EEVblog #897 - Radiation Effects On Space Electronics

[EEVblog]

Dave talks with Karsten Becker from PT Scientists about radiation in space and it's effect on electronics and the design challenges involved for space probes, satellites, and cubesats.
The Van Allen belt and types of cosmic radiation.
What are "radiation hardened" components?
What are "Space Grade" components?

[MK14]

Thanks, I really enjoyed that video.
I knew radiation and cosmic rays could adversely affect electronics while operating. But did not realize that it could actually damage/destroy them, as with living things.
He is a very interesting person to interview/chat with.

[EEVblog]

He is a very interesting person to interview/chat with.

Yes, we chatted for hours about all sorts of stuff, I have a lot more material.

[Brumby]

Did you work out Tantalum? (@ 8:55)

[MK14]

Did you work out Tantalum? (@ 8:55)

I thought he was trying to say "Titanium" ?

A bit of searching seems to confirm the possibility that it was Titanium to protect Electronics.

The strategy? Give Juno a kind of six-sided lead apron on steroids.

With guidance from JPL and the principal investigator, engineers at Lockheed Martin Space Systems designed and built a special radiation vault made of titanium for a centralized electronics hub. While other materials exist that make good radiation blockers, engineers chose titanium because lead is too soft to withstand the vibrations of launch, and some other materials were too difficult to work with.

Each titanium wall measures nearly a square meter (nearly 9 square feet) in area, about 1 centimeter (a third of an inch) in thickness, and 18 kilograms (40 pounds) in mass. This titanium box -- about the size of an SUV's trunk – encloses Juno's command and data handling box (the spacecraft's brain), power and data distribution unit (its heart) and about 20 other electronic assemblies. The whole vault weighs about 200 kilograms (500 pounds).

Source:
http://www.nasa.gov/mission_pages/juno/news/juno20100712.html

EDIT:
On the other hand, it could be Tantalum.

http://pelagiaresearchlibrary.com/advances-in-applied-science/vol3-iss1/AASR-2012-3-1-446-451.pdf

[Brumby]

I listened to the sounds being spoken and figured it out in a couple of seconds...

What was said was 'Tan - tal - um'.  We normally say it as 'Tanta - lum'

I checked (Google is your friend) and found tantalum is also used in radiation shielding - which confirmed my original interpretation.

[MK14]

I listened to the sounds being spoken and figured it out in a couple of seconds...

What was said was 'Tan - tal - um'.  We normally say it as 'Tanta - lum'

I checked (Google is your friend) and found tantalum is also used in radiation shielding - which confirmed my original interpretation.

I agree Tantalum can be used in radiation shielding.

I can believe he was trying to say Tantalum OR Titanium, I'm NOT sure which it was (from listening to it).

Sometimes it sounds like "Tantalum", and at other times "Titanium", the human brain is funny when it becomes biased.

EDITED: Corrected.

[Brumby]

I'm pretty sure the last syllable was 'lum' - beginning with an 'L'.

Dave should have a periodic table at hand, the you could get Karsten to point at the element.

[MK14]

I'm pretty sure the last syllable was 'lum' - beginning with an 'L'.

Dave should have a periodic table at hand, the you could get Karsten to point at the element.

The first time he says it, it DOES sound like Tantalum, I agree.

But then Dave seems to say "Titanium"

Then he (Karsten) says something which also sounds more like Titanium (but said wrong).

So maybe Dave's "Titanium", confused him or something and it was Tantalum.

[Mike_H]

I am not a big poster, but that was a great video - very enjoyable.

Thanks

Mike

[nwvlab]

Mh, I do not perfectly agree with the engineer.
 
Even if the total ionizing dose (TID) effects should not depend on the  feature size (gate length), one should take into account that as the gate length scales down, the gate dielectric thickness scales down too (therefore TID effects are at least technology-node dependent).  And the TID effects on ultra-thin oxides are extremely different to those on thin or thick oxides. For instance, if the oxide thickness is below 3nm, charge trapping in the gate oxide (which causes threshold voltage variation) is suppressed, because trapped charges (mainly holes in SiO2. Electrons could be trapped in other dielectris) are quickly neutralized by tunneling, as they are (at most) only 1.5nm apart from the gate or the channel interface (with a such thin barrier, the quantum tunneling rate is extraordinarily high).

Furthermore let's think about Flash memories. The smaller the floating gate, the smaller the dose you require to neutralize a critical amount of stored charge. As the feature size scales down, they could become more and more sensitive. Also radiation induced-leakage currents impacts on the data retention and they depend on the dielectric thickness.

[jnissen]

Space grade components are most assuredly designed from the start with energetic particle emission in mind. I have done a number of ASIC's that have flown on all sorts of high altitude aircraft and some spacecraft. There are many "tricks" involved with these designs and in most all cases you design an active region with good well ties and shapes that promote easy current flow paths back to the substrate. If a substrate less (SOI, SOS) design then you can effectively eliminate bipolar type structures (lateral devices are still present) so this significantly improves the performance out of the gate.

In all cases good testing regimes, and yes lots of paperwork, is required to validate the intended performance. Rarely do you take off the shelf components and just "hope" they work well in an energetic environment!

BTW - The comments above on feature size is not a prediction of performance is partially true. Normally as feature sizes shrink the gate oxide and critical dimensions all shrink so you expect to see thinner oxides and dielectrics. Clearly the author has some background in non-volatile memory storage in energetic environments. That is a very tricky design field indeed.

[apis]

Very interesting

looking forward to the teardown!

(yeah, he definitely said tantalum)

[Howardlong]

Tantalum and aluminium sandwiches are commonly suggested after some experimental work was done a couple of decades ago.

It also depends on which order they are applied as to how good the shielding capabilities are.

Typically just the tops of the chips have the shielding applied, rather than the whole space frame to mitigate weight but what about the bottom? The board can be designed so chips are placed back to back top and bottom.

What this doesn't deal with are secondary radiation effects, although it does mitigate them to some degree.

Regarding space radiation effects, the point is to accept that it's not if, it's when it happens.

[MK14]

(yeah, he definitely said tantalum)

Tantalum and aluminium sandwiches are commonly suggested after some experimental work was done a couple of decades ago.

Thanks, everyone and sorry for any confusion on my part.

Ok, Tantalum it is.

Somehow I thought Tantalum was a weak/brittle insulator material (like Mica). Probably because of Tantalum electrolytic capacitors. Many capacitors seem to be named after the main insulator, used in their construction.

I suppose standard electrolytic's, can be called aluminium capacitors, so I should have realized that electrolytic's are named after the CONDUCTOR, rather than the insulator, material. (Apparently). A bit weird (the naming scheme).

EDIT: But I suppose it probably is the INSULATOR as well, as it is probably chemically transformed to be an insulator as well, I guess.

[Brumby]

Mh, I do not perfectly agree with the engineer.
 
Even if the total ionizing dose (TID) effects should not depend on the  feature size (gate length), one should take into account that as the gate length scales down, the gate dielectric thickness scales down too (therefore TID effects are at least technology-node dependent).  And the TID effects on ultra-thin oxides are extremely different to those on thin or thick oxides. For instance, if the oxide thickness is below 3nm, charge trapping in the gate oxide (which causes threshold voltage variation) is suppressed, because trapped charges (mainly holes in SiO2. Electrons could be trapped in other dielectris) are quickly neutralized by tunneling, as they are (at most) only 1.5nm apart from the gate or the channel interface (with a such thin barrier, the quantum tunneling rate is extraordinarily high).

Furthermore let's think about Flash memories. The smaller the floating gate, the smaller the dose you require to neutralize a critical amount of stored charge. As the feature size scales down, they could become more and more sensitive. Also radiation induced-leakage currents impacts on the data retention and they depend on the dielectric thickness.

I'm inclined to agree with the engineer who is actually building stuff for space...

Also, as you scale down, I concede it is quite possible that gates, etc. may require a smaller dose to be affected .... but the critical zones will be a much smaller target for the radiation to strike.

[EEVblog]

The first time he says it, it DOES sound like Tantalum, I agree.
But then Dave seems to say "Titanium"
Then he (Karsten) says something which also sounds more like Titanium (but said wrong).

I thought he said Titanium

[EEVblog]

I am not a big poster, but that was a great video - very enjoyable.

Thanks glad you liked it.

[Howardlong]

Another area of great interest is tin whiskers. There have been spacecraft losses from this.

There was an EEVBlog video some time ago about this but I've never been able to find it.

We use full fat solder, but for COTS parts they are still unleaded. You can treat the exposed pins, it's not something I've every done though.

[EEVblog]

Another area of great interest is tin whiskers. There have been spacecraft losses from this.

Forgot to ask that!
But for an 11 day mission, shouldn't be a problem.

There was an EEVBlog video some time ago about this but I've never been able to find it.

Yes, I recorded an entire 3 hour lecture on tin whiskers. I got permission to show some footage from it provided "I didn't show the whole thing"
Turns out they spat the dummy at my 20-30min video edit or whatever it was, claiming I was costing them hundreds of dollars for every view!
I keys getting panic emails every 10 minutes as they watched the view counter go up until I took it down 

[nwvlab]

I'm inclined to agree with the engineer who is actually building stuff for space...

I did for some years radiation testing on non-volatile memories. Beside there is a huge amount work in the literature on radiation effects on devices (see for instance IEEE Transaction on Nuclear Science).

Also, as you scale down, I concede it is quite possible that gates, etc. may require a smaller dose to be affected .... but the critical zones will be a much smaller target for the radiation to strike.

Actually, I didn't say: "IN GENERAL, the smaller the size, the larger the TID effects". On the contrary, I showed two opposite examples for which you can't say that there is no TID effects depedence on the technology node.

In particular:
1) Some degradation mechanisms (in this case, I was referring to radiation induced trapped charge in the oxide, which causes a threshold voltage variation) do actually depend on the gate oxide thickness (which, in turn, depends on the technology node). In particular, for ultra-thin gate oxides, the (semi-permanent) threshold voltage variation is a negligible mechanism, as there is no enough energy barrier width to prevent a quick charge neutralization by quantum tunneling. Therfore. in this example, the smaller the technology node, the smaller the permanent threshold voltage variations effects.

2) However, for non-volatile memories, things might go in the opposite direction. For instance radiation induced leakage currents permanently degrade the retention capability. It  is true that, if you have a thinner oxide, radiation has a smaller probability of creating a defect inside it (merely because you have a smaller volume in which radiation can interact). However, once a defect is created, the leakage current due to trap-assisted tunneling exponentially (and not only linearly) depends on the oxide thickness and, of course, on the trap position. Keep also in mind that the number of stored electrons scales with the technology node (for technology node around 90nm you have about 1000 electrons/bit. Therefore with smaller technology nodes you have less charge and higher chance of critically high leakage currents). The radiation-induced prompt charge loss also depends on many factors, which are technology node-dependent.

[Kleinstein]

Tantalum metal is a rather heavy hard material, but still a little ductile. So you can bend the foil, but not to often. So it's more similar to steel. Way more expensive, but at least you can buy the foil as a standard product. The high atomic weight (not much lower than lead or gold) helps for shielding, so titanium would not make much sense except for mechanical strength at low weight.

[apis]

Did Karsten say there was mostly protons in the Van Allen belt? If so couldn't you shield the craft by polarizing the hull? Or with magnets...

[Howardlong]

The inner van Allen belt is the proton belt. The amount of radiation it'll be exposed to from the van Allen belts in the few orbits before it heads to the moon will be minimal.

Magnets are used on spacecraft, particularly Earth satellites: it's a used as free means of attitude adjustment.

The amount and type of radiation a spacecraft is exposed to depends on a number of factors, including the orbital parameters and the time in the solar cycle that the spacecraft is operating.

[retrolefty]

Tantalum metal is a rather heavy hard material, but still a little ductile. So you can bend the foil, but not to often. So it's more similar to steel. Way more expensive, but at least you can buy the foil as a standard product. The high atomic weight (not much lower than lead or gold) helps for shielding, so titanium would not make much sense except for mechanical strength at low weight.

 Tantalum or titanium I think more info/facts would be useful on this. I just read this on Huffington post, but of course they could get it wrong also:

To protect Juno from the harsh environment of extreme radiation and intense magnetic field surrounding Jupiter, the team has armor-plated the craft in titanium, “and no other spacecraft has ever had to go through that kind of a design,” Bolton said. “In no other mission have we looked at it and said that we’d better armor plate this thing.”

http://www.huffingtonpost.com/entry/juno-jupiter-mission-nasa_us_577d4954e4b0a629c1ab94d2?yptr=yahoo