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Professor angry as I clean old PIC devboard with nylon brush, and warned me to use horsehair brush next time.

I have been using nylon brush for long time, even to clean my PC and audio amp and they still not damaged.

Is horsehair brush one of the ESD myth or really very much better than nylon in reality?

Did anyone really kill PCB using nylon brush, or people use horsehair brush only out of scare?

Asking because horsehair brush very thin and expensive but nylon brush in three different sizes and very cheap and easy to cleaning using only water.

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  • \$\begingroup\$ Lack of ESD compatibility makes a lot of things cheap. \$\endgroup\$ – Mike DeSimone Aug 31 '11 at 12:57
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    \$\begingroup\$ ESD protection has many features of religion: An invisible power, current virtue vs. eventual punishment, etc. If your professor is a strong believer, you probably won't change his mind. \$\endgroup\$ – markrages Aug 31 '11 at 23:10
  • \$\begingroup\$ Wiping a dev board with a brush is also weird. But home works at electronic classes are often weird. \$\endgroup\$ – Fredled Apr 25 at 23:47
  • \$\begingroup\$ Why are you using a brush? isopropyl and kemtec wipes. Manufacturers usually wash with (de-i) water, local touch up with iso \$\endgroup\$ – crasic Apr 25 at 23:59
  • \$\begingroup\$ @crasic I find a brush on top of a wipe is best. The wipe picks up the flux and easily swapped out when saturated while the brush is just to apply pressure into knooks and crannies where your finger pressure can't reach. For that reason, I prefer stiff bristles. It is meant to apply pressure like many thin little fingers, not wipe. Horse hair is for wiping and is not stiff enough. \$\endgroup\$ – DKNguyen Apr 26 at 0:29
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Natural Bristol brushes such as horse hair generate less static electricity. There are some Nylon brushes designed to reduce ESD, but a general purpose nylon brush can cause ESD damage.

ESD damage is a cumulative effect. While there are occasional catastrophic effect that destroy device immediately, most ESD damage shortens the live of the device rather then causing it to fail immediately.

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There are two properties of a material that matter related to ESD (ElectroStatic Discharge): How much they generate static electricity when they rub against something, and how well they bleed off any charge that might accumulate.

Being even a little bit conductive helps a lot in reducing ESD problems. It's hard to generate lots of static charge, so a little bleeding off of the charge usually keeps it below the level where it can cause damage. Unfortunately, nylon is a very good insulator so won't help much in bleeding off any charge.

I don't know the properties of horse hair in this regard, but it's quite possible that it has lower bulk resistivity, especially when there is some humidity in the air. Perhaps horse hair produces less charge when rubbed. Materials vary in that regard, and I don't know about horse hair. Cat hair is notorious for generating charge, especially against rubber. Human hair is fairly good when clean. Think of rubbing a balloon against your hair. You can usually make it stick to something after that due to its static charge. Dirty hair or hair with various conditioners in it (really a form of deliberate dirt) works less well because the dirt provides a bleed path for the static charge. Some conditioners do this deliberately. Perhaps horse hair has this sort of thing built in. You'd have to ask a horse for details, or failing that perhaps your professor.

In any case, he's probably right about nylon being a bad idea.

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  • \$\begingroup\$ So, better not wash your hairs when you do electronics. LOL. Seriousely, one explanation is that horse hairs are porous and gather humidity making it slightly conductive. \$\endgroup\$ – Fredled Apr 25 at 23:43
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Horsehair, tin-handle acid brushes are under $20 a gross (144 pieces) or $0.14 each. A quick search shows that nylon brushes of the same size are (perhaps surprisingly) twice the cost for the same size brush. Maybe your professor wouldn't mind buying a box and handing them out. Also, nylon can be static-dissipative or not, so whether there's a concern depends on what you're using.

For example: https://www.gordonbrush.com/brushes/acid-sash-parts-cleaning-brushes/acid-brush

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If you are using insulative fibers it MUST be kept wet which helps alleviate the charge build up. Even horse hair is subject to this (rub your hair against a balloon and watch the static build) but natural hair builds up less charge than regular nylon bristles (i.e. nylon not treated to be dissipative) and it also absorbs liquid more than nylon which helps it stay wet.

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