What Non-conductive Liquid Can I Use To Clean Keyboard

In the process of assembling, reworking or repairing printed circuit boards (PCB) for electronic devices, the give-and-take inevitably turns to whether or not to clean the PCB. Cleaning adds time and expense to the procedure and doing information technology wrong tin cause more harm than good. This guide will walk you through the reasons to clean PCBs and the best practices for electronics cleaning.

Index of topics

Why Make clean a Printed Circuit Board (PCB)?
What Is Ionic Contamination?
What Are The About Common Ionic Contaminants From The Blank Board Fabrication?
What is White Residue on an Electronic Circuit Board?
How Exercise You lot Perform Ionic Contamination Testing?
How Do You Remove White Rest From an Electronic Circuit Board?
What are the Different Methods of Cleaning Electronic Excursion Boards?
Does the Flux Type Affect the Effectiveness of the PCB Cleaning Process?
What Factors Cause Difficulty Cleaning Flux Residues from PCBs?
How do you clean a PCB after soldering?
How Do I Employ the Harbinger Zipper On The Aerosol Flux Remover to Improve Cleaning Effectiveness?
How Do I Clean Under Components With An Aerosol Flux Remover?
Does the Bending of The Spray Affect Cleaning Effectiveness When Using an Aerosol Flux Remover?
Are There Correct and Wrong Ways To Employ Cleaning Tools Like Brushes, Swabs and Wipes?
When Is a Final Rinse Required When Cleaning a PCB?
What is the near popular electronic cleaner?

Why Make clean a Printed Circuit Board (PCB)?

Since cleaning PCB's is not always required and adds fourth dimension and cost to the production or repair process, some justification may be required.

Improve Aesthetic Appearance of PCB

If you are a contract manufacturer of PCB's, the visual advent of the board reflects on your work. A articulate, greasy-looking residuum around a solder joint may raise flags for your customer'south incoming QC inspectors. If the flux residue chars and forms spots on the solder joints it may await similar a true defect like a solder joint void or "blow hole". If the flux residue is from a rework process, it acts as a mistake tag in the rework expanse calling attention to the work even if in that location shouldn't exist a business organisation.

Improve Reliability of PCB

Reliability requirements are generally driven by the nature of the concluding product. For a disposable product similar a computer keyboard, nobody loses their life if information technology stops working. In that example, an Ems supplier may use no-clean flux and forgo the cleaning process. On the other terminate of the scale, requirements for pacemaker electronics, where board failure could directly atomic number 82 to death, are going to be much stricter. In that example, cleaning volition be required after assembly and any subsequent rework, and the process will exist thoroughly tested for effectiveness and repeatability. Long-life durable goods may fall somewhere in-betwixt, with cleaning a requirement but without the rigid testing and controls.

Foreclose Corrosion on Components and PCB

Flux residues left on electronic circuit boards are acidic. If they aren't removed with a cleaning process, the residues tin can depict in ambient wet from the air and atomic number 82 to corrosion of component leads and PCB contacts.

Corrosion on failed assembly in QFP expanse (photo courtesy of Foresite)

Avoid Adhesion Problems with Conformal Coating

Virtually people understand that when painting something the surface must be prepared so it is admittedly clean. Otherwise the paint will quickly pare off. The same logic applies to conformal blanket, even when the contagion is from no-clean flux. "No-clean" refers to the amount of ionic cloth left after soldering; it has cypher to exercise with whether or non coating can stick to information technology.

When there are flux residues left on the PCB before the coating process, information technology is mutual to see the coating lift or delaminate from the surface of the lath. This is axiomatic when the pockets are isolated around solder joints rather than the overall surface (the exception beingness the bottom of a wave-soldered PCB).

To make matters worse, coatings are generally semi-permeable and "breathe" to a certain extent. Moisture tin enter and soak into the flux balance and potentially lead to corrosion.

Flux residues causing blanket uplift (photograph courtesy of NPL)

Prevent Dendritic Growth from Ionic Contagion

Polar or Ionic particles left from flux residue and other sources, when exposed to moisture from the ambient air and when current is applied, can connect into a chain or branch chosen a dendrite (Fig 1). These dendrites are conductive so form an unintended trace that crusade current leakage or, over a longer menses of time, even a short excursion.

Fig 1 – dendrite formation

Dendritic grown between solder pads, caused past ionic contamination (photos courtesy of Foresite)

What Is Ionic Contamination?

What is Polar Contamination?

Ionic contaminants are remains of flux that are left backside during the assembly process. Ionic compounds are held together by electrostatic forces and the compound itself has a zero internet charge. These materials will disassociate when exposed to water. These are composed of positively charged cations and negatively charged anions. A simple example is tabular array salt (sodium chloride), equanimous of a single positive sodium cation which lacks i electron, and a negatively charged chloride anion (Cl), which has an actress electron. Polar compounds, on the other hand, can have a positive charge on i side of the molecule and a negative accuse on the other side of the molecule; these molecules never split up autonomously. Water and Isopropanol (or IPA) are examples of polar molecules.

When populating the board with components, the components themselves can acquit various ionic/conductive contaminants to your associates including cutting oils/fluids, biocides, and corrosion preventatives. Be aware of mutual nonionic materials that can also affect the assembly steps – process oils, mold releases, etc. tin exist detrimental downwardly the line.

What Are The About Common Ionic Contaminants From The Bare Lath Fabrication?

Common Moisture Trapped in the "Layering" Process

Water is a polar contaminant. It is conducive for dissociating other ionic materials which then lays the foundation for conductive mishaps (dendritic growth, ECM, etc). It is common practice to "bake" the boards to remove extraneous moisture.

Corrosion from PCB fabrication contagion (photo courtesy of Foresite)

Carving Chemicals

Etching chemicals are highly conductive and can exist corrosive equally well. They must be chemically neutralized and removed/rinsed and are well-known as sources for current leakage.

Flux Residues from Soldering

Heavy no-make clean flux residue with visible copper corrosion (photo courtesy of Foresite)

Anybody is familiar with flux residues. Fluxes, whether in liquid, cored wire, or compounded as a paste, can leave residues that tin cause serious reliability defects if not removed. Mutual conductive flux residues from the soldering process tin can include various unreacted activators, binders, rheology components, and saponifiers. Amid 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. All of these must be cleaned from the substrate, whether by strict solvent cleaning such as vapor degreasing or by aqueous chemistries in the mutual batch or inline cleaners seen on the manufacturing floor.

Inter-Layer Residues from Drilling and Via Plating Processes

Dendritic grown between solder pads, caused by ionic contamination (photograph courtesy of Foresite)

In addition, residues from the cleaning process chemistry itself must as well be removed. This is noticed more in the aqueous cleaning systems. Many use saponifiers to neutralize and emulsify the flux residues and make them easier to rinse and remove from the substrate. These components themselves are highly polar and ionic and tin can too heighten the dendrite and/or ECM machinery if not removed. In addition, corrosion preventatives and surfactants are usually employed in these products. This is not a bad thing in itself, simply care must be taken to ensure they are removed along with the soils during the cleaning process.

How Do Y'all Perform Ionic Contamination Testing?

Poor quality control in fabrication, poor soldering or component population, and even concluding cleaning stages are all potential sources of contamination. Many of these tin be found by ionic contamination testing and analysis such as ROSE testing, ion extraction, and chromatography. Initial high humidity validation testing at the beginning of the project can also place potential bug.

Strict quality control and standard operating procedures during the PCB associates, manufacturing stages, and validation testing tin go a long fashion in preventing a reliability nightmare. Simply think – simple mishandling of a role past an operator not using gloves can transfer salts and oils from skin to the substrate that could potentially exist catastrophic for your particular!

What is White Residue on an Electronic Excursion Board?

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

White flux residual with visible copper corrosion (photograph courtesy of Foresite)

How Exercise You Remove White Remainder From an Electronic Circuit Board?

White residues can more often than not be cleaned by a flux remover. If the residues are the result of insufficient solvency of the original cleaning procedure, a stronger solvent cleaner may be required. Often agitation is required to remove the residues, which may include a wipe, swab, castor, or an droplets with a brush attachment. Follow these steps to remove white residuum:

Spray the rest with a strong solvent.
While the surface area is still wet, scrub with a make clean tool like a wipe, swab, or brush.
Spray the cleaned area and surrounding areas with the same solvent, angling the board so the rinse is able to run off.

Flux-Off® Rosin with a castor attachment

What are the Unlike Methods of Cleaning Electronic Excursion Boards?

PCB flux removal can either happen at the benchtop, which generally requires a manual cleaning method, or in automatic or semi-automatic processes. This is common for low volume electronic PCB associates, rework, and repair. Manual cleaning methods are generally more laborious and less repeatable, so results may vary from operator to operator. For college volume assembly or reduced variability, more automatic cleaning methods are used.

Manual Flux Removal Methods

Aerosol– Aerosol flux removers accept the advantage of a sealed system (ensuring fresh solvent) and agitation (provided by the spray pressure and blueprint). A straw attachment is generally included to spray into areas with greater precision.
Aerosol w/brush attachment– A brush tin can be added to the aerosol nozzle, so the solvent sprays through the brush as y'all scrub.
Trigger spray– Trigger spray bottles are more common for water-based cleaners and isopropyl alcohol (IPA), but not for aggressive solvent cleaners.
Liquid immersion– The PCB can exist immersed into a tray or bucket of solvent cleaner, with cleaning tools similar swabs and brushes used as needed for tenacious soils. Cleaning performance can exist farther improved by heating the solvent but this should only exist done with nonflammable flux removers.
Spot cleaning with a swab– A cotton or foam swab can exist saturated with a balmy solvent like isopropyl alcohol, frequently from a pump dispenser or "dauber".
Presaturated wipes and swabs– For added convenience, wipes and swabs are bachelor presaturated with a balmy solvent like isopropyl alcohol.

Automated or Semi-Automated Flux Removal Methods

Ultrasonic– Ultrasonic cleaning equipment use sound waves to create implosions within the flux residue, breaking information technology autonomously and lifting information technology off the PCB. About equipment have the option of heating the solvent to increase cleaning performance. Only use this option with a nonflammable flux remover. Cross-contamination can be a business organization so modify the solvent regularly. Ultrasonic cleaning might exist too rough on sensitive components like ceramic-based resisters.
Vapor degreaser– Vapor degreasing is the go-to procedure for the highest precision cleaning, as in aerospace and medical electronics. PCBs can be submerged in a sump of boiling solvent, in a rinse sump with ultrasonics, or rinsed in solvent vapors. Special solvents need to be used that are azeotropes or almost-azeotropes, so will not change as the solvents are boiled off and reconstituted in a continuous cycle.
Batch flux remover– This is basically a dishwasher for electronic excursion boards. PCBs are stationary in a rack, and the flux remover (usually water-based) is sprayed over the assembly. The PCB stays in place as the machine goes through the launder, rinse and dry cycles.
Inline flux remover– An inline washer is more like a carwash for electronic circuit boards. PCBs travel on a conveyor through launder, rinse and dry zones. H2o-based flux removers are used.

Does the Flux Blazon Affect the Effectiveness of the PCB Cleaning Process?

The blazon of flux can accept a large impact on the cleaning process. R, RA and RMA fluxes are generally easier to remove with standard flux removers and isopropyl alcohol. No-make clean fluxes are intended to stay on the PCB, and then tin be more hard to remove. They may require a more aggressive solvent flux remover, additional agitation like brushing, or a heated solvent. Aqueous fluxes are generally designed to be removed in a batch or inline cleaning system with straight deionized water or water with a saponifier. Alcohol-based or especially formulated solvents tin can too be used to clean aqueous fluxes, but the same cleaners may have mixed results on other types of fluxes.

The short answer is to match the flux remover with the flux blazon. However, this tin be challenging for an EMS supplier that may take to apply a variety of fluxes as required past their diverse customers. Flux removers are available that tin break down a large diversity of fluxes while changing the variables, like cleaning time, agitation, or boosted oestrus, can treat distinctive needs adroitly.

For water-based cleaners in batch or inline cleaning systems, cleaner concentration tin can be adapted, cycle fourth dimension increased, and temperature increased to meliorate performance against various flux types.

What Factors Crusade Difficulty Cleaning Flux Residues from PCBs?

Any process engineer will tell y'all that the primal to designing a repeatable process is to control the variables. When removing flux from electronic circuit boards, in that location are a number of variables that can drastically modify the cleaning operation of a cleaner and procedure:

Flux type – The blazon of flux can have a big impact on the cleaning process. R, RA and RMA fluxes are generally easier to remove with standard flux removers and isopropyl alcohol. No-clean fluxes are intended to stay on the PCB, and then tin be more difficult to remove. They may require a more aggressive solvent flux remover, additional agitation like brushing, or a heated solvent. Aqueous fluxes are mostly designed to exist removed in a batch or inline cleaning arrangement with straight deionized water or water with a saponifier. Alcohol-based or specially formulated solvents can also be used to clean aqueous fluxes, just the same cleaners may have mixed results on other types of fluxes.
College solids flux – Cleaning a PCB made with a mix of soldering technologies can exist a particular challenge. Tacky fluxes or other types with a high level of solids can be more than challenging to clean, require more cleaning time, soak time, or additional agitation.
Amount of flux – A thicker layer of flux residue is more than soil to remove and can create flux dams nether low stand up-off components. This prevents flux remover from fully penetrating under the component.
Soldering temperature – Higher temperatures take a greater trend to bake-on flux residues, making them more than difficult to remove. High temperature soldering may require more cleaning time, soak time, or additional agitation.
Atomic number 82-complimentary solder> – Lead-free soldering by and large requires higher soldering temperature and more highly activated fluxes. Flux residues left from a lead-free soldering process may require more cleaning time, soak fourth dimension, or additional agitation, and you may really have to consider a more aggressive flux remover that is engineered for lead-free processes.
Time between soldering and cleaning process – It is not unusual to cease the assembly on Fri, come dorsum on Monday to clean and exist surprised with white flux residues. As flux residues sit on the PCB, volatiles continue to flash off and it becomes more difficult to remove.

If you are suddenly surprised by white residues or some other clear show of a cleaning problem that didn't be before, step back and look at your process earlier calling for help. Has anything changed? That will be the first question a technician volition ask, and necessary to know earlier you tin can place and solve the trouble.

How practice you clean a PCB after soldering?

How do you remove solder flux?

The well-nigh mutual mode to clean flux residues from a repair area is to saturate a cotton fiber or cream swab with isopropyl alcohol or another cleaning solvent, and rub information technology around the repair surface area. While this may be adequate for no-clean flux, where the goal is a visually clean PCB, this may not be clean plenty when more heavily activated fluxes are involved, like RA or aqueous. The dirty little undercover 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, just almost of the residues will settle back onto the board surface. Many times these white residues are more difficult to remove than the original flux.

Flux residues don't evaporate along with the solvent.

Ane quick and piece of cake improvement to this process is to rinse the lath after swabbing effectually the repair expanse. While the solvent is even so moisture, spray over the entire board with an aerosol flux cleaner. Agree the PCB at an bending to let the solvent to menstruation 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 skilful way to increase the spray force and penetrate under the components.

Aerosol with straw practiced for cleaning under components

Chemtronics offers the BrushClean™ arrangement with many of their flux removers. The cleaning solvent sprays through the brush, so agitation can exist increased by scrubbing while spraying. To absorb the flux residues, a lint-free poly-cellulose wiper can be placed over the repair expanse, and the spraying and scrubbing tin can occur over the material. And then remove the wipe and castor attachment, and spray over the board for the last rinse.

Aerosol castor attachment over a wiper dissolves and absorbs flux residues at the same fourth dimension.

How Do I Employ the Straw Attachment On The Aerosol Flux Remover to Improve Cleaning Effectiveness?

The use of the straw zipper allows for a more controlled spray, thus eliminating excessive solvent waste matter. The straw is also useful in directing exactly where the solvent goes. This allows the user to guide the solvent under the component. Without the harbinger zipper, the solvent would exist sprayed at the target area (for instance, the sides of the component), but would be wasted and not accomplish beneath the component .

Visual comparing of an droplets spray without (left) and with a straw attachment.

How Practice I Clean Under Components With An Aerosol Flux Remover?

All-time results are obtained when both the corners and sides of each contaminated component are addressed. Directing solvent direct into the corners helps to break up whatsoever flux dams located there. Because the corners were cleared kickoff when the sides of the components are addressed, this allows more channels for the solvent to pass through. The more than open up channels available, the greater the opportunity for the flux to be exposed to the solvent, and equally a result, the higher likelihood that all flux trapped nether the component volition be able to flow out from beneath it.

The pick to use an aquiver or stationary spray is dependent on the size of the component. For a pocket-sized component information technology is sufficient to utilize a stationary spray on the component sides; even so, for larger components, a cleaner board tin be achieved when the spray oscillates back and forth beyond each side of the component. This oscillating spray gives the solvent the opportunity to catamenia up, under the component from many angles, much every bit the flux had.

Does the Angle of The Spray Bear upon Cleaning Effectiveness When Using an Droplets Flux Remover?

In our testing, an exact straw bending of 30^o, 45^o, or lx^o to the lath has no differing impact on the cleanliness of the board. Full general downward or upward angles are sufficient. In guild to make the nearly of the straw, remember virtually the direction in which the residues need to travel. When trying to remove residues from under a component, spray close to the board at an angle that guides the solvent under the component. When all of the residues take been removed from underneath the component, spray from on pinnacle of the component, line-fishing out along the edges to push any residues out, away from the component.

Are There Correct and Wrong Ways To Utilise Cleaning Tools Like Brushes, Swabs and Wipes?

In our testing, handheld brushes and swabs left the lath looking dirtier than it started. They spread partially solvated flux around the components which then stale, leaving a white residuum. None of the polyurethane cream swabs performed well in this application. Cream swabs became flimsy when saturated with aggressive solvents and were easily torn. Another problem with handheld tools was that the solvent evaporated too quickly. All-time results were achieved when a final rinse was utilized. The key is not to let the board dry out. When the board dries, the partially solvated flux dries leaving behind white residue. A slower evaporating solvent, like IPA, would avert the evaporation issue but should be followed by a rinse (run into more details on rinsing below). In addition, some solvent may travel under the component during scrubbing, but without the force of an aerosol spray the likelihood that the residues below the component will exist removed is slim..

Lath cleaned with a handheld brush. The components were wetted, so the brush was wetted and used to scrub the contaminated expanse. The board in the first picture did not undergo a final rinse. The lath in the 2d picture did (not all flux was removed).

Some solvent cleaners come up with a brush that attaches direct to the spray caput, and the solvent flows through the brush at a tedious rate. This is peculiarly common in defluxers available in Europe. Brush attachments produced results that were a step above handheld tools, due to the benefit of a constant supply of virgin solvent. However, they did not produce the same level of cleanliness observed in aerosol-merely cleaning. The castor attachment allowed for scrubbing problem areas, which tin can exist beneficial. Notwithstanding, the force of an aerosol through a straw attachment produced like results.

Brush attachments, like handheld tools, have the potential to introduce new contaminants. In addition, for a brush attachment to reach its total potential, a dissever aerosol is required for cleaning under components and for the final rinse. Like handheld tools, without the forcefulness of an aerosol spray, some solvent may travel nether the component during scrubbing; however, the likelihood that the residues under the component will be pushed out is slim. Because the apply of a castor zipper requires that the target area remain saturated, the target area remains in a solvent puddle throughout the cleaning menses. This increases the likelihood that residues may only be relocated on the lath instead of being removed completely. A final rinse, so, is especially important.

One commercially available brush system provides a carve up brush mechanism for cleaning, which is continually fed by the aerosol can. No cleaning advantages to this arrangement were observed compared to a brush attachment during our testing. A brush system or attachment is often used to reduce solvent usage, simply this advantage is greatly decreased if a proper rinse is applied later.

Castor attachment
Lath cleaned with brush zipper (no separate droplets was used). No pre-rinse or final rinse utilized. White residue shown around QFN B and QFP, respectively.

Board cleaned with castor attachment (divide aerosol was used for pre-rinse and final rinse). Some white residual shown around QFN B and QFP, respectively.

When Is a Final Rinse Required When Cleaning a PCB?

In our testing, the final rinse was found to exist a necessary footstep. This step ensures that all of the solvated flux residues, which have been removed from under and effectually components, flow off the board completely and are non simply relocated.

At get-go glance, what we recommend may seem over-the-peak. Why become through all the trouble and expense of thoroughly cleaning under the components when no i tin see the difference? It all comes downwardly to the reliability requirements of the electronics. For dispensable electronic devices assembled with no-clean flux, an overall rinse may be all that is needed for adequate results. If higher reliability is required, greater care is needed, with the techniques noted above, to foreclose latent failure of the final device from ionic contamination. Spending the fourth dimension and effort up-front is often money well spent.

What is the most popular electronic cleaner?

Chemicals are constitute throughout the electronic assembly and repair process, but no solvent is more common than isopropyl alcohol. It is universally used for cleaning and as a main constituent of fluxes, simply how much practice you really know about isopropyl booze?

Isopropyl alcohol (CAS #67-63-0) is also referred to as IPA, isopropanol, two-propanol, and even rubbing booze. Information technology dissolves a wide range of polar and non-polar soils, is it is often used to dissolve and remove light oils, fingerprints, cutting fluids, flux residues, carbon deposits, and mold release. It is also readily miscible in water, and then can be used as a drying amanuensis besides.

For electronic printed circuit board (PCB) assembly, you lot volition find isopropyl booze being used to clean flux residues from recently soldered circuit boards or in PCB repair and rework. IPA is likewise used to remove solder paste or adhesive from SMT stencils. Maintenance cleaning with isopropyl alcohol is common for removing caked-on and burnt-on flux from SMT reflow ovens, wave soldering fingers, selective soldering nozzles, pallets, and anywhere else flux tends to collect in automatic soldering processes.

Many other flux removers are available to clean specific fluxes, a broader mix of fluxes, and for specific cleaning processes. Contact Chemtronics for more information on how we can meliorate your PCB cleaning functioning: askchemtronics@chemtronics.com or 770-424-4888.

Source: https://www.chemtronics.com/ultimate-guide-to-cleaning-electronics

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