App. Note 18 - Card Connector Cautions
What precautions have to be taken when using Stabilant 22 on card edge
When using Stabilant 22, Stabilant 22A, or Stabilant 22E,
card-edge connectors some precautions should be used to ensure that the
material can work to best advantage. On equipment that has been in use
for some time, and which may have had its card edge connectors cleaned
previously using conventional cleaners, or by using an eraser, it is important
to ensure that the female receptacle in which the card edge is inserted
is cleaned out thoroughly. Because of the design of most of these connectors,
they have a tendency to accumulate particulate contamination within the
connector body itself, especially if used in a dusty environment, or in
If any type of Stabilant is used on the card edge connector without
removing this accumulation of contamination, the detergency of the Stabilant
will loosen the dirt and it may accumulate, in the case of vertically mounted
units, at the bottom of the connector. This is especially true of the diluted
We have encountered some isolated cases where this has caused erratic operation
o the bottom contacts in the card edge row.
We would suggest that under similar circumstances, the female connector
be cleaned out using isopropyl alcohol, ethyl alcohol, or one of the numerous
spray cleaners or other type of cleaner, to be sure that al particulate
material is removed.
In rare instances, there may be a small residue of solder-flux which
has been trapped between the connector and the circuit-board,. This is
not a major problem with production equipment unless a connector has been
replaced. Once again, the surfactant action of the Stabilant could
soften this hardened flux and cause it to migrate further into the connector.
Usually this will take place within the first week to ten days after the
connector has been treated.
If erratic operation is noted on card edge connectors treated with Stabilant
22, Stabilant 22A or Stabilant 22E, we would suggest removing
the card, re-cleaning both the male card edge component as well as the
female receptacle, re-applying the Stabilant, and re-inserting the
card once again.
If silicones have been used in the past, there is a small probability
that they may have cross-linked (some metals have ions that catalyze silicone
to form a "cured" silicone or a silane, such as waterglass) to form a layer
of cured material a few molecules thick on the contact's surface. This
may be removed from the card-edge component with vigorous cleaning but
in some isolated cases replacement of the female part may be the only way
to eliminate the problem. The silicone might be removed by an alternating
washing in kerosene and isopropyl alcohol
The greases used in electronics are basically the same as other greases,
being composed of a volatile oil mixed with a soap. Sometimes the soap
is a metal, hence the term lithium-grease, or sodium-grease. Problems occur
when the oil evaporates; the residue, besides being a physical contaminant,
can often cause leakage between pins, especially if it is hygroscopic.
Once again, it is sometimes difficult to remove in this state, but to ensure
connector reliability all traces of it must be cleaned out of the female
connector. This is an obvious problem with silicone-treated connectors!
Because some of the oil treatments used on connectors employ non-saturated
oils, users should be aware, that under the proper conditions, these oils
may cross link, leading to a scummy, almost varnished appearance to the
contacts. Cross linking agents include sulfur, which is often found in
cutting-oils, and in free machining metals. Elastomers (rubber) and thermoset
plastic components of the connectors also contain cross-linking promoters
and accelerants which can make a non-saturated oil cross-link. This would
suggest that the use of rubber erasers can sometimes create a problem when
used to clean card-edge connectors.
The "varnishing" problem is sometimes countered through the inclusion
of cross-linking inhibiting chemicals in the non-saturated oils. These,
however, are usually volatile enough so that within six-to-nine
months most of their efficiency has gone.
Service personnel should never use the penetrating oils designed
for loosening bolts and nuts, to treat connectors. Not only are some of
the solvents that are often added to the material a hazard to many elastomers
and plastics, but some of the oils themselves may be very-light non-saturated
types. If the type of penetrant oil is also suggested for use when threading
metal parts, it may be based on a "sour" or high sulfur crude.
Stabilants are not subject to the problem of cross-linkage.