I need a solder/flux/cleaning system. - Page 1
Forum section: electronics / general

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: December 05, 2019, 10:53:01 pm
content: Backstory: I am building PCBs (of my own design) that must be cleaned and waterproofed (urethan conformal coating), as they are used outside in industrial environments.Leaded is just fine, we are not subject to ROHS as we re-use some old components that contain leaded solder anyway.We clean with an ultrasonic cleaner, we currently have Flux-Off Aqueous and Branson EC cleaners available.The Branson EC works pretty good on our Rosin flux, left in long enough, but by that point its starting to tarnish (leave some kind of film) on aluminum heat sinks. This makes application of conformal coating problematic. The Flux-Off just isn't removing the rosin flux (like its supposed to, even when we let PCBs soak and give them a good 20 minutes of ultrasonic action).So I'm shopping for a new solution, basically I need a solder/flux that will work with either one of the cleaners we have. All PCBs are washed, so I'm thinking of diving into water soluble flux which MUST be cleaned instead of the ChipQuik no-clean/water wash offerings that have so far given us crap performance with both flux core solder wire AND solder paste.

author: Ian.M
author_rank: Super Contributor
timestamp: December 05, 2019, 11:12:17 pm
content: What happens with the Branson EC and your heatsinks if you pre-soak the boards in IPA for long enough to soften the Rosin flux residue to reduce the time it needs in the EC in the ultrasonic cleaner tank?

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: December 06, 2019, 06:44:28 pm
content: Wouldn't really be practical to soak in IPA first. I'd need a 1.5 gallon tank of IPA to fit the entire finished assembly into!I did an order from DigiKey last night. I got:no-clean/water washable liquid fluxsome ChipQuik no-clean/water wash flux core solder wireSome Kester water soluble flux wire (must wash)I guess its down to trials. I like the Flux-Off as it doesn't damage the aluminum in any way. Its supposed to get off hard, dried on rosin fluxes, but I even increased the concentration to no avail, at least not nearly as quickly as the Branson EC.

author: Cloud
author_rank: Regular Contributor
timestamp: December 07, 2019, 06:20:33 pm
content: How I clean my PCBs:Flux remover (in a can with a brush) and clean where the flux is burned.Clean flux residues with ethanol or acetoneIf needed use flux removerThan heat flux removing solution to 70C and turn on ultra sound for 2-3minBlow it dry with air compressorWhat you want to avoid is multiple exposure to ultrasound. Had a few delicate circuits fail if they were exposed multiple times to it

author: jmelson
author_rank: Super Contributor
timestamp: December 09, 2019, 08:28:29 pm
content: Quote from: Rat_Patrol on December 06, 2019, 06:44:28 pmOn some of our boards I use water-washable flux, either liquid flux for dip soldering, or WS solder wire for the hand-soldered connections.This has worked very well. My procedure is to wet the board, and then scrub for 5 seconds with a toothbrush, then rinse in running water. They look as clean as they couldever get.Jon

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: December 09, 2019, 09:34:21 pm
content: Well, ChipQuik continues to disappoint.It washes well, but the actual flux action is not great. Just can't get it to flow well. Oddly enough, their flux when used on its own works fine. Dunno.The Multicore Hydro-X works wonderfully. While not a problem for us, you MUST wash it or it will damage the boards. It flows well, washes well. I'm not gitty about the possibility of damaging boards if 100% of the flux isn't removed. We don't have (nor have the budget for) ionic testing equipment, so if we keep using this solder, we will just have to wash and rinse very well.We will keep playing with the ChipQuik to see if we can get satisfactory results since its a no-clean.

author: jmelson
author_rank: Super Contributor
timestamp: December 11, 2019, 08:13:54 pm
content: Quote from: Rat_Patrol on December 09, 2019, 09:34:21 pmNo Clean is horrible stuff, if you need to clean the board! I use a lot of no-clean solder paste and wire, but if it DOES need to be cleaned, then water soluble is MUCH better.If you DO have to clean a board soldered with no-clean, it takes several cycles of alcohol and ultrasonic bath, and maybe scrubbing with a toothbrush.Jon

author: Rat_Patrol
author_rank: Frequent Contributor
timestamp: December 12, 2019, 04:25:29 pm
content: I'm playing with ChipQuik more, and I think I've got their water-wash wire working (well enough) for the THT parts, and I've found a water wash ChipQuik paste (leaded, 183 degree melt) that reflows well. I ordered another LF version paste with the same flux type and mesh size, hopefully I can get that to reflow properly as well. Since the LF melts at 227-ish, I'm going to put a piece of welding blanket under the PCB when I do the second reflow, hopefully that keeps temps low enough as to not have issues when I run the leaded reflow on the top of the board since the melt temps are so close.I would have used their low temp paste, but it melts at 138 degrees, and my boards are rated to operate at 110 degrees, and those two are too close for comfort.

author: 1276-2449-1-ND
author_rank: Regular Contributor
timestamp: December 19, 2019, 01:29:18 pm
content: I went through this problem last year and found that water-based fluxes are a lot harder to clean.Solders with RA fluxes clean very easily with IPA, and then water (if necessary).Solders with water-based fluxes (especially "no clean") have a waxy film that needs hot water and scrubbing to remove. IPA just makes a mess.