequently, PCB thermal management is today a major issue. The main purpose of thermal management is to drain enough heat away from device’s active region efficiently so that the device is maintained within its rated temperature.
Chipmakers and their IC designers as well as PCB design/layout engineers are accountable for thermal management responsibility. And the PCB layout engineer must apply proven layout practices and techniques to assure the best PCB thermal performance possible.
Read our article to get a better understanding of PCB thermal management.
Meanwhile, here are a few key tips and hints to know about PCB thermal management.
- At layout the PCB designer should start with the PCB’s power section since switching power supplies are noisy and their thermal management challenging.
- It’s good design practice to maintain some distance between switching transistors and bulk electrolytic capacitors. Creating large copper areas with power supply circuitry is one way to reduce the power supply temperature.
- But caution with those large copper areas. Overestimating the required copper amount can be ineffective and detrimental to circuit performance by contributing to electro-magnetic interference.
- Perfect thermal conduction requires an ample surface area and a heat sink thick enough to radiate enough heat away.
- The PCB’s thermal pad should ideally be created as the same size as the spreader underneath the package to help the device to self-center during reflow. See Fig. 1.
- QFP or QFN packages have a row of perimeter pads around a larger central pad encapsulated in a plastic body. The pad lowers the package’s thermal resistance.
The PCB must be designed so that all the semiconductor devices on the board are maintained at or below their maximum rated temperature. Thermal management can sometimes be problematic for dense boards employing fine pitch devices. But if certain layout guidelines are not followed and due considerations are not given to PCB’s thermal performance, one can end up with product that has sub-par performance and reliability on the field.