PCB Thermal Management – Thermal Via
- To operate efficiently and ensure reliability, heat must be removed from heat-generating power components.
- As a result of faster speeds, reduced format, and more devices being populated on PCBs, more heat is being generated that must be removed for efficient operation.
- The move to sustainable energy increased the demand for energy management electronics which also create much heat because of the high electrical currents used on these applications (Power inverters for solar and wind energy, powertrain electronics for HEV)
- Thermal management through various applications aids in directing heat away from heat-generating system components.
Thermal Conduction In PCBs
Thermal Management Types Offered
Thermal Vias
Thermal vias are the most easily produced form of thermal management
- Thermal vias or ‘via farms’ are tightly grouped vias that are patterned and located under heat-generating devices.
- They are the least efficient for heat removal but are cost-effective for devices with low power and heat generation.
- The vias can be plated with an additional copper thickness (1.5 to 2.5 mils) to enhance the thermal conduction of the heat from the device through the board to a secondary heatsink or chassis.
- This process will add cost and may affect outer layer feature capability.
- Disadvantage – when attaching components soldier tends to flow through the vias.
Double-sided or multi-layer PCB
Holes drilled. As part of the drill process, the thermal vias or via farm are produced in a tight pattern in the required location.
Thermal vias are plated along with the other required holes. In some cases the thermal vias may be plated with thicker copper to enhance thermal heat transfer.
If GND planes are connected to the Thermal vias, they will act as a ‘heat-spreader’ which will further improve the heat transfer and reduce the ‘hot-spot’.
Thermal Vias
Hot Spot Cooling Thermal Via and Heatsink
Component side
Heatsink side
How to avoid Solder flowing through the thermal-vias
Modify solder mask and solder-paste stencil
Min DHS = 0.35mm to avoid blocked holes
Soldermask Plug for Thermal Vias
Only to use with ENIG (or HASL) as it is a thermally cured ink applied after the surface finish
Cap-plated Epoxy-filled Via
Expensive option with a huge impact on process flow and design-rules.
Vias Resistance vs Length
Thermal Resistance: Parallel Thermal Vias
Method to Increase Thermal Via Conductivity
Thermal Resistance vs Via Technologies
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