Energy measurement: The main metric for high strain rate bond testing of solder balls
Energy measurement:
The main metric for high
strain rate bond testing of
solder balls
by Dr. Stephen Clark, Dage Precision Industries, Aylesbury, UK
introduction
and reproducibly aligning the sample with
Solder joint integrity may be
High strain rate bondtesting methods have
respect to shear height such as an X-Y
compromised through
gained in importance with the legislated
positioning table and an adjustable Z-axis.
mechanical shock, particularly
introduction of lead-free solder and have
These devices have some value in the
proven to be an important alternative to
in portable electronics using
research laboratory, but are unsuited for
board level drop testing for incoming ma-
area array devices with solder
rapid screening or production monitoring.
terials screening, and process optimization
balls for interconnections. The
as well as design in research and develop-
high strain rate bondtesting
use of lead-free solder in these ment. It is well known that board level
The high strain rate bond tester addresses
packages makes them suscepti-
drop testing is an expensive, cumbersome
all these shortcomings. Testing is rapid
ble to brittle fracture failures at
and time-consuming process, ill-suited to
and economic, yielding quantitative data
the solder ball to pad interface.
production control.
through the measurement of bond fracture
High strain rate methods are
Other test instruments such as the
energy. Furthermore, it has been shown
Charpy and Izod pendulum based impact
needed to detect these failures
to correlate with board level drop testing.
testers, widely used in materials evalua-
Force displacement curves are generated
and board level drop testing has
tions, have been adapted to the testing of
and in shear testing, the shear height is
been the traditional method to solder joints. Although these devices can
under close control.
assess this type of solder joint yield energy values for bond failure, only
Developed in response to the electron-
reliability. Unfortunately it is
total energy is measured and force versus
ics industry’s need to swiftly evaluate new
time consuming, expensive and
displacement curves are not generated.
alloys and bond materials introduced in
the results may be ambiguous.
The tests do not occur at constant velocity
order to meet the lead-free legislation, the
High strain rate bond testing
and generally there is no means of quickly
high strain rate bondtesting instrument
using energy as a quantita-
tive metric is suggested as an
economic, rapid, and easy to use
method, applicable equally to
product design and production
monitoring.
Keywords: Solder Ball Intercon-
nection, Brittle Fracture Failure,
Bond Testing, Energy Measure-
ment, Board Level Drop Testing,
High Strain Rate Bond Testing
Figure 1. Brittle fracture and ductile failure force displacement curves.
14 – Global SMT & Packaging – June 2009 www.globalsmt.net
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51