Should flux be cleaned from pre-assembled boards?

Recently, several Vendors have shipped me "fully assembled & tested" boards, that contain all of the flux from the assembly process. Not only does this look sloppy and unprofessional, but depending on the type of flux, may be corrosive.

Is it just me, or don't you expect that a vendor should remove flux before they sell a product? Sure, its an extra step in the manufacturing process. But if done in batch, it would add less than a minute to the assembly time for each board.

When a board contains an LCD screen, it is very hard to clean without getting solvent on the screen. (Whereas the manufacturer could have easily soaked the board in a flux removal agent before attaching the LCD.)

This is particularly annoying when a vendor does not offer a "kit" or "PCB only" option, and we are forced to pay for this type of manufacturing.

I'm not naming vendors, as my goal is not to call anyone out - I just want to see what the community thinks.

Thoughts? Comments?

Time to get a new vendor. And...we're primarily a consumer forum, I certainly don't mind if you name or hint at the vendors. Nothing will change if you protect them.

Thanks for the reply. Unfortunately, these two vendors make unique products, so I can't source them from someone else.

I don't' feel comfortable calling them out until I get a few more replies. I will say that's it's not SparkFun, or Adafruit - they're both GTG! (and it's not an Asian factory either!)

If it's "no clean" flux, I don't see why a vendor should be expected to remove it; it is rather greener to leave it on (no volatile solvents polluting anything.) OTOH, I wouldn't there to be so much left that it's an eyesore, and I'm not sure how you as the customer can know whether or not it's a non-corrosive flux... (although, it's the water-soluble fluxes that tend to be more corrosive...)

Thanks for the feedback. I'm surprised more people haven't commented, despite a large # of reads; I guess most people just don't care.

I agree that as the end consumer, I have no idea what type of flux it is. Since it looks horrible and could be corrosive, I'm forced to clean it off.

I've never had a problem cleaning flux off with a 50-50 mix of acetone and isopropyl alcohol, both of which simple evaporate if left exposed to air... so I don't really see how those could be considered non-green.

I guess I got spoiled by SparkFun's quality.

acetone and isopropyl alcohol, both of which simple evaporate if left exposed to air… so I don’t really see how those could be considered non-green.

well, when they evaporate they don’t just go away, they dissolve into the atmosphere as pollutants, therefore non-green.

(I’m not arguing against using these solvents; I use acetone and alcohol as well as other solvents as needed myself.)


Okay - i admit my previous statement was wrong, and this mixture does indeed enter the atmosphere.

It does however break-down relatively quickly by both sunlight and microorganisms in earth - as it's half-life is only 22-days. So as far as chemicals that impact the environment, acetone is certainly far from the worst.

Back to the original question - is anyone else besides myself and the 2nd poster bothered when they receive new boards that contain all of the Flux from the assembly process?

I personally wouldn't like it at all, as it seems sloppy at the very least.

Objectively, if it's no-clean it probably wouldn't hurt the device. But it's still ugly.


I dunno. “some flux” wouldn’t bother me much. I don’t expect or require boards to be spotless (and actually having them conformally coated, which might be considered the next step up in professionalism, would definately be a BAD thing), but I don’t expect them to be “messy”, either. It sounds like your boards have a LOT of flux; perhaps significantly more than I would leave behind if I soldered them myself. Care to post a picture?


Can you tell us what boards you are referring to and where are they made?

Also it could be that you had the bad luck to get a few that didn't look perfect....


Okay, at the request of the Administrator, I'll disclose the boards.

Unfortunately, I have already cleaned them, so I cannot post any pictures. This is an oversight on my part, but at the time I didn't expect that I would need pics. (I thought it more of a yes/no answer vs. "how much flux")

But first, I must re-iterate that my goal from this thread was to check the community "standard" before I emailed the vendors - It may be that my expectations are abnormal. I've purchased several thousand dollars worth of boards and components from SparkFun and never received any items that contained ANY flux. I'm used to "factory new" looking products - so that is where my expectations come from.

Also, I should note, that all of the items work fine and perform exactly as advertised, and I do not wish a refund. I would just like to see them add an extra bit of "care" to their manufacturing process.

The specific products I'm referring to are the Touch-Shield-Stealth from Liquidware and the Ethernet Shield from Nuelectronics. (Although other "pre-assembled" products that came from these vendors had the same "bonus flux", these two were the worst offenders.)

I really like Liquidware products, and I think the double-wide and double-tall are great products! In fact, I probably could have overlooked the flux on their products entirely, if one of them wasn't their $140 Touch-Shield-Stealth. When I'm paying $140 for a shield, I feel like they should take the time to clean the flux off it. I was also particularly frustrated since removing the flux was very tricky because the LCD is permanently attached to the board, and trying to keep the solvent away from the LCD was very hard.

I also like Nuelectronics products, and really dig their stack-able proto-shield (Awesome design!!), and they function well, and are relatively inexpensive for their functionality. Perhaps they "cut corners" to keep their prices low. Unfortunately, their SMT assembly process may be the cause of my angst - on the Ethernet Shield, all of the SMT components were entombed in solidified Flux. This wasn't merely dots of flux at the solder points, it was gobs of flux all over every SMT component. The thru-hole solders on these boards were normal, and had a normal amount of Flux. But the nasty-look of the SMT parts made the whole board look dingy.

To summarize: I like these companies, I have had no problems with their customer service, I like the product functionality, and I will continue to buy from them. I merely wish they would enhance their product "fit & finish", as isn't up to the standard that many other suppliers provide.


(Edited to soften the tone a bit.)

IMHO, A photo would be great... before you clean it up.

For mass production, it is very neccessary to discuss with supplier on these details, even specify the solder used or demand an extra cleaning process.

For small batch manufacturing, the factory uses hand soldering. As far as I have seen, there are 3 most popular flux: 1. the yellow solid one, which would probably leave many messy to the soldering point, most difficult to clean (chemical solvent). 2. Light yellow solid one, it leaves flimsy white residue after soldering, even your finger nail could remove them easily. 3. Light yellow fluid-like, it leaves some oily residue, a tissue will remove it perfectly.

The third one is the most expenisve, but the final result is only on visual part. They all contain flux, cleaned away or left messy.

Oh no, you're totally right, and I'm so embarrassed... my soldering skills are getting better, but it's actually pretty tough so if it's that bad, or it's messed up, I'll just send you another one. This is the first time anyone's even mentioned this to me, but that's no excuse!

The real problem is that I have to put the screen on first manually before I place the right angle header that passes through the pins that I cover up with the shield when it snaps onto the Arduino. I really didn't like the idea of not passing those pins through because then it wouldn't really fit the "physical computingness" of it all. So I guess I thought pin access was important, but I could only use a screen that folded a connector down-wise like you see in the pictures. In order to keep all the Arduino pins accessible, I had to solder on that header myself.

Anyway, it's also really hard to clean the residue away :( Because of the screen, I can't use water or liquid chemicals like acetone from CVS or the hardware store. Acetone can leak into the screen, and it ruins $140 of electronics in a split second! I know because I've messed up quite a few trying...

It's like a big jigsaw puzzle, really, since I tried to cram a lot of different layered components into a same space. And that's not even talking about the touchscreen overlay part.

Oh well, I feel really bad, kind of like I brought home a bad report card ... is there anything I can do to make it up? I'm gonna go back to the drawing board and see if I can think up a better way to do this... there must be some way... if you want a new TouchShield, just shoot me an email at


inthebitz -

I'm very sorry that I made you feel bad, and please do not worry any more. That's why I really didn't want to divulge specific products, as I didn't want to hurt anyone's feelings or make it appear that the products were flawed.

The boards work perfect, and as I mentioned in the post, I have no issues with them or your company. I was just trying to understand what the "industry standard" was regarding flux removal. As you can see from the responses, people's thoughts on this vary widely - so I wouldn't worry about it. (If I was that unhappy I would have contacted you.)

On the TouchShield, I did get most of the flux off via VERY careful use of an acetone/isopropyl alcohol mixture used with wooden cotton swabs. I had to be really careful around the screen - and that's what got me a little annoyed (temporarily). From your post I now realize that there is an assembly order that makes it hard for you as well.

Ironically, since I made the original post, I've bought robotics boards and controllers from several companies (like Pololu and Trossen) and I've noticed that many of these components have residual flux on them.

So, it actually now appears that "fluxxed boards" are common in these hobby-ist boards, so I guess I was just spoiled by Sparkfun's super-clean boards.

Peace - 33\/\/