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 PCB’s , 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 as 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.

PCB Thermal Management  - Thermal Via
Thermal resistance at each level of an electronic system will impact conduction…
Heat generated must go somewhere

Thermal Management Types Offered

PCB Thermal Management  - Thermal Via

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 additional copper thickness (1.5 to 2.5 mils) to enhance 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 component Solder tends to flow through the vias.

Double sided or multi-layer PCB

Double sided or multi-layer PCB

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.

Thermal vias

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.

thermal heat transfer.

If GND-planes will be connected to the Thermal vias, they will act as a ‘heat-spreader’ which will further improve the heat transfer and reduce the ‘hot-spot’

 GND-planes

Thermal Vias

Hot Spot Cooling Thermal Via  and Heatsink

Component side

Heatsink side

RThPCB=1.3 K/W

RThPCB=1.3 K/W

How to avoid Solder to flow through the thermal-vias

Modify solder mask and solder-paste stencil

Min DHS = 0.35mm to avoid blocked holes

Min DHS = 0.35mm to avoid blocked holes

Soldermask Plug for Thermal Vias

Soldermask Plug for Thermal Vias
Only to use with ENIG (or HASL) as it is a thermal cured ink applied after surface finish

Cap-plated Epoxy-filled Via

Cap-plated Epoxy-filled Via
Expensive option with huge impact on process-flow and design-rules.

Vias Resistance vs Length

Vias Resistance vs Length

Thermal via length in mm

Thermal Resistance: Parallel Thermal Vias

Thermal Resistance: Parallel Thermal Vias

Number of thermal vias

Note: Thermal via’s placed in a 1.0 cm (0.0394) square

Method to Increase Thermal Via Conductivity

Common thermal via constructions:                                                 Copper = 380 W / m KConductive filler =

                                                                                                           3.5 to 6.7 W /m K

Method to Increase Thermal Via Conductivity

Thermal Resistance vs Via Technologies

Thermal Resistance vs Via Technologies

Thermal via length in mm

Cerra Systems Boards Fabrication capabilities support high-frequency PCB, High-temperature Boards, Thick PCB, ultra-thin PCB, heavy copper PCB, Metal Core PCB, HDI boards with Blind Vias, Buried Vias, Micro vias,  Embedded passives, bonded heat sink, Impedance Control, Depth control drilling, Back drilling, Edge Plated PCB, Bump Pads, cavity with ledge, Via on pad and stacked micro-Via technology.

For more details on PCB manufacturing Capability ( HDI PCB , Rigid Flex PCB, RF PCB ) visit us- http://cerrasystems.com/

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