App. Note 39 - Stabilant use on PLCC's
What is Stabilant 22?
Stabilant 22 is an initially non-conductive block polymer
which when used in a thin film between metal contacts becomes conductive
under the effect of an electric field. This occurs at an electric field gradient
such that the material will remains non-conductive between adjacent
contacts in a multiple pin environment. In addition Stabilant 22 exhibits
surfactant action as well as lubrication ability providing a signal component
resident solution to virtually all contact problems.
When applied electromechanical
contacts, Stabilant 22 can provide the connection reliability of soldered
joint without bonding the contact surfaces.
How can Stabilant 22A/22E improve the performance of PLCCS?
Stabilant 22A or Stabilant 22E provide a quick an effective way of increasing
the reliability of PLCC devices through improvement of the device
The application is simple. Using the dropper-insert on the 15 mL or 50 mL bottle of Stabilant 22A (or 22E),apply small amount to the connections on the edges of the device and/or o the contacts in the socket before insertion of the device.
A soft camel's hair brush can also be used to spread the material some
saving in the amount that has to be applied. As Stabilant 22A or Stabilant
22E is just the Stabilant 22 concentrate thinned 4:1 with an
alcohol, the diluant will evaporate leaving a thin film of the concentrate
resident on the contacts. Note that from 0.25 t 0.5 Mil film-thickness
of the concentrate is all that is required. The concentrate has a very
low vapor pressure, and a life expectancy of over 12 years in service During
application the usual precautions should be taken against static discharge.
Is Stabilant 22 just another contact cleaner?
No, Stabilant 22 is a resident potentially electrically-active
which through a synergistic combination of effects enhances conductivity
within a contact without causing leakage between adjacent contacts. Thus
large quantities of the material do not have to be "hosed" on as is the
case with cleaners.
Is Stabilant 22 cost effective?
As Stabilant 22 can be quickly applied to all contacts and connectors
in a system, the often difficult diagnostic determination as to which one
of many contacts are erratic, can often be eliminated. This can significantly
reduce service time in the field and in many cases eliminates the need
to return boards for shop service or remanufacturing. As any service manager
knows, the diagnosis of electronic problems, especially where intermittent
failures are concerned, is often much more difficult than the actual part
replacement; as well as requiring service personnel of exceptional caliber.
In many cases the use of Stabilants can thus increase the efficiency
of existing staff as well as allowing many connector-related problems to
be handled at a much lower cost.
How does Stabilant 22 work?
Contact failure is rarely caused by a single factor. Thus, treatments
that solve only one problem don't necessarily offer a reliable long term
solution. For example, cleaners do not prevent the re-entry of contaminants
or the reformation of contaminant films; nor do they offer any lubrication.
They must be used each time a connector gets dirty. Lubricants in themselves
are rarely cleaners. Corrosion inhibitors are neither cleaners nor lubricants
and are often specific to one type of metal or plating. Unsaturated oils
used as contact treatments can cross-link under the influence of elastomer
or thermoset plastic curing agents and accelerants.
While resident in the connector, Stabilant 22 performs several
concurrent functions. Its very presence in the contact gap will prevent
the entry of outside contaminants. It has sufficient surfactant action
to lift surface contaminants and hold them in suspension. In cases where
corrosion products are present Stabilant 22 will penetrate them
and prevent rectification effects. Due to its high dielectric constant
it will act to form a capacitative layer which is in parallel with whatever
residual resistance exists in the contact increasing the passage of AC
signals. Given sufficient DC bias within the gaps of the contact the thin
film of Stabilant will "switch", conducting by quantum tunneling
and thus limit the resistance of the contact to a serviceable level.
Is it environmentally acceptable?
Yes. Stabilant 22 itself is non-toxic and only the isopropanol-diluant
in Stabilant 22A represents a flammability and a very minor health
Even Stabilant 22A has only about 11200th the solvent impact
as conventional contact cleaning solvents over a three year time span.
As Stabilant 22 contains no solvent, it has absolutely minimal environmental
impact and is, therefore, becoming the treatment of choice for many service
Can Stabilant be used by untrained personnel?
Thousands of applications of the consumer version of Stabilant 22
been made over a period of several years now without any reported problems.
What is the best way to apply Stabilant to a contact?
The 15 mL and 50 mL containers have a "dropper" type caps that allow
22A/22E to be applied directly to such components as socketed IC's,
switches, connectors, etc. Some en users prefer to use industrial syrettes
to apply the material. Camel's hair brushes ca be used to brush it on card-edge
connectors or they could be dipped into the dilute material. Most metering-type
liquid dispensing systems can be used as well.
Does the action of Stabilant deteriorate with age?
No. Stabilants have been used in military applications for almost fifteen
years and are also being employed in Avionics, Flight-instrumentation,
Computers, Automotive Process controls, Bio-medical electronics, and telecommunications,
to name but a few of the fields where they have been used to meet major
reliability requirements. There, they have proven themselves as an efficient,
long-term solution to both eliminating and preventing connection problems.
In some field trial applications lasting over twelve years Stabilant
22 has shown n sign of reduced effectiveness. With a high molecular
weight and a very low vapor pressure, little is lost by evaporation. Unlike
some other contact protection oil, Stabilant 22 will not cross-link
when exposed to free-machining materials such a high-sulfur brass, or when
used on contacts where agents used to promote cross linking of thermosets
or elastomers are present in the environment or in the actual connector
components. Unlike non-saturated oils, Stabilant 22 does not "varnish".