Brushing over a small IC with a Non-ESD brush? - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: December 17, 2021, 10:42:29 pm
content: Hi,I need to solder on some 10MSOP chips (TPS5401's) onto a PCB. Because i use the "mop-up soldering" technique to remove excess solder from the pin rows, the boards tends to get dirty with residue. This is because its difficult to do it in one go...several "Mops" are needed to get rid of shorts, and after each attempt, the chip needs cleaning and brushing off with an ESD brush dipped in IPA....I have tried to order one of these ESD brushes...https://uk.farnell.com/duratool/d03142/conductive-brush-pp-ergonomic/dp/2543026?st=esd%20brush..But i am not allowed to order it..They have said i should just use one of the wooden-handled, small paint-brushes that are already in the lab.These small paint brushes look like the attached.Do you believe that the "small paint brush" will cause ESD damage to the 10MSOP when i brush over it?What material is used in the ESD brush, which avoids this ESD damage?TPS5401https://www.ti.com/lit/ds/symlink/tps5401.pdf?ts=1639772598229

author: SMdude
author_rank: Frequent Contributor
timestamp: December 17, 2021, 10:50:21 pm
content: You need to start tracking every dollar management spend on useless shit that doesn't contribute to getting anything done. As well as every hour you spend trying to workaround their ridiculous tight-assedness.I use an old toothbrush! Never caused me any issues, but you may not be so lucky

author: ataradov
author_rank: Super Contributor
timestamp: December 17, 2021, 11:03:22 pm
content: Indeed, just use a toothbrush. Life must be so hard when you overthink and over-complicate everything.Also, this soft bristle brush will take forever to remove anything.

author: fourfathom
author_rank: Super Contributor
timestamp: December 18, 2021, 12:06:17 am
content: For my prototype boards I use a toothbrush and scrub with rubbing alcohol. I assume that the water content of the alcohol makes it very unlikely that ESD will be a problem, and I've never had an ESD failure that I am aware of. Of course, I don't live in a low-humidity high-static area.

author: m98
author_rank: Frequent Contributor
timestamp: December 18, 2021, 03:19:26 am
content: SomeTI switching regulator ICs are real mimosas that will die in all kinds of ungraceful ways if you turn them a wrong look, so taking some ESD precautions is certainly a good idea. Probably not to the extend of ESD-safe brushes though. I just have a set of hog hair brushes of varying sizes that work perfect for cleaning. That material should also be quite dissipative by nature.

author: helius
author_rank: Super Contributor
timestamp: December 18, 2021, 07:27:02 am
content: Indeed, all plant and animal fibres are dissipative, although they can have triboelectric properties. Horse hair and hog bristle are normally used in "ESD safe" brushes and when set in wood handles there is no special treatment required. However, the brush you pictured appears to have a possible insulating lacquer coating which is not an ESD safe material.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: December 18, 2021, 07:44:10 am
content: Just use more alcohol during the cleaning and make sure you don't wipe it dry with the brush. Use hot air or just compressed air to clean it dry.But I'm wondering what sort of a management disapproves an essential item costing few $.

author: Shock
author_rank: Super Contributor
timestamp: December 19, 2021, 02:30:38 am
content: You can get ESD brushes that are more like toothbrushes or acid brushes, better for cleaning in my opinion. With acid brushes you can trim the length to get a more aggressive bristle profile. It's probably the same with toothbrushes but they are a bit more awkward to trim.Once the board and brush are wet with ipa or flux cleaner soaked I suspect it's far harder to damage the board with ESD but if you are working for a company why take the risk for a few bucks. Worse case scenario but say an ESD issue leads to some weird issue arising, a $5 brush could turn into thousands of dollars of lost productivity.

author: MarkF
author_rank: Super Contributor
timestamp: December 19, 2021, 10:08:58 am
content: I use the acid plumbing brushes with half of the bristles cut off to make them firmer.You can get 100 of them for next to nothing.I also use them unmodified for gluing woodworking projects in addition to actual plumbing jobs.

author: Faringdon
author_rank: Super Contributor
timestamp: December 19, 2021, 01:19:31 pm
content: Thanks,It seems that any brush can be used as long as the PCB is soaked in Iso propyl alcohol.As such, IPA is rather expensive, and i actually wonder if its possible to use "Clean spirit", "White spirit", or "turpentine" instead of IPA?https://www.diy.com/departments/diall-clean-spirit-0-75l/1059029_BQ.prd

author: jc101
author_rank: Frequent Contributor
timestamp: December 19, 2021, 03:45:16 pm
content: Quote from: Faringdon on December 19, 2021, 01:19:31 pmI'd have thought all those would leave a residue behind. 1L of IPA is ~£12 ex VAT, which lasts ages. You don't need huge quantities. I use a little with a brush, then some compressed air to dry things off. As an aside I gave up buying tins of compressed air last year, buying a small oil-less compressor instead. It's probably paid for itself by now, and no shipping tins of air around the country either.https://uk.farnell.com/pro-power/ppc104/ipa-solvent-tin-1l/dp/1206536?st=ipa

author: Gyro
author_rank: Super Contributor
timestamp: December 19, 2021, 07:00:35 pm
content: Quote from: Faringdon on December 19, 2021, 01:19:31 pmNo, they're entirely different things - you need to havesomeconsideration for the component on the board, and the residues, not to mention thesmellthese will leave. Stop cheaping out!

author: Faringdon
author_rank: Super Contributor
timestamp: December 21, 2021, 05:27:18 am
content: QuoteThanks, smell and residue dont worry me for these few prototypes...but if if damages the component?.....then that is something that worries me

author: Nusa
author_rank: Super Contributor
timestamp: December 21, 2021, 05:45:35 am
content: Well, if they won't buy you a brush, clearly you aren't paying overhead costs. So why are you sweating the cost of IPA? You aren't buying it.

author: Gyro
author_rank: Super Contributor
timestamp: December 21, 2021, 09:47:22 am
content: Quote from: Faringdon on December 21, 2021, 05:27:18 am"...but if if damages the component?" Well I suppose it's some sort of positive that you're concerned about that! You have no clue what the ingredients of the brush cleaner are, so how are you going to assess materials compatibility? White spirit and Turpentine will most likely give compatibility issues with plastics and markings. Shame you're not concerned about residues though....... Why am I wasting my time typing this - do youstillknow nothing? Let me guess, you've imported a bunch of cheap faulty shit and now the customer has insisted that you go to London to fix them!BUY IPA!

author: nali
author_rank: Frequent Contributor
timestamp: December 21, 2021, 10:07:17 am
content: When you've convinced "them" buying some IPA is a good thing, add some flux to the list and look at a couple of videos on drag soldering else you'll be spending quite some time "mopping". The time saved should eclipse the cost.I find it a bit incredible that "someone" has decided to go on a field trip to change some ICs, ordered the components but not the solder, cleaner, tools (as per other thread) ..?

author: PlainName
author_rank: Super Contributor
timestamp: December 27, 2021, 11:43:42 pm
content: Are you trying to wash the stuff off with IPA? I used to do that, but then I realised that the better way is to let the IPA dissolve the flux residue and then just soak up the IPA with kitchen towels. Uses far less IPA, is quick, and no danger from rubbing too hard with a toothbrush (which previously used to scrub it all off).If you do it this way it is tempting to keep wiping until the board is dry. Not necessary - just soak up most of the mix and the rest will evaporate after a short while. Doing it this way also lends itself to doing it often and a little at a time.

author: Faringdon
author_rank: Super Contributor
timestamp: December 29, 2021, 09:11:41 pm
content: QuoteThanks, sounds good, but even though you are not wiping repeatedly with the kitchen towel, and it sounds like you are just "pressing" it down a bit, can this still cause "some" ESD damage?

author: PlainName
author_rank: Super Contributor
timestamp: December 29, 2021, 09:28:18 pm
content: If you're grounded with a suitable wrist strap and your bench is similarly ESD-aware, I can't see how it might be a problem.But note that I don't do it like this because of possible ESD mitigation but simply because it's easier, less messy and uses fewer resources. I imagine it might well depend on your brand of flux, though.

author: helius
author_rank: Super Contributor
timestamp: December 30, 2021, 04:54:20 am
content: The principal technique for cellulose wipes is to lay the wipe across the board, saturate it with solvent and use a brush from the top side to agitate the soil trapped between the board and the wipe. Since the wipe is flexible and porous, suspended/dissolved soils migrate into it and away from the board. Note that electronic wipes are available made from cellulose, polyester, or a blend of both. I would avoid the polyester ones for ESD sensitive components; the solvent should dissipate charge but why take the chance.

author: mzzj
author_rank: Super Contributor
timestamp: January 02, 2022, 05:27:19 pm
content: Quote from: jc101 on December 19, 2021, 03:45:16 pmOP has always his own very "special set of problems" ...Anyhoo, here in Finland IPA is easiest to find in auto stores sold as gasoline anti-icing additive. 4eur/l or so.Some versions contain trace amount of some sort of oil but I have managed to find also pure IPA that leaves no residue on glass after evaporation.And if you need more than just a few litres the price is less than 1 eur/l in 200L barrels or 1000L IBC tote