Improve PCB Reliability by Removing Corrosive Flux Residues
Chemtronics manufactures a wide range electronic cleaners. From clean room cleaning supplies to production quantity flux removal or even blasting derbies from sensitive electronics with compression dusters we are your one-stop shop for the care of your electronic equipment.
Chemtronics® dusters are microscopically clean, oil and moisture free sources of "canned air" developed for applications where safe, ultra-pure cleaning is required. Compact and portable, Chemtronics dusters deliver powerful jet action to instantly remove particles from even the most inaccessible areas. Ultrajet® Dusters economize solvent usage by removing layers of dry particulate allowing the solvent to work immediately on encrusted soils. Ultrajet Dusters also accelerate surface drying when using slow evaporating cleaners.
Flux removal is critical to ensure reliable circuitry. Not only unsightly, some flux residue can promote short circuits and corrosion, degrading or destroying the printed circuit board. The type of flux to be removed, solvent compatibility and ease of application are all factors to consider when choosing a flux remover or electronic cleaner. Flux-Off® Flux Removers are specially formulated to remove all types of lead-free, rosin (types R, RA, and RMA), no-clean, water-soluble and synthetic (type SA) flux.
Electro-Wash® Cleaner Degreasers are engineered to clean a wide variety of soil, oil, grease, oxides and handling contamination, from equipment and assemblies.
Chemtronics Swabs and Applicators are engineered for use in a variety of environments and applications. They are ideal for use with our cleaner degreasers, head cleaners, flux removers and other solvents for fast, precision cleaning. From the innovative no-lint Chamois Tips Swab to the general purpose Cottontips Swab, Chemtronics has the right swab or applicator for your job.
How do you set-up a new PCBA cleaning process?
The best cleaning method for your operation depends on your volume, throughput desired, criticality of the electronics, regulatory restrictions, and floor space.
The main options for board cleaning are…
- Manual cleaning - This can involve aerosol or pump sprays, or solvents in a pan or tray. Agitation can be applied with a brush, swab or wipe.
- Ultrasonic - This method uses sound waves to create bubbles, which implode on the PCBA surface to break up the flux residues.
- Vapor degreasing - The cleaning is done either in the vapor phase of a solvent, or submerged in a sump, which often includes ultrasonic action.
- Batch or inline systems - Spray equipment with water-based cleaners wash, rinse, and dry the PCBAs.
I’ll focus on aerosol cleaning, because that is the most practical if you are setting up a new cleaning operation. All defluxing processes basically involve…
- Dissolving the flux residue: Choose a cleaner that works best with your flux. A good match will reduce the need for extra soak time and agitation. When flux has been sitting for a long period of time, or has been baked on at high temperature or long reflow cycle, addition brushing might be required.
- Flushing or rinsing off the dissolved residues: Remember, once flux residues are dissolved, they won’t just evaporate off. They need a chance to flow off the circuit board. Holding the board at an angle while you are cleaning can help. A final rinse is always a good idea, and required if you are using a water-based cleaner.
- Drying the printed circuit board assembly (PCBA): For fast-drying solvents, this isn’t usually an issue. For water-based cleaners, you can accelerate drying with a duster, or use alcohol as a drying agent.
What is a flux remover?
A flux remover, also known as a flux cleaner or solder flux remover, is a chemical cleaning agent used in electronics and soldering applications to remove flux residues from circuit boards, electronic components, and other soldered connections.
Flux is a substance used during soldering to facilitate the flow of molten solder and promote good solder joints. It prevents oxidation of the metal surfaces, enhances wetting, and ensures a reliable electrical connection. However, after soldering, some flux residues may remain on the surface, which can be detrimental if left uncleaned. Flux residues can be conductive and corrosive, potentially causing short circuits, reduced performance, or even long-term damage to the electronic components.
A flux remover is designed to effectively remove these flux residues without causing harm to the electronic components or the circuit board. It typically comes in the form of a spray, liquid, or solvent, and it contains specific chemicals that dissolve and remove the flux residues.
Flux removers vary in their composition, and some may be suitable for cleaning specific types of flux or for different materials. It's essential to choose the right flux remover for the type of flux used in the soldering process and follow the instructions and safety precautions listed in the safety data sheet (SDS).
Proper cleaning of flux residues with a flux remover is crucial for maintaining the reliability and functionality of electronic devices, especially in the manufacturing and repair industries. It helps ensure that soldered connections are clean, free of contamination, and function as intended.
For more information, check out "Ultimate Guide to Cleaning Electronics: Improve PCB Reliability Safely & Effectively"
How do I remove flux from a printer circuit board (PCB)?
The cleaning method best for your operation depends on your volume, throughput desired, criticality of the electronics, regulatory restrictions, floor space and other practical considerations. All defluxing processes basically involve 1) dissolving the flux residue, 2) flushing off the dissolved residue, and 3) drying the printed circuit board assembly (PCBA). The following are the general methods used to clean PCBAs:
- Manual cleaning - This can involve aerosol or pump sprays, or solvents in a pan or tray. Agitation can be applied with a brush, swab or wipe. This method is best for low volume cleaning of non-critical electronics (e.g. IPC class 1), because it is operator dependant, so not easily repeatable.
- Ultrasonic - This method uses sonic (sound) waves to create bubbles, which implode on the PCBA surface to break up the flux residues. This is an aggressive cleaning method, which can be a problem for sensitive components (e.g. ceramic). Because the dissolved flux residues flow back into the cleaning solution, the cleaner needs to be monitored and changed often to prevent cross-contamination.
- Vapor degreasing - The cleaning is done either in the vapor phase of a solvent, or submerged in a sump, which often includes ultrasonic action. Since the final rinse always happens in the vapor phase, this is an ideal cleaning method for critical applications where residue cannot be accepted.
- Batch or inline systems - Spray equipment is used to wash, rinse, and dry the PCBAs. Water or water-based cleaners are most commonly used as the cleaning solution. This cleaning method is good for high volume cleaning, and is repeatable enough for critical applicaitons.
Click here for a how-to video on PCB cleaning.
When should I clean off no-clean flux?
If it is not fully activated (brought up to solder temperature), you 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.
2. The non-ionic residue can impede with the function of the devise either short-term or long-term.
How can you reduce chemical exposure?
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.
How do you know the safe exposure limit of a degreaser, contact cleaner, or flux remover?
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).
Are swabs available for cleaning static sensitive electronics?
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.
Is air duster (canned air) safe on my computer and other electronics?
Yes, air duster is generally designed for use on electronics. There are a few things to watch out for:
- 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.
- 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.
Why is there white residue when I clean my PCB?
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.
How do you clean excess flux?
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.