In a message dated 06/02/2000 10:52:38 AM Central Daylight Time,
[log in to unmask] writes:
<< I am using an equipment of max. 160 kV and until now I was very happy
with it, inviting my friends to test BGA's with metal covers , their
equipment being too weak.
I don't know if we should be happy or not having this discussion, but I have
a bad
feeling. If there is something we don't know, research should be done. >>
Hi Gaby!
I've been searching to try and find something that talks specifically about
possible damage from x-ray inspection and as Paul said; I'm hitting a silent
wall. However, there's tons of information about radiation damage to
electronics in space. From reading some of it, there's no question that x-ray
radiation can degrade and damage electronic components. The question is how
much radiation does it take to damage something. I don't have the kind of
knowledge to know that...maybe somebody on the list that's a lot smarter than
me knows?
Below is a paste from a web page of an organiztion that's been studying the
effect of radiation on solar panels. I think there's a few good statements in
there that illustrate we should be a little concerned when using higher
powered x-ray equipment.
-Steve Gregory-
Radiation effects
The behaviour of solar cells in a radiation environment can be described in
terms of the changes in the engineering output parameters of the devices.
This approach limits the understanding of the physical changes which occur in
the device. Since other environmental factors may need consideration, an
understanding of a physical model provides a basis for estimates of the
behaviour in a complex environment. In addition, solar arrays of the future
will become more complex and may utilise materials which are affected by
different aspects of radiation damage. For these reasons, one should be aware
of the process by which radiation interacts with matter, and understand the
physical models which describe the processes.
Ionisation
Ionisation occurs when orbital electrons are removed from an atom or molecule
in gases, liquids, or solids. The measure of the intensity of ionising
radiation is the roentgen. This unit is defined by a charge generation of
2.58x10 -4 C/kg of air. The measure of the absorbed dose in any material of
interest is usually defined in terms of absorbed energy per unit mass. The
accepted unit of absorbed dose is the rad (100 erg/g or 0.01 J/kg). The SI
unit of absorbed dose is the Gray (Gy), defined to be 1 J/kg. Through the use
of the concept of absorbed dose, various radiation exposures can be reduced
to absorbed dose units which reflect the degree of ionisation damage in the
material of interest. This concept can be applied to electron, gamma, and
X-ray radiation of all energies.
The use of silicon dioxide as a surface passivation coating and dielectric
material in silicon devices results in a wide range of ionisation related
radiation effects. The development of trapped charges in the silicon dioxides
can cause increased leakage currents, decreased gain, and surface channel
development in bipolar transistors and increased threshold voltages in MOS
field effect transistors (MOSFETs). Ionising radiation in silicon excites the
electrons of the valence band to the conduction band, creating electron-hole
pairs in much the same way that carrier pairs are generated by visible light.
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