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JAC
Joined: 24 Jul 2005
Posts: 3469
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 Posted: Tue Dec 12, 2006 11:22 am Post subject: |
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Probably the best course of action is to get some high quality air tight containers and use somthing like silica gel bags to control the moisture in the containers.
Also find a suitble location to store these containers! |
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wepwawet
Joined: 18 Mar 2004
Posts: 3019
Location: Seligenstadt - Germany
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| Posted: Tue Dec 12, 2006 11:39 am Post subject: |
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| JAC wrote: | Probably the best course of action is to get some high quality air tight containers and use somthing like silica gel bags to control the moisture in the containers.
Also find a suitble location to store these containers! |
... and wait for somebody to tell how to get them clean sometimes:-)
btw, the boards that I have displayed at home are fixed in air tight frames (I used silicone for that - the silicone itself didn't seem to harm boards or chips) |
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chip68
Joined: 19 Oct 2004
Posts: 1024
Location: Central Pennsylvania
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| Posted: Tue Dec 12, 2006 2:52 pm Post subject: |
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| wepwawet wrote: | | What about this. My guess is that a try to clean the rust will result in a total damaged lid. |
Yes, that's why the safest course of action is to DO NOTHING to clean or remove rust/oxidation (whatever you choose to call it). The only way to slow or arrest further damage is to control the environment. Silica gel, as JAC suggested, is one very good way to keep humidity at bay. Heat also speeds up reaction rates, so the chips need to be kept cool as well... But not so cold that condensation becomes an issue.
The pitting you see in Michael's MMI chip is a result of halides - i.e., salt - diffusing through the gold plating and acting as nucleation sites for corrosion. Finger oils and other surface contaminants will do the same thing over time. That stuff can be removed with a bath of denatured alcohol followed by distilled water. Let the chip air dry - do not RUB with a cloth (or anything else for that matter).
- CMW |
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metalmaker
Joined: 06 Dec 2004
Posts: 161
Location: St. Louis, MO, USA
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| Posted: Tue Dec 12, 2006 2:56 pm Post subject: |
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my background is as a mechanical engineer and I have had some study in materials corrosion process. There are several processes at work. The gold coating helps provide a barrier to EXTERNAL corrosion factors like air moisture, skin oil etc. However, INTERNAL corrosion due to poor quality metals underneath the gold cause the first symptoms. This can be from dis-similar metal under the gold, or contaminants in the metals under the gold from manufacturing (most likley). After the gold coating has started to be attacked from underneath, and the gold begins to flake away, then the external factors like moisture can begin to penetrate and accelerate the corrosion process.
Sometimes the gold coating itself has impurities, or is too thin - remember all these chips are made by companies out to make money that are supplied by other companies out to make money. That is why you will sometimes see finger prints in the "gold". It is not the gold that corroded - it is the impurities in the gold. If the product can survive its expected useful life that is good enough for the manufacturers. They are not trying to make fine art for a museum to last centuries - probably not made to last even decades - even though we would like to think of chips as immortal art.
You can try to protect from the external factors, but there is no way to protect from the internal factors. If the chip was made from impure metals it IS going to corrode over time, you can only slow it down. If you have "valuable" chips - store them in a relatively air tight cabinet with a desiccant to keep the air dry. In the US you can buy "damp-rid" in the hardware stores in bulk package to keep clothes closets dry. You can get smaller desiccant packets from some pharmacy shops for absorbining moisture in medication pill bottles - like you see in your vitamin bottles - alway has a sign on it that says "do not eat" for the idiots and lawyers.
Anyone who has seen many old IC in original 1970s foam can see that the foam itself often degrades over time and begins to attack the metals. Do not store chips in old foam! Change it out every few years if you have "investment grade" chips.
A chip that is actively corroding is like a car that has spreading rust - worth more now than later - unless extremely rare and in demand.
sorry for the diatribe
edit - I was typing this post when chip68 posted his - good info chip68
MM
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Last edited by metalmaker on Tue Dec 12, 2006 3:00 pm; edited 1 time in total |
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chip68
Joined: 19 Oct 2004
Posts: 1024
Location: Central Pennsylvania
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| Posted: Tue Dec 12, 2006 2:58 pm Post subject: |
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You can see similar pitting on the lid and pins of this C8255:
- CMW |
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chip68
Joined: 19 Oct 2004
Posts: 1024
Location: Central Pennsylvania
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| Posted: Tue Dec 12, 2006 3:15 pm Post subject: |
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| metalmaker wrote: | | However, INTERNAL corrosion due to poor quality metals underneath the gold cause the first symptoms. |
That certainly occurs, although I still maintain that it's primarily external contaminants diffusing through the gold. Deposited gold is inherently porous at the microscopic level, and the plating is so thin on these ICs that most ionic species have no problem going straight through it. When you see a fingerprint on a gold-plated chip, it's usually the metal underneath that's corroded, not impurities in the gold itself.
Oxidation actually helps protect exposed surfaces by forming a barrier between the raw material and the outside world. That's why the surface of a die is passivated - a layer of silicon dioxide (glass) is formed on top in the final stages of the manufacturing process. Damage from "oxidation" really comes from subsequent pitting or spalling.
- CMW
Edit - re: "good info chip68" - thanks! |
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wepwawet
Joined: 18 Mar 2004
Posts: 3019
Location: Seligenstadt - Germany
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| Posted: Tue Dec 12, 2006 4:26 pm Post subject: |
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I am asking myself what are generations after us will think if they read what we discussed about thirty years after the chips came up.
They maybe live threehundred years later (if mankind does it until that time) and have just 1 percent left of what we collected.
This thread may be one of the most important in case of the other "preservationist"-thread!
I guess to preserve the hardware we all should take highres-scans of all our chips and then put them in best environment for hundred years aside.
Maybe kidding but seriously I am thinking over what I do with most of my chips...
no, not kidding.
Last edited by wepwawet on Tue Dec 12, 2006 4:59 pm; edited 1 time in total |
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JAC
Joined: 24 Jul 2005
Posts: 3469
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| Posted: Tue Dec 12, 2006 4:54 pm Post subject: |
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I am going to take my own advice  |
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wepwawet
Joined: 18 Mar 2004
Posts: 3019
Location: Seligenstadt - Germany
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| Posted: Tue Dec 12, 2006 4:58 pm Post subject: nice chips are sexy |
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right said fred/JAC:-)
... just to underline it:-) |
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chip68
Joined: 19 Oct 2004
Posts: 1024
Location: Central Pennsylvania
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| Posted: Tue Dec 12, 2006 9:51 pm Post subject: |
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See my posts above.
- CMW |
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x86sniper
Joined: 19 Mar 2004
Posts: 179
Location: Hong Kong
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| Posted: Tue Dec 12, 2006 11:46 pm Post subject: |
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| wepwawet wrote: | What about this.
My guess is that a try to clean the rust will result in a total damaged lid. |
this is the case why I said eraser technique and remove corrosion is a case by case action
I would said the same thing as wepwawet for the C3 600 below
btw, chip68, is it call pitting not oxidation? |
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