Webinar: Thermal simulation helps in choosing the right ......Thermal dissipation per unit area is rising Higher clock frequencies, higher packaging densities Installation of populated

06.11.2014 www.we-online.com/thermal_management Page 1

Webinar: Thermal simulation helps in choosing the right thermal management concept

Würth Elektronik Circuit Board Technology

www.we-online.com/thermal_management Page 2 06.11.2014

Basics

Drivers for ever more effective thermal management concepts

Further miniaturisation of components

Increasingly powerful components

Thermal dissipation per unit area is rising

Higher clock frequencies, higher packaging densities

Installation of populated PCBs on warm assembly units and

machine parts or in hermetically sealed housing

The need for circuit carriers with carefully planned thermal management

is increasing

The temperature resistance of LED applications is especially limited

Change in light and colour properties / Reduction in working life


Basics

Over 50 % of electronic system failures

are caused by increased temperatures

Heat dissipation influences the system

efficiency

Sufficient cooling is essential for an

improved reliability and lifetime.

Source::US Air Force Avionics Integrity Program (AVIP)

Dust

6% Vibrations

20%

Temperature

55%

Humidity

19%

PCBs play an important role in the development of efficient

thermal management


Basics

thermal resistance Rth =

Length of thermal path d

thermal conductivity λ * cross section of thermal path A

GOAL: Reduction of thermal resistance

Layer thickness d reduced by

thinner circuit board

thinner isolation layers

Thermal conductivity λ increased by

higher copper content

parallel thermal vias in the z - axis

Cross section of thermal path A increased by

min. 25µm copper in the barrel ! parallel thermal vias

large copper area for heat distribution (x/y)

large contact surface area of copper / heat sink


Basics

Radiation: Emission of photons

Convection: heat transfer through gases or

fluids

Conduction: Heat dissipation via solid objects

Vertical: Thermal via / microvia / buried via

Horizontal: Copper foil heat distribution/heatsink

Types of heat dissipation


Layout


Boundary conditions simulation

Size of the pcb 45 x 45 mm

Power loss of the LED 3W

Ambient temperature 20 °C

Pcb vertical free-standing in

laboratory

Heat transfer to the air 12 W/m²K


Thermal simulation

Variant 1

Copper layer: 50µm

FR4: 1550µm

Layout


Variant 1

Thermal simulation


Variant 2

Copper layer: 50µm

FR4: 1550µm

Improved Layout

Thermal simulation


Variant 2

Variant 1

Copper plane

Thereby spread of heat

Reduction in temperature of

LED from 552°C to 170°C

Thermal simulation


Variant 3

Copper layer: each 50µm

FR4: 1550µm

Improved Layout

Additional copper

layer BOTTOM

Thermal simulation


Additional copper layer

BOTTOM

Reduction in temperature of

LED from 170°C to 144°C

Variant 2

Variant 3

Thermal simulation


Variant 4


FR4: 1550µm

Thermovia hole 25 µm copper

Improved Layout


BOTTOM

Thermovia from 1 to 2

Thermal simulation


2 layer and Thermovia

Reduction in temperature of LED

from 170°C to 113°C

Variant 2

Variant 4

Variant 3

Thermal simulation


Variant 5


Reduced FR4 thickness: 1550µm

Thermovia hole 25 µm copper

Aluminum heatsink: 1000µm

Improved Layout


BOTTOM

Thermovia from 1 to 2

Thermal simulation


2 layer, Thermovia and heatsink

Reduction temperature LED from

170°C to 89°C

Variant 2

Variant 3

Variant 5

Thermal simulation


Sufficient cooling is not given in the variants 1, 2 and 3.

The variant 4 is located in the limit area. If we consider that in the LED itself, a

temperature increase of 4-6 degrees takes place, the allowable junction

temperature may have already been exceeded.

With the use of Thermovia and Heatsink in variant 5, a reliable heat dissipation of

the LED can be guaranteed.

Thermal simulation - conclusion


Copper layer 2: each 50µm

Reduced FR4 thickness: 500µm

Thermovia barrel 25µm copper

Aluminum heatsink: 1000µm

Heatsink 15mm larger all around

Thermal simulation

Documents

Webinar: Thermal simulation helps in choosing the right ......Thermal dissipation per unit area is rising Higher clock frequencies, higher packaging densities Installation of populated