Contact Cleaning Demands, Dangers, and Developments

by: Mike Jones and Jay Tourigny
Pages: 31 - 36; January, 1995

Over the past decade, chemists and engineers around the world have put enormous resources into the development of ozone-safe electronics cleaners. While it has not been an easy battle, their success has become clear as CFC consumption has plummeted. One industry estimate puts current CFC usage down 60 to 70 percent from the 1986 high-water mark.

Despite all of this innovation, all we’ve done is "shoot all the slow rabbits" as they say in Texas. Many precision cleaning applications remain tied to CFCs because none of the new alternatives meet the performance requirements. Of these, one of the largest remaining CFC applications is contact cleaning.

Contact cleaning is essentially a manual procedure that does not readily lend itself to automated or batch cleaning practices. Dispensed as an aerosol spray, these cleaners are found in virtually all aspects of the maintenance, repair, and system integration of precision electronic devices and mechanical equipment.

Though contact cleaners are effective only for the removal of light contamination such as oils, dust, fingerprints, and grime, many of today’s precision electronics are sensitive to such limited contamination.

Test for the Best

Feedback from engineers and technicians has proven that contact cleaning is an important industrial process that cannot be ignored without risk to workers, the public, and the economy at large.

At Tektronics (Gaithersburg, MD), eliminating noise on the circuits of highly-advanced electronic test equipment is critical to calibration processes. No longer able to use CFCs, the company has tried HCFCs, ethanol, and several slow-drying solvents — none of which have been satisfactory.

Warranty repair supervisor Bob Pelton reports that the main problems included long drying times, residues, solvent entrapment inside potentiometers, and safety issues. Low flash points are often cited as the primary safety concern.

Contact cleaners commonly are used on equipment that’s electrically energized, often with high voltages. While it would be simpler to clean with the power off, often the costs associated with shutting down a machine are high, the machine must be running to confirm cleaning effectiveness, or a system’s function is so essential that it does not allow for even a brief shut-down for cleaning.

Examples include process controllers for high-speed textile looms, telephone switching equipment, power-generating stations, and the radar and radio systems at every major airport.

Electrically-energized circuits produce heat and open electrical arcs; both are potential sources of ignition and represent an unacceptable risk of fire, worker injury, and property damage.

Sometimes, even when the machine can be shut down, flammable contact cleaners remain a hazard, as witnessed by Alloy Piping Products (Shreveport, LA). This maker of butt-welded pipe fittings uses contact cleaners on assorted plant machinery and systems.

Industrial safety engineer Donny Perkins reports that three electricians on his staff experimented with the alcohol-based cleaners. "We found out quickly we couldn’t use them," he says. "One of my guys powered the machine up too quickly after cleaning it and got a flash [momentary fire] from it."

Dangers Documented

This is not the only time flammables have presented a hazard. A company from the Pacific Northwest, which requested not to be named, was cleaning elevator motors with an isohexane/isopropyl blend described as a contact cleaner. But, the motor was hot; heat volatilized the cleaner, and the fumes ignited.

Even the U.S. Government is concerned. The Veterans Administration has issued a safety warning about the fire hazards from cleaning personal computers and CRT screens with flammable liquids, including isopropyl alcohol. The warning cautions about the use of cleaners containing flammable propellants.

In one case, where the cleaner was being absorbed into a paper wipe, "the static electricity inherent in all CRTs discharged into the employee’s hand and set the tissue on fire." At least one government-stocked product had to be recalled.

Ventilation also was reported to be an issue. Contact cleaners are frequently used in poorly ventilated areas such as closets, electric cabinets, control panels, and racks. Even when a machine is located in a larger manufacturing space, its electrical controls are normally inside a confined protective housing that’s relatively compact in size.

As a result, users are subjected to repetitious direct-skin contact with the liquid as well as direct exposure to solvent fumes. This makes it imperative that the cleaning agent be nonflammable and low in toxicity.

Solvent Attack

Since contact cleaning is widely accepted as a general maintenance task, cleaners must not harm components. Old-style contact cleaners were widely used because of their mildness and broad-based materials compatibility.

Many of the new cleaners react with metal or plastic components, presenting a substantial risk since maintenance workers cannot identify the plastics used in most devices. The wrong solvent could destroy connectors and motor mountings made from polycarbonates and ABS-based plastics.

Howard Montone of DBS Logics (Kanata, Ontario, Canada), in the electronics business for 25 years, is unequivocal about the new solvents.

"Ninety percent of the contact cleaners attack plastics, and that’s a serious problem," he says. "There are now many good alternatives for flux cleaning and other manufacturing situations, but the new contact cleaners need work."

Montone cites the problems of cleaning variable-resistance potentiometers, which have sensitive gold contacts. "The slow-drying solvents seem to make their own contamination," he asserts, worsening the cleaning problems.

Another engineer at a large midwestern electronics plant agrees that plastics compatibility is a major issue. "One product had been widely used throughout the plant, on our [finished] products and as a maintenance or crib-type item," he reports.

When the solvent manufacturer changed the chemical formulation, trying to remove the CFCs from the blend, "their new ingredient had a history of attacking plastics," the engineer observed. This resulted in an unexpected qualification problem, so the reformulated cleaner has been restricted to a few maintenance applications.

Because cleaning often is performed while a machine is in operation, a contact cleaner must evaporate quickly and be non-conductive. A conductive solvent can cause short circuits, destroying the machine instead of repairing it; and the longer the solvent remains on the board the greater the chance for a problem to occur.

The engineer at the midwestern plant noted that non-conductive solvents allow the technicians to bring manufacturing systems back on-line quickly, which is critical to keeping the assembly lines productive. "We’ve got almost 7000 employees making 3000 products a day, and the system must keep moving," he emphasized.

Residues a Persistent Problem

Residues from slow-drying solvents also can negate the effectiveness of the cleaning process by attracting airborne dust to the wet surfaces. Perkins’s company discovered the residue problem on its own. His team found that "anything with petroleum distillates in it leaves an oily film that we can’t tolerate."

Montone agrees that the new contact cleaners need work. "The slow-drying solvents seem to make their own contamination" and aggravate cleaning problems, he says.

Ken Lester, a manufacturing engineer at the printed circuit board subcontractor PrimeTech (Montreal, Canada), notes that his people clean more than 5000 circuit board connectors every day. Even if the slow-drying solvents added just a few seconds to the labor required on each connector, the costs could make their company uncompetitive.

Slow-drying solvents also can migrate from the surface being cleaned onto adjacent areas. They can be absorbed into softer materials or even become trapped under wiring insulation. Capillary action can wick up stranded metal wire surprisingly long distances under the wire’s insulation. The solvent then slowly leaches back down the wire and contributes to new problems such as shorting, corrosion, or slow destruction of the insulation.

Blair Weeks, a process engineer at Hughes Aerospace (Tucson, AZ), and associates found several alternative cleaners, including isopropyl alcohol, unacceptable because they became entrapped in female connectors, attracting contamination and potentially causing corrosion.

At TRW (Redondo Beach, CA), Fred Cottrell works on integrating spacecraft systems into their final assemblies. Among other things, his team is cleaning ultra-precise radio frequency (RF) cable harnesses. These complex assemblies are unique because they have virtually no signal loss over their entire length.

However, TRW’s testing indicates the insulation may absorb the slow-drying solvents, resulting in a phase shift in the RF signals. In this case, the long-term complications presented by a slow-drying contact cleaner make fast evaporation an important physical necessity.

Alternatives Explored

UNEP — the United Nations subcommittee working on environmental problems, including the ozone issue — discussed contact cleaning at a recent meeting in Nairobi, Kenya. Speakers stated that contact cleaning remains a problem and unless good alternatives are found, industry may need an exemption from the 1995 CFC phaseout.

In France alone, more than 400,000 pounds of CFCs were used as contact cleaners; if that number is extrapolated to the global market, perhaps as much as 8 million pounds of CFCs may be required.

Table 1 outlines the physical characteristics of every new alternative solvent which could have been considered for use as a contact cleaner. It’s clear that no material is completely safe for the environment and meets all of the required physical and performance attributes.

The perfluorocarbons (PFCs) are close to the ideal answer with one overwhelming exception: They are very poor solvents. In fact, very few contaminates are dissolved by the PFCs. Blending PFCs with other ingredients can compensate for this disadvantage, however.

With these requirements in mind, chemists and engineers at a number of companies have been working with PFCs to develop an interim contact cleaner until the ozone-safe HFC solvents become available in 1996.

At least three PFC blends were introduced in 1994. According to the various manufacturers, each formulation has been found to be suitable for most precision cleaning applications, including surface mount boards, hybrids, delicate mechanical assemblies, optics, precision bearings, and connectors.

Cleaners of Choice

While specific formulations vary, they’re all considered plastic-safe, nonflammable, non-conductive, and fast-drying. If these claims can be validated, these products would make excellent cleaning choices for electronic repair depots, field repair environments, and R&D prototype labs where wide varieties of components and materials are found.

Very mild, they might even be suitable for light defluxing and degreasing, although one might doubt the economic wisdom of using such costly blends when less expensive, ozone-safe defluxers and degreasers are available.

Despite their expense, PFC blends are likely to become the replacement of choice for many cleaning applications that currently rely on CFC-11 and CFC-113. The market for this premium-priced product could be as high as 725,000 pounds per year, or about 10 percent of the total contact cleaning market, with the remainder going to less expensive solvents in less critical applications.

With the impending phaseout of CFCs, the last-minute introduction of PFC-based contact cleaners will smooth the transition and serve as an interim option until other alternatives fill this market need.

About the Authors

Michael Jones, vice president of sales & marketing for Micro Care (Bristol, CT), has extensive background in the telecommunications and computer industries. He helps electronics engineers and technicians work through the complex tradeoffs these new solvents require.

Jay Tourigny, Micro Care vice president of engineering and production, actively tests and selects non-CFC alternative cleaners. He has testified before the EPA on environmental matters and, at various industry conventions, has presented a series of papers on the new cleaning chemistries.