Nickel-gold plating a whole board

On a sunny day (Mon, 22 Aug 2011 20:05:57 -0700) it happened John Larkin wrote in :

I guess one of those through-head piercings that go in one ear and come out the other, balls on each side.

On Aug 23, 1:03 pm, snipped-for-privacy@yahoo.com wrote: > On Aug 22, 8:57 pm,Bill Sloman wrote: >

Since the point that was being made was that the 1988-to-2008 study released in 2010 study was totally irrelevant - a point that John Larkin had missed - you might have seen the point if you had read on.

That's precisely the wrong way around. I was making the point that the lawyers presumably had different and better evidence, otherwise PG&E would never have settled as they did.

It might scan if you knew how how exposure to hexavalent chromium pre-disposes people to cancer. It's apparently a genotoxic carcinogen, and the kind of cancer produced will depend on which tissue got the benefit of its mutagenic capacity. Are you claiming that the residents of Hinkley should only have been allowed to sue if hexavalent chromium caused just one kind of cancer?

No. The sentence I quoted, which you don't seem to be able to comprehend, quite explicitly says exactly the opposite - that many of the people who had been exposed to the contamination had already died of cancer before the survey started, and many others had moved away.

The Hinkley population in 1988 might well have already lost many of the people who might otherwise have survived to die of cancer later in their lives.

It's possible that some of the people who had cancer hadn't got it from exposure to the contaminated ground-water - it's impossible to say what has caused a specific cancer - but obviously there had been enough extra cancer cases in the town in 1993 for Erin Brokovich to make a convincing case that the 1952-1966 exposure had caused a significant proportion of these extra cancers. Since the modern cancer rate in Hinkley seems to be about ten per year, and Erin Brokovich managed to get settlements for some 600 plaintiffs - presumably reflecting no more than 41 years worth of cancers (1952-1993) this isn't implausible.

Oh, I believe in science. The problem comes in persuading you that scientifically established facts demonstrate something that you don't want to believe in.

Not totally inconsistent, it merely indicates that the toxic agent damaged a fairly basic element in every cell. A genotoxic carcinogen messes up the DNA, which drives all the rest of the cell machinery in every cell.

Unfortunately, you can't run the logic backwards. A variety of cancers doesn't rule out exposure to a single environmental toxin. Think about radioactive isotopes as another versatile toxin.

All perfectly true. but a genotoxic carcinogen can mess up any organ - it's a universal mechanism.

Hexavalent chromium does seem to be one exception to this less than universal rule.

You've once again demonstrated that you can't do joined up logic.

--
Bill Sloman, Nijmegen

And your evidence for this claim is?

No single farmer is going to dump a massive quantity of phenol into a river, but there are a lot of them, and collectively they could well dump a significant amount.

But everybody was drinking water extracted from the river, after it had been cleaned up to some extent in a municipal water plant, and there are common-law restrictions on what you can dump into some-one else's source of drinking water that go back centuries.

Formalising common-law rights. The earliest US national legislation was in that area was the Rivers and Harbors Act of 1899, and in 1910, USACE used the act to object to a proposed sewer in New York City, but the judge ruled that pollution control was a matter left to the states alone, so obviously there were pre-existing mechanisms that allowed local authorities to lower the boom on polluters.

--
Bill Sloman, Nijmegen

She didn't come up with anything new, presumably thinking that arguments that got $333 million in damages have got some kind of natural plausibility.

Fumento works for the Hudson Institute, which is the kind of right-wing think tank that James Arthur quotes uncritically, whose employees can be relied on to say things that large industrial operations would like to hear

Apparently Fumento also thinks that secondary smoking is perfectly okay and has "disputed whether the nicotine in cigarettes is addictive". He didn't go to the trouble of producing a counter-argument to the paper published in 1997 by the Nelson Institute of Environmental Medicine of New York, which suggests that ingested Cr-VI might have the effects observed in Hinkley

Perhaps he didn't know about it, or perhaps he didn't have an effective counter-argument

Which is not evidence that their health wasn't being damaged in a variety of ways by a single tolerably versatile toxin.

begs to differ.

You will certainly get ill from inhaling oxidised chromium. This doesn't guarantee that ingesting it in drinking water is always safe. One of the more interesting aspects of transition metal chemistry is that way that certain molecules can chelate the metal atom, and ship it around in a relatively inert form. Nobody seems to have looked at the drinking water supplied in Hinkley from 1952 to 1966 to work out if there were any other interesting contaminants that might have protected the hexavalent chromium in the stomach and allowed it get into the system without being reduced to the relatively innocuous Cr-III.

0.58 parts per billion is a remarkably low concentration, and you wouldn't need much chelating agent in the water to lock up all the chromium.

I did my M.Sc. in Inorganic Chemistry in 1963-64 when chelated transition metal ions were a relatively hot topic, and we got to hear a lot about them.

0.23 parts per billion, compared with the 0.58 parts per billion quoted for Hinkley. And it doesn't seem to have generated any cancer clusters so far. Perhaps the other contaminants aren't as helpful as Hinkley's might have been.

Seems unlikely. Dubbya's local influence does seem to be confined to Texas, but you wouldn't let an inconvenient fact stand between you and a sound-bite.

--
Bill Sloman, Nijmegen

other,

Well, tiny ones maybe.

John

You've cited a leftist environmental loon, proud author of such fine works as "Expanding Test and Treat in Correctional Populations: A Key Opportunity to Reduce Racial Disparities in HIV Infection."

and paid consultant for the Erin Brockovich plaintiffs.

Here's the definitive, current EPA statement:

(oral reference dose assessment)

Critical effect: None Reported Dose: 25ppm (!!)

The level they recommend as "daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk" is 3 ppb of bodyweight per day! (note: that's of body weight, not concentration in the drinking water!)

And here's a more recent literature review: J Toxicol Environ Health A. 2002 May 24;65(10):701-46. Is hexavalent chromium carcinogenic via ingestion? A weight-of- evidence review.

[...] (2) the preponderance of evidence from recent epidemiological studies of Cr(VI)-exposed workers does not support an increased risk of cancer outside of the respiratory system; (3) studies of four environmentally exposed populations are negative;

Agreed.

I saw articles to the effect that high Cr-VI levels have recently been discovered not just in Chicago, but in many, many major cities' water. If it does anything you'd think we'd know by now. I s'pose time will tell.

-- Cheers, James Arthur

Yeah, my board house talked me into trying their gold flash surface instead of pure tin for lead-free boards. It was a NIGHTMARE! If the solder paste wetted the gold, it seemed to make a decent contact. If it didn't wet, then the pad became unsolderable. The only fix was to wick off the solder, bend up the pin, scrape the pad with an Xacto blade to remove the black surface, re-tin and then solder the pin back down. if this happened on a dozen leads on a chip, I could be futzing with it for an hour per board! ARRGH! never again!

I'm not sure this is the same finish you are talking about, I don't think mine had any Nickel under the gold.

Jon

Just as you cited the response of a right wing anti-environmentalist loon.

t/0144.htm(oral reference

ll

t r g

mium.

The attention the concentration of chromium atoms in the water may be seen as a distraction from the interesting question, which would be an inventory of the chromium-containg molecules in the drinking water.

Assessing the danger of ingesting platinum on the basis of the number of platinum atoms wouldn't capture the difference between cisplatinum (cis-diamminedichloroplatinum(II))and carboplatin (cis-diammine-[1,1- cyclobutanedicarboxylato]platinum(II))

The former was the first effective treatment for testicular cancer, while the latter did roughly the same job while being much less toxic to the kidneys.

Interestingly, the effectiveness of these drugs depends on their capacity to react with DNA - they are both genotoxins, and damage all rapidly dividing cells, so the dose of carboplatin is limited by the way it also damages bone marrow and stops it generating new red-blood cells. Happily, it does mostly seem to let you kill the even-more rapidly dividing cancer cells before it completely kills your bone marrow.

We've got no idea what chromium-containing molecules were contaminating the water supply in Hinkley. We do know what the researchers cited by the FPA fed their rats, and those molecules don't seem to be toxic on oral ingestion, primarily because oral ingestion seems to reduce those Cr-VI containing moelcules to molecules containing the less toxic Cr-III. It's an open question whether a molecule including a Cr-VI atom that wasn't susceptible to reduction in the stomach might be as toxic to other organs as inhaled Cr-VI containing molecules are toxic to the lungs.

-- Bill Sloman, Nijmegen

If it didn't have the nickel undercoat, copper will diffues up and tarnish. Bad news.

We get gold/nickel boards and they solder beautifully. "White tin" is terrible.

John

So, instead of mouthing off, show the shovel..

The most interesting thing then is why the hell was there no disclosure as to exactly what occurred?

Chinese board house. Communication was not that reliable. It was 4 boards out of a batch of 50.

Hey, I found a photo from the incident!

Oh that's really bad... :) Looks like all the parts would fall off if you tapped the board.

I wonder if it is more likely there is a thin layer of solder resist remaining? Maybe it wasn't the gold at all.

--

John Devereux

Gold is like thirsty for solder. I've soldered flyleads to board-edge connectors plated with the standard gold over nickel, but you gotta be quick. Lay the tinned wire on the tab, hit it with the soldering iron and the tiniest bit of solder, and the solder flows like it's in love with gold. But if you don't take the heat away as soon as it makes a fillet, the gold will dissolve in the solder, and the solder/gold alloy generally doesn't stick to whatever was under the gold.

Good Luck! Rich

Oh it wasn't the gold, because not only did those parts not wet, but the plating didn't either, because that is COPPER! :-)

I think plain copper would have soldered better than that, eventually. Even 10 year old copper-clad solders OK after a few seconds at temperature. I remember these boards simply *would not solder*.

--

John Devereux

It sure doesn't look like gold. Maybe it was copper that had fallen off the truck on the outskirts of Longhuazhen :-)

Or maybe the same truck was hauling muriatic acid the day before ...

--
Regards, Joerg

http://www.analogconsultants.com/

learn

are

Now i get it, you tussle with Dimmie because that is a significant source of self-esteem for you. I would be much more impressed if you never responded to that group of grade school kiddies, trying to pretend to be knowledgeable.

?-))

No good. Those wouldn't keep it from the keyboard.

?-(

Nah, I just have to listen to your carping for that.