Mixed-mode fracture of organic chip attachment adhesives

166 Pages·2015·6.11 MB·English

by  Peter Brandenburger

Lehigh University
Lehigh Preserve
Theses and Dissertations
1995
Mixed-mode fracture of organic chip attachment
adhesives
Peter Brandenburger
Lehigh University
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Brandenburger, Peter, "Mixed-mode fracture of organic chip attachment adhesives" (1995).Theses and Dissertations.Paper 390.
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Brandenburger,
Peter
Mixed-Mode
. Fracture of
Organic Chip
Attachment
Adhesives
···October 8, 1995
MIXED-MODE FRACTURE OF
ORGANIC CHIP ATTACHMENT ADHESIVES
/
By Peter Brandenburger
A Thesis
Presented to the Graduate and Research Committee
of Lehigh University
, .
in Candidacy for the Degree of
Master of Science
in
Material Sciences and Engineering
Lehigh University
August, 1995
."

ACKNOWLEDGEMENTS
The author would like to take this opportunity to express his appreciation to the many
individuals who assisted this research. I would like to thank my advisor, Dr. Raymond
Pearson, for his expert advice and technical support, as well as his time and effort. He
successfully created a dynamic group that fostered technical growth through casual
conversations and discussions. Special thanks to Hamid Azimi, whose ability to clarify and
discuss my troubling questions, allowed me to fully comprehend the material. The Polymer
Laboratory group all helped spirit a ftin environment to accomplish the necessary tasks. Jen
""
Chou Hsiung, Jason Goodelle, John Mikitka, Ramesh KodnanC Vinay Mishra, Mahesh
Sambasivam all helped not only with technical support, but also took part in enhancement of
life outside of the lab. This workwould not be accomplished without the help of the many
staff and colleagues at Lehigh; Jack, Andrea, Adan, Dave, Kathy, Jim, and Virginia.
The author would like to thank Semiconductor Research Corporation (SRC Contract
Nos. SRC95-PJ-554) for their financial support of the SRC program Fundamentals of Adhesion,
Manufacturability, and Reliability of Organic Chip Attachment Adhesives and Processes.
The author would also like to thank the industrialmentors on this SRC program who provided
insight through their active participation; Dan Belton, Andrea Chen, Sally Foong, Gail
Heinen, Lidia Lee, and Tien Wu. I would like to also acknowledge National Science
Foundation (NSF-RI Grant No. MSS-9211664) for their financial support of the thermoplastic-
toughenedepoxywork.
love, and guidance and direction that my parents, Don and Jean, my sister, Ann, and her
husband, Bruce Foukehas provided to me. Iwould like to thank Lisa Glaser also for her love
andencouragementtowardmeasaperson, andhersupportand understandingofthe longhours
at the laboratory..
iii
TABLE OF CONTENTS
Title Page
I
Certificate of Approval
11
Acknowledgements 111
Table of Contents
IV
List of Figures vi
List of Tables
X111
Abstract .................................................................................................................. 1
1 Introduction 2
1.1 Adhesion 3
1.1.1 Thermodynamic Work of Adhesion
1.1.1 Practical Work of Adhesion
1.2 Fracture Mechanics for Bimaterial Interface 6
1.2.1 Fracture Mechanics Review for Homogeneous Material·
1.2.2 Modes of Loading
1.2.3 Mechanics of Interface Cracks
1.3. Mode MixityEffects on Toughness 17
1.4 Bond Thickness Effects on Toughness 23
1.5 Processing Effects on Toughness 27
1.6 Fracture Mechanics Based Tests for Adhesive Strength 29
1.7 Objective 34
2. Experimental 35
2.1 SpeJiID~nJ:>re12~U·,ttiQn '- 35
2.1.1 Substrate Preparation
2.1.2 Specimen Processing
2.2 Techniques 39
2.2.1 Double Cantilever Beam
,2.2.2 Mixed Mode Bending
2.3 Fractography 46
iv
3 Results and Discussion .............................................................................. 47
3.1 Interlaminar Fracture Energy in Laminar Composites 47
3.2 Effect of Mode Mixity 53
3.2.1 Effect of Mode Mixity on Crack Trajectory
3.2.2 Effect of Mode Mixity on Fracture Energy - Failure Envelope
3.3 Effect of Bond Thickness on Fracture Energy.... 78
3.4 Effect of Processing Conditions on Fracture Energy.................. 81
4. Conclusions ...................................................................................................... 84
5. Recommendations for Future Work 85
6. References 86
Appendix A - Nylon Modified Epoxies ...................................................... 90
vita
v
LIST OF FIGURES
Figure
1 Separation of two elastic bodies incalculation 3
of the thermodynamic work of adhesion.
2 a) The case of a crack with length 2a in an infinite slab. 8
b) Stresses around a crack tip. (from Hertzberg)
3 Schematic representation of adhesive or cohesive failure. 10
4 The three modes of loading; a) mode I or pure tensile, 11
b) mode II or in-plane shear, and c) mode III or
tearing (anti-plane shear).
5 Schematic drawing of a generic interfacial crack. ........................ 13
6 Crack direction resulting from a mixed mode 1111 loading; 18
a) drawing showing the direction of the mode II component
for the MMB test and b) drawing showing the crack deviation
from the crack plane.
7 The variation of crack deviation angle ~ with ........................ 20
the change of mixity \jf
8 A plot of fracture energy versus phase angle \jf showing 21
the general trend that toughness increases with the addition
of a mode. II componentand that the minimum is not at \jf =O.
[from Chiralambides et al.l9].
9 A schematic plot of fracture energy G versus thickness 24
.showing the general types ofdependence onthickriess.
Type A exhibits strong dependence while Type Band C show
moderate or no effect [from Mall and Ramamurthy26].
10 Schematic drawings showing the competition between 25
restricting the plastic zone size and the constraint at the
crack tip. [from Kinloch and Shaw28]
, ....
vi
11 A possible representation of a processing diagram. ............ 28
12 Drawing of a double cantilever beam (DCB) specimen. ............ 31
13 Drawing of a end notch flexure (ENF) specimen. ........................ 31
14 Drawing of the mixed mode bending (MMB) fixture ............ 32
and specimen.
15 Graphical representation of the various cure schedules. ............ 38
16 Apparatus used to fabricate the mixed mode bending ............ 39
(MMB) specimens.
17 Schematic drawing of the load versus displacement 40
diagram for a DCB specimen. This plots shows 5 different
loops which can produce 5 data points.
18 Plot of the phase angle as a function of fixture parameters 42
band c. Note that the phase angle is independent with crack length.
19 Drawing of the MMB specimen under a mixed mode 44
loading showing the deflection of the arms and the specimen.
20 Interlaminar failure envelope of FR-4 obtained by the 48
MMB obtained by the MMB fixture and DCB, ENF, and MENF.
Good comparison was found. Charalambides equation [1.26]
is also plotted.
21 Drawing showing the various hinge settings; 49
a) hinge "in" position and b) hinge"out" position.
.
22 Effect of hinge position on fracture energy as a function 49
of MMB fixture parameter, b, while maintaining constant
phase angle of 46° for alumina filled adhesive on copper/FR-4.
Shows the strong effect of hinge position on global fracture energy.
23 Effect of hinge position on fracture energy as a function 50
of MMB fixture parameter, b, while maintaining constant
phase angle of 46° for alumina filled adhesive on aluminum.
Shows little effect of hinge position on global fracture energy
vi(
..
"'
24 Interlaminar failure envelope of the FR-4 composite as 53
measured by MMB tests. The hollow circles were obtained
using 5 mm samples with the "in" hinge position and the
solid squares used the '~out" hinge position.
. 25 Fracture energy for various cure conditions obtained by............ 54
DCB ('I' =0) and MMB ('I' =46) for alumina filled (H65) adhesive on
aluminum. Note: 3 of 5 DCB failed cohesively and all MMB failed
adhesively, and the highest fracture energy was found for the
160°C for 1 hour cure.
26 Fracture energy for various cure conditions obtained by............ 55
DCB ('I' = 0) and MMB ('I' = 46) for silver filled (H35) adhesive
on aluminum. Note: all DCB failed cohesively and all MMB
failed adhesively, and the highest fracture energy was found
for the 200°C for 26 minutes cure..
27 Load- displacement plots from typical MMB 56
specimens.Two types of crack growth were observed;
stable and unstable.
28 Typical plot of load versus displacement for a DCB 56
specimen showing multiple loading loops allowing
for multiple data points from one specimen.
This plot resulted in nine separately attained GIc values.
29 Compliance as a function of crack length for a 9 inch 57
aluminum DCB specimen showing both adhesives
(alumina and silver) and the theoretical equation [2.3].
The curve fit equation of the data is also shown below the plot.
30 Photographs of fracture surface of the aluminum DCB 60
specimens for a) the alumina filled epoxy and b) for the
silver filled epoxy. Note that the top one in a) was adhesive
failure while the bottom one in a) and the two in b) were cohesive.
31 Schematic drawing showing the three areas of the MMB 61
specimen; the precrack region, the MMB test region, and
the post-test region. The latter region represents cohesive
failure while the precrack and test region failed adhesively.
viii