Essential Guide to Precision Cleaning Brushes - Techspray

When cleaning sensitive devices and electronics, including printed circuit boards, the safest method is to allow the solvent to its job without additional agitation. Unfortunately, with oxidation, heavy greases, and other tenacious soils, there is no substitute for a technical cleaning brush. The article covers brush specifications, bristle types, and special considerations when working with precision cleaning brushes.

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Brush Design Specification

When selecting a brush for your application, the first challenge is to interpret the dimensions. Brush dimensions are expressed in length (L), width (w), and trim (T) (see fig. 1). Length and width are the dimension of the bristle groupings, and impact the amount of cleaning precision possible from the particular brush. Small brushes, similar to fine art paint brushes, are available for cleaning dense circuit board designs. Brushes are also available for larger applications, like sweeping debris from broad surfaces.

Trim is the length of the bristle from the handle. This directly affects the touch or stiffness of the bristles. Shorter trimmed brushes generally have a firmer touch and are better for more aggressive cleaning. Bristles are often trimmed straight, but can be trimmed in a rounded, or conical shape, and even angled. Techspray offers brushes that are angled to a point, for cleaning that is both precise and aggressive.

Brush Bristle Type

The type of bristle has a major impact on whether a brush is better for fine work, like conformal coating touch-up, or aggressive scrubbing:

• Goat hair – Goat hair is fine and soft, but fairly inelastic. It is naturally kinked, so is normally used for short bristled brushes like for cosmetics and in “acid” brushes commonly used for applying conformal coating in quality control rework. Natural hair brushes are considered static neutral, so are better suited for sensitive electronics than nylon bristles, like those found in common toothbrushes.
• Hog bristle – Hog bristles are stiff and ideal for more aggressive scrubbing. They are also very durable and water resistant. Natural hair brushes are considered static neutral, so are better suited for sensitive electronics than nylon bristles.
• Horse hair – Horse hair is slightly stiff and allows for dry cleaning without the risk of scratching. It is also durable and absorbent, so able to carry away liquids in a cleaning process. Horse hair is not resistant to acids or alkalis. Natural hair brushes are considered static neutral, so are better suited for sensitive electronics than nylon bristles.
• Brass wire – Brass is the softest metal available for brushes. Brass brushes are used for more aggressive cleaning and finishing work.
• Stainless steel wire – Stainless steel wire brushes provide very aggressive cleaning, deburring, removing rust, and surface roughing, like preparation for epoxy adhesive. These bristles are very corrosion and heat resistant. Sulfuric acid, commonly used as an industrial cleaning agent for removing rust and grease, should not be used with stainless steel brushes. Some types of inks can also react to stainless steel fibers. For those types of applications, natural fiber brushes are recommended.

Avoid Hair Loss with Quality Brushes

A frequent complaint with brushes is hair loss. This is a common problem with low cost, disposable brushes. A cheap acid brush used in quality control retouch of conformal coating can actually lead to FOD (foreign object debris), a defect than can actually reduce the service life of electronic devices.

Wire drawn, or hand laced brushes are made by sewing the brush filaments into place with metal wire or nylon cable. This method involves tying the wire or cable around the middle of the bristle and bending it in half. The wire and bend point is then drawn through the core’s pre-drilled holes and secured with a knot to lock the tuft into place. Wire drawing is an extremely secure method of attaching the filament tuft to the core and requires extensive labor as each tuft must be individually placed and secured.

Cleanliness of Natural Bristle Brushes

Not many people will look at a horse or hog and say “I want to clean my sensitive electronics with THAT”. Techspray takes special care to ensure our natural fiber brushes are clean and free of contamination.

The horse and hog hair used in Techspray brushes are “dressed”, meaning cleaned, sterilized, combed, and bundled. Horse hair is sterilized using steam in an autoclave at 257°F (125°C) or higher, for at least 45 minutes. For hog hair, this procedure requires sterilization with boiling water or steam of at least 212°F (100°C) for 2 hour or longer.

These cleaning processes meet or exceed sterilization requirements of the US Department of Agriculture for manufacturing brushes.

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When cleaning sensitive electronics, close attention needs to be paid to whether or not a brush can be grounded, or at least not generate a static charge. With this in mind, it is surprisingly common to find consumer-grade toothbrushes on electronic PCB rework and repair workbenches.

Natural hair brushes are considered static neutral, so are better suited for sensitive electronics than nylon bristles, like those found in common toothbrushes.

Conductive brush materials, like brass and stainless steel bristles, have surface resistivity less than 1 x 105 Ω/sq or a volume resistivity less than 1 x 104 Ω-cm, so allow electrons to move freely.  If both bristles and handle are conductive, brushes are grounded if the operator uses a wrist or heel strap to connect to a common ground point. A common misconception is that conductive brushes cannot generate a charge. If ungrounded, there is still a risk of generating and holding a static charge, which can lead to a damaging ESD event.

Techspray Technical Cleaning Brushes

Techspray's TechClean brushes are made of premium grade materials. Don't be fooled by cheap imports. The bristles on our cleaning brushes are securely stapled in place, eliminating loose hairs. Choose the Right Bristle Material for Your Needs:

• Natural — Soft, resilient and long lasting. Hog bristles are stiffer than horse hair.
• Metal — For burnishing, polishing, non-sparking static dissipation and deburring. Brass is a softer bristle than stainless steel.

General Cleaning Brushes - A wide variety of sizes and bristle material for general maintenance cleaning. All handles are made of strong, static neutral wood.

Static Sensitive Brushes - Ideal for cleaning static sensitive electronics or components. Anodized aluminum falls within the static dissipative range. Steel bristles are conductive, and horse hair is dissipative when saturated with solvent.

Technical Brushes - Small, precision brushes for technical cleaning and coating or adhesive application. Double-sided brushes include tapered end for tight areas. Five tons of pressure are applied to each metal brush handle to ensure that the bristles remain intact during the most rigorous applications. Bristles securely stapled to prevent bristle loss. Two brushes have horse hair bristles that are trimmed at a tapered angle for cleaning tight areas, like along the sides of a BGA or other low stand-off components.

Brush Attachments for Aerosol Cleaners

Some Techspray flux removers include a horse hair brush attachment. This fits over the actuator (spray nozzle), allowing the operator to scrub a PCB surface as the solvent cleaner is sprayed. The solvent passes through an embedded needle and then through the brush in a controlled fashion. The end result is more aggressive cleaning with minimal solvent usage. To ensure proper removal of flux residues once they are dissolved and separated from the board’s or component’s surface, the brush can be used over an absorbent wipe. A final rinse, holding the PCB at an angle to allow for proper flow of the solvent solution, is recommended for critical electronics.

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Is there a correct, safe method for cleaning PCBs?

I've been reading a lot of threads and the amount of conflicting info is pretty staggering. There are users who dump them in a dishwasher, other guys who use water and a toothbrush, really intense guys who remove every component, clean them individually, then reinstall them on the PCB.

Every possible cleaning product on the market seems to be recommended by at least someone, and at least called out by at least two other users.

We even have high rollers using ultrasonic baths.

I got this Sega ST-V board that is crusty as all hell, It's.. revolting. I suspect the previous owner used it to scrach the hair off his back. OR MAYBE WORST

I purchased a jar of Isopropyl Alcohol 99%, and I'm thinking about just giving it a bath of that and scrubbing the dirty out with a toothbrush.. But then I found a post somewhere here or on another forum saying that the alcohol will eat the capacitors.

Some people even recommend using distilled water instead.

THIS IS CONFUSING.

Is there a definitive solution? I like a nice soft bristle scrub with a diluted simple green along with a really good rinse of alcohol or distilled. I have crappy water. Air dry for days.

I did the dishwasher route once but it messed up a Defender PCB, made it white like it messed up the PCB epoxy or something. Was probably too hot.

If anything you put on or do to the board ruins a component, it was already on its way out. Pull your socketed chips. Just think of places water will get trapped and be aware of them. I usually prefer to treat logic boards more gently, IE compressed air and nylon brush dry cleaning.

To be fair I don't run across a lot of boards that justify a heavy cleaning though.

In some cases it's unavoidable, I clean those the same way I would a monitor. Simply green and water, dry with regulated compressed air (making sure to force air into all recesses to get most of the water out), finish with hair dryer to get any trapped moisture.

Removing socketed chips is a great suggestion, but ain't nobody got time for that. :/ I do this for my outrun repairs:

1. I take all socketed ICs and clean them individually
2. Using a nylon bristle brush and simple green (a lot), I scrub vertically and horizontally on the pcb, gently around capacitors sitting high on the pcb
3. Rinse with plenty water
4. Final rinse with deionized water (purified)
5. Dry in front of a fan overnight, but a few hours should be ok.
5. I blow the water out of sockets and connectors about 2-3 hours after starting the fan
6. Visually inspect the following day
7. Insert all cleaned ICs
8. Burn in the pcb to verify functionality or start a repair if the pcb was really dirty to begin with.

If the pcb has corrosion (green crusty looking residue), I use a vinegar solution (Home Depot) and scrubbing prior to Simple Green wash. Some people have used acidic toilet bowl cleaner (Zep) but I have no experience with that.

Pics here

Before


After



My "Drying rack"


Paris No... there is no consensus. So why are we replying with our preferences? As you already said, everyone has their own...

NOTHING ELSE gets a board looking awesome and new like the dishwasher (might use low heat, I've even skipped the soap and it still did a great job). But you have to balance your time, and the risk and cost of failure.

I've dishwashed probably over a hundred classic boards and all my pinball boards -
but I've skipped it on newer boards that cost several hundreds of dollars each. I lost a board once while washing it, but that type went bad all the time anyway.

When they're super expensive, or make up a big part of the value of a game, I just stick with blowing off the dust.

Thankfully, I restored most of my games and washed their boards many years ago, when the replacement cost was low. They don't get dirty again in a home gameroom.

Wade While I do clean a lot of boards. The best one was out of an Operation Wolf. You know, the game with a nice flat surface where people can set their soda can down and then knock it over when they swivel the gun? Oh yeah and what's right below the seam in front of the gun? The board!! This game is at a KOA camp ground I do work for, and when I came in I noticed there was nothing on the screen. I opened the back and see the board covered in soda pop, not only that but it was dry and sticky! No idea how long it ran that way. Pulled the board out took it home and went after it with Simple Green and a paint brush, stuck it in front of a fan for about a week, then took it back and installed it. That's been 2 - 2 1/2 years ago and it's still running great! This topic has been discussed to death, and there's no reason to start another thread about it.

I repair boards for a living. Hundreds of other peoples' boards, some of them worth $- or more. And I wash every one.

Greased Lightning, a medium-stiffness paintbrush, get in all the crannies, hot water rinse, and immediately stick in front of a fan overnight to dry.

Never had a problem.

You don't need purified water. You don't need to rinse with alcohol to remove the water. You don't need to remove the chips first. You don't need to worry about getting boards completely wet. You can submerge these completely and they'll be fine, as long as you completely dry them.

Nothing against dishwashers, but that's more heat than is needed, plus you can't get into cracks and crevices the way you can with a brush. I'm sure it works fine, but it seems like overkill. And you don't have to put dirty boards covered with nicotine and other grime where you put your food dishes. But whatever works. water medium: sprayer; bath tub (once)
chemicals: Simple Green (straight)
tools: toothbrush (thanks for the idea mom)
drying procedure: commercial hair dryer (or whatever southern outdoor method you use)

I would not use dishwasher or ovens or other psychotic measures that have been discussed here in my near 13 year existence on the site. I often am able to power whatever it was I washed up again within 30 minutes, that's how effective my method is with the stuff I have available to me. I have also done this probably 100 times without killing anything, so I'm apparently good at it too.

but, YMMV

if ever you wash a monitor chassis I strongly encourage removal of the flyback and neck socket from the neckboard. I had a negative experience cleaning a flyback with glass cleaner a couple weeks ago, so just leave the filth on it or wipe it off the best you can.