PCB Thermal Analysis
In today’s extremely large and complex PCB designs, power dissipation has become a major challenge for design teams. Every printed circuit layout engineer must take power dissipation into account, ensuring that hot components are placed in a cooler area, using ‘forced-cooling’ , or heat sinks so that the circuit board doesn’t overheat.
fiXtress uses the components package information and the calculated components’ power dissipation to estimate the board’s average temperature rise relative to the ambient temperature, as well as the individual junction temperature for active components. The impact of different cooling methods (heat-sink, a selected airow or a combination of methods) on various components or on the entire board can also be explored using fiXtress. The fiXtress PCB Thermal Analysis module estimates, even before the layout procedure, the exact junction temperature for each semiconductor and IC. With this information, the designer can place the hot components in a cooler area. Additionally, assumptions can be made regarding the Air Flow (CFM) required (i.e. fan spans) for reducing the temperature of the entire PCB.
With fiXtress, thermal engineers can ensure that the system and its electrical components are continually cooled and operating within the safe operating temperature range, without having to resort to cumbersome manual calculations.
The amount of power consumed by some devices can cause significant design problems. For example, IC fan-out is determined by the input current drawn by a gate load, and the output current supplied by the driving gate. In reality, there is a limit beyond which a gate output cannot drive any more current into subsequent gate inputs. Attempting to surpass this limit will cause the voltage to fall below the level defined for the logic level on that wire, resulting in a design failure.
Another example: When the current across the resistor is increased by a design fault, and approaches its maximum power rating, the resistor will develop more voltage and therefore dissipate more power. This can cause overheating, burning the area around the resistor, and in some cases, will cause the entire circuit to fail.