Abstract

Although the reliability of flexible electronics during bending deformation is of great interest nowadays, the mechanical reliability that has mainly been investigated is of single electronic components or simple devices, such as metal interconnect, transparent conductive electrode, or thin-film devices, rather than that of the real package sample having complex structure and various materials. This study systematically investigated the mechanical reliability of flexible Si package sample consisting of Si die, polymer bump, and polymer substrate, by using individual resistance monitoring of the metal line, bump array, and total interconnect. For the bending test, the sample consisting of only Si die and polymer substrate shows abrupt electrical resistance increase below a bending radius of 3 mm, due to cracking of the Si die. For the bending fatigue test, the electrical resistance increases after 2000 cycles in 5 mm bending radius, due to fatigue failure of the metal line and bump array. Both the maximum bendability and fatigue lifetime can be significantly improved by covering with the molding layer. Finite element method simulation is conducted to analyze the mechanical stress distribution of the flexible package with and without molding layer during bending deformation. This study based on experimental results and simulation analysis can provide helpful guidelines for the design of highly reliable flexible packages.

References

1.
Forrest
,
S. R.
,
2004
, “
The Path to Ubiquitous and Low-Cost Organic Electronic Appliances on Plastic
,”
Nature
,
428
(
6986
), pp.
911
918
.10.1038/nature02498
2.
White
,
M. S.
,
Kaltenbrunner
,
M.
,
Glowacki
,
E. D.
,
Gutnichenko
,
K.
,
Kettlgruber
,
G.
,
Graz
,
I.
,
Aazou
,
S.
,
Ulbricht
,
C.
,
Egbe
,
D. A.
, and
Miron
,
M. C.
,
2013
, “
Ultrathin, Highly Flexible and Stretchable PLEDs
,”
Nat. Photonics
,
7
(
10
), pp.
811
816
.10.1038/nphoton.2013.188
3.
Nam
,
K. T.
,
Kim
,
D.-W.
,
Yoo
,
P. J.
,
Chiang
,
C.-Y.
,
Meethong
,
N.
,
Hammond
,
P. T.
,
Chiang
,
Y.-M.
, and
Belcher
,
A. M.
,
2006
, “
Virus-Enabled Synthesis and Assembly of Nanowires for Lithium Ion Battery Electrodes
,”
Science
,
312
(
5775
), pp.
885
888
.10.1126/science.1122716
4.
Li
,
Y.
,
Lee
,
D.-K.
,
Kim
,
J. Y.
,
Kim
,
B.
,
Park
,
N.-G.
,
Kim
,
K.
,
Shin
,
J.-H.
,
Choi
,
I.-S.
, and
Ko
,
M. J.
,
2012
, “
Highly Durable and Flexible Dye-Sensitized Solar Cells Fabricated on Plastic Substrates: PVDF-Nanofiber-Reinforced TiO2 Photoelectrodes
,”
Energy Environ. Sci.
,
5
(
10
), pp.
8950
8957
.10.1039/c2ee21674d
5.
Coakley
,
K. M.
, and
McGehee
,
M. D.
,
2004
, “
Conjugated Polymer Photovoltaic Cells
,”
Chem. Mater.
,
16
(
23
), pp.
4533
4542
.10.1021/cm049654n
6.
Someya
,
T.
,
Sekitani
,
T.
,
Iba
,
S.
,
Kato
,
Y.
,
Kawaguchi
,
H.
, and
Sakurai
,
T.
,
2004
, “
A Large-Area, Flexible Pressure Sensor Matrix With Organic Field-Effect Transistors for Artificial Skin Applications
,”
Proc. Natl. Acad. Sci.
,
101
(
27
), pp.
9966
9970
.10.1073/pnas.0401918101
7.
Majeed
,
B.
,
Delaney
,
K.
,
Barton
,
J.
,
McCarthy
,
N.
,
O'Mathuna
,
S. C.
, and
Alderman
,
J.
,
2006
, “
Fabrication and Characterization of Flexible Substrates for Use in the Development of Miniaturized Wireless Sensor Network Modules
,”
ASME J. Electron. Packag.
,
128
(
3
), pp.
236
245
.10.1115/1.2229221
8.
Baek
,
J.-Y.
,
An
,
J.-H.
,
Choi
,
J.-M.
,
Park
,
K.-S.
, and
Lee
,
S.-H.
,
2008
, “
Flexible Polymeric Dry Electrodes for the Long-Term Monitoring of ECG
,”
Sens. Actuator A Phys.
,
143
(
2
), pp.
423
429
.10.1016/j.sna.2007.11.019
9.
Hwang
,
D.
,
Fuentes-Hernandez
,
C.
,
Kim
,
J.
,
Potscavage
,
W.
Jr.
, and
Kippelen
,
B.
,
2011
, “
Flexible and Stable Solution-Processed Organic Field-Effect Transistors
,”
Org. Electron.
,
12
(
7
), pp.
1108
1113
.10.1016/j.orgel.2011.04.002
10.
Yun
,
Y. H.
,
Jang
,
S. A.
, and
Oh
,
Y. J.
,
2013
, “
Formation of Stretchable Metal Bi-Layer Interconnects Using a Deformed Elastomeric Polymer Substrate
,”
Korean J. Met. Mater.
,
51
(
2
), pp.
151
158
.10.3365/KJMM.2013.51.2.151
11.
DeFigueiredo
,
B. P.
,
Zimmerman
,
T. K.
,
Russell
,
B. D.
, and
Howell
,
L. L.
,
2018
, “
Regional Stiffness Reduction Using Lamina Emergent Torsional Joints for Flexible Printed Circuit Board Design
,”
ASME J. Electron. Packag.
,
140
(
4
), p.
041001
.10.1115/1.4040552
12.
Lu
,
N.
,
Suo
,
Z.
, and
Vlassak
,
J. J.
,
2010
, “
The Effect of Film Thickness on the Failure Strain of Polymer-Supported Metal Films
,”
Acta Mater.
,
58
(
5
), pp.
1679
1687
.10.1016/j.actamat.2009.11.010
13.
Sim
,
G.-D.
,
Hwangbo
,
Y.
,
Kim
,
H.-H.
,
Lee
,
S.-B.
, and
Vlassak
,
J. J.
,
2012
, “
Fatigue of Polymer-Supported Ag Thin Films
,”
Scr. Mater.
,
66
(
11
), pp.
915
918
.10.1016/j.scriptamat.2012.02.030
14.
Mao
,
L.
,
Meng
,
Q.
,
Ahmad
,
A.
, and
Wei
,
Z.
,
2017
, “
Mechanical Analyses and Structural Design Requirements for Flexible Energy Storage Devices
,”
Adv. Energy Mater.
,
7
(
23
), p.
1700535
.10.1002/aenm.201700535
15.
Seo
,
S.-H.
,
Lee
,
J.-H.
,
Song
,
J.-Y.
, and
Lee
,
W.-J.
,
2016
, “
Control of Position of Neutral Line in Flexible Microelectronic System Under Bending Stress
,”
J. Microelectron. Packag. Soc.
,
23
(
2
), pp.
79
84
.10.6117/kmeps.2016.23.2.079
16.
Moon
,
C.-H.
,
2018
, “
Encapsulation of a Flexible OLED Using a Sealing Line
,”
Korean J. Met. Mater.
,
56
(
4
), pp.
313
320
.https://www.researcherapp.com/paper/2353277
17.
Carta
,
R.
,
Jourand
,
P.
,
Hermans
,
B.
,
Thoné
,
J.
,
Brosteaux
,
D.
,
Vervust
,
T.
,
Bossuyt
,
F.
,
Axisa
,
F.
,
Vanfleteren
,
J.
, and
Puers
,
R.
,
2009
, “
Design and Implementation of Advanced Systems in a Flexible-Stretchable Technology for Biomedical Applications
,”
Sens. Actuator A Phys.
,
156
(
1
), pp.
79
87
.10.1016/j.sna.2009.03.012
18.
Kim
,
D.-H.
,
Song
,
J.
,
Choi
,
W. M.
,
Kim
,
H.-S.
,
Kim
,
R.-H.
,
Liu
,
Z.
,
Huang
,
Y. Y.
,
Hwang
,
K.-C.
,
Zhang
,
Y.-W.
, and
Rogers
,
J. A.
,
2008
, “
Materials and Noncoplanar Mesh Designs for Integrated Circuits With Linear Elastic Responses to Extreme Mechanical Deformations
,”
Proc. Natl. Acad. Sci.
,
105
(
48
), pp.
18675
18680
.10.1073/pnas.0807476105
19.
Endler
,
S.
,
Rempp
,
H.
,
Harendt
,
C.
, and
Burghartz
,
J. N.
,
2012
, “
Compensation of Externally Applied Mechanical Stress by Stacking of Ultrathin Chips
,”
Solid-State Electron.
,
74
, pp.
102
107
.10.1016/j.sse.2012.04.019
20.
Hwang
,
J.-S.
,
Seo
,
S.-H.
, and
Lee
,
W.-J.
,
2016
, “
Effect of Design Parameters on Thermomechanical Stress in Silicon of Through-Silicon Via
,”
ASME J. Electron. Packag.
,
138
(
3
), p.
031006
.10.1115/1.4033923
21.
Lee
,
C. W.
,
Lee
,
J. H.
,
Song
,
J. Y.
,
Kim
,
S. M.
,
Kim
,
Y. J.
, and
Kim
,
C.
,
2018
, “
Polymer Elastic Bump Formation Through Photodefinable Thermal Reflow Process for System in Foil Package
,”
J. Micromech. Microeng.
,
28
(
11
), p.
115008
.10.1088/1361-6439/aadbd9
22.
IEC
,
2018
, “
Printed Electronics – Part 202-5: Materials – Conductive Ink – Mechanical Bending Test of a Printed Conductive Layer on an Insulating Substrate
,” IEC, Geneva, Switzerland, Report No.
IEC 62899-202-5
.https://webstore.iec.ch/publication/26826
23.
Haq
,
J.
,
Vogt
,
B. D.
,
Raupp
,
G.
, and
Loy
,
D.
,
2012
, “
Finite Element Modeling of Temporary Bonding Systems for Flexible Microelectronics Fabrication
,”
Microelectron. Eng.
,
94
, pp.
18
25
.10.1016/j.mee.2012.01.003
24.
Gupta
,
S.
,
Navaraj
,
W. T.
,
Lorenzelli
,
L.
, and
Dahiya
,
R.
,
2018
, “
Ultra-Thin Chips for High-Performance Flexible Electronics
,”
NPJ Flex. Electron.
,
2
(
1
), pp.
1
17
.10.1038/s41528-018-0021-5
25.
Kim
,
B.-J.
,
Lee
,
J.-H.
, and
Joo
,
Y.-C.
,
2016
, “
Effect of Cyclic Outer and Inner Bending on the Fatigue Behavior of a Multi-Layer Metal Film on a Polymer Substrate
,”
Jpn. J. Appl. Phys.
,
55
(
6S3
), p.
06JF01
.10.7567/JJAP.55.06JF01
You do not currently have access to this content.