A fundamental understanding of the dynamics of the PCB assembly when subjected to a half-sine acceleration has also been obtained through analyzing the PCB as a spring mass system, a beam, and a plate, respectively. The magnitude of stresses in solder interconnection due to flexing of the PCB is two orders higher than the magnitude of the stresses induced by acceleration and inertia loading the IC package. By ignoring the inertia loading, computational effort to evaluate the interconnection stresses due to PCB flexing can be reduced significantly via a two-step dynamic-static analysis. The dynamic analysis is first performed to evaluate the PCB bending moment adjacent the package, and is followed by a static analysis where the PCB bending moment is applied around the package. Parametric studies performed suggest a fundamental difference in designing for drop impact and designing for temperature cycling. The well-known design rules for temperature cycling—minimizing package length and maximizing interconnection standoff—does not work for drop impact. Instead, drop impact reliability can be enhanced by increasing the interconnection diameter, reducing the modulus of the interconnection materials, reducing the span of the PCB, or using either a very thin or a very thick PCB.

1.
Goyal
,
S.
,
Uasani
,
S
, and
Patel
,
D. M.
, 1999, “
The Role of Case Rigidity in Drop-Tolerance of Portable Products
,”
IJMEP
, pp.
175
184
.
2.
JEDEC Standard JESD22-B111, “
Board Level Drop Test Method of Components for Handheld Electronic Products
.”
3.
Seah
,
S. K. W.
,
Lim
,
C. T.
,
Wong
,
E. H.
,
Tan
,
V. B. C.
, and
Shim
,
V. P. W.
, 2002, “
Mechanical Response of PCBs in Portable Electronic Products During Drop Impact
,”
Proc. 4th EPTC
, Singapore, pp.
120
125
.
4.
Lim
,
C. T.
,
Ang
,
C. W.
,
Tan
,
L. B.
,
Seah
,
S. K. W.
, and
Wong
,
E. H.
, 2003, “
Drop Impact Survey of Portable Electronic Products
,”
Proc. 53rd Electronic Component Technology Conference (ECTC)
, New Orleans, pp.
113
120
.
5.
Wong
,
E. H.
,
Lim
,
K. M.
,
Lee
,
N.
,
Seah
,
S. K. W.
,
Hoe
,
C.
, and
Wang
,
J
, 2002, “
Drop Impact Test—Mechanics & Physics of Failure
,”
Proc 4th EPTC
, Singapore pp.
327
333
.
6.
Wong
,
E. H.
, and
Seah
,
S. K. W.
, 2003, “
Fundamentals of Drop Impact
,” presented in JEDEC working group meeting.
7.
Seah
,
S. K. W.
,
Wong
,
E. H.
,
Rajoo
,
R.
, and
Lim
,
C. T.
, 2004, “
Experiments and Failure Drivers in Drop Impact of Portables
,”
JEDEX
, San Jose, CA.
8.
Sogo
,
T.
, and
Hara
,
S.
, 2001, “
Estimation of Fall Impact Strength for BGA Solder Joints
,”
Proc. International Conference on Electronic Packaging
, Tokyo, pp.
369
373
.
9.
Zhu
,
L.
, 2001, “
Submodeling Technique for BGA Reliability Analysis of CSP Packaging Subjected to an Impact Loading
,”
Proc. International Electronic Packaging Technical Conference
, Hawaii, IPACK2001-15873.
10.
Wang
,
J.
,
Hoe
,
C.
,
Wong
,
E. H.
, 2002, “
Modeling Solder Joint Reliability of BGA Packages Subject to Drop Impact Loading Using Submodelling
,”
Proc. Abaqus Conference
.
11.
Suhir
,
E.
, 1988, “
On a Paradoxical Phenomenon Related to Beams on Elastic Foundation: Could External Compliant Leads Reduce the Strength of a Surface-Mounted Device?
,”
J. Appl. Mech.
0021-8936,
55
, p.
818
.
12.
Wong
,
E. H.
, 2005, “
Dynamics of Board Level Drop Impact
,” ASME Trans. JEP,
127
, pp.
200
207
.
13.
Williamson
,
D. M.
,
Palmer
,
S. J. P.
,
Kennedy
,
C. F.
,
Siviour
,
C. R.
,
Siviour
,
G. B.
,
Walley
,
S. M.
,
Proud
,
W. G.
, and
Field
,
J. E.
, 2002, “
Spall, Quasi-Static and High Strain Rate Shear Strength Data for Electronic Solder Materials
,” Internal Report Cavendish Laboratory No. SP 1113.
14.
Date
,
M.
,
Shoji
,
T.
,
Fujiyoshi
,
M.
, and
Tu
,
K. N.
, “
Impact Reliability of Solder Joints
,”
Proc. 54 ECTC
, Las Vegas, pp.
668
674
.
15.
Wong
,
E. H.
,
Rajoo
,
R.
,
Mai
,
Y.-W.
,
Seah
,
S. K. W.
,
Tsai
,
K. T.
, and
Yap
,
L. M.
, “
Drop Impact—Fundamentals and Impact Characteristics of Solder Joints
,”
Proc. 55th ECTC
, Florida, pp.
1202
1209
.
16.
Newman
,
K.
, “
BGA Brittle Fracture—Alternative Solder Joint Integrity Test Methods
,”
Proc. 55th ECTC
, Florida, pp.
1194
1201
.
17.
Singiresu
,
S. R.
, 1995, “
Mechanical Vibrations
,”
3rd ed.
,
Addison-Wesley
, Reading, MA.
You do not currently have access to this content.