Materials and Manufacturing in Electronics Prof. Dr.-Ing. Jürgen Villain University of Applied Sciences Augsburg, Germany Department of Electrical Engineering.

Materials and Manufacturing in Electronics

Prof. Dr.-Ing. Jürgen Villain

University of Applied Sciences Augsburg, Germany

Department of Electrical Engineering

COST 531 Meeting

14.1.2003

Berlin

Lectures and Team

Lectures• Materials Science for Engineers• Manufacturing in Electronics• Packaging• Design and Strength of Materials

Team in the Lab• Dipl.-Ing. T. Qasim (material science)• Dipl.-Ing. Ch. Weippert (crystallography)• Dipl.-Ing. (FH) A. Svetly (mechanical engineering)• J. Pahl (material test)• E. Hundt (measuring technique)• Students, candidate for a doctor`s degree

Topics of Research

• Influence of structure on the mechanical behaviour of metals• Determination of mechanical properties of small specimens depending on temperature and strain rate• Size effect on mechanical properties of metals in electronics • Vapour-phase soldering of lead-free solder materials• Creep behaviour of solder materials• Formation of intermediate phases in small solder volumes

Equipment of the Lab

Macro and micro tension test machines (0.5 N – 500 N, -55 °C/250 °C)Pull- and Shear-TestCreep Test (RT/200 °C)Laser extensometerSpecial clamping jaws for small specimensMicro-hardness testerSEM with EDX (tension and creep tests inside possible)X-ray fluorescent analysisThermal shockVapour-Phase solderingWetting testerOvens

Special clampingjaws for

small Cu-Foils (10 µm - 250 µm)

Tensile module for small specimens(part of SEM)

Tools for small specimens

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23 °C 50 °C 70 °C 100 °C

Ten

sile

Str

engt

h [N

/mm

2]

0,003 1/s

0,01 1/s

0,03 1/s

0,05 1/s

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23 50 70 100Temperature [°C]

Elo

ngat

ion

[%]

0,003 1/s

0,01 1/s

0,03 1/s

0,05 1/s

Material parameters describing exactly the material behaviour of electronic devices under working conditions are necessary for thermo-mechanical

simulations.

Elongation at rupture of Sn43Bi57for different temperatures and strain rates

Tensile strength of Sn43Bi57for different temperatures and strain rates

Determination of mechanical properties of small specimens depending on temperature and strain rate

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Elongation at rupture [%]

10 20 25 100 250

Cu Thickness [µm]

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Ultimate tensile strength [N/mm2]

10 20 25 100 250

Cu Thickness [µm]

Size Effect on Mechanical Properties of Copper Foils

The smaller the tested volume the lower the ductility !

Manufacturing and Reliability of Lead-Free-Solders

Topics: Manufacturing parameters, shear and tensile strength, creep-behaviour, migration, intermediate compounds

Solder materials: Sn91Zn9, Sn43Bi57, Sn96.5Ag3.5, Sn93.5Ag3.8Cu0.7Bi2(4)

Phase Formation in Small Solder Volumes (intermediate phases)

Sn43Bi57, device Sn,Pad: Cu/Ni/Au

Sn91Zn9, device Sn,Pad: Cu/Ni/Au

Small solder volumes are out of thermodynamic equilibrium and consist mainly of intermediate phases (3 – 5 elements) with almost completely unknown material properties.

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0,01 0,1 1 10 100 1000 10000

Time [h]

Stra

in e

[%]

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Time [h]

Str

ain

[%

]

60Sn40Pb, Qm = 0.73 eV

43Sn57Bi, Qm = 0.76 eV

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0,01 0,1 1 10 100 1000 10000Time [h]

Str

ain

[%

]

91Sn9Zn, Qm = 1.01 eV

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0,001 0,01 0,1 1 10 100 1000 10000Time [h]

Str

ain

[%

]

96.5Sn3.5Ag, Qm = 0.87 eV

Lowest homologoues temperature, highest homologoues stress

Creep behaviour of solder materials

The creep behaviour ofsolder materials at highhomologous temperaturescan be described using a viscoplastic equation.

(t,T,)=o J(t) a a

Comparison of Activation Energies and Time-Temperature Shift-Factor

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Activation energy [eV]

Tim

e-te

mpe

ratu

re s

hift

fact

or m

ax a

T

42Sn58Bi

60Sn40Pb

91Sn9Zn9

96.5Sn3.5Ag

Round phases

Dendritic or scorched phases

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Time [h]

Elo

ngat

ion

[%]

5 mm-Probe 1 mm-Probe2

1.78 mm3

785 mm3

Sn60Pb40, stress 5 N/mm2, same structure, same strain rate.

The smaller the tested volume the lower the creep resistance.

Size Effect on Creep Behaviour of a Solder Material

Further investigations

Analysis of metallic and intermediate phases of small solder volumes

Determination of the mechanical behaviour of eutectic and non eutectic solder materials with regard to

structure and tested volume under experimental and numerical view