Is this just a weird/ random application of conformal coating, or is it flux? - Page 1
Forum section: electronics / general

author: Razor512
author_rank: Regular Contributor
timestamp: January 04, 2024, 08:11:59 am
content: While opening up a battery pack (planning to ultimately replace the individual cells, I noticed what seems to be conformal coating. I was also suspecting flux, but in trying to clean it with 99% alcohol, the residue does not come off at all. This is overall leaving me to suspect some kind of conformal coating. The only issue is the application seems random as some components have it and others do not. This randomness of the coating applies to both passives, and ICs. Added a 2 additional images to imgur since total attachment sizes are limited and even compressing to 8MB leads to noticeable detail loss.https://imgur.com/a/Qo9RSR2The battery is a Dell 7WMM7 (I have 1 extra one that I swapped in), and since it is a rather old product, 3rd party replacements are pretty overpriced (in the $50 range).The battery back suffered a weird failure where something leaked from the top right cell and corroded its connector, that failed cell also caused the pack to refuse to charge.My plan is to simply remove the old cells, and find new pouch cells of the same size, and spot weld the tabs onto the tab leading to the resettable fuse for each cell.Anyway, I was just wondering why some components seem to have a bunch of conformal coating while others have none.

author: elektryk
author_rank: Regular Contributor
timestamp: January 04, 2024, 12:40:14 pm
content: QuoteSo the BQxxx can be locked now and it may need to be resetted.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 04, 2024, 01:53:00 pm
content: Just some high impedance nodes that they don't want (slightly) conductive dust messing with.

author: wraper
author_rank: Unknown
timestamp: January 04, 2024, 02:02:36 pm
content: Quote from: elektryk on January 04, 2024, 12:40:14 pmNearly guaranteed to be locked and most likely is either is not possible to unlock or requires expensive software that does not make sense for one-off.

author: tooki
author_rank: Super Contributor
timestamp: January 04, 2024, 04:44:06 pm
content: Quote from: Razor512 on January 04, 2024, 08:11:59 amYou could have cropped off 80% of the image and just left the relevant part of the board visible. (We don’t need to see the cell pouches or bubble wrap to answer your question.) Or just add additional images in replies. Offsite hosting is the worst, because if/when the offsite server goes offline, the images in the thread vanish. Much better to use the forum’s own hosting.Quote from: Razor512 on January 04, 2024, 08:11:59 amGiven that, with the protection/authentication chips creating the risk of the pack not working even after cell replacement, $50 seems quite reasonable.Quote from: Razor512 on January 04, 2024, 08:11:59 amOne possible answer is simply cost. Another is the possible need to attach some components (like the cells) after conformal coating.I suspect that what looks like flux is, in fact, flux. It’s just had conformal coating applied over it.

author: thm_w
author_rank: Super Contributor
timestamp: January 04, 2024, 09:28:48 pm
content: It is conformal coat or some sort of clear glue/epoxy.They've specifically covered most of the passives (corrosion or impact resistance) as well as the wires soldered on (for strain relief). As Tooki said you can't cover the battery contacts because you need to spot weld those later.You can: hand/machine dip, spray, or brush glues like this. In this case it appears to be machine dispensed onto the board.