Fraunhofer IZM Berlineps.ieee.org › images › files › webinars › webniar 2 mar...© Fraunhofer IZM Dr. Rafael Jordan, SIIT Forschungsschwerpunkt Technologien der Mikroperipherik

© Fraunhofer IZM

Dr. Rafael Jordan, SIIT

Forschungsschwerpunkt

Technologien der Mikroperipherik

Fraunhofer IZM Berlin

Advanced Packaging for High Power LEDs

Dr. Rafael Jordan

SIIT

© Fraunhofer IZM




Agenda

• Gluing

• Soldering

• Sintering

• Transient Liquid Phase Bonding/Soldering

• Thermo Compression

• Junction Temperature Measurements

© Fraunhofer IZM




Optics

Cooling

Board

Phosphor

Submount

Underfill

Filling

Wire Bond

1st & 2nd Level

Interconnect

Chip

Power

LED Packaging Taks

© Fraunhofer IZM




Agenda

• Gluing

• Soldering

• Sintering




© Fraunhofer IZM




Avago Excelitas

Glued Moduls

~ 1-2

© Fraunhofer IZM




Rth,int1

Rth,int2

Rth,TIM dA

RRbulk

theffth

10,,

2int,,1int,, thTIMththeffthRRRR

0 200 400 600 800 10000,0

0,5

1,0

1,5

2,0

2,5

Rth0

Rth

,eff [

K/W

]

BLT [µm]

TIM ~ 1/slop

Linear function

Q

TR

effth ,

Characterization of Thermal Interface Materials

© Fraunhofer IZM




Nanotechnologies to improve heat transfer

Multi modal

particles

Polymer fibres &

metallic alloy Surface micro-

structuring

Nano sponge

interfaces

Vertically aligned

CNT

Nano-scale optimization

Increase thermal

conductivity

Increase thermal

conductivity

Reduce BLT Reduce

interface resistance

Improve phonon transfer

Increase thermal

conductivity

TIM optimization Surface optimization Nano-scale optimization

Challenges for Glued Interfaces

© Fraunhofer IZM




overview focus diebond

Failure Analyses Glued Die Bond

© Fraunhofer IZM




0,0 0,5 1,0 1,5 2,0

0

5

10

15

20

A11

F1

F3

F7

F8

F9

F16

I [m

A]

U [V]

F9

Failure Analyses by Diode Characteristic

© Fraunhofer IZM




Agenda

• Gluing

• Soldering

• Sintering




© Fraunhofer IZM




OSRAM

Soldered Moduls

© Fraunhofer IZM




Wireless GaN - Chips

wire

fo

r p

rod

uct co

mp

atibili

ty, b

ut n

ot e

sse

ntie

ll

Cree DA1000 OSRAM UX:3

© Fraunhofer IZM




Supplier B 40 mil (LM) Supplier B 24 mil (LM)

Wetability of LED Dice

© Fraunhofer IZM




Supplier A old design Supplier A new design


© Fraunhofer IZM




Supplier A new design Supplier A new design


© Fraunhofer IZM




217°C

e1

278°C

e2

252°C

p: +L1 L1+Au

Au-rich Sn-rich

AuSn Phase Diagram

~ 60

© Fraunhofer IZM




Copper Based LED on Silicon Substrate Reflow Soldering with AuSn no Activating Atmosphere

x-ray

x-ray LED-Module 1 x-ray LED-Module 2

© Fraunhofer IZM





cross section

Cross Section Chip on Silicon

© Fraunhofer IZM





cross section close up look


© Fraunhofer IZM





Copper Based LED on Silicon Substrate Thermode Soldering with AuSn no Activating Atmosphere

x-ray

© Fraunhofer IZM





cross section


© Fraunhofer IZM




~ 30

SnAgCu Phase Diagram

© Fraunhofer IZM




Copper Based LED on Silicon Substrate Reflow Soldering with SnAg with Activating Atmosphere

x-ray


© Fraunhofer IZM





cross section


© Fraunhofer IZM




• AlN/Si test board

for optical,

electrical, and

thermal LED

characterisation

Exsample (rigth):

• 8 SemiLeds LEDs

soldered on AlN

with AuSn

BMBF-Projekt

Nanolux - White

LEDs for General

Lighting

COB assembly LEDs on AlN

© Fraunhofer IZM




OSRAM LEDs on AlN MC-PCB Subassembly mit Drahtbonds

Test Assembly with OSRAM LEDs

© Fraunhofer IZM




OSRAM LED Dice on metallized AlN Watercooler, 600 W

http://www.excelitas.com/Index.aspx

© Fraunhofer IZM




OSRAM LED Dice on metallized AlN Watercooler, x-ray


© Fraunhofer IZM




Agenda

• Gluing

• Soldering

• Sintering




© Fraunhofer IZM




Chip to Chip

Chip to copper

Assembly with Ag Sintering

© Fraunhofer IZM




SEM Pictures

Ag-Powder

after drying

Ag-Powder

heat without force

Ag-powder

heat and force

Ag Sintering

© Fraunhofer IZM




Ag Sintered Interconnects comparing of two suppliers Cross Section with SEM

Cu

Ag Bond Ag Bond

Ag Plated Layer Ag Plated Layer

preparation effect AlN

© Fraunhofer IZM




well defined

interface

Ag plated

Ag sintered

Ag Sintered Interconnection, FIB Analysis

© Fraunhofer IZM




Ag Sintered Interconnection, FIB Analysis

small pores almost

disoluted ~ 370

© Fraunhofer IZM




OSRAM LED Dice on metallized AlN Watercooler, 1200 W


© Fraunhofer IZM




Shear Forces for Pressure Less Sintered LEDs

Temperature Chip A

on Ceramic

Chip B

on Ceramic

Chip A

on IMS

Chip B

on IMS

225 °C (8,4 ± 2,1) N (8,8 ± 3,0) N (7,6 ± 3,1) N (7,5 ± 1,5) N

275 °C < 0,5 N (8,3 ± 1,9) N < 2,0 N (12,7 ± 2,9) N


© Fraunhofer IZM




Pressure Less Sintering pro/contra

Standard Equipment (Screen printer + P&P + Reflow)

No mechanical fixing of parts during sintering

No special atmosphere during sintering

Lower Shear forces than sintered/soldered dice

Metallization of die bond pad must be suitable

Smaller process windows (especially regarding drying)


© Fraunhofer IZM




Agenda

• Gluing

• Soldering

• Sintering




© Fraunhofer IZM




soldering

annealing

Cu

Cu6Sn5

Cu3Sn

Si

Cu3Sn

TLPB using electroplated Cu/Sn

© Fraunhofer IZM




20 wt.-% Cu

40 wt.-% Cu

( Cu6Sn5)

Sn

Cu Cu6Sn5

Cu3Sn

40 wt.-% Cu (Cu6Sn5)

After soldering

Pore

40 wt.-% Cu

TLPS – SAC-paste plus Cu spheres

© Fraunhofer IZM




Si-Chip

DAB

Proprietary Process and Paste

TLPS – SAC-paste plus 40 wt.-% Cu spheres

© Fraunhofer IZM




Agenda

• Gluing

• Soldering

• Sintering




© Fraunhofer IZM




densified

zone

bonding

zone

Flip Chip Sintering

80% pore

volume

13 nm pore size

Potential Application:

- low pressure, low temperature bonding (MEMS,

laser)

- compressible bonding (acommodate topography)

- containment for medical applications

- large surface area (sensors, catalytics)

- bio compatible (e.g. neuronal interface)

- optical devices (plasmonics, SERS)

H. Oppermann, M. Hutter, R. Jordan, et al. (Fraunhofer IZM)

Nano - Sponge

© Fraunhofer IZM




Junction Temperature Measurement Principles

1) Wavelength shift

The recombination of the electron from the conducting band (n-type

semiconductor) with the holes of the valence band (p-type) is a light emitting

process. As the wavelength is directly correlated to the recombination energy and

therefore depending on the forward voltage, the wavelength is increasing with

decreasing forward voltage and increasing temperature.

2) Forward Voltage

The Forward voltage is depending on the electron band gap and the Boltzmann

distribution. The Boltzmann distribution is temperature depending and therefore

the voltage is decreasing with increasing temperature.

© Fraunhofer IZM




Concept of measuring Tj with the forward voltage

0 1 2 3 4

0

50

U [V]0 1 2 3 4

0

50

I [mA]

U [V]

Uv UvI

II

IdealRp

Ri

Real

I [mA]

An ideal light emitting diode is

closed up to a certain voltage, the

forward voltage, and afterwards

open without any influence of the

current.

The real LED has a different behavior and

can be described in an easy equivalent

circuit diagram as shown above. It is

influenced by resistors parallel and in

serious to the junction.

© Fraunhofer IZM




The measurement current must be kept small, not to heat the die up, but out of the

horizontal area of the UI characteristic, as otherwise the recalculation of the

temperature will be imprecise. As Rp and Ri are different for every die, even within

one lot, each LED must be calibrated.

20 25 30 35 40 45 50 55 60 65 70 75 80 85

2,47

2,48

2,49

2,50

2,51

2,52

2,53

2,54

2,55

2,56

2,57

2,58

2,59

2,60

2,61

2,62

2,63

2,64

T = -t1 * ln (U/A1)

03B 2,637: T = -1152,913 ln(U/2,66220)

16B 2,620: T = -1398,438 ln(U/2,64008)

19B 2,640: T = -1220,828 ln(U/2,67310)

08B 2,642: T = -1179,331 ln(U/2,66607)

11B 2,634: T = -1423,025 ln(U/2,65662)

Sp

an

nu

ng

[V

]

Temperatur [°C]

2,4 2,6 2,8

0,000

0,001

0,002

0,003

0,004

0,005

Str

om

[A

]

Spannung [V]

testing range

Measuring Tj with the forward voltage, calibration

© Fraunhofer IZM




Measurement Setup

The internal resistance of the LED is strongly current depending and due to further

distortions of higher order it is not possible to recalculate the pure forward voltage

under running conditions. The running current must be lowered immediately to the

measuring current, to measure the calibrated forward voltage without cooling down

the LED. A possible circuit can look like the following.

© Fraunhofer IZM




Measurement Interpretation

Even within the realized switching time below 10 µs, a cooling of the LED is visible.

Therefore the record transient is fitted with a biexponential curve with offset. The first

half-value period is related to the thermal equilibration of the junction with the LED

die, the second for the equilibration of the die with the substrate. The offset is

simplified sum for the equilibration with the ambient and the final forward voltage at

ambient temperature.

0 1000

2,55

2,56

2,57

Sp

an

nu

ng

[V

]

Meßpunkt [Einheit]

0400mA = 2,58783 V = 25,1 °C

0 1000 2000

2,6

2,8

3,0

3,2

Sp

an

nu

ng

[V

]

T [µs]

© Fraunhofer IZM




Example of a Flat Panel Light Source

0 200 400 600 800 1000 1200

2,505

2,510

2,515

2,520

2,525

2,530

2,535

LED@010mA at secundary current = 010mA = 2,535113 V = 24,16 °C










Vo

lta

ge

[V

]

Time [µs]

© Fraunhofer IZM




Test Szenario:

LED auf MC-PCB, MC-PCB auf Kühlkörper, T = 25,0

C

I1 = 100 mA, I2 = 350 mA, I3 = 700 mA

Thermal comparative study gluing/soldering/sintering

© Fraunhofer IZM




0,000 0,002 0,0042,34

2,36

2,38

2,40

2,42

2,44

sample 1

sample 2

sample 3

U [V

]

t [s]

Thermal comparative study gluing/soldering/sintering

e.g. blue LED glued

I1 = 100 mA

I2 = 350 mA

I3 = 700 mA

© Fraunhofer IZM




Thermal comparative study: blue LED

25.00

30.00

35.00

40.00

45.00

50.00

55.00

60.00

65.00

70.00

100.00 300.00 500.00 700.00 900.00 1100.00 1300.00 1500.00 1700.00 1900.00

T [

°C]

thermal load (optical emission corrected) [mW]

blue glued

blue soldered

blue sintered

© Fraunhofer IZM




25.00

30.00

35.00

40.00

45.00

50.00

55.00

60.00

65.00

70.00

100.00 300.00 500.00 700.00 900.00 1100.00 1300.00 1500.00 1700.00 1900.00

T [

°C]


'white' glued

'white' soldered

'white' sintered

Thermal comparative study: „white“ LED

© Fraunhofer IZM




25.00

30.00

35.00

40.00

45.00

50.00

55.00

60.00

65.00

70.00

100.00 300.00 500.00 700.00 900.00 1100.00 1300.00 1500.00 1700.00 1900.00

T [

°C]


red glued

red soldered

red sintered

Thermal comparative study: red LED

Documents

Fraunhofer IZM Berlineps.ieee.org › images › files › webinars › webniar 2 mar...© Fraunhofer IZM Dr. Rafael Jordan, SIIT Forschungsschwerpunkt Technologien der Mikroperipherik