Energy measurement: The main metric for high strain rate bond testing of solder balls
correlates with board level drop testing
2
. Another way
When comparing different packages and to use energy is to
the number of drops to failure (brittle look at thresholds
fractures on the component side), there associated with the
is a direct relationship to the output onset of undesir-
parameters from the high strain rate bond able failure modes.
testing, including energy. Indeed it is sug- In this case the data
Affordable, intelligently designed x-ray
gested that high strain rate bond testing needs to be plotted
could be used as a predictor of drop test in a different way
inspection systems since 1983.
performance
3
. and the failure
Energy values can be used to facilitate mode assignments
Patented real-time x-ray imaging
materials screening. In such a situation from the baseline technology that creates high resolution,
there will be a control or reference sample data collection
compact systems.
for which the transition speed should need to be used. In
be determined and the mean total and Figure 3 a frequency
post-peak energy values recorded across all distribution for
tests, irrespective of failure mode (as in the post-peak energy
bottom row of Table 1). Tests at the same has been plotted
speed should then be carried out on the with the various
experimental variants and the same energy failure modes
parameters recorded. Shifts in the mean colour coded.
energy will show improvements or deterio- For this example
rations in bond strength; checking failure it is suggested
modes is unnecessary. that choosing a
The same principle lies behind the use threshold of 1.1 mJ
of energy in monitoring production bond and above for good
strength quality. Hundreds of tests should product would
be carried out on normal production to exclude that with
establish baseline energy values and set brittle or quasi-
up SPC charts. This is illustrated in the brittle failures.
following example. The mean values from
To learn more, go to:
Table 1 above are used as the baseline for conclusions
batch testing in which 10 balls in each We believe that suf-
www.GlenbrookTech.com
of five batches are tested and the mean ficient evidence has
energy values compared to the established been presented to
selection, process set-up and production
baseline (Table 2). support the use of energy as the principal
monitoring as an accurate, economic,
It can be clearly seen that batches 2 metric for reliable and repeatable high
time saving and simple alternative to other
to 5 are not significantly different from strain rate bond testing, analogous to the
test methods used to evaluate solder joint
the baseline values when looking at total use of force in conventional bond testing.
integrity and reliability.
energy or post-peak energy. Depending on High strain rate shear and pull energy mea-
the tolerance bands which have been set, surement correlates with the resilience of
references
it would be recommended that batch 1 a solder ball interconnection to mechani-
1. Sykes, B., “High-Speed Bondtesting:
should be retested. cal shock. Energy can be used in material
Understanding the Technology,” Chip
Scale Review magazine, October 2008
2. Song, F., Lee, S., Newman, K., Sykes,
B. and Clark, S., “High-Speed Solder
Ball Shear and Pull Teats vs. Board
Level Mechanical Drop Tests: Cor-
relation of Failure Mode and Loading
Speed,” Electronic Components &
Technology Conference, Reno, NV,
June 2007, pp. 1504-1513
3. Clark, S., “Testing the Entire Solder
Joint”, AP China magazine, January/
February 2009
Dr. Stephen Clark is Bond Tester Product Man-
ager for Dage Precision Industries, a Nordson
Company, in Aylesbury, Buckinghamshire, UK.
In his role he has gained worldwide recognition
for demonstrating, training and problem solving
using advanced bondtesting technology through-
out the semiconductor and electronics assembly
industries. He may be contacted at
Figure 3. Ductile, quasi-ductile, quasi-brittle and brittle failure frequency versus energy.
s.clark@dage-group.com.
www.globalsmt.net Global SMT & Packaging – June 2009 – 17
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