Thermal and mechanical optimisation of diode laser bar packaging [Elektronische Ressource] / vorgelegt von Christian Scholz

Scholz

Informations

• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2007
• Nombre de lectures: 25
• Langue: Deutsch
• Poids de l'ouvrage: 21 Mo

Extrait

Thermal and Mechanical Optimisation of
Diode Laser Bar Packaging


Von der Fakultät für Maschinenwesen der
Rheinisch-Westfälischen Technischen Hochschule Aachen
zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften
genehmigte Dissertation

vorgelegt von
Diplom-Physiker
Christian Scholz
aus Duisburg

Berichter:
Universitätsprofessor Dr. rer. nat. R. Poprawe M.A.
Universitätsprofessor Dr. rer. nat. P. Loosen


Tag der mündlichen Prüfung:
23. Mai 2007


Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar


Bibliografische Information der Deutschen
Bibliothek:

Die Deutsche Bibliothek verzeichnet diese

Publikation in der Deutschen Nationalbibliografie;
detaillierte bibliografische Daten sind im Internet
über http://dnb.d-nb.de abrufbar.























© July 2007 Christian Scholz
Herstellung und Verlag: Books on Demand GmbH, Norderstedt
ISBN-13: 9783837002607










“If we knew what it was we were doing, it would not be called, research, would it?”
Albert Einstein (1879-1966)
German Physicist, Nobel prize winner


i


I Introduction and Technical Basics
1. Introduction....................................................................................................... 3
2. Components of Diode Laser Bar Package and Packaging Process ................. 7
2.1. Laser Bar...................................................................................................................... 7
2.1.1. Temperature Dependent Properties of Laser Bar ........................................................................ 9
2.1.2. Influence of Mechanical Stress................................................................................................. 11
2.2. Heat Sink.............. 14
2.2.1. Conductively Cooled Heat Sink................................................................................................ 15
2.2.2. Actively Cooled Heat Sink........................................................................................................ 17
2.2.3. Expansion Matched Heat Sink 17
2.3. Solder.......................................................................................................................................... 19
2.3.1. Indium............ 20
2.3.2. Indium-Tin............................................................................................................................... 21
2.3.3. Gold-Tin .................................................................................................................................. 22
2.3.4. Oxidation and Reduction of Solder .......................................................................................... 23
2.3.5. Plating and Diffusion Barrier .................................................................................................... 25
2.4. N-Contact Sheet and Isolation Foil........................................................................................... 28
2.5. Packaging of Diode Laser Bars ................................................................................................. 28
3. Properties of Diode Laser Bars and Measurement Methods........................ 30
3.1. Electro-Optical Properties ......................................................................................................... 30
3.2. Measurement Methods of Electro-Optical Properties............................................................ 34
3.3. Lifetime of Diode Laser Bars..................................................................................................... 35
3.4. Thermal Properties of Heat Sinks............................................................................................. 37
3.5. Measurement Methods for Packaging Induced Stress........................................................... 40
3.5.1. Photo-Current Spectroscopy (PCS)........................................................................................... 42
3.5.2. Micro-Photoluminescence Spectroscopy .................................................................................. 43
3.5.3. DoP-Electroluminescence.........................................................................................................44
3.6. Metallurgical Analysis ............................................................................................................... 46
3.6.1. Analysis of Solder Cross Section .............................................................................................. 46
3.6.2. Shear Tests .............................................................................................................................. 49 ii


II Analysis
4. Thermal Influence of the Packaging .............................................................. 53
4.1. Thermal Resistance ....................................................................................................................53
4.1.1. Simulation................................................................................................................................53
4.1.2. Experiment..........56
4.2. Thermal Contact between Heat Sink and Laser Bar................................................................57
4.2.1. Avoiding Oxidation of Solder ...................................................................................................58
4.2.2. Solder Voids Experiment...........................................................................................................63
4.2.3. Simulation of Solder Voids .......................................................................................................66
4.3. Influence of Solder Layer Thickness ............................69
4.3.1. Simulation...........69
4.3.2. Experiment...............................................................................................................................71
4.4. Thermal Influence on Degradation...........................................................................................75
5. Mechanical Influence of the Packaging......................................................... 76
5.1. Basic Principal of Mechanical Load ...........................................................................................76
5.2. Expansion-Matched Heat Sinks.................................................................................................78
5.2.1. Design and Simulation .............................................................................................................79
5.2.2. Fabrication and Properties........................................................................................................85
5.2.3. Stress Level of Laser Bar on Expansion-Matched Heat Sinks......................................................87
5.3. Metallurgy of the Solder Interface ...........................................................................................90
5.3.1. Stress Reduction by Solder Creeping ........................................................................................90
5.3.2. Diffusion Barrier.......................................................................................................................97
5.3.3. Lifetime Dependent upon different Solder Layer Thickness.....................................................102
III Outlook
6. Summary........................................................................................................ 105
7. Zusammenfassung ........................................................................................ 107
iii


IV Appendix
8. Material Properties ....................................................................................... 111
9. Abbreviation and Symbols........................................................................... 115
10. Literature....................................................................................................... 118





Part I

Introduction
and
Technical Basics