Chemicals for Electronics
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Freon has for so long been demonized as a destroyer of the ozone layer and has so thoroughly disappeared from consumer grade products that I had forgotten that many moons ago I and others used it on a regular basis for cleaning electronics assemblies. Freon 12, methyl chloroform (aka 1,1,1-Trichloroethane ), and methyl ethyl keytone (MEK, aka butanone) were all very common cleaners for removing contaminants prior to soldering and for removing flux after soldering in the days of 60/40 Sn/Pb solder and RMA (rosin, mildly activated) flux. Call me a heretic of the green movement, but I still use 60/40 rosin core solder for all my electronics work. In fact, I just ordered a new 1-pound roll of it from Kester, along with a bottle of liquid RMA flux. I have changed over to Pb-free solder for plumbing, although I'm still a bit nervous when using it - especially when soldering into installed pipes that have been plugged with a piece of bread to (hopefully) keep the area dry long enough to sweat a good joint. The higher melting temperature of Pb-free solder versus 60/40 (430°F vs. 370°F, respectively) requires either holding a propane torch on the joint for a really long time (especially for >½" pipe) or using MAPP gas (which costs 4x as much). The Pb-free water-based flux does, admittedly, clean off much easier than RMA flux. Here is Part 2. Getting to Know Degreasers, Cleaners, and Polishing Agents
It is surprising that so few electronic-experimenters make use of the many chemical aids available to them from innumerable jobbers and distributors. Store shelves hold a wide variety of chemicals and cleaners in either convenient aerosol cans or bottles. Many of these chemical tools should be as important to the experimenter as a good screwdriver or a pair of pliers. Chemicals can be used for everything from heat sinks to troubleshooting, although this particular article will concentrate on control and contact cleaners, chemicals for the audiophile, and tuner or bandswitch spray cleaners. Types of Cleaners. Sooner or later every electronics hobbyist encounters problems with "noisy" contacts, raspy potentiometers, erratic switching and/or sticking relays. If you know what is behind the advertising claims and verbiage, you can pick the right cleaner off the shelf to solve each problem. In the very early days of radio and electronics, carbon tetrachloride was the most universally used cleaner. Many experimenters think carbon tet is still the basis for most cleaning chemicals - but in 9 cases out of 10, this is not so. Carbon tet is both an inefficient and dangerous cleaner. Fumes from carbon tet are approximately 200 times as toxic as those of most modern electronic cleansing compounds. Today, cleaners are usually blends of Freon solvents. Freon is Dupont's registered trademark for chlorofluora derivatives of methane and ethane. There are two types of Freon generally used in aerosol contact and control cleaners: Freon 12 - a propellant that provides only slight cleaning power, but supplies the necessary pressure to spray the cleansing formula out of the can. Freon 11, on the other hand, is similar, but in itself is an excellent cleaning agent.
This is exactly what you want a cleaner in an aerosol can not to do - be flammable. Though spectacular, a test like this is relatively safe in a wide open area. Freon is nonflammable, relatively nontoxic and stable in use. Freon 11 is a selective solvent meaning that it dissolves oils and greases, yet will not affect most metal contacts, common plastics, or carbon-type potentiometers. In cleansing action Freon 11 ranks above hydrocarbons and just below chlorinated solvents. Besides dissolving oils and greases, Freon 11 also provides a "washing" action, especially if sprayed on the target area under high pressure. The high density and low surface tension of Freon 11 enables this solvent to thoroughly wet the surface of most materials thereby washing away dirt and "gunk." The Allied Chemical name for a solvent roughly equivalent to Freon 11 is Genesolv-D. In fact, Genesolv-D has the same mouthful of a name as Freon - trichlorotrifluoroethane. The Dow Chemical Company sells two similar types of chemicals used by some manufacturers in the electronics industry - Chlorothen NU and Dow Clene EC. The above basic chemicals are blended by the various manufacturers of electronic cleansing chemicals to produce commercial products, None of the manufacturers is willing to reveal the formulation of its cleaners, so it is impossible to know - by true chemical definition - exactly what you're buying. Nevertheless, any cleaner incorporating any of the above mentioned chemicals is good. The problem in electronics is to avoid the cheaper products which use kerosene, benzine, or denatured alcohol as solvents. You can usually detect any of these products by the smell. They are also flammable and should be so identified on the can or bottle. These products may also be cheaper, but you pay for this cost saving through detuned circuits and deformation of soft plastic parts. For every experimental application you are better off to pay a little more money for a better and safer cleaner. To Lubricate or Not to Lubricate. Aside from the cleansing action, some electronic aerosol chemicals also include lubricants. Lubricants not only reduce the friction of moving contacts, they may also minimize arcing and provide a protective coating to inhibit further corrosion. Lubrication, however, is not an undisguised and unmixed blessing. A heavy residue of a lubricant can detune a critical circuit and for this reason, most electronics technicians prefer non-lubricating cleaners for work around critical tuned circuits. Until the late 1960's, hydrocarbon lubricants were seen in most cleaning solutions incorporating a lubricant. Since hydrocarbon lubricants are organic, they are not particularly long lasting or known for their chemical stability. In addition, the hydrocarbon lubricant is itself flammable. Today, some of the newer electronic chemical cleaners use silicone lubricants. Organic lubricants are hydrocarbon polymers, but silicone lubricants are derived from silicon-oxygen linkages which should give this sort of lubricant better high temperature capabilities. Silicone lubricants generally last longer and are inert. Whereas hydrocarbon lubricants sometimes break down under application of high voltage or heat, leaving a carbon residue, synthetic silicone lubricants seem to withstand greater variation of voltage and temperature without noticeable ill effects.
Read the label before buying. For most cleansing operations around tuned circuits you will probably be better off with a non-flammable chemical that leaves no residue. Look for a possible warning about use around plastics and if in doubt check as described on the next page. As with all aerosol cans, be circumspect about disposing the empty can. Caution: Contents under pressure, do not puncture, throw into fire or store in direct sunlight or in temperatures above 120°F. Avoid prolonged breathing of the vapors. Do not spray open flames as the contents can decompose and produce toxic gasses. Not to be taken internally, Keep Away From Children. Polishing. Recently a new dimension has been added to switching contact sprays: polishing. In addition to cleansing and lubrication, these new products attempt chemically to assist the polishing of switching contacts through the normal wiping action of the switch itself. However, cleaners containing polishing compounds must be used with care. Many switch contacts in electronic equipment use a precious metal plated on a base metal. It is quite possible for the polishing agent - if it is abrasive - gradually to serape away the thin precious metal plating - along with the dirt. Once the base metal is exposed, it tends to corrode rapidly, ruining the contact. Various manufacturers are currently emphasizing the incorporation of polishing compounds in their cleaners. One manufacturer calls polishing, "the continuous cleaning method," while another emphasizes the non-abrasive polishing agent in his cleaner. Regardless of the advertising claims, all cleaners that clean, lubricate and polish have particular applications. The basic ground rule calls for a moderately thick permanent lubricant that is less likely to "run" into adjacent circuitry. These cleaner/polishers must be applied with considerable care - just on the contacts - and in the case of TV tuners or band switching components in receivers or transmitters - never near capacitive, sensitive devices. Making Your Own Tests. A few "recommendations" prepared by the Editors of Popular Electronics appear in conjunction with this article. However, if you encounter an unknown chemical cleaner, here's a quicky test you can use to get an idea of just what you have bought: 1. Spray the cleaner onto a clean piece of white paper. Smell it carefully to see if you can detect the odor of alcohol, kerosene, or camphor. If any of these odors are detected, use this cleaner ONLY on equipment that you can sacrifice. 2. Feel the paper you have just sprayed with your fingertips. If the product is advertised as including a lubricant, you should be able to feel it. Rub the paper between your thumb and forefinger to see if there is any decrease in lubricating action. Simultaneously, if the product is supposed to contain a polishing agent, you should be able to feel an initial grittiness. This grittiness should disappear after a few rubs. If the grittiness persists, this product should be rejected or used with care. 3. If in doubt as to the action of the unknown cleaner on plastic, lightly spray it on several types of scrap plastic. A good cleaner will have no effect on plastic-neither dissolving it or making it turn cloudy.
For effective spraying many aerosols have hollow extension tubes that plug into the release button. 4. As illustrated in the photograph on page 26, carefully spray the unknown cleaner directly at a lighted match. There should not be a "flame thrower" effect and if the product supports combustion it should be rejected. However, certain reputable products will decompose in a flame and produce toxic gasses. Do this experiment last - and do it carefully. Chemicals for Audio Equipment Maintenance. Chemicals can be very useful in maintaining hi-fi and stereo equipment. The most obvious use is in cleaning. Aerosol chemicals can be used to wash away dust and dirt from records and a few chemicals leave an antistatic charge which tends to repel the accumulation of future dust. It pays to clean your discs before use. Record changers and turntables should be cleaned with a good washing type degreaser that leaves no residue. Spindles on changers often "gunk up" and refuse to drop records properly, but this problem is easily resolved with an application of a good Freon 11 or equivalent spray. One of the more important uses of chemicals for audio is to clean tape recorder heads. Recorder heads accumulate the oxidized coatings of tapes and if they are not cleaned periodically, the heads will wear excessively and eventually ruin the tapes themselves. Some technicians still use alcohol to clean tape heads, but this is not a good idea. Alcohol is flammable, is not a particularly good cleaner, and has an adverse effect on some plastics. Even today, some commercial tape head cleaners are based on the use of isopropanol alcohol, but the better products use blends of fluorocarbons (Freons). Cleaner chemical manufacturers are at odds as to whether or not a tape head cleaner should include a lubricant. At least one manufacturer has a cleaner containing a minor amount of silicone. The claim is made that this product leaves a thin coating which permits the tape to slide freely across the head, but other manufacturers, while acknowledging this good effect, say that lubricants tend to accumulate excessive oxide coating particles. Oddly enough, tape equipment manufacturers appear to have no firm views on the subject saying that any good effect may result from a lessening of wear from excessive tape tension (a mechanical defect).
As above, choose your tape head cleaner by the smell and feel. Reject anything that feels abrasive or smells like alcohol. Chemicals for Cleaning R-F Circuits Many hams and SWL's tolerate erratic bandswitches when these defects could be readily cured through the application of a TV tuner spray cleanser. Generally speaking, although these products are advertised for TV tuners, they will obviously have the same beneficial effect in a receiver, transceiver, or transmitter. Tuner sprays usually fall into one of four relatively distinct categories: 1. Pure cleaners. Sometimes referred to as "wash" cleaners, these products are generally based on a blend of Freons and may be sprayed on TV tuner contacts or band switches with the assurance that they will leave no residue. These cleaners are especially recommended where foreign matter of any kind might unbalance a critical r-f circuit. 2. Cleaners with light lubricants. It's probably safe to say that these are the traditional TV tuner spray cleaners. These products work reasonably well, but may need to be reapplied to the same switching or contact area within a year. 3. Cleaners with heavy lubricants. This type of spray cleaner is becoming increasingly popular. They may usually be distinguished by the "foaming" action. Many technicians believe these products to be preferable, since they tend to keep tuners and bandswitches in good operating condition for longer periods of time. 4. Cleaners with heavy lubricants and polishing agents. This is a relatively new category and may well eventually replace those cleaners mentioned above in category 3. Any cleaner should be applied to a tuner or a bandswitch with care and the degree of care should follow the numerical order indicated above with category 4 being applied only to switching contact surfaces. Virtually any bandswitch or tuner cleaner will temporarily detune an r-f circuit, but if the cleaner is a good one, the chemical preparation will evaporate in about three minutes and unless the cleaner has been misapplied, no touching up or slug tuning adjustments should ever be necessary. A follow-up article will describe the use of highly specialized chemicals for electronics - including insulating compounds, coolers, etc. with emphasis on troubleshooting techniques.
Posted March 1, 2019 |
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