Greg,
I don't remember if the foam in the HP boxes was glued in or if it was
cast in place but I thinnk it was glued in. But it was a very dark gray and
almost black color and it was an open cell foam with very tiny (~ 1/32")
cells. In the open areas where nothing had touched it the foam would look
fine until you touched and when you did, it just collapsed with no
resistance. It usually crumbled to a dark powder and you could wash most of
it out with soap and water but it always left a certain amount behind that
was nearly impossible to remove.
Besides that used by HP, i've also seen sheets of anti-static foam that
ICs were stored in and it did pretty much the same. It would just crumble
without being touched and it would attack the legs of the ICs and
occasionally completely eat them away from the IC body.
I will look around on the internet and see if i can find any pictures.
On Tue, Mar 16, 2021 at 12:11 PM Greg Muir via groups.io <big_sky_explorer=
[email protected]> wrote:
A couple of questions and comments.
I see you have indicated that there is a foam product present in the
container. Can you better describe the appearance of it to help define
what it is? Yes, there are foam products releasing agents that can cause
deleterious effects on metals and such.
What type of container are the plug-ins housed in? You mention that the
container is ¡°¡almost fully sealed¡¡±. One must remember that through
ambient temperature changes air tends to expand and contract. This allows
any container that is not totally sealed to ¡°breathe¡± and allow any
external humidity inside.
Is the foam being held in place by any adhesives? I once encountered a
waterproof transit case that had standard low density foam fastened inside
with an adhesive. Over time the contents of the case showed signs of
deterioration similar to what you are experiencing. It turned out that the
adhesive was releasing a product that caused the problem. And since the
container was totally sealed from any environmental effects the inside of
the case was a perfect chamber to contain the corrosive atmosphere.
Do you live in an area that has a relatively humid environment? While
working in the tropics I came upon an older piece of HP equipment that was
supposedly in ¡°safe¡± storage but the room was not dehumidified. When I
picked it up there was heard rattling inside. Opening it up I found that
all of the discrete transistors had lost their gold plating (gold was
frequently used I those days to plate leads) and the moisture had attacked
the steel wire thereby corroding it to the point where there was no metal
left and the transistors simply fell off the printed circuit boards.
Obviously there were also signs of corrosion on other parts as well
including ¡°worm tracks¡± on the anodized front panel where the moisture went
under the sealed anodic oxide surface and made very fine random tracks on
the raw aluminum as it made its way along.
Greg
