Heat sinks are a proven solution for electronic cooling. These structures, made of either aluminum or copper, absorb and disperse heat from components to the ambient.
Fin height is the distance of the fin from the heat spreader or backplane. As the fin height increases, the heat transferred by the fin to the coolant fluid decreases.
Using a heat sink material of high thermal conductivity and decreasing the aspect ratio of the fins can improve the fin efficiency of the heat sink.
Reduce device failure rates by improving the thermal management in electronic circuits
As electronic devices are downsized, they begin to generate more heat. Unfortunately, heat generation in electronic components is not good for their operating life—it can lead to premature failure. That is why using proper thermal management techniques in electronic circuits is critical to reducing device failure rates.
Heat sinks are a proven thermal management solution for electronic cooling. These structures, made of either aluminum or copper, absorb and disperse heat from components to the ambient. Among heat sink structures, plate-fin type heat sinks are widely used due to their simple structure and low cost.
When designing optimized heat sinks, one must consider factors such as a large heat transfer rate, low-pressure drop, and simple structure. Heat sink optimization should focus on decreasing thermal resistance, capital costs, and operational costs.
Let’s take a closer look at heat sink design optimization.
The Different Types of Heat Sinks
Heat sinks remove heat by varying the temperature difference and thermal resistance between the electronic package and the ambient air. There are a variety of heat sinks with different types of fins available on the market, including:
These heat sinks all improve the thermal control of electronic components by increasing the exterior surface area through the use of fins.
For each specific application, an appropriate heat sink is required. Choosing the right material, heat sink geometry, fin array spacing, fin array geometry, fin efficiency, and forced convection are all critical to improving thermal performance. The design of a heat sink with optimum geometry and associated parameters establishes optimal thermal performance within practical limitations such as pressure drop, airflow dynamics, volume, and weight.
For an example of heat sink optimization, let’s take a look at how a fin-type heat sink might be optimized.
Fin-Type Heat Sink Optimization
Plate fin-type heat sink
In fin-type heat sink optimization, the highest priority is to minimize the heat sink temperature.
Let’s consider natural air convection cooling fin-type heat sinks. In such heat sinks, the arrangement of fins influences the airflow through its gaps. Optimizing the fin shape, size, and location of the heat sink helps to reduce the coolant fluid flow resistance. The reduction in flow resistance allows more air displacement through the heat sink and faster heat removal. The optimization of the shape and size of the heat sink maximizes the heat transfer density.
It is the heat sink fins that conduct heat from the electronic component package to the ambient air or any coolant fluid. At this point in our discussion, it is important to clarify two key definitions:
Fin height is the distance of the fin from the heat spreader or backplane.
Aspect ratio is the ratio of fin height to fin spacing.
As the fin height increases, the heat transferred by the fin to the coolant fluid decreases. This is a physical parameter of the fin-type heat sink that requires optimization. By using heat sink material with high thermal conductivity and decreasing the aspect ratio of the fins, the fin efficiency of the heat sink can be improved.
The spacing between the fins, called fin spacing, has a critical role in the thermal performance of the heat sink. The amount of heat removed from a heat sink is directly proportional to the fin surface area. The more fins, the more heat is removed. However, it is not advisable to put as many fins as possible on the heat spreader because of the heat transfer coefficient. This factor depends on the temperature rise and fin length. When the fins are spaced close together, more pressure is required to remove the heated air from the fins.
If fins are not spaced optimally, choking occurs at the boundary layers in between the fins
Apart from pressure requirements, the viscosity of the air also demands certain fin spacing in naturally convective fin-type heat sinks. If fins are not spaced properly, choking can occur at the boundary layers in between the fins. With optimized fin spacing, it is possible to reach heat sink volumes much larger than forced convective heat sinks.
Heat sink optimization should be used to achieve higher heat removal rates and efficient electronic cooling. Cadence’s software offers CFD simulations that can help designers optimize heat sinks in electronic circuits.