[volt-nuts] What made a HP3458A so expensive

[Bill Gold]

There is one other issue with the stability of the LTZ1000A besides aging.
In leaving it unpowered for a long period of time the junctions are not
biased and if there is any contamination present from the fabrication of the
wafers, the free contamination ions can migrate back to the junctions and
change the parameters for a time after being powered up again until the
biasing causes the free ions to move away from the junctions again.  I am no
semiconductor fab engineer but I have observed this when testing
semiconductors.  The breakdown voltage can change, being lower after a long
shutdown period and then be higher after it has been under power for some
period of time.  One would hope that LT would be very careful on their
products, but I have seen that when wafer fab is moved to China the product
degrades because of the dirty environment that exists there, even though
measures are taken to avoid this.  When fab occurs in the USA there is a
much better chance that the whole fab process will be much much cleaner.

I do know a lot about final testing.  I have seen this happen again and
again where the product is tested in the Far East and passes, but when it
comes back to the USA for QA sampling it fails simply due to this problem.
A lot of times the product is simply shipped to distributors for sale and
when the final customer gets it and tests it for incoming QC the whole lot
is returned to the manufacturer as defective.  Of course the manufacturer
blames the test equipment maker but in most cases I had found that the
product had indeed changed over a period of time and did not meet specs.
When left under power for a while it would return to it's original specs.
Bill

----- Original Message ----- 
From: "Frank Stellmach" <frank.stellmach at freenet.de>
To: <volt-nuts at febo.com>
Sent: Saturday, January 18, 2014 8:41 AM
Subject: [volt-nuts] What made a HP3458A so expensive


Well,

the 3458A now is in production for about 25 years , and only around 50k
units have been sold.
(That's an estimation by Joe Gellers series number collection)

As the 3458A is a niche product with homeopathic series volume, the
development, verification/validation, special reliability engineering,
selection and burn-in measures, QA costs had to be paid per unit in the
beginning.

To my opinion, especially the 3458A was designed mainly for military
requirements (Tamb 55°C). The military was willing to pay a premium (HP
= High Price) at that time. So HP was able to realize that price.

All that development budget is long paid, and after end of the Cold War,
the military does not order so many devices anymore, what caused the
problems of the T&M business (finally => Keysight, urgh!).

But as that market is tight, competitors are few, so the price is not
going down, instead it's increasing over the years, from $5900 to around
$8500.

It would be interesting to calcualte the BOM of the 3458A.
As they use many custom specific components, it should be relatively
expensive.



There is no parameter in the HP3458A specifications, that the device has
to be powered constantly to meet the specs.
Those very high 8ppm/yr. drift might apply only during continuous
operation.
During power down, the LTZ should not drift at all, as the ageing
mechanism is driven by temperature.
But there might be (there are indeed) considerable hysteresis effects.

I have set the temperature of my HP3458A to ~ 60°C, I shut it down after
usage, and the periodical comparison to 3 other references shows a drift
of less than 1ppm/year.

Frank




_______________________________________________
volt-nuts mailing list -- volt-nuts at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.