Have I done right - Flux for hobby soldering - Page 1
Forum section: electronics / beginners

author: jewelie
author_rank: Regular Contributor
timestamp: January 23, 2018, 04:24:23 am
content: Hi folksMy dodgy fake eBay flux pen ran out. On the upside, it did introduce me to using separate flux and it was a revelation (see my first anxious attempt at SMD soldering below.)I scanned the forum to see what my best options would be to replace it. It seems as great as the pens are they can become pricey. Budget is tight, but I don't mind paying up front when it'll work out okay in the long run. So, based on what I've read...I've ordered 1L of MG 835 from Amazon (not 3rd party) for UK£18 (=US$24) delivered and a set of 6 glass nail varnish bottles* for UK£3 (=US$4) delivered to apply it.I've got some bushes coming and IPA (which I always have anyway because it's so very useful for so many things) for when I need to clean up a board afterwards, but I gather the MG 835 is generally safe to leave on for most general purposes.Did I do okay?JulieX* About the most girly thing I've bought this month. FML.

author: jewelie
author_rank: Regular Contributor
timestamp: January 23, 2018, 04:59:02 am
content: Thanks for the useful feedback!I did wonder if it might be too much. I need to have faith that less is more. I'm not at all used to working with such tiny components.After just discovering that they have two different focus distance/zooms (only knew about the highest zoom before), it seems those cheap eBay USB microscopes, combined with a mobile and an OTG adapter, aren't too bad for inspecting it all afterwards.

author: Shock
author_rank: Super Contributor
timestamp: January 23, 2018, 01:34:39 pm
content: Good attempt so far, but you need more practice.Some pointers are:- Start with a clean pcb if there are oils oxides and surface contaminants this will cause bad wetting (spreading) and the solder to ball up. You can use a clean cloth or wipe and IPA. For more aggressive cleaning there is PCB (abrasive) erasers etc.- Components can have oxidized surfaces as well, so having new quality parts helps.- Keep the solder clean and dirt free by wiping a few inches down at a time with IPA on a clean cloth or wipe.- Prior to soldering the iron tip should be cleaned of all contaminants. Something like the Hakko 559B works really well (I prefer this to the damp sponge).- Apply solder to the work not the tip.- Practice getting the melting point of you solder down and just enough heat for quick thermal transfer. With enough heat and flux the solder should naturally settle to coat any solderable surface, surface tension will keep more solder near the joint which you want to become a smooth concave "fillet" (see picture below).- Too much heat and the solder bubbles, and does not wet (spread) correctly.- Too much solder and your joints ball up and becomes harder to inspect (they hide other issues like cold joints).- The way you exit with the soldering iron is everything, try to wipe away in the direction of the component or across the pad. Pulling up can leave a blob of solder especially if too much solder is used.- Clean the tip regularly between uses. Excess solder will naturally want to wet to the iron tip (if it's nice and clean) so you can use this to your advantage to keep just the right amount of solder on the work.- Clean and wet the iron tip well when returning it to the stand and switching off, this will prevent the bare tip oxidizing and burning contaminants that make soldering harder.

author: kalel
author_rank: Frequent Contributor
timestamp: January 23, 2018, 01:41:29 pm
content: Quote from: jewelie on January 23, 2018, 04:59:02 amYes, they are pretty amazing for the price. Focus depends on distance, and so does zoom. You have "two levels of zoom/focus", but they depend on distance. The highest zoom is achieved when the focus is set almost to "maximum" (turned to one side almost fully) and distance to object is extremely tiny (it's practically touching the object).I can't give you much advice on the work, beside say that it's much better than what I would likely achieve (I'm not working with SMD yet). Good job.

author: zvonex66x
author_rank: Contributor
timestamp: January 23, 2018, 02:46:16 pm
content: If this is your firsth job with smd, then this is nice and good job. When i have started with smd, i'm figured out that is better to put some solder on clean pads and then put component over this pads and solder it without any extra solder. You will see the nice soldering....

author: jewelie
author_rank: Regular Contributor
timestamp: January 23, 2018, 04:12:11 pm
content: Ironically when I wrote the post and asked if I did right, I meant with the purchase of the flux and empty nail brush bottles, but re reading my original post that was far from clear, doh, sorry.However, thanks all for all the useful, detailed and constructive SMD soldering advice and feedback too, VERY much appreciated and I can put it into practise soon as I've another identical board and set of components!

author: jewelie
author_rank: Regular Contributor
timestamp: January 23, 2018, 04:15:22 pm
content: Quote from: zvonex66x on January 23, 2018, 02:46:16 pmI originally thought to do it that way but then Dave's video on the subject suggested to put solder on one pad, place the component, then when it's set to solder the other side. I imagine this is to make sure the component is flat against the board on both sides without being subjected to unnecessary mechanical stress?

author: jewelie
author_rank: Regular Contributor
timestamp: January 23, 2018, 04:16:30 pm
content: Quote from: Shock on January 23, 2018, 01:34:39 pmYou're a star! 🌟 Thanks.

author: nanofrog
author_rank: Super Contributor
timestamp: January 23, 2018, 05:21:33 pm
content: In regard to the flux and nail polish bottles, you did just fine.And Yes, you can leave it on the boards if you wish in most cases.Oh, and the 1L size will last you a good long while (likely = years).

author: agehall
author_rank: Frequent Contributor
timestamp: January 23, 2018, 05:25:32 pm
content: I would highly recommend this stuff:https://www.bga-reworking.co.uk/flux-solder-paste/amtech-nc-559-v2-bga-reflow-reball-tacky-flux-10cc.htmlIt's the same kind Louis Rossmann uses and as do I. It is by far the best stuff I've come across.