For high(er) heat flux applications, such as a 28 W/cm² (250W IC at 30×30mm), achieving a thermal resistance below 0.2°C/W (50°C delta-T) often requires a heat sink using two-phase devices. Selecting the best configuration among a heat pipe heat sink, direct contact heat pipe, or vapor chamber heat sink requires careful analysis to balance performance and cost.
Comparing Heat Sink Designs: Performance & Cost
Three two-phase heat sink configurations were analyzed (Figure 1)
Figure 1: Three Common Types of 2-Phase Heat Sink Design
- Heat Pipes Embedded in an Aluminum Base (Standard)
- Performance: Delta-T = 53.9°C, Thermal Resistance = 0.216°C/W
- Cost: Baseline cost of 1X
- Direct Contact Machined Heat Pipes
- Performance: Delta-T = 49.3°C, Thermal Resistance = 0.197°C/W
- Cost: 10% higher cost (1.1X)
- Improvement: 8.5% reduction in delta-T
- Vapor Chamber Heat Sink (Direct Contact VC)
- Performance: Delta-T = 38.7°C, Thermal Resistance = 0.155°C/W
- Cost: 15% higher cost (1.15X)
- Improvement: Significantly lower thermal resistance, ideal for demanding applications.
As shown in Table 1, the standard heat pipe solution has a delta-T above ambient of 53.9 oC (0.216 oC/W) with a baseline cost of 1X. By spending and additional 10% on this solution (cost of 1.1X), a solution where machined heat pipes make direct contact with the heat source results in an 8.5% improvement to the delta-T; down to 49.3 oC which equals a thermal resistance of 0.197 oC/W.
If a further reduction to delta-T is needed, a move to a direct contact vapor chamber reduces thermal resistance to 0.155 oC/W or 38.7 oC. The cost adder for this configuration is on the order of 15% from the standard heat pipe design.
Choosing the right heat sink for high heat flux applications depends on performance and cost requirements. Engineers can start with a standard heat pipe heat sink and progress to direct contact heat pipes or vapor chamber heat sinks for enhanced thermal performance. Each design provides specific trade-offs that should align with your system’s thermal and budgetary goals.
Click here for the full analysis showing an additional 2 configurations
