Webinar: Thermal management - a decisive aspect in the

03.12.2013 www.we-online.com/thermal_management Page 1

Webinar: Thermal management - a decisive aspect in the development of LED applications

Würth Elektronik Circuit Board Technology

Agenda

Basics/Possibilities

Thermal Management

LED High Power Module –

Internal Development

Further Applications

www.we-online.com/thermal_management Page 2 03.12.2013

Agenda


Thermal Management






Thermal Management 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

In order to solve thermal problems analyse the whole system

(component, circuit board, assembly, housing and environment)

Heat cannot be “destroyed” the only possibility is to dissipate it from

the hot component

Cooling strategies depend on different requirements of electronic

systems

– Amount of thermal output

– Available space / size of elements

– Assembly technologies for components used

– Complexity of circuit

Cooling concepts have to meet specific demands

– Guarantee sufficient reliability

– Provide for cost-benefit ratio





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



PCB without thermal

management

Heat sources: Power components, arrangement

Heat sink: Where can / where should the heat travel to?

What is the thermal path?

Which thermal resistances are present on this path?

Better distribution and/or dissipation of the heat

PROBLEM

CONCEPT

RESULT PCB with successful

thermal management



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

QUESTION: “In which way can the PCB manufacturer have the biggest influence on the thermal transfer?”


a) Radiation

b) Conduction

c) Convection

Agenda


Thermal Management




www.we-online.com/thermal_management Page10 03.12.2013


LED High Power Module

IDEA: Development of a freely configurable, multi-

coloured high power LED module

– Complete modular system

– Compact overall construction, protection against vandalism

– Uniform distribution of light, no spots

– Optimised thermal management

– Energy saving through daylight-dependent control

– Support of the (individual) biorhythm

– Improved well-being

– Improvement of the quality of work and safety through

“relaxed” seeing

Cooling concept for

150-200 W LED power loss

3.

Which type of PCB is suitable

2.

What are the requirements placed on the (control) electronics

1.

Which LEDs should be utilised

4.

How will the assembly and connection technology be realised





Which LEDs should be utilised

Source: OSRAM

Decision made on thermal

considerations: Use of bare dies (Thermal resistance casing eliminated)

SMD LEDs

Advantages:

Good availability

Large range of various types and

manufacturers available

Tried and tested standard assembly process

But:

Thermal resistance

Junction layer Solder pad 6,5 - 11 K/W (Datasheet OSRAM Golden DRAGON Plus)



What are the requirements placed on the (control) electronics

LED Light Source

Edge-light input

High power RGB and/or cold white, warm white

Integrated light sensor

Daylight-dependent light control

Constant colour and intensity of light

Integrated temperature protection sensor

LED Drivers (Control)

Optional Protocalls

Bluetooth

Wifi

Zigbee

Arduino

DALI

Smartphone

Central building control systems (Lonworks, KNX, …)

Individual LED Control

Lighting schemes (Scenes)

Biorhythm Ultra Compact LED Power supply envisaged



Which type of PCB is suitable

IMS = Insulated Metal Substrate

Quelle: Bergquist

Only suitable for the simplest circuits,

normally one copper layer, from 35µm in

etch technology, soldermask

More than one copper layer is complex and

quickly becomes expensive

Clearances in aluminium and isolation layer

are very expensive

Multilayer mit Thermovias

Utilisation of through hole connections as

“Thermal Vias”

Mechanically drilled Vias

Good thermal conduction in z-axis through

the copper barrels (min. 25 µm barrel

thickness)



How will the assembly and connection technology be realised

Double sided PCB or multilayer

with individual bare die

assembled and wire bonded

Individual heatsinks glued

Miniaturisation through

reduction of the overall height

Optimised thermal management

Adjustment of the projection

angle Heatsink

Bare Die



The application in practice PCB production

Thermal management

Sourcing bare die LED diodes in small

quantities

Placement and wire bonding of the diodes

Encapsulation and protection of the diodes

System solution



The application in practice


LED High Power Module Extract from optical laboratory evaluation

CCT 3319

Agenda


Thermal Management





www.we-online.com/thermal_management 03/12/2013

Heatsink circuit boards used in aircraft “hybrid” lighting

Applications

Optimal thermal management for very bright LEDs with high

heat dissipation

Complex outline in a multi-panel

Blister-free bonding between heat sink and PCB

Weight saving with a 1.0 mm thin aluminum heatsink element

Page 21


Modular power LED light bar

Applications

Extremely high luminance, lamp control is already

integrated onto the PCB

Heat spreading already in two additional inner layers

Good solderability through filled and capped thermal

vias

Source: WE

Page 22


LASERCAVITY® LEDs + thermal management

400µm ~ 12000 LEDs / 1dm²

Source: WE

Applications

Page 23


Applications

Replacement bulb for E10 socket

Double-sided FR4 PCB

• 2,4 mm core

• Edge plating

Bare die LED is glued to the edge of the PCB,

wire bonded and encapsulated

Internal Study: “WELED”

Quelle: WE

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Webinar: Thermal management - a decisive aspect in the