[volt-nuts] LTZ1000 project build

[David]

Could this be caused by ionic contamination of the printed circuit
board?  The quick test I have used for this is to blow on the board
with a straw.

In extreme cases solving it usually involved dropping the board into
an ultrasonic cleaner with water and a bit of dish soap or TSP, then a
rinse in pure (deionized, reverse osmosis, distilled, whatever) water,
and then another cycle in the ultrasonic cleaner with pure water.  Dry
with an air compressor and then bake out in an oven.

In production, we had to run boards through a dishwasher using
detergent and pure water before loading them with parts.

On Fri, 3 Jun 2016 23:47:05 +0200, you wrote:

>
>My experience is that boxes makes the time constants for humidity longer but does not take it away. Heating in boxes takes the change due to humidity down a little but it doesn´t go away. I have had boxes with LM399 and amps for 7-10v with wirewounds for more than 20 years and they have definitely had seasonal variations. Also if you have a completely sealed box with varying temperatures the relative humidity in the box changes if the humidity is not close to zero.
>
>A 10V 2ppm ref on Ebay was said to have no humidity effect but my unit definitely varied about 20ppm due to humidity during a long humidity test. One guess I have is that some units have much longer time constants due to better sealing but I am quite sure it doesn´t go away complete. Another problem with humidity I have seen is that you may be cheated by humidity changing over the season and cancelling the aging. This happened during my first tests of AD587KRZ many years ago. During the first four months two samples both had less than 2ppm drift and the humidity in the room changed from 45 to 25%RH so they looked very promising. But during the next four months when the humidity went up they drifted 15ppm.
>
>Probably the 5 and 2ppm/C versions is manufactured in the same way. The humidity graph under severe humidity and temperature testing shows a 500pm difference for your chosen resistors. So doesn´t say so much. Hopefully they are below 1ppm/%RH with low loads.
>
>Lars