Last week and this week I have been conducting a
course on "Principles of Reliability Testing For the Semiconductor &
Microelectronics Industry", two days in Singapore and two days in Alabang,
part of Metro Manila in the Philippines. Was quite surprised, in the best
possible way, to find that five of the course participants in Singapore were from Apple in China , four from Shenzen and one from Shanghai Manila
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With some of the course participants in Alabang |
One of the topics in reliability which catches
people's interest is drop impact
testing. This has become a hot topic since almost everyone now carries a
sophisticated computer, camera, video-camera ,TV etc, etc around in their pocket
or handbag and they expect it to work after they drop it on the floor. From the
point of view of someone in electronics packaging this is most inconsiderate.
In general, electronic modules don't like to be subjected to a g force of over
1000 g (Yes, that's what the phone experiences!). PCBs deform and
solder joints crack. And screens crack! You
can watch an amusing YouTube video of someone abusing smart phones to
destruction Click here for video (and there are plenty more!) but, sadly, the only real benefit to come from the expensive
sacrifice of four innocent phones is an amusing video. Dropping phones like this, in an uncontrolled, non-reproducible. way tells us nothing about the mechanisms of failure and therefore
nothing about how we can improve the reliability. One of the things we have
learnt is that the g-force experienced inside the phone is strongly dependent
on the orientation of the phone when it hits the ground so we need to do
controlled drop testing using one of the labs set up to do this such as Halt
and Hass in New Zealand.
I like their motto "You make it, we break
it"
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| Controlled Drop Test (From Halt & Hass Website) |
There are other companies offering similar services such as:
Then you need to measure the local g-force at
different locations within the phone and measure the deflection of the PCB within the phone. It turns out that the phone killer isn't the direct
inertial shock on the components but flexing of the PCB damaging the solder
joints. The behaviour of the PCB is quite complex:
From Drop Impact Reliability – A Comprehensive Summary, E.H. Wong et al,
Once you
understand the fundamental mechanisms you can model the phones performance
without any destruction at all.
Although I bet
they do a few physical tests to verify the results.
Time for me to relax with a beer.
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