Heatsink design
Heatsink is one of the most important part in thermal management , we should put below factors in consideration when designing the heatsink.
1. Heat flux density of heat source
2. Temperature requirements for heating components
3. keep out zoom of the product
4. Tightening force of heatsink installation
5. manufacture cost
6. Industrial design requirements
About Heat flux density of heat source:
The heat transfer mode from heating components to heatsinks is heat conduction. Generally, the substrate area of the heatsink will be larger than the heating area of the heating components. When the heat flux density of components is large, the influence of spreading resistance on heat transfer will appear.
Spreading Resistance means when the area difference between the heat source and the bottom plate is large, the heat spread from the center of the heat source to the edge to form the thermal resistance. We can use below example simulation to describe how to consider the spread thermal resistance in the design of heatsink.
Basic information:
working temperature： 20℃
cooling mode: forced convection
air flow rate: 5CFM
chip TDP: 20W
chip module: simplified block， thermal conductivity：15 W/m.K
heatsink dimension：40*40*20MM
TIM material： for heatsink design only , no TIM material setup in simulation
We used 2 sizes chips of 30*30mm and 10*10mm , below shows the result:
And the spreading resistance of two chip size are as below:
30 mm * 30 mm：Pdens = 20 /30/30 = 0.022 W/mm2 = 2.22 W/cm2
10 mm * 10 mm: Pdens = 20/10/10 = 0.2 W/mm2 = 20 W/cm2
As you can see, after the chip size is reduced, the heat flux is increased by 9 times. Without making any changes to the heatsink, the chip increased by about 8C. The thermal resistance of the heatsink increased from 2.18 C / w to 2.59 C / W, and the overall thermal resistance of the heatsink deteriorated by 19%.
10*10mm size chip heatsink surface temperature distribution:
30*30mm size chip heatsink surface temperature distribution:
Due to the existence of spreading thermal resistance, when the chip heat flux is high, the temperature at the edge of the radiator will be significantly lower than that at the chip. The utilization efficiency at the edge of the radiator decreases. Therefore , this should be taken in consideration when designing the heatsinks.
Thermal solutions for every industry is very important as the power is gradually higher and higher, Sinda Thermal can provide varieties heatsinks and coolers which inlcuding aluminum extruded heatsink, high performance heatsink, copper heatsink, skived fin heatsink, liquid cooling plate and heat pipe heatsink. please contact us if you have any questions about thermal solution.
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