Application Note 17 - Navigational Equipment
- 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 electrical field. This occurs
at an electric field gradient such that the material will remain non-conductive between adjacent
contacts in a multiple pin environment. In addition, Stabilant 22 exhibits surfactant action,
as well as lubrication ability providing a single component resident solution to virtually all
When applied to electromechanical contacts, Stabilant 22 can provide the connection reliability of a soldered joint without bonding the contact surfaces.
- What are its uses in avionics and navigational equipment?
- Stabilant 22 can be used wherever electrical contacts are used, whether this is in connectors, or in switches. Whether it's ground, marine,
or airborne applications, the number of places where Stabilant 22/22A or 22E, can be employed are almost too numerous to list.
As any avionics technician can well attest, one of the major problems in avionics, has been that equipment that performs flawlessly on the service bench, often fails where-installed in the aircraft. This usually involves connector or wiring harness failures, these are a difficult thing to service for the technician who is often faced with working in hard-to-reach places, and expensive to the aircraft operator as well, because the aircraft is tied up during this service. Although the reduction in power requirements and the use of more complex integrated circuits has enabled avionic equipment manufacturers to reduce the size of the equipment. In this case, many installations can be handle with a one-package-unit. This permits manufacturers to offer a host of new feature on both commercial and general aviation avionics. But, as any technician or aircraft operator well knows, these improvements have not been totally free of problems.
While some of the connector problems have been moved from the previously complicated multi-chassis aircraft harness, into the equipment itself, where the complexity of the circuitry together with the very-low current levels in the contacts has increased the connector-related service problems! The use of microprocessors in avionics has made it much easier for a host of extra features to be added; once the microprocessor is there, because implementation of these features is simply a matter of adding the extra routines to the internal software (via the ROM or EPROM)> This type of system is more prone to "crashing" because of a contact problem.
There is also the problem of EPROM-based databases to consider. In Loran-C equipment, as in GNS, for example, the requirement for databases that can be updated periodically in order to accommodate new frequency, or other airport /nav-aid information means that EPROMS have to be socketed. Because of the vibration and cyclic pressure environment, these sockets, as is the case with most aviation connectors, are much more prone to contaminant-penetration; an IC socket that is virtually 100% trouble free in an on-the-ground application, such as a computer; may be quite prone to contaminant-based failures in an airborne avionics application.
Increasingly, the Stabilants are being used to overcome these problems. The increased contact integrity in this environment is a result of several factors. Under vibration conditions, small relative movements of contacts, because of "stiction" effects, are usually more abrupt, and thus accompanied by microphonics that can introduce spurious signals. As the thin-film contaminant level increases, the microphonics grow worse as the contacting surfaces encounter a non-homogeneous distribution of contaminants, some of which, being corrosion by-products may also exhibit rectification effects. The latter can not only alter waveforms and change critical timings, but can made the connector prone to RF interference. Simple lubrication of the connector can sometimes minimize these problems by allowing a wiping action that can wipeout some of the layer of contaminants. But if the use of this type of treatment is accompanied by problems of "varnishing, i.e., cross- linking of the oil, the solution is only of a temporary nature.
By providing a lubricating film that won't cross-link, Stabilants address this part of the problem. But they also have a good detergency and thus will keep existing contaminants both from adhering to, and being burnished onto the contact surfaces. The electrically active properties of the Stabilants also counter any rectification effects by penetration corrosion films. And, of course, the very presence of the Stabilant material prevents many contaminants from entering the interstices of the contacts.
The Stabilants thus can substantially improve the reliability of multiple (interdependent) package installations as well as improve the reliability of single package units. With the increasing costs of avionics service the savings can be considerable.
In instrument landing systems, the use of the Stabilants has been proven to cure most connector related problems, especially where the operating environment is less than ideal. This is also true of VOR'S, VORTAC'S, NDB's and marine beacons. Often these navigational aids are located in remote, difficult-to-access places, where a major part of the maintenance time is just getting to and from the site! Added to these costs is the necessity, in many cases, of verifying that the repair work is in calibration.
Many navigational aids are more likely to fail under severe weather conditions, which is often when they are needed most. When connections are less than perfect, thin film rectification effects may occur, making the system more susceptible to the electromagnetic-pulse side-effects of lightning. These same connector faults can also make the system more susceptible to RF interference from the facility itself, or from other sources.
With the increasing sophistication of the equipment, it is not unusual to find that the power level of the individual circuits has been substantially reduced in order to conserve power and/or minimize heat-dissipation requirements. The result is that man of the connections in the system are operating at much lower current levels, and thin film effects are proportionally more important in determining reliability of the connections.
The number of connections in most systems has also increased substantially. And while microprocessor control is now making it easier to perform self-checks on some of the new equipment, it has made the same equipment much more sensitive to connector problems, whether they be card-edge connectors or those in socketed IC's.
While the material was designed to substantially increase the reliability of all forms of contacts, Stabilant 22 is also finding increased use as an insertion lubricant for multiple-pin IC's. Here it almost eliminates the possibility of bending-under a pin on a IC.
We have even been told that some maintenance personnel, are applying Stabilant 22 to the pins, as well as to the finger stock contacts used on transmitting tubes in order to reduce parasitics.
- Why should we use Stabilant over less expensive alternatives?
- Granted that the material itself is expensive, however it is unique in having a very long useful life once in place. Unlike other so-called
contact treatments, Stabilant 22 will not cross-link (becoming varnish-like) under the action of sulfur based curing agents in
elastomers, cutting oil residues, or the sulfur-bearing free-machining metal alloys used in some contacts. In most types of service work,
the cost of the down-time involved in removing and replacing a board will be much greater than the cost of the Stabilant used to treat the
board. Here what is important is that not only will the proper board treatment cure existing contact problems, it will prevent others from
occurring, thus eliminating the necessity of repeating the treatment at a later date!
In other words, why do a job more than once?
- In what forms is Stabilant available?
- The Stabilants are available in several forms. As a concentrate (Stabilant 22), an isopropyl
alcohol-diluted form (Stabilant 22A), and an ethyl alcohol diluted form (Stabilant 22E).
For example, a given size container of Stabilant 22A will cost about one-fifth the amount of a
container of Stabilant 22 as it contains only one-fifth the amount of the concentrate. Another form
of packaging is available. Stabilant 22S packages the concentrate such that it occupies one-fifth the
volume of an otherwise empty container. This allows the end-user to add his own diluent, and thus saves the
added costs of shipping the diluent (e.g.: isopropyl alcohol), as well as allowing the end-user to use an
alternate diluent such as one of the Freon-based solvents.
In addition a 0.5 ml vial of Stabilant 22A is available for manufacturers to include with plug-in circuit boards
- What is the difference in use of these materials?
- Stabilant 22 is most useful where the connections are out in the open - such as card-edge connectors or where the lubricating properties of the material are useful -such as an aid to installing microprocessor IC's or on switches. Where the connections are not too easy to get at or where the user wishes to apply the material to something such as a socketed IC (without removing the IC from its socket), it is easier to use the alcohol diluted form (Stabilant 22A or Stabilant 22E). The alcohol diluent serves ONLY to carry the concentrate into the connector.
- Is it available in a spray can?
- No. Why waste the material? We would like to think we are environmentally responsible and safety conscious. This ruled out
the use of either a chlorofluorocarbon or highly inflammable mixture of butane and propane as a propellant.
In addition even Stabilant 22A for example, has only about 71200th 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 organizations!
- Is Stabilant 22 just another contact cleaner?
- No, Stabilant 22 is a resident potentially electrically active material 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.
- Just how much should be used?
- Normally, a final film thickness of from 0.5 to 2 mils of the concentrate is all that it necessary. In other
words, you want just enough to fill up the interstices between the contact's faces. When using Stabilant 22A,
or Stabilant 22E, use enough so that once the isopropyl alcohol (or ethyl alcohol), evaporates the desired
0.5 to 2 mil film of Stabilant 22 remains.
In applications to moving surfaces, such as in slip-rings or potentiometers, film thickness should be minimized to the point where "hydroplaning" won't occur.
- What is the 15 ml service kit?
- This was made up at the request of several manufacturers who wanted a standard kit that they could issue to their service personnel. It consists of a 15 ml dropper bottle of Stabilant 22A and some applicators, all in a small capped cardboard tube that can be tossed into a tool box without damage. As noted, we can provide these kits with special labels when large volume orders are involved.
- Why would anyone want to buy large quantities of the concentrate?
- Many manufacturers make large volume purchases, diluting the material for specific applicators used on their production lines.
Many end users have found that the material cuts their service costs so much that is more economical to purchase Stabilant 22 in the larger container sizes rather than run any risk of being without the material. The number of uses tends to increase users discover the large number of problems that can be solved by the material. One user routinely applies it to the flashlight switches and batteries it issues to its security guards and has reported that the number of requests for replacement units has dropped appreciably.
- How can I be sure that Stabilant works?
- The best way to find out just how well it works is to try it out; that's why we have samples available. Almost every service shop or manufacturer has equipment available where the switches or connectors have become erratic over the years. Use Stabilant 22/22A/22E on them and satisfy yourself. A word of caution. Don't try to evaluate Stabilant 22's performance on brand new connectors. Instead, use it on connectors that are corroded, or dirty or just plain unreliable. We are sure that any organization dealing with electronics will have at least one piece of unreliable equipment on which the Stabilants can be tested!
- Can I use Stabilant 22 in other equipment?
- Yes, it can be used in test equipment, cameras, just about everywhere there's a low-voltage signal or control connection. For example,
the effect of Stabilant 22 in Computers is to reduce the number of times the system locks-up or crashes, sometimes it even
eliminates non-software crashes completely.
When used on socketed IC's, photo-couplers/isolators, rotary, push button, or slide switches, or even on BNC connectors, the net effect is usually to make the proper operation of the equipment less erratic, and in the case of IEEE-488A buss- controlled equipment, to cut down on the potential for system lock-ups.
- Stabilant 22 has already been TSO'D by a major avionics manufacturer.
- The Stabilants have also been used in flight simulators.
- Is Stabilant hazardous to use?
- Stabilants have very low oral toxicity. Under normal workplace conditions no skin sensitization effects have been noted. In the undiluted form, it is non-flammable although if heated above 200° Celsius the decomposition products would burn. And Stabilants are environmentally friendly materials.
- What is the best way to apply Stabilant to a contact?
- The 15 ml (and the 50 ml) container have "controlled-dropper" type caps that allows Stabilant 22A to be applied directly to such components as socketed IC's, switches, connectors, etc. Some end users prefer to use industrial syrettes to apply the material. Camel's hair brushes can 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?
- In some field trial applications lasting over fifteen years Stabilant 22 has shown no 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 oils, Stabilant 22 will not cross-link when exposed to free machining materials such as 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".
Stabilants™ are a product of Dayton Wright research & development and are made in Canada
NATO Supply Code 38948
15 ml of S22A has NATO Part # 5999-21-900-6937