Flux Paste for SMD soldering? - Page 1
Forum section: electronics / beginners

author: JenniferG
author_rank: Frequent Contributor
timestamp: November 18, 2022, 11:37:41 am
content: Watched this cool video for soling smd with soldering iron. He used Mechanic brand flux paste -- he shows the particular one he uses at seven seconds into the video:LHe did a pretty great job and I'd like to try his technique for MSOP VSSOP etc..I looked on Amazon and other places and I can't seem to find this exact paste. Should I grab the popular SRA rosin flux paste? I've never used flux paste before but it seems like a very good idea.. really makes things easy.

author: JohanH
author_rank: Frequent Contributor
timestamp: November 18, 2022, 01:03:49 pm
content: I use cheap flux paste that comes in a syringe and really like it. I prefer it over the more solid stuff and neither do I use the flux pen (liquid) after I got the paste. You need flux remover to clean up the remains.

author: JenniferG
author_rank: Frequent Contributor
timestamp: November 18, 2022, 01:44:47 pm
content: Quote from: JohanH on November 18, 2022, 01:03:49 pmThanks yeah I've seen the liquidy syringes too and they worked very well. Which syringe should I buy?I've used alcohol in the paste to remove flux.. worked well I thought.

author: Hendrik
author_rank: Contributor
timestamp: November 18, 2022, 01:50:30 pm
content: https://de.aliexpress.com/item/4000216497015.html?spm=a2g0o.productlist.main.1.56ca6d32lGVqOQSeems like the flux in question (atleast the naming matches MCN-UV80, don't know if genuine). If you don't mind waiting a couple of weeks.

author: ledtester
author_rank: Super Contributor
timestamp: November 18, 2022, 02:06:59 pm
content: Dave's video on SMD soldering:EEVblog #997 - How To Solder Surface Mount Components -- EEVbloghttps://youtu.be/hoLf8gvvXXUDave uses a pen flux dispenser in the video.

author: rstofer
author_rank: Super Contributor
timestamp: November 18, 2022, 03:03:33 pm
content: I use MG Chemical No Clean Flux Paste:https://www.digikey.com/en/products/detail/mg-chemicals/8341-10ML/2233037This will also work:https://www.howardelectronics.com/smd-rework/chip-quik-low-temp-smd-rework/smd291/chip-quik-smd291-flux-10cc-syringe/

author: JenniferG
author_rank: Frequent Contributor
timestamp: November 18, 2022, 04:09:17 pm
content: Quote from: Hendrik on November 18, 2022, 01:50:30 pmOrdered it, good price. Thanks

author: JenniferG
author_rank: Frequent Contributor
timestamp: November 18, 2022, 04:49:16 pm
content: For those in the USA, do you use 0.25mm diameter solder? Another guy which did a great job SMD soldering on youtube suggests 0.25mm solder. I see some on amazon for $10.

author: jmelson
author_rank: Super Contributor
timestamp: November 18, 2022, 05:02:56 pm
content: If you can get 0.25mm (0.010") solder, that is great. I have some at work for micro soldering. I do down to 0.65mm lead pitch parts with thicker solder, around .75mm and it is no problem. But, I occasionally have to do 0.4mm lead pitch ICs. For those, I usually want the finest solder, and wipe liquid flux on the leads first. I now prefer using water-soluble flux, and then just wash it off at the sink.Jon

author: rstofer
author_rank: Super Contributor
timestamp: November 18, 2022, 11:32:21 pm
content: Quote from: JenniferG on November 18, 2022, 04:49:16 pmThat's what I have been using for years and years. Works well for small components.ADD: messed up on the units. I use 0.025 INCH diameter solder.

author: JenniferG
author_rank: Frequent Contributor
timestamp: November 19, 2022, 10:11:37 am
content: Quote from: rstofer on November 18, 2022, 11:32:21 pmHere's what I found. it's actually $11.99 and 0.3mm :https://www.amazon.com/Ultra-Thin-0-11lb-Precision-Electronics-Soldering/dp/B07VT4MLD1Should I grab it?

author: EPAIII
author_rank: Super Contributor
timestamp: November 19, 2022, 10:20:37 am
content: Been using paste type flux for over 60 years. A tin like that can last a long, long time if it is used properly.To me it looks like he was using about 100 times too much of the paste flux. For ICs like that, I often just spin a cotton swab in the flux to get a small amount and then just swipe it across the contacts leaving a VERY THIN layer. Just enough to see. That will clean everything but the very worst corrosion.With all the flux he was using I hope there aren't any switches, relays, or connectors near. I once had to spend an hour and use a whole can and a half of flux solvent to clean a board that I made the mistake of washing the excess flux from. On that initial "washing" the solvent carried the dissolved flux into relays and it was the Dickens to get it all out. At the very least be sure any switches, relays, or connectors are physically higher than the place where you use the flux so it flows away from them, not toward them.Just use a LITTLE bit. Not gobs and GOBS! And a second application of flux is NOT needed the same day. OR WEEK! Besides, rosin core solder has more flux IN IT. Probably too much!

author: rstofer
author_rank: Super Contributor
timestamp: November 19, 2022, 03:00:22 pm
content: Quote from: JenniferG on November 19, 2022, 10:11:37 amIt seems too thin to me. I messed up the units above; my solder is 0.025INCH, not mm. There is every likelihood that you will wind up owning more than one roll of solder.Sorry for the oopsie above...

author: mariush
author_rank: Super Contributor
timestamp: November 19, 2022, 03:06:08 pm
content: SDG electronics evaluated a bunch of fluxes and made a video about it :

author: JenniferG
author_rank: Frequent Contributor
timestamp: November 19, 2022, 05:01:16 pm
content: Quote from: mariush on November 19, 2022, 03:06:08 pmOh sweet thank you! Going to watch this now

author: EPAIII
author_rank: Super Contributor
timestamp: November 21, 2022, 11:27:31 am
content: I have used Kester paste for decades and never had a problem with it. And the guy in the video had it in his top four with a comment that it was the best for "solder flow".