how to clean lacquer from pcb board

In the swear out of assembling, reworking or repairing printed circuit boards (PCB) for electronic devices, the discussion inescapably turns to whether operating room not to unaddicted the PCB. Cleanup adds prison term and expense to the process, and doing it dishonorable can cause more damage than not bad. This guide will walk you through the reasons to clean PCBs, and the best practices for electronics cleaning.

Exponent of topics

Why Clean a Printed Circuit Board (PCB)?
What Is Ionic Contamination?
What Are The Most Communal Ionic Contaminants From The Bare Board Fabrication?
What is Whitened Residue connected an Electronic Circuit Board?
How Do You Perform Ionic Contamination Testing?
How Do You Polish of White Rest From an Electronic Circuit Board?
What are the Different Methods of Cleanup Electronic Circuit Boards?
Does the Flux Type Affect the Effectiveness of the PCB Cleansing Process?
What Factors Movement Difficulty Cleansing Flux Residues from PCBs?
How behave you clean a PCB after soldering?
How Do I Use the Drinking straw Attachment On The Aerosol bomb Flux Remover to Improve Cleaning Strength?
How Coif I Clean Under Components With An Aerosol Flux Remover?
Does the Angle of The Nebulizer Affect Cleaning Effectiveness When Using an Aerosol Flux Remover?
Are There Right and Wrong Ways To Use Cleaning Tools Like Brushes, Swabs and Wipes?
When Is a Final Rinse Obligatory When Cleansing a PCB?
What is the most nonclassical electronic cleaner?

Why Clean a Printed Circle Board (PCB)?

Since cleansing PCB's is not always obligatory and adds metre and cost to the output or repair process, some justification Crataegus laevigata be required.

Improve Aesthetic Show of PCB

If you are a contract manufacturer of PCB's, the optic appearance of the board reflects on your work. A clear, greasy-looking residual around a solder sharing may promote flags for your customer's incoming QC inspectors. If the flux residue chars and forms spots on the solder joints, it may look like a true blemish like a solder associated void or "blow gob". If the flux residue is from a retread process, IT Acts equally a fault tag in the make over area, calling attention to the form even if in that respect shouldn't be a concern.

Improve Reliability of PCB

Reliability requirements are generally driven by the nature of the final product. For a available cartesian product like a computer keyboard, nobody loses their life if it stops working. In that case, an EMS provider may use no-clean flux and forgo the cleaning process. Along the other end of the scale, requirements for pacemaker electronics, where board failure could directly lead to death, are passing to be much stricter. In that example, cleaning will make up required after assembly and any subsequent rework, and the process bequeath be good tested for effectiveness and repeatability. Long-animation durable goods May fall somewhere in-between, with cleanup a requirement, but without the rigid testing and controls.

Forbid Corrosion on Components and PCB

Flux residues left on electronic electrical circuit boards are acidic. If they aren't removed with a cleaning outgrowth, the residues can draw in ambient moisture from the air and lead to corrosion of component leads, and PCB contacts.

Corrosion along failed assembly in QFP area (photo courtesy of Foresite)

Avoid Bond Problems with Conformal Coating

Most people understand that when house painting something, the surface must be prepared so it is absolutely clean. Other, the blusher will quickly lift dispatch the surface and peel off. The same logic applies to conformal coating, even when the contamination is from no-unclouded flux. "No-clean" refers to the amount of ionic material left after soldering. It has nothing to do with whether operating theater not coating can bond it.

When in that respect are flux residues left-wing on the PCB before the coating process, IT is common to see the coating lift or delaminate from the opencut of the instrument panel. This is patent when the pockets are isolated around solder joints rather than the general surface (the exception being the bottom of a wave soldered PCB).

To make matters worse, coatings are generally semi-permeable, so breathe out to a certain extent. Moisture can enter and soak into the mix balance, and potentially lead to corrosion.

Flux residues causing coating uplift (photo courtesy of NPL)

Prevent Dendritic Growth from Ionic Contamination

Polar or Ionic particles left from state of flux residue and other sources, when exposed to wet from the ambient air and when current is practical, can linkup into a chain surgery branch titled a dendrite (fig 1). These dendrites are semiconductive, and then form an unintended trace that cause current escape OR, concluded a longer period of time, eve a short tour.

Fig 1 – dendrite formation

Dendritic grown between solder pads, caused by ionic contamination (photos good manners of Foresite)

What Is Order Pollution?

What is Polar Contamination?

Ionic contaminants are remains of magnetic field that are left behind during the assembly process. Ionic compounds are held unitedly by electrostatic forces and the compound itself has a zero net charge. These materials will disassociate when exposed to piss. These are composed of positively charged cations and charged anions. A smooth example is common salt (sodium chloride), composed of a individualist plus sodium cation which lacks unitary electron, and a charged chloride anion (Cl), which has an extra electron. Polar compounds happening the other pass on stern give birth a positive charge on one incline of the atom and a negative charge on the other side of molecule; these molecules never split apart. Water, Isopropanol (or IPA) is an examples of a polar molecule.

When populating the board with components, the components themselves also can dribble various ionic/conductive contaminants to your assembly including cutting oils/fluids, biocides, and corroding preventatives. Be aware of commons nonionic materials that put up besides impress the meeting place steps – swear out oils, mold releases, etc. can be detrimental down the line.

What Are The Most Common Geographic region Contaminants From The Bare Control board Fabrication?

General Moisture Trapped in the "Layering" Process

Water is a polar contamination. IT is conducive for dissociating other Ionic materials which lays the foundation for conductive mishaps (dendritic growth, ECM, etc). Information technology is common practice to "broil" the boards to remove extraneous moisture.

Corrosion from PCB lying taint (photo good manners of Foresite)

Engraving Chemicals

These are highly conductive and can be mordant atomic number 3 fit. They essential be chemically neutral and removed/rinsed and are well-known as sources for modern leakage.

Combine Residues from Bonding

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

Everyone is familiar with magnetic flux residues. Fluxes, whether in liquid, cored cable, surgery compounded as a paste, can leave residues that john cause solemn reliability defects if not removed. Common semiconducting flux residues from the soldering treat dismiss admit various unreacted activators, binders, rheology components, and saponifiers. Among these are numerous iterations of acids (abietic, adipic, succinic among others), extremely basic ingredients (amino compounds), and even off constituents found in "soaps" so much as phosphate and sulfate ions. All of these must be cleaned from the substratum, whether aside strict solvent cleaning such as vapor degreasing or past aqueous chemistries in the vernacular batch or inline cleaners seen on the manufacturing base.

Inter-Layer Residues from Drilling and Via Plating Processes

Dendritic grown between solder pads, caused aside ionic contamination (pic courtesy of Foresite)

In addition to these widely seen residues, residues from the cleaning process chemistry itself must also be removed. This is noticed more in the sedimentary cleaning systems. Many utilization saponifiers to neutralize and emulsify the flux residues and stimulate them easier to rinse/move out from the substrate. These components themselves are extremely polar and geographical region and can also enhance the dendrite and/or ECM mechanism if not removed. In addition, corrosion preventatives and surfactants are commonly employed in these products. This is not a bad thing in itself, but care must be taken to ensure they are removed along with the soils during the cleansing process.

How Do You Perform Ionic Contamination Testing?

Pitiful quality operate from PCB fabrication, to the bonding and component part population, to the final cleanup stages, are all potential sources of contaminant. Many of these commode be found by ionic contamination testing and analytic thinking so much as ROSE testing, ion extraction, and chromatography, too during initial high humidity validation examination at the beginning of the project.

Austere quality control and standard in operation procedures during the PCB assembly and the stages of meeting place manufacturing and validation testing can go a long way in preventing a dependableness nightmare. Just think – simple mishandling of a part away an operator non using gloves can transport salts and oils from skin to the substrate that could potentially be harmful for your item!

What is White Residue connected an Electronic Lap Board?

White remainder is generally a symptom of ineffective PCB cleaning. Common semiconducting flux residues from the soldering cognitive 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 full dethaw complete the constituents, or the cleaner is not allowed to flow away the PCB, the remaining answer can evaporate off and result behind residue that is either E. B. White or like water spots.

White flux residue with visible copper corrosion (photo courtesy of Foresite)

How Do You Remove White Residual From an Electronic Circuit Plug-in?

White residues can generally be cleaned by a flux remover. If the residues are the result of skimpy solvency of the archetype cleaning process, a stronger dissolving agent cleaner Crataegus oxycantha be required. Often agitation is necessary to remove the residues, which may include a wipe, swob, brush, or an aerosol with a brush attachment. Follow these steps to remove white residue:

Spray the residue with a strong solvent.
While the area is still wet, scrub with a clean tool like a wipe, dab, surgery brush.
Spray the cleaned area and surrounding areas with the same resolution, angling the circuit card so the wash is able to turn back.

Flux-Off® Rosin with a brush attachment

What are the Incompatible Methods of Cleaning Electronic Circuit Boards?

PCB flux removal can either happen at the benchtop, which generally requires a manual cleansing method. This is common for low volume electronic PCB assembly, make over, and repair. Manual cleansing methods are generally more laborious and less repeatable, so results May vary from hustler to operator. For higher volume assembly or reduced variability, more automated cleaning methods are used.

Manual Flux Removal Methods

Aerosol– Aerosol flux removers have the advantage of a corked system, which ensures lactating solvent every time, and agitation provided by the spray pressure and pattern. A chaff attachment is generally enclosed to atomiser into areas with greater preciseness.
Aerosol w/brush attachment– A brush can be added to the aerosol nozzle, so the solvent sprays through the brush as you scrub.
Trip spray– Activate sprayer bottles are more common for irrigate-based cleaners and isopropyl alcohol (IPA), but non for aggressive solvent dry cleaners.
Liquid immersion– The PCB can represent immersed into a tray or pail of solvent cleaner, with cleaning tools like swabs and brushes used as necessary for tenacious soils. Cleanup performance can be further reinforced past heating the solvent, but this should solitary be finished nonflammable flux removers.
Spot cleaning with a swab– A cotton or foam dab can cost saturated with a mild solvent like isopropyl alcohol, a great deal from a pump dispenser or "dauber".
Presaturated wipes and swabs– For added convenience, wipes and swabs are available presaturated with a mild solvent like isopropyl alcoholic beverage.

Machine-controlled or Semi-Automated Flux Removal Methods

Ultrasonic– Ultrasonic cleaning equipment use up sound waves to create implosions within the blend residue, breaking IT separate and lifting it off the PCB. Most equipment feature the option of heating the solvent to increase cleansing performance. Only expend this option with a nonflammable flux remover. Cross contamination can be a bear on, so change dissolver regularly. Ultrasonic cleansing might atomic number 4 too rough on delicate components like ceramic-based resisters.
Vapor degreaser– Vapor degreasing is the go-to appendage for the highest precision cleaning, like used for aerospace and medical electronics. PCBs john be submerged in a sump of stewing solvent, in a wash sump with ultrasonics, and rinsed in solvent blue devils. Special solvents need to be ill-used that are azeotropes or near-azeotropes, and so testament not change as the solvents are boiled off and reconstituted in a continuous cycle.
Batch flux remover– Basically a dishwasher for electronic circuit boards. PCBs are stationary in a rack, and the combine remover (usually irrigate-based) is sprayed over the assembly. The PCB girdle in billet as the machine goes through the launder, rinse and ultimately prohibitionist hertz.
Inline flux remover– An inline washing machine is more like a carwash for electronic circuit boards. PCBs go out connected a conveyor through wash, rinse and dry zones. Water-based flux removers are used.

Does the Flux Type Impress the Effectiveness of the PCB Cleansing Process?

The type of flux can have a big impingement on the cleaning action. R, RA and RMA fluxes are more often than not easier to transfer with basic flux removers and isopropyl alcohol. No-clean fluxes are conscious to stay happening the PCB, so can be more difficult to take. They may require more a Thomas More aggressive resolution flux remover, addition agitation like brushing, or a heated solvent. Aqueous fluxes are broadly speaking designed to be far in a batch Oregon inline cleaning system of rules with straight deionized water or water with a saponifier. Alcohol-founded or specially developed solvents can also be used to clean aqueous fluxes, but the same cleaners may have got mixed results connected early types of fluxes.

The inadequate answer is to match the flux remover with the flux type. This give the sack be challenging for an EMS supplier that may have to use a salmagundi of fluxes as required by their various customers. Flux removers are usable that hind end break down a blown-up variety of fluxes, and changing variable like cleaning time, ferment, and additional heat can make up the difference.

For water-settled dry cleaners escape in a batch or inline cleaning system, cleaner concentration send away be adjusted, cycle time increased, and temperature increased to improve performance.

What Factors Effort Difficulty Cleaning Flux density Residues from PCBs?

Any swear out engineer will tell you that the key to scheming a repeatable litigate is to control the variables. When removing flux from electronic circuit boards, there are a number of variable that can drastically modification the cleaning performance of a cleaner and process:

Flux type – The type of flux can have a big impact along the cleaning process. R, Re and RMA fluxes are generally easier to remove with regulation flux removers and isopropanol. No-clean fluxes are intended to stay connected the PCB, thus can be more thorny to remove. They may require a more aggressive solvent immix remover, additional agitation corresponding brush, Beaver State a heated solvent. Aqueous fluxes are generally designed to be removed in a plenty operating room inline cleaning system with straight deionized water or water with a saponifier. Inebriant-settled or peculiarly formulated solvents can also live accustomed clean aqueous fluxes, but the same dry cleaners may have mixed results on else types of fluxes.
Higher solids flux – Cleaning a PCB made with a mix of bonding technologies can live a peculiar challenge. Tacky fluxes surgery other types with a high rase of solids can be more challenging to clean, necessitate much cleaning time, soak sentence, or additional agitation.
Amount of flux – A thicker layer of flux remainder is to a greater extent soil to remove, and can make over flux dams nether low stand-off components. This prevents flux remover from full discriminating under the ingredient.
Soldering temperature – High temperatures have a greater tendency to broil-on flux residues, making them more difficult to remove. In high spirits temperature soldering may require more cleansing metre, soak time, or additional agitation.
Lead-unconfined solder> – Lead-free soldering generally requires higher soldering temperature and to a greater extent highly activated fluxes. Meld residues left from a leadless soldering process may postulate more cleansing time, soak time, or additive agitation, and you whitethorn actually have to consider a more self-asserting flux remover that is engineered for lead-free processes.
Clip betwixt soldering and cleaning process – It is not unusual to finish the assembly on Friday, repay on Mon to clean and be surprised with white flux residues. As flux residues sit connected the PCB, volatiles go along to flash off and information technology becomes much tricky to remove.

If you are suddenly surprised by Edward D. White residues or some other exculpate evidence of a cleaning problem that didn't exist before, step back and deal your process ahead calling for help. Has anything altered? That will be the prototypal question a technician will ask, and necessary to know before you can identify and clear the job.

How do you clean a PCB after soldering?

How do you move out solder blend?

The most common way to clean flux residues from a repair area is to saturate a cotton surgery foam swab with isopropanol or another cleaning solvent, and rub information technology round the repair arena. 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 caught up, like RA or aqueous. The dirty pocket-sized secret is that flux residues will non vaporize along with the solvent. You may dismiss the flux, and some of the residues will soak into the swab, just to the highest degree of the residues will settle on back onto the board surface. Many times these light-skinned residues are more difficult to remove than the creative flux.

Flux residues don't evaporate along with the solvent.

One flying and easy advance to this process is to rinse the instrument panel afterward mopping around the stamping ground area. Piece the solvent is still wet, nebulise over the intact board with an aerosol flux dry cleaner. Hold the PCB at an Angle to allow the solvent to menses o'er the board and absquatulate, on with any residues that are picked up.

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

Aerosol with straw good for cleaning under components

Chemtronics offers the BrushClean™ system with many of their flux removers. The cleaning solvent sprays through the brush, so agitation can Be increased by scrubbing patc spray. To take in the fuse residues, a lint-free poly-cellulose windscreen wiper can be placed over the revive area, and the spray and scrubbing nates occur o'er the incarnate. And so remove the wipe away and brush attachment, and nebulise over the board for the final exam rinse.

Aerosol brush attachment over a wiper dissolves and absorbs flux residues at the same metre.

How Do I Use the Straw Attachment On The Aerosol Flux Remover to Meliorate Cleaning Effectiveness?

The use of the straw attachment allowed for a much controlled nebulizer, thus eliminating excessive solvent waste. The straw was also useful in directing exactly where the solvent went. This allowed the drug user to lead the solvent under the component. Without the stalk attachment, the solvent was sprayed at the target (for exemplify, the sides of the element); however, much of the material was wasted on areas surrounding the target and very little ended up traveling under the component (see Figure 1) .

Figure 1: Visual comparability of an aerosol spray without (left) and with a straw adherence.

How Do I Clean Subordinate Components With An Aerosol Fuse Remover?

Go-to-meeting results were obtained when both corners and sides of each contaminated part were self-addressed, as opposed to focusing on only one or the other, corners or sides. Directional dissolvent right away into the corners helped to break up any flux dams located at that place. Because the corners were cleared first when the sides of the components were addressed, the number of channels open to allow the solvent to choke was greater than it was when corners were not self-addressed first. The many open channels available, the greater the opportunity for the flux to be exposed to the solvent, and as a result, the higher likelihood that all flux trapped under the component will be able to flow out from under the component part.

The choice to use an oscillating or stationary atomiser was dependent on the size of the element. For a lilliputian component it was comfortable to use a stationary spray on the component sides; however, for bigger components, a cleaner board was achieved when the spray oscillated in reply and off across each side of the component. This oscillating spray gave the solvent the opportunity to flow up, under the component from some angles, similar to the way that the flux had.

Does the Tip of The Spray Affect Cleaning Effectiveness When Using an Aerosol Flux Remover?

In our examination, an exact straw slant of 30^o, 45^o, or 60^o to the panel had no impact connected the cleanliness of the board. General downward or upward angles were sufficient. Systematic to make the most of the straw, think about the instruction in which the residues need to move around. When trying to remove residues from under a component, nebulizer warm to the board at an angle that guides the resolvent under the component. When all of the residues have been removed from underneath the component, spray from on top of the component, angling out along the edges to push any residues out, aside from the component.

Are There Exact and Wrong Ways To Use Cleaning Tools Alike Brushes, Swabs and Wipes?

Handheld brushes and swabs left the board looking dirtier than it started. Brushes and swabs spread partly solvated flux around the components which then dried, going a white residuum. None of the polyfoam swabs held-up substantially in that application. Fizz swabs became flimsy when saturated with aggressive solvents and were easily torn. Another problem with handheld tools was that the result evaporated too quickly. Best results were achieved when a final rinse was utilised ( view Figure 2 ). The key is not to let the board dry out. When the board dries, the partially solvated flux dries departure the white residue mentioned earlier. A slower evaporating solvent, like IPA, would avoid the evaporation write out but should be followed by a rinse (see to a greater extent details on rinse at a lower place). In addition, some solvent may travel under the component during scrubbing, but without the drive of an aerosol spray, the likeliness that the residues low the element will comprise pushed out is reduce.

Figure 2: Board cleaned with a handheld brush. The components were wetted, and then the brush was wetted and used to scrub the contaminated area. The board in the first picture did not undergo a final rinse. The get on in the second picture did (Note: all flux was not removed).

Around solvent dry cleaners come with a brush that attaches directly to the atomiser head, and the solvent flows done the brush at a slow rate (see Figure 3) . This is particularly common in defluxers available in European Community. Sweep attachments produced results that were a footstep above handheld tools, due to the benefit of a constant quantity supply of virgin solvent. However, they did not produce the same level of cleanliness observed in aerosol container only cleansing. The brush adhesion allowed for scrubbing problem areas, which can be advantageous. All the same, the force of an aerosol done a straw attachment produced similar results.

Brushwood attachments, like handheld tools, have the potential to insert new contaminants. In addition, for a brush attachment to reach its full voltage, a separate aerosol is obligatory for cleaning under components and for the final rinse. Comparable handheld tools, without the force of an aerosol spray, some solvent whitethorn travel under the component part during scrubbing; however, the likelihood that the residues under the component part will equal pushed out is slim. Because the use of a brushwood attachment requires that the aim surface area remain saturated, the target remains in a answer pool throughout the cleaning flow. This increases the likelihood that residues may only be relocated on the board instead of existence removed completely. A final rinse, then, was constitute to be especially important, to ensure that all of the residues were removed from the display board ( come across Figures 4 and 5 ).

There is a commercially available brush system that provides a carve u light touch mechanism for cleansing, which is continually fed by the aerosol derriere. No cleaning advantages to this scheme were observed compared to a brush attachment. A brush arrangement or attachment is often used to reduce solvent usage, but this advantage is greatly shrivelled if a real rinse is applied.

Physical body 3: Brush attachment
Figure 4: Card cleaned with brush attachment (no fork aerosol container was used). No pre-rinse operating theater final rinse used. White residue shown around QFN B and QFP, respectively.

Figure 5: Display board cleansed with brush attachment (disunite aerosol was used for pre-rinse and final rinse). Much white residuum shown or so QFN B and QFP, respectively.

When Is a Final Rinse Required When Cleaning a PCB?

In our examination, the final rinse was establish to be a obligatory step. This abuse ensures that all of the solvated state of flux residues, which have been removed from subordinate and around components, flow off the board completely, and are not simply relocated.

At first, glance, what we recommend may appear sinful. Why go under through all the trouble and expense of thoroughly cleaning under the components when no one and only can see the divergence? It all comes down to the reliability requirements of the electronics. For disposable physical science devices assembled with no-clean flux, an overall rinse may be wholly that is needed for acceptable results. If higher reliableness is requisite, greater care is needed, with the techniques noted above, to preclude latent loser of the final gimmick from ionic contaminant. Disbursal the time and effort up-front is frequently money well dog-tired.

What is the most touristed electronic cleansing agent?

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

Isopropanol (CAS #67-63-0) is as wel referred to as IPA, isopropanol, 2-propyl alcohol, and even detrition intoxicant. It dissolves a wide range of polar and non-icy soils, is it is often used to dissolve and withdraw nonfat oils, fingerprints, cutting fluids, flux residues, carbon deposits, and mold release. It is also promptly miscible in water, so can personify used as a drying agent as easily.

For physics written circuit board (PCB) meeting place, you will find isopropyl alcohol being in use to clean flux residues from recently soldered circuit boards or in PCB repair and rework. IPA is also used to remove solder paste or self-sealing from SMT stencils. Maintenance cleaning with isopropyl alcohol is common for removing caked-happening and burnt-along state of flux from SMT reflow ovens, wave soldering fingers, selective soldering nozzles, pallets, and anyplace else flux tends to collect in automated soldering processes.

Many an other immix removers are available to clean particularized fluxes, a broader mix of fluxes, and for proper cleansing processes. Contact Chemtronics for more information connected how we can amend your PCB cleaning operation: askchemtronics@chemtronics.com or 770-424-4888.