Creep in Microelectronic Solder Joints: FE vs ... · 24 Technische Universität Berlin Fakultät...

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Technische Universität BerlinFakultät für Verkehrs- und Maschinensysteme , Institut für Mechanik

Lehrstuhl für Kontinuumsmechanik und Materialtheorie, Prof. W.H. Müller

Copyright © Prof. Dr. rer. nat. W.H. Müller, e-mail: [email protected], 2006

Creep in Microelectronic Solder Joints:

FE vs. Semianalytical Methodsby

W.H. Müller, T. Hauck

6th German-Greek-Polish Symposium

Recent Advances in Mechanics

September 17-21, 2007

Hotel Thraki Palace, Alexandroupolis

Technische UniversitTechnische Universitäät Berlint BerlinInstitut fInstitut füür Mechanikr Mechanik

Lehrstuhl fLehrstuhl füürr KontinuumsmechanikKontinuumsmechanikund Materialtheorieund Materialtheorie

FreescaleFreescale HalbleiterHalbleiterDeutschland GmbHDeutschland GmbHSchatzbogen 7Schatzbogen 781829 M81829 Müünchennchen

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Outline

Motivation and problem statement

Model 1: A clamped 1D-solder column

Coupling of the 1D-model with FE-simulations

Model 2: A 1D-solder column with a free end

Conclusions and outlook

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Outline






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Typical SMT Components I

• The trend towards extreme miniaturisationchip carriersLCDs and

displays

resistors andcapacitors

5




Typical SMT Components II• MiniMELF ceramic resistor:

aging of SnPb solderfalse alignment of parts on the PC-Boardthermal mismatch of materials

6




Typical SMT Components III• Ball Grid Arrays (BGAs):

micro-structural coarsening of solder during thermal aginginterface cracks

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SMT solder joints: Formation of interface cracksspinodal decompositionmicrostructural coarsening

Ball Grid Arrays and solder ball before and after 4000 temperature cyclesAging @ RT after (a) 2h, (b) 17d and (c) 63d

(a) after first reflow, (b) 3h and (c) 300 h @ 125°CMELF miniature resistor and solder joint before and after 3000 temperature cycles

Microstructural Change in Eutectic SnPb (and Leadfree ) Solder

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Lifetime assessment of a typicalmicroelectronic package and its solder joints

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FE analysis performed in order to predict the lifetime andreliability of the solder joint of a TQFP

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Chambers used for TCTs together with experimentally determinedtemperature profiles of a -65°C to 150°C test

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Outline






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Model 1:Firmly clampedsolder column:

additive decomposition of 1D strain rates:

crtheltot εεεε &&&& ++=

0≡⎟⎠⎞

⎜⎝⎛=

•

ll

tot∆ε& with:

•

⎟⎠⎞

⎜⎝⎛=Eelσε& ( )( )tTEE = , (elastic strain rate)

( )( )tTαα = ,( )•= Τth αε& (thermal strain rate)

( )[ ] ⎟⎠⎞

⎜⎝⎛ −=TCCC C

cr43

21 expsinh σε& (creep strain rate)

Solution of the resulting ODE to obtain the stress resulting from a prescribed TCT:

( )tTT =

0=++ crthel εεε &&&( )tσσ =

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Typical Temperature Profiles

Temperature Cycle Tests (TCT): Temperature Shock Test (TST):

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Typical Stress-Strain-Hysteresis for Eutectic SAC Predicted by using“Generic” Creep Data from Dudek / Schubert

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Attempts of Lifetime Prediction:Empirical Coffin-Manson Equations

Creep energy density based:

( )Bacccr

f WAN ∆ =

Creep strain based:

( )bacccr

f aN ε =

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Influence of Ramp Time demonstrated for SnAg2.7Cu0.4Ni0.05

• Decreasing ramp times lead to higher energy dissipation• Shock test has a high potential for destruction > 20 %

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Influence of Hold Time demonstrated for SnAg2.7Cu0.4Ni0.05

• Increasing hold times increases energy dissipation slightly• Impact of hold time less than impact of ramp time

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Material data used (I)

Young’s modulus for Sn95.8Ag3.5Cu0.7 after Dudek EPTC 2005 tutorial, pg. 4 used for Innolot, SnAg3.0Cu0.5, SnAg2.7Cu0.4Ni0.05:

( )K 293K

GPa2933734750GPa 50 −

−−

−= TE

Young’s modulus for SnPb37 after Dudek EPTC 2005, pg. 4 tutorial:

( )K 223K

GPa2234231936GPa 36 −

−−

−= TE

CTE for SnPb40Ag1 after Dudek EPTC 2005, pg. 4 tutorial used forSnPb:

( )K

ppmK 293293423

9.2624 24 ⎟⎠⎞

⎜⎝⎛ −

−−

−= Tα

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Material data used (II)

CTEs used for Innolot, SnAg3.0Cu0.5, SnAg2.7Cu0.4Ni0.05 from Wilke (SAG):

( )( ) Innolot , K

ppm19.951K 2730.0323 +−= Tα

( )( ) .5SnAg3.0Cu0 , K

ppm19.838K 2730.0092 +−−= Tα

( )( ) .4Ni0.05SnAg2.7Cu0 , K

ppm19.694K 2730.0243 +−= Tα

Creep constants used for SnPb from Darveaux (SnPb36Ag0.2), for Innolot, SnAg3.0Cu0.5, SnAg2.7Cu0.4Ni0.05 from Röllig, Wiese, Dudek:

dε/dt=C1* sinh(SIG/C2)^C3 *exp(-C4/RT[K])

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Stress-Strain-Hystereses Predicted for Various SAC/SAC+

-40

-20

0

20

40

60

80

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008

mechanical strain εel + εcr

stre

ss [M

Pa]

SnAg3.5 [4]

generic eutectic SAC [2]

SnAgCu (eutectic) [7]

SnAg3.0Cu0.5 [5]

SnAg3.8Cu0.7 [6]

SnAg3.9Cu0.6 [4]

SnAg3.9Cu0.6 [8]

SnAg4.0Cu0.5 [4]

SnAg1.3Cu0.2Ni0.05 [5/9]

SnAg1.3Cu0.5Ni0.05 [5/9]

SnAg2.7Cu0.4Ni0.05 [5/9]

SnAg3.8Cu0.7Bi3.0Sb1.4Ni0.2 [5]

Pb97Sn3 [10]

SnPb36Ag2 / SnPb40 [11]

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Dissipated Energy Densities Predicted for Various SAC/SAC+

00.010.020.030.040.050.060.070.080.090.1

SnAg3

.5 [4]

gene

ric eu

tectic

SAC [2

]

SnAgC

u (eu

tectic

) [7]

SnAg3

.0Cu0

.5 [5]

SnAg3

.8Cu0

.7 [6]

SnAg3

.9Cu0

.6 [4]

SnAg3

.9Cu0

.6 [8]

SnAg4

.0Cu0

.5 [4]

SnAg1

.3Cu0

.2Ni0.

05 [5

,9]

SnAg1

.3Cu0

.5Ni0.

05 [5

,9]

SnAg2

.7Cu0

.4Ni0.

05 [5

,9]

SnAg3

.8Cu0

.7Bi3.

0Sb1

.4Ni0.

2 [5,9

]Pb9

7Sn3

[10]

SnPb3

6Ag2

/SnP

b40 [

11]

ener

gy d

ensi

ty [M

J/m

3 ]

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Outline






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Profile of a Slow TCT:45 min Ramp in between –40°C and 150°C

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Sn59Pb40Ag1: Secondary double power+ primary law after Schubert

Sn95.5Ag3.8Cu0.7Secondary sinh+ primary creep law after Schubert

SnAg2.7Cu0.4Ni0.05SnAg2.5Cu0.5Secondary sinh after Röllig/Wiese

Shear stress vs. shear strain3rd slow thermal cycle (45 min ramp)150°C to –40 °C

Shear strain

She

ar s

tress

(MP

a)

∆ γ = 0.87%nach R. Dudek

SnAg3.8Cu0.7Schubert

∆ γ = 0.65%

SnAg2.5Cu0.5Röllig/Wiese

SnAg2.7Cu0.4Ni0.05Röllig/Wiese

∆ γ = 1.8%

CeramicCapacitor 0402

INNOLOT-1Röllig/Wiese

∆ γ = 0.5%

Sn63Pb37Grivas

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highest stressesfor Innolot

higheststrainrange

for SnPb

higher stressesthan FE

lower strainsthan FE

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Temperature profiles

TS-40°C / 125°C: TS-40°C / 150°C:

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TS-40°C/125°C

Increasingthe Hysteresis=EnergyDissipation

TS-40°C/150°C

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Results for Different Thermal Cycles SAC 305 vs. INNOLOTE

nerg

y D

issi

patio

n D

ensi

ty (N

mm

/mm

³)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

TS 125…

-40 C

Innolo

t,TS 12

5…-40

C

TS 90…

-20 C

TS 150…

-40 C

TW 150…

-40 C

Creep Energy

Creep energy averaged along the solder gap underneath CR1206

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Rescaling

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TS-40°C/125°C

Increase of thestrain range

TS-40°C/150°C

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Results for different Thermal Cycles SAC 305 vs. INNOLOT

Equi

vale

nt c

yclic

cre

ep s

trai

n (%

)

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

TS 125…

-40 C

Innolo

t,TS 12

5…-40

C

TS 90…

-20 C

TS 150…

-40 C

TW 150…

-40 C

Creep Strain

Creep strain averaged along the solder gap underneath CR1206

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Rescaling

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Outline






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crtheltot εεεε &&&& ++=

Model 2:1D solder beamdisplacementcontrolled, at afixed temperature

additive decomposition of 1D strain rates:

( )[ ] ⎟⎠⎞

⎜⎝⎛ −=TCCC C

cr43

21 expsinh σε&

with:

Numerical solution of the resulting ODE for the stress for a prescribed external displacement:

( )TEE = ,

( )tl∆

Eel

σε&

& =

( )( ) 0=−= •

refth TΤαε&

0≠⎟⎠⎞

⎜⎝⎛=

•

ll

tot∆ε&

(elastic strain rate)

(thermal strain rate)

(creep strain rate)

( )tll ∆∆ =( )tσσ =•

⎟⎠⎞

⎜⎝⎛=ll∆

crthel εεε &&& ++

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Impact of Temperature demonstrated for SnAg3.5

0 200 400 600 800 1000 1200Zeit @secD

-0.0015-0.001-0.0005

00.00050.001

0.00150.002

gnunheD

@-D

-0.002 -0.001 0 0.001 0.002Dehnung -

-100

-50

0

50

100

gnunnapS@

aPM

DT decreasesT decreases

• Elastic properties dominate at low temperatures• Size of hysteresis (= energy dissipation) depends on temperature

• Optimum temperature for maximum dissipation

@ D

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Impact of Temperature demonstrated for SnAg3.5

RT

• Optimum temperature leading to maximum dissipation can now be estimated for a given solder

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Impact of Loading Frequency demonstrated for SnAg3.5

0 200 400 600 800 1000 1200Zeit @secD

-0.0015-0.001-0.0005

00.00050.001

0.00150.002

gnunheD

@-D

• Elastic properties dominate at high frequencies• Frequency range for best testing of elastic or inelastic material

properties can now be estimated

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Dissipated energy densities for various solderssubjected to a loading rate

ε0 = +/- 0.002

0

0.05

0.1

0.15

0.2

0.25

SnAg3

.5 [4]

gene

ric eu

tectic

SAC [2]

SnAgC

u (eu

tectic

) [7]

SnAg3

.0Cu0

.5 [5]

SnAg3

.8Cu0

.7 [6]

SnAg3

.9Cu0

.6 [4]

SnAg3

.9Cu0

.6 [8]

SnAg4

.0Cu0

.5 [4]

SnAg1

.3Cu0

.2Ni0.

05 [5

,9]

SnAg1

.3Cu0

.5Ni0.

05 [5

,9]

SnAg2

.7Cu0

.4Ni0.

05 [5

,9]

SnAg3

.8Cu0

.7Bi3.

0Sb1

.4Ni0.

2 [5,9

]Pb9

7Sn3

[10]

SnPb3

6Ag2

/SnPb4

0 [11

]en

ergy

den

sity

[MJ/

m3 ]

0 200 400 600 800 1000 1200Zeit @secD

-0.0015-0.001-0.0005

00.00050.001

0.00150.002

gnunheD

@-D

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Outline






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Conclusions and Outlook

• Simple 1D-models can be used to model creep strain and dissipated energy density accumulation of ductile solders

• The impact of thermal cycle test parameters on creep dissipationhas been studied in great detail at a minimum of computationaleffort

• In comparison to time-consuming FE-analyses of solder joints inmicroelectronic components it turns out that the stresses predicted from the 1D-models are too small

• A re-calibration procedure can be applied to generate more accurate dissipation data

• Experiments are currently underway to link these to lifetime equations for the various new lead-free solders currently considered by industry

Creep in Microelectronic Solder Joints: FE vs ... · 24 Technische Universität Berlin Fakultät...

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