Electronic Cleaner

If it is fully activated (brought up to solder temperature), it should not leave any ionic residue behind. You might have to clean if...
1. Flux is being used so liberally that it all isn’t being heated along with the solder.
or
2. The non-ionic residue can impede with the function of the devise either short-term or long-term.

Every organization using hazardous chemicals within their facility has the responsibility to equip their facility and personnel to maintain exposure levels below the TLV. Personal monitoring badges can be used to measure exposure of a specific material. Then, depending on the threshold limit and the application, exposure can be controlled with PPE like masks, face shields, respirators, and even coveralls. If they don’t reduce exposure below the recommended limit, you will need to consider a special ventilation hood or even containment booth. As you can see, as the exposure limit gets down to a certain level, the equipment required to safely use the solvent can get impractical. At that point, your best option is to consider a safer alternative.

The personal hazard associated with a solvent is often defined using Threshold Limit Value (TLV), which is the recommended average exposure in an 8-hour day, 40 hour work week. The lower the TLV of a particular substance, the less a worker can be exposed to without harmful effects. TLV is stated on the SDS of chemical products, in additional to recommended personal protection equipment (or PPE). The threshold limit value of a solvent is generally set by the American Conference of Governmental Industrial Hygienists (ACGIH). The unit of measure is Parts Per Million (PPM). 

Yes, Chemtronics offers a full line of ESD swabs. They include foam, knit polyester, or knit microfiber heads with static dissipative handles. The proprietary handle material has surface resistivity of 1.0 x 10_10 ohms/sq, and will dissipate 99% of (5 kV) charge in 0.5 seconds. This avoids static generation, and can dissipate a charge when the user is grounded.

Yes, air duster is generally designed for use on electronics. There are a few things to watch out for:

1. Avoid spraying the refrigerant liquid, which can happen if you shake the can, or angle it too much. The refrigerant is very cold, so can damage some sensitive electronics.
2. Avoid cheap retail dusters that contain bitterant. Many retail dusters have bitterant added to prevent huffing. When duster is used in the home, there is concern that the material will be purposely inhaled (called “huffing” or “dusting”) by minors, which can sometimes lead to tragic consequences. To avoid this, bitterant is added to make the duster taste bad. This same bitterant can lead to unwanted and potentially harmful residues on sensitive surfaces like electronic circuit boards.

White residue is generally a symptom of ineffective PCB cleaning. Common conductive flux residues from the soldering process can include various unreacted activators, binders, rheology components, and saponifiers. Among these are numerous iterations of acids (abietic, adipic, succinic among others), highly basic ingredients (amino compounds), and even constituents found in “soaps” such as phosphate and sulfate ions. When a cleaner does not fully dissolve all the constituents, or the cleaner is not allowed to flow off the PCB, the remaining solvent can evaporate off and leave behind residue that is either white or like water spots.

The most common way to clean flux residues from a repair area is to saturate a cotton or foam swab with isopropyl alcohol or another cleaning solvent, and rub it around the repair area. While this may be adequate for no-clean flux, where the goal is a visually clean PCB, this may not be clean enough when more heavily activated fluxes are involved, like RA or aqueous. The dirty little secret is that flux residues will not evaporate along with the solvent. You may dissolve the flux, and some of the residues will soak into the swab, but most of the residues will settle back onto the board surface. Many times these white residues are more difficult to remove than the original flux.

One quick and easy improvement to this process is to rinse the board after swabbing around the repair area. While the solvent is still wet, spray over the entire board with an aerosol flux cleaner. Hold the PCB at an angle to allow the solvent to flow over the board and run off, along with any residues that are picked up.

The straw attachment that comes with aerosol flux removers is a good way to increase the spray force and penetrate under the components.

Some aerosol flux removers come with a brush attachment. The cleaning solvent sprays through the brush, so agitation can be increased by scrubbing while spraying. To absorb the flux residues, a lint-free poly-cellulose wiper can be placed over the repair area, and the spraying and scrubbing can occur over the material. Then remove the wipe and brush attachment, and spray over the board for the final rinse.