Application Note 13 - Mobile Radio
- 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 connector problems are encountered in mobile and ham radio?
- While we will be talking about connectors, let's not forget that these problems are also encountered with switches.
Generally, contaminants causing problems in connectors can be broken down into four classes;
- plain contamination,
- corrosive contamination,
- contamination modified by materials present in the connector itself or by other contaminants
- galvanic corrosion.
Apart from contamination, vibration of connectors can also lead to failure. The could be caused by wearing away of a protective plating, or even an action that would promote the entry of contamination into the connector itself.
Plain contamination can come from many sources as diverse as: road salts, tar and nicotine, paving material, oils, resins from trees, industrial origin airborne materials, plant resins and plasticizers given off by upholstery, carpeting, undercoating or paints and plastics. While these contaminants are more often found in mobile applications an may actually be concentrated through location of equipment modules near heating vent, or air-conditioning outlets. They are may also be found in the home or office environment as well.
Typically, the contaminant materials will form a thin film on the contact's surface where they will cause problems ranging from simple intermittence and distortion, to RF demodulation. In data circuits or microprocessor-controlled equipment even a single malfunctioning contact can crash the system.
Corrosive contaminants are, as their name implies, chemicals that once in place within a connector, can and will cause corrosion either of the surface plating on the connector parts, or, more serious, cause corrosion of the underlying substrate metal. Because corrosion products occupy more space than the original; metal, they can form pockets which can force clean contacting surfaces away from each other causing the connector to fail. Some contaminants can even penetrate the thin gold plating that is commonly used, destroying the underlying material. This is often encountered in card-edge connectors in the chemical or pulp-and-paper industries.
Some metal plating can micro-crack when they and the materials on which they are plated are formed during the process of manufacturing the connector. A good example of this would be tin-plating, which during temperature changes, undergoes a crystalline-lattice-modification which actually alters the dimension of the material, leading to enlargement of the cracks and, as a parallel problem, "spalling" of the plated surface from the substrate. In this situation, potential corrosive materials can accumulate under the plating; leading to premature failure of the connector. We have encountered cases where storage and shipment of these types of connectors in corrugated cartons (without a sealed plastic protective bag) can cause failures due to the migration of sulfate and sulfides present in the cardboard itself!
We don't think we have to dwell on the effects of the salts used to melt ice on the highways, or salt contamination in ocean-side areas, but people forget that various salts such as calcium chloride, are also used to hold moisture in gravel roads and road foundations.
The third class of contaminants are those, such as low saturation oils, which while they themselves don't cause problems in their original state, can be cross-linked into polymer films because of the presence of other contaminants. For example, many plastics used in connectors are thermosetting resins and contain catalysts or curing agents which can act on unsaturated oils or partially saturated oils to make them cross link into gummy varnish-like films. The same sort of thing can be caused by some of the rubber materials encountered in connectors or even in automobiles. Where connector materials use the so-called free- machining alloys, the presence of the sulfur which gives these alloys their machinability can cause cross-linking of oils and subsequent connector failure.
The final class is that of galvanic corrosion. This occurs where two dissimilar metals are used in contact in the connector. Not normally found in connectors supplied as mating pairs by reputable manufactures, they are most often found where the male and female connector parts are obtained from different sources. One of the worst matches of this type would be the use of a good gold-plated connector mated to an aluminum bodied connector. More typical are die cast connector shells (forming the ground circuit) which are mated with silver plated components.
The dissimilarity of the metal itself will generate a potential between the connector components which can result of disintegration of the donor metal and or plating of the donor metal onto the other component.
- What are Stabilants' uses in mobile radio equipment?
- Stabilant 22 can be used wherever electrical contacts are Used, whether this is in connectors, or in switches. Whether the application
is ground, marine, or airborne based the number of places where Stabilant 22, Stabilant 22A or Stabilant 22E, can be employed, are almost
too numerous to list.
Whether the radio installation is a small compact unit as carried by personnel, a car or truck mounted unit, or even a large base station, it will usually have bee designed in a series of modular units interconnected using a variety of connectors. It is on these connectors, as well as the various switches and integrated circuit contacts, that the Stabilants can be used to increase reliability. With many circuits designed to use minimum of power, such as CMOS frequency synthesizer modules, the power level in the individual contacts are often so low that even a very small amount of contaminant film will either prevent the units from functioning, or lead to false frequency information being entered. With the increasing sophistication of mobile equipment, it is not unusual to find this power-conservation type of design excepting in the final power-amplifier itself. This is done in order to conserve power and/or minimize heat-dissipation requirements.
Many portable units are more likely to fail under severe usage and environments conditions, which is often when they are needed most. A good example of this might be a severe storm when radio communications are imperative because of power outages. The very weather conditions encountered, together with the intensive usage of the equipment can often combine to knock it out of service, just when it is desperately needed.
When connections are less than perfect, thin-film-rectification or oxide-film-rectification effects may occur, making the system more susceptible to the electromagnet pulses caused by lightning. These may also cause side-band spatter or reduce side-band rejection as well as leading to lowered signal to-noise ratios by making the system more susceptible to RF interference from many from other sources. The result is often a jamming of the unit when it is used near high-power sources of RF such as AM, FM or TV transmitters.
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 multi-pin IC's. Here it almost eliminates the possibility of bending-under a pin on a IC.
The Stabilants function from DC up through several Gigahertz, at current densities covering the complete range of available connectors. They are used from -70°C up t 210°C and even higher when under pressure.
- 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.
- 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.
- 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