4 ms·

Caltech had a freshman course like this in the mid-80s, using a homebrew low-tech process. The dire warnings about hydrofluoric acid have stuck with me ever sin

Caltech had a freshman course like this in the mid-80s, using a homebrew low-tech process. The dire warnings about hydrofluoric acid have stuck with me ever since. It was fun to try to lay out your gate to take as little area as possible -- fun you can revisit at http://www.zachtronics.com/kohctpyktop-engineer-of-the-people/ http://www.zachtronics.com/kohctpyktop-engineer-of-the-peopl... I was 17 at the time too, but doing it on your own is something else.

s0rce 9y ago
HF is dangerous and you definitely need proper PPE and calcium gluconate + a shower accessible but lots of us, myself included, work with it routinely. warning: I'm not advising you go home and start etching silicon oxide and cleaning wafers with vats of HF without doing adequate research and preparation to do it safely.
- wrycoder 9y ago
  This! Working on a small scale, say 40 mm wafers, you’ll be dealing with small amounts of HF - approximately 250 ml. But. There are two problems with HF: first, it doesn’t give a burning sensation like other acids, so there is a tendency to discount the seriousness of a major spill once you get past the shower off stage. Second, it is rapidly absorbed transdermally and causes an insidious necrosis, but, more importantly, it can affect blood potassasium balance and cause heart failure after some delay. While the emergency rooms on the peninsula are aware of the risk and the treatment, that may not be the case in rural Iowa. So do the homework, have a supply of gluconate on hand, and get to the emergency room right away (with the msds) if you wet, say, more than 50 sq cm of skin with HF. Not all people are susceptible, but EKG monitoring is essential following major bodily contact. Always wear gloves, and test them. Since HF doesn’t give a burning sensation, it’s easy to get a small puncture and an HF burn. I remember one older tech who was lax about this and he lost fingernails over time. He would joke about soaking his hand in a bucket of water by his bed so he could get to sleep. Pioneer days!
  - s0rce 9y ago
    If you do get some on your hands/fingers I've been told to carefully wash your nails and cuticles because it can linger there unnoticed.
kurthr 9y ago
APh9 -a great class. Of course you can still buy HF chrome cleaner in a spray bottle! https://hpd.nlm.nih.gov/cgi-bin/household/brands?tbl=brands&id=22001046 https://hpd.nlm.nih.gov/cgi-bin/household/brands?tbl=brands&... It doesn't look as strong as the 2% solution PepBoys used to sell, though.
- abecedarius 9y ago
  Looks like they still have it! http://nanofab.caltech.edu/classes/aph9.html http://nanofab.caltech.edu/classes/aph9.html I'd forgotten the course name.
- s0rce 9y ago
  I think some rust removers also contain HF.
  - zzazzdsa 9y ago
    Yep, Whink brand rust remover is 4% HF. It's a somewhat useful source of hydrofluoric acid in a pinch. I recall a procedure for making uranium tetrafluoride from uranium trioxide (which in turn was extracted from uranium ore) using that brand of rust remover as the acidic fluoride source.

s0rce 9y ago

HF is dangerous and you definitely need proper PPE and calcium gluconate + a shower accessible but lots of us, myself included, work with it routinely. warning: I'm not advising you go home and start etching silicon oxide and cleaning wafers with vats of HF without doing adequate research and preparation to do it safely.

wrycoder 9y ago
This! Working on a small scale, say 40 mm wafers, you’ll be dealing with small amounts of HF - approximately 250 ml. But. There are two problems with HF: first, it doesn’t give a burning sensation like other acids, so there is a tendency to discount the seriousness of a major spill once you get past the shower off stage. Second, it is rapidly absorbed transdermally and causes an insidious necrosis, but, more importantly, it can affect blood potassasium balance and cause heart failure after some delay. While the emergency rooms on the peninsula are aware of the risk and the treatment, that may not be the case in rural Iowa. So do the homework, have a supply of gluconate on hand, and get to the emergency room right away (with the msds) if you wet, say, more than 50 sq cm of skin with HF. Not all people are susceptible, but EKG monitoring is essential following major bodily contact. Always wear gloves, and test them. Since HF doesn’t give a burning sensation, it’s easy to get a small puncture and an HF burn. I remember one older tech who was lax about this and he lost fingernails over time. He would joke about soaking his hand in a bucket of water by his bed so he could get to sleep. Pioneer days!
- s0rce 9y ago
  If you do get some on your hands/fingers I've been told to carefully wash your nails and cuticles because it can linger there unnoticed.

kurthr 9y ago

APh9 -a great class. Of course you can still buy HF chrome cleaner in a spray bottle! https://hpd.nlm.nih.gov/cgi-bin/household/brands?tbl=brands&id=22001046 https://hpd.nlm.nih.gov/cgi-bin/household/brands?tbl=brands&... It doesn't look as strong as the 2% solution PepBoys used to sell, though.

abecedarius 9y ago
Looks like they still have it! http://nanofab.caltech.edu/classes/aph9.html http://nanofab.caltech.edu/classes/aph9.html I'd forgotten the course name.
s0rce 9y ago
I think some rust removers also contain HF.
- zzazzdsa 9y ago
  Yep, Whink brand rust remover is 4% HF. It's a somewhat useful source of hydrofluoric acid in a pinch. I recall a procedure for making uranium tetrafluoride from uranium trioxide (which in turn was extracted from uranium ore) using that brand of rust remover as the acidic fluoride source.