Conductive Chemtronics flux? - Page 1
Forum section: electronics / general

author: SolarSunrise
author_rank: Regular Contributor
timestamp: August 04, 2013, 01:28:41 pm
content: Recently, I've been soldering SMD parts for my little EEG amplifier. When I was soldering the components for the active electrodes, I found out the residue left by my Chemtronics water soluble flux (part no. CW8300) were sort of conductive (ranging between 10M ohms and 200K ohms!!!).Is it suppose to be like this or is there a fault on my Extech EX330? (By the way, the resistance of the flux residue keeps on changing when measuring with my multimeter.)Thanks!

author: Unknown
author_rank: Unknown
timestamp: August 04, 2013, 01:45:55 pm
content: Water soluble flux is conductive and corrosive and should always be washed off after use. Rosin and especially no-clean flux is much less conductive and may only have to be cleaned for high impedance or high-reliability applications.

author: plesa
author_rank: Frequent Contributor
timestamp: August 04, 2013, 01:52:45 pm
content: Thats why the sensitive circuits needs to be cleaned properly. E.G fingerprints can affects such a sensitive measuremets. Sometimes is also used conform coating which prevent surface contamination and possible leakage ( Scotch in manufacturing one of them).I higly reccommended the Keithley low level measuring handbookhttp://www.keithley.com/knowledgecenter/knowledgecenter_pdf/LowLevMsHandbk_1.pdfI'm using the Chemitronix CW8510 9 NoClean, the residues are also conductive in megohm range.

author: wraper
author_rank: Unknown
timestamp: August 04, 2013, 02:39:09 pm
content: Amtech so called no clean flux NC559 is also highly conductive, something like 10M if measuring a strip of it with 1 cm distance between probes. It's genuine BTW, from authorized distributor, not from ebay. Didn't cause any problems with BGA chips however, maybe it's not conductive after reflow. But with soldering iron it's impossible to heat it throughly. I measured some fluxes and they were ~500M measuring the same strip. The flux with highest resistance I tested so far is Edsyn FL-22, there is almost no conductivity.

author: free_electron
author_rank: Super Contributor
timestamp: August 04, 2013, 03:40:52 pm
content: Almost all flux is conductive. Especially water soluble. It absorbs moisture from the air and saponifies... That is its intended function !

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 05, 2013, 04:34:12 pm
content: i have similar experience with plumbing (zinc chloride) flux. kinda my fav flux right now, just have to not forget about cleaning it later. certainly no no for app where it can sneak below the chip or sensitive components.

author: wraper
author_rank: Unknown
timestamp: August 05, 2013, 05:20:51 pm
content: Mechatrommer, are you seriously soldering PCBs with that shit? You just can't wash that away completely, it penetrates into board and it will remain conductive despite how much you wash it.

author: G7PSK
author_rank: Super Contributor
timestamp: August 05, 2013, 05:39:11 pm
content: Zinc chloride is very conductive which is why you should never use it with an electric soldering iron, after all it is acid based along with a highly conductive metal. Also very corrosive not just to the components being soldered but also to human tissue such as skin and lungs etc.

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 05, 2013, 06:26:18 pm
content: thats why a said, only for through holes or easy smd'si know i know i surrender! it just tasted good on the iron.

author: nukie
author_rank: Frequent Contributor
timestamp: August 07, 2013, 12:45:35 pm
content: Those high activity acid flux will eat away your tips quickly. Water soluble and no clean flux is no angels they also dissolves your tips.

author: SolarSunrise
author_rank: Regular Contributor
timestamp: August 14, 2013, 09:21:11 am
content: Thank you for the replies! After soaking the board in hot water for few minutes, my circuit is working again.For those of you who have the same problem, just soak your flux-stained board in 60C hot water for several minutes. It then should be good to go!

author: Stonent
author_rank: Super Contributor
timestamp: August 20, 2013, 02:01:44 am
content: Quote from: SolarSunrise on August 14, 2013, 09:21:11 amI would recommend distilled water (sometimes the jug will say for steam irons) that will prevent any dissolved minerals from settling on the board. Sodium Fluoride and other salts can be conductive.