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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
Basics/Possibilities
Thermal Management
LED High Power Module –
Internal Development
Further Applications
www.we-online.com/thermal_management Page 3 03.12.2013
www.we-online.com/thermal_management Page 4 03.12.2013
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
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Thermal Management Basics
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Thermal Management 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
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Thermal Management Basics
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
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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
QUESTION: “In which way can the PCB manufacturer have the biggest influence on the thermal transfer?”
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a) Radiation
b) Conduction
c) Convection
Agenda
Basics/Possibilities
Thermal Management
LED High Power Module –
Internal Development
Further Applications
www.we-online.com/thermal_management Page10 03.12.2013
www.we-online.com/thermal_management Page 11 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
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LED High Power Module
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LED High Power Module
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)
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LED High Power Module
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
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LED High Power Module
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)
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LED High Power Module
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
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LED High Power Module
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
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LED High Power Module
The application in practice
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LED High Power Module Extract from optical laboratory evaluation
CCT 3319
Agenda
Basics/Possibilities
Thermal Management
LED High Power Module –
Internal Development
Further Applications
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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
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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
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LASERCAVITY® LEDs + thermal management
400µm ~ 12000 LEDs / 1dm²
Source: WE
Applications
Page 23
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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