We have uncovered another interesting phenomena which has impacted our collection. As the subject line indicates, we have identified a failure mode concerning the gold finger contacts on the numerous circuit boards in our large systems. Specifically, a hard, mostly carbon (with an amalgam of other unknown atmospheric particles) film has adhered selectively to the plated gold. It is highly resistant to cleaning with anything from alcohol to acetone. The only way to remove the film is with mild abrasion ( 3M Scotchbrite ).
When the collection was first started, the large mainframes suffered from reliability issues that was subsequently tied to buildup of soot and dust on the gold finger contacts of the printed circuit boards. This was back in 2002, and alcohol cleaning did not entirely solve the reliability issue as the intermittency recurred after several months. In doing our research, we found a product online called “Stabilant 22”. It is a polymer substance that becomes conductive when a voltage differential occurs between two planes of metal, as between the contact fingers of a printed circuit board and the PCB connector. When we applied it, the problem was solved and did not recur for several years.
In the last couple of years, two of our large mainframes ( and other machines ) have became unstable once again. But this time, alcohol cleaning and application of Stabilant 22 has not fixed the problem. While evaluating the nature of the problem, I experimented by applying mild abrasion to the circuit board contact fingers, and then cleaned them with Kim-Wipes and alcohol. Previously, where no visible residue was left on the wipe, there was now a significant quantity of dark residue removed.
Once the contacts were again treated with the contact enhancer, the intermittent failures went away.
We applied this fix to all of the circuit cards in both machines and re-established the robust reliability we had experienced previously.
Our speculation for this phenomenon is that the carbon deposited on the PCB contact fingers is in the form of 2D graphene glass, which is a good insulator and quite transparent. The abrasion breaks the surface of the glass and the carbon converts to the particulate form we are used to which is easily removed with alcohol.
The step by step process we have developed to successfully restore the contact integrity is:
- Use an alcohol soaked KimWipe to first clean the contact of loose surface material.
- Lightly rub the contact fingers with a super fine grade Scotchbrite pad.
- Use an alcohol soaked KimWipe to remove the carbon rich material shown in the photo.
- Repeat step 3 till the wipe no longer accumulates material.
So far, we have reached out to a number of resources for a definitive determination of the nature of the material we are cleaning off, with no confirmation. We invite the assistance of the technical community at large to help us with this determination.