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Gamma irradiation of components - results

R

Richard Rasker

Jan 1, 1970
0
Hi all,

Some weeks ago, I posted a few questions about gamma sterilization of
certain electronic components. From the reactions, the conclusion could be
drawn that gamma sterlization of electronics is quite a tricky business.
This also became obvious when an irradiated test circuit showed
multiple component failures.

Nevertheless, I decided to put a small batch of components through the
gamma irradiation process again, and an identical batch through steam
sterilization, for comparison purposes. Most of the selected components
are included in the design of a medical implant. Here are the results, for
those interested.


Components tested (one batch):
FDC6305N Dual N-channel MOSFET (4x)
FDC6306P Dual P-channel MOSFET (4x)
FDC6327C N- & P-channel MOSFET (4x)
TL084 quad opamp (1x)
TC1047A temperature-to-voltage converter (2x)

Sterilization procedures:
- Autoclave (steam), 134 degrees Centigrade at 2 bars of pressure
- Gamma irradiation, 1 dose of 25 kGray Co60 exposure

Steam: All components were unaffected, and behaved well within their
specifications.

Gamma: All MOSFET's were severely affected:
FDC6305N - all 8 devices exhibited short circuit from drain to source; no
response to Vgs at all.

FDC6306P - all devices exhibited dramatically lower Vgs threshold values,
with a Vgs-on between -2.1V and -2.5V (normally -1V), and a maximum drain
current Id-max (set at 0.33 A) at Vgs = approx. -3.2V (normally -1.6V).

FDC6327C - P-FET's: same as FDC6306P.
N-FET's: lower Vgs values: Vgs-on between -0.2V and -0.4V
(normally +1.1V) and Id-max at Vgs = +0.2V (normally +1.6V)

Something rather unexpected is the difference between the N-FET's in the
FDC6327C (which merely showed lower Vgs values), and the N-FET's FDC6305N,
which were completely destroyed. All P-FET's behaved in the same manner.
Apart from the changed Vgs values, other parameters seemed mostly
unaffected.

TL084 - tested in unity-gain circuit (output connected to - input, driving
voltage on + input). Two of the four opamps exhibited a massive offset
voltage of approximately +0.5V, probably as a result of damage to the
input JFET's; the other two devices in the same package seemed unaffected.

TC1047A - both devices tested seemed to operate within specifications;
however, the small number of components tested makes it difficult to say
anything definitive about the sensitivity for gamma radiation.

Conclusion: gamma sterilization of electronic circuits is quite
troublesome; especially FET's (both MOSFET's and JFET's, such as
employed in the TL084) are at risk. The most prominent effect is a
drastically lower value for Vgs, rendering the devices near useless for
most practical purposes.

If any more gamma ray testing is carried out, e.g. with bipolar
semiconductors instead of FET's, I will post the results here as well.


Richard Rasker
 
J

Joerg

Jan 1, 1970
0
Hi Richard,

Thanks, that was pretty interesting. Same experience here, radiation had quite
disastrous effects whenever someone insisted that we test it. Most everything
remotely related to semiconductors was toast afterwards. But even some
plastics were affected in ways such as changing their color tint.

With steam, do you mean EtO? That's what we generally use.

Regards,

Joerg.
 
R

Richard Rasker

Jan 1, 1970
0
Hi Richard,

Thanks, that was pretty interesting. Same experience here, radiation had
quite disastrous effects whenever someone insisted that we test it. Most
everything remotely related to semiconductors was toast afterwards. But
even some plastics were affected in ways such as changing their color
tint.

Nevertheless, the people I work for still want to look into radiation
hardened semiconductors. I don't think that much will come of it - if I
understand correctly. 'radiation hardened' means a much larger
electronically active area, and therefore larger components as a whole. I
selected the FDC type MOSFETs especially for their combination of
very small size, high current handling capabilities and low drive voltage,
and I think that even if rad-resistant types exist, these will almost
certainly be much bigger ...
With steam, do you mean EtO? That's what we generally use.

No, I really mean steam, heated water, at 134°C (273°F, 407K), under a
pressure of 2 bar (about 30 PSI), in an autoclave - standard hospital
issue. As said, this didn't harm the components in any way. And as long as
I don't use electrolytical capacitors, I expect no problems with this
method. We didn't test EtO; based on the experiences of others, this seems
a very well-proven method for electronics, so rigorous testing in advance
of this method is not really necessary.

Regards,

Richard Rasker
 
J

Joerg

Jan 1, 1970
0
Hi Richard,

Rad hard parts are very expensive and the selection you can pick from becomes
quite limited. Some degradation will still occur since they are hard but not
immune.

Electrolytics aren't the only problem. Switches, buzzers, display panels could
also be affected in an autoclave process especially if it is done repeatedly.

I don't know whether you meant EtO to be so well proven that it wouldn't need
advance testing. My experince is that it requires lots of validation and
testing. EtO can have quite nasty corrosive and other effects on contacts,
glues parts with soft materials and so on. Then there is the outgassing phase
which needs to be extremely carefully validated.

Regards, Joerg

www.analogconsultants.com
 
R

Richard Rasker

Jan 1, 1970
0
Hi Richard,

Rad hard parts are very expensive and the selection you can pick from
becomes quite limited. Some degradation will still occur since they are
hard but not immune.

Hallo Joerg,
Thank you for your much valued remarks; I figured so much already, and I'm
not overly confident that gamma irradiation is a feasible option in this
case - to put it mildly.
Electrolytics aren't the only problem. Switches, buzzers, display panels
could also be affected in an autoclave process especially if it is done
repeatedly.

That won't be much of a problem, since the circuit contains no
electromechanical or otherwise "special" parts. It's all semiconductors
and standard passive components (resistors, capacitors, inductors).
I don't know whether you meant EtO to be so well proven that it wouldn't
need advance testing. My experince is that it requires lots of
validation and testing. EtO can have quite nasty corrosive and other
effects on contacts, glues parts with soft materials and so on. Then
there is the outgassing phase which needs to be extremely carefully
validated.

Sorry, I wasn't quite clear here. Of course several (semi-)complete
prototype implants will be thoroughly tested in all respects, probably
including EtO sterilization. But I don't expect EtO-testing of a handful
of separate off-the-shelf components to yield much in the way of valuable
or unexpected information, especially not in relation to their electrical
characteristics.
With gamma irradiation, I wanted to make sure that indeed the majority of
components would suffer damage - which was established in a rather
convincing way. The steam procedure was chosen as an alternative, to see
whether prolonged exposure to temperatures close to the absolute maximum
ratings would have any measurable effects - which was not the case.

However, any remarks, thoughts, or other bits of information are still
very welcome.

Richard Rasker
 
J

Joerg

Jan 1, 1970
0
Hi Richard,

The autoclave process isn't so familiar to me since everything I ever designed
for med goes through EtO. But one thing comes to mind and that is cabling. If
your design has wires with PVC insulation the high temps might be an issue.
But that can easily be solved by changing to another type of insulation.

Another concern would be chips. An autoclave may cause a chip with a damaged
package to fail which then may not be testable because you can't touch sterile
goods. Unless it had already been autoclaved some time before final test this
could be a problem.

I looked up your web link. Reminds me of the good old times back in NL where
Grolsch was my standard beer. Even visited the brewery in your town. Speaking
Dutch got rusty but I could still read the profiles page on your web site.

Regards, Joerg
 
F

Fritz Schlunder

Jan 1, 1970
0
Richard Rasker said:
Hi all,

Some weeks ago, I posted a few questions about gamma sterilization of
certain electronic components. From the reactions, the conclusion could be
drawn that gamma sterlization of electronics is quite a tricky business.
This also became obvious when an irradiated test circuit showed
multiple component failures.

Nevertheless, I decided to put a small batch of components through the
gamma irradiation process again, and an identical batch through steam
sterilization, for comparison purposes. Most of the selected components
are included in the design of a medical implant. Here are the results, for
those interested.


Components tested (one batch):
FDC6305N Dual N-channel MOSFET (4x)
FDC6306P Dual P-channel MOSFET (4x)
FDC6327C N- & P-channel MOSFET (4x)
TL084 quad opamp (1x)
TC1047A temperature-to-voltage converter (2x)

Sterilization procedures:
- Autoclave (steam), 134 degrees Centigrade at 2 bars of pressure
- Gamma irradiation, 1 dose of 25 kGray Co60 exposure


Hi there Mr. Rasker.

Interesting post, but is 25 kGy really necessary? I don't think I would
want to be exposed to that being that (IIRC) the LD 99/60 (lethal dose for
99% of the population within 60 days of exposure) for mid-line absorbed dose
(mid-line being average exposure over the abdominal region) for people is
around 5 Gy for X-ray or gamma radiation. Of course some particularly
robust organisms can handle allot more than people, but gee...
 
R

Richard Rasker

Jan 1, 1970
0
.....



Hi there Mr. Rasker.

Interesting post, but is 25 kGy really necessary? I don't think I would
want to be exposed to that being that (IIRC) the LD 99/60 (lethal dose
for 99% of the population within 60 days of exposure) for mid-line
absorbed dose (mid-line being average exposure over the abdominal
region) for people is around 5 Gy for X-ray or gamma radiation. Of
course some particularly robust organisms can handle allot more than
people, but gee...

Well, I was a bit surprised at the dosage as well - especially when
confronted with the extent of damage done to something as relatively
simple as a semiconductor device.
But then again, this seems to be the standard dose for medical implants -
my guess is that they want to make absolutely certain that nothing even
remotely protein-like will survive the irradiation unchanged. And of
course one doesn't just have to worry about bacteria and viruses, but also
about prions (BSE and scrapie pathogens), which are much more robust. Come
to think of that, I wonder if the autoclave treatment takes care of that...


Richard Rasker
 
R

Richard Rasker

Jan 1, 1970
0
Hi Richard,

The autoclave process isn't so familiar to me since everything I ever
designed for med goes through EtO. But one thing comes to mind and that
is cabling. If your design has wires with PVC insulation the high temps
might be an issue. But that can easily be solved by changing to another
type of insulation.

OK, thanks, point duly noted :)
Another concern would be chips. An autoclave may cause a chip with a
damaged package to fail which then may not be testable because you can't
touch sterile goods. Unless it had already been autoclaved some time
before final test this could be a problem.

Yes, I can imagine water vapour being able to creep in; plans are, however
to encase the electronics in resin or seal them off in some other way.
We're very much in the early stages of solving these particular problems
with sterilization, so all information is appreciated.
I looked up your web link. Reminds me of the good old times back in NL
where Grolsch was my standard beer. Even visited the brewery in your
town. Speaking Dutch got rusty but I could still read the profiles page
on your web site.

Hehe, well, Grolsch is as fine a lager as you can wich for - still my
favourite as well. And if you can't follow the Dutch, there's always the
English (and German) version.



Richard Rasker
 
J

Joerg

Jan 1, 1970
0
Hi Richard,

Grolsch beer is even available here in the US but it doesn't taste the same as
in NL. Maybe it doesn't like to travel much. It comes in the same flip top
bottles (beugelfles in Dutch?). But we now have many local micro breweries
that make great beers of all types. A lot has changed for the better here in
the brewing scene. We can even go to a local pub for a refill into a 2 liter
glass bottle. Like in them good ol' times. Talking about sterilization, these
bottles that are called growlers over here need to be meticulously sterilized.

Once in a while we treat ourselves to a nice Belgian Saison Regal. People here
watch in amazement when you pull out the cork with a loud pop and a cloud
comes out of the top.

Groetjes, Joerg
 
J

Joerg

Jan 1, 1970
0
Yes, Fritz, as Richard said this process is meant to eradicate anything that
lives, plus a healthy dosage margin on top of that. So you can't compare it to
danger levels for humans. There will be no people present when the dosage is
applied.

In sterilization validation there are certain bacteria "planted' in your device
at places where it is assumed that the process has the least effect. Later it is
measured whether any of those are alive and at which dosage. This is quite a
labor intensive process.

The same goes for other processes such as EtO. The quantities administered would
definitely not be survivable by a human or any other living being. Even during
outgassing the products are quarantined for several days. Which is why I keep a
very safe distance whenever I see a tanker truck with EtO on the highway.

Regards, Joerg
 
R

Richard Rasker

Jan 1, 1970
0
Hi Richard,

Grolsch beer is even available here in the US but it doesn't taste the
same as in NL. Maybe it doesn't like to travel much. It comes in the
same flip top bottles (beugelfles in Dutch?).

Yup, that's the name, and this particular bottle is still a very strong
marketing icon. Grolsch decided to keep it, where most other breweries
have fully switched to identical, uniform "euro" bottles. Grolsch does
however sell its beer in these standard, lightweight bottles as well.
But we now have many local micro breweries that make great beers of
all types. A lot has changed for the better here in the brewing scene.
We can even go to a local pub for a refill into a 2 liter glass bottle.
Like in them good ol' times. Talking about sterilization, these bottles
that are called growlers over here need to be meticulously sterilized.

Indeed, here as well, the "beerscape" has become increasingly varied over
the past 20 years or so. In the late 1970's, one could choose from at most
five or six brands of beer (and all lager) in the supermarket, and maybe
double this figure in liquor stores. Nowadays, the choice is overwhelming,
with some stores offering up to 50 or 60 brands of beer :)
Once in a while we treat ourselves to a nice Belgian Saison Regal.
People here watch in amazement when you pull out the cork with a loud
pop and a cloud comes out of the top.

Hmm, never tried one of those, but I'm looking forward to the moment when
I'll descend on a sunny terrace, and order my first wonderfully
refreshing Hoegaarden Witbier ("white beer") of this summer season - after
an electronics job well done of course, that's when they taste best :)

Regards,

Richard Rasker
 
K

Ken Taylor

Jan 1, 1970
0
Rob said:
Has anyone experienced hard disks being corrupted by customs xray
inspection? Equipment my employer exports often arrives with the hard disks
unreadable. The HDDs are part of a system built into a sea container. The
problem has been attributed to US customs xraying the sea container. It only
seems to happen when the equipment goes into the US. There have been 3 or 4
instances of this occuring.

Any thoughts/similar experiences?

regards
rob
Normally I'd say that wasn't possible, as the levels used aren't enough.
However that was valid for baggage screening - container-level screening may
involve much higher doses. Having said that, we haven't had similar problems
and we're shipping stuff in and out of the US all the time via container.

Ken
 
M

Mike

Jan 1, 1970
0
Has anyone experienced hard disks being corrupted by customs xray
inspection? Equipment my employer exports often arrives with the hard disks
unreadable. The HDDs are part of a system built into a sea container. The
problem has been attributed to US customs xraying the sea container. It only
seems to happen when the equipment goes into the US. There have been 3 or 4
instances of this occuring.

Any thoughts/similar experiences?

I don't know how Maxtor, Seagate, and WD import their drives, but I'd guess
that they're all being shipped in containers...

-- Mike --
 
R

Rob

Jan 1, 1970
0
Has anyone experienced hard disks being corrupted by customs xray
inspection? Equipment my employer exports often arrives with the hard disks
unreadable. The HDDs are part of a system built into a sea container. The
problem has been attributed to US customs xraying the sea container. It only
seems to happen when the equipment goes into the US. There have been 3 or 4
instances of this occuring.

Any thoughts/similar experiences?

regards
rob
 
R

R.Legg

Jan 1, 1970
0
Rob said:
The HDDs are part of a system built into a sea container.

A permanent part of the shipping container? Re-used?

Rad effects are cumulative.

RL
 
R

Rich Webb

Jan 1, 1970
0
Has anyone experienced hard disks being corrupted by customs xray
inspection? Equipment my employer exports often arrives with the hard disks
unreadable. The HDDs are part of a system built into a sea container. The
problem has been attributed to US customs xraying the sea container. It only
seems to happen when the equipment goes into the US. There have been 3 or 4
instances of this occuring.

Are the components operational with the exception of bad/scrambled data
on the hard disk? If so, rather than the X-Ray flux, the culprit may be
the focusing coils.
 
R

Rob

Jan 1, 1970
0
Rich Webb said:
Are the components operational with the exception of bad/scrambled data
on the hard disk? If so, rather than the X-Ray flux, the culprit may be
the focusing coils.

Thanks for all the replies.

You make a good point Rich, all the electronics functions fine, so perhaps
it is magnetic rather than xray based.

To clarify a couple of the replies;

The equipment is physically built into a modified sea container, which is
then treated like any other container for shipping purposes. We believe the
container itself is being xrayed to inspect its contents.

The displays/monitors used in the product are all LCD based - perhaps if
they were CRTs we would see some effect on the CRT display purity - if the
power on degauss didn't clean it up first.....
I think pan is to ship the hard drives as hand luggage with the installation
techs.

regards
rob
 
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