Two soldering questions.... - Page 1
Forum section: electronics / beginners

author: alank2
author_rank: Super Contributor
timestamp: August 02, 2020, 09:05:53 pm
content: The first is that while soldering some SMBJ5.0A-TR, sometimes the heat seems to travel through it - it takes quite a bit of heat to solder these where the solder flows into it nicely. I've got a Pace ADS200 set to 700 deg F using traditional leaded solder (water soluble). On occasion, maybe 1 out 15 or so, if it takes a little bit of time, the other side of the diode does this strange thing where its surface bubbles and changes color. Is this heat traveling through the diode at a certain temperature? Some sort of flux reaction? Does this suggest that it is too much heat for it? They seem to work, or at least I should say they don't cause a failure.Second question, I've got some metal on the tip of my iron that looks like solder, but it won't melt! I use a copper cleaner and it doesn't matter how many times I push it into that, it won't go.

author: Shock
author_rank: Super Contributor
timestamp: August 02, 2020, 11:03:23 pm
content: If you can see a reaction on the other leg of the package it sounds like the flux or flux solids in your solder. I assume you are using a genuine component and reasonable quality solder to start with, if you aren't look at that being a contributor.As they are those wide J style legs you want external flux. So ideally clean and apply flux to the pcb, if you are pretinning the pads remember to clean and apply new flux before reflowing.Heats not so much a problem if you are working fairly quickly and getting good wetting between the legs and pcb, but if you are struggling then yes you are probably unnecessary heating the component up. To get optimal wetting and minimal soldering time, both external flux and preheating may be required (along with cleaning and using the right sized tip).Have you been cleaning the tip regularly? Perhaps attach an image of it.

author: alank2
author_rank: Super Contributor
timestamp: August 03, 2020, 12:55:59 am
content: The component was from Digikey/Mouser and I'm using Kester solder. I flux the pcb/component legs ahead of time with a flux pen. By clean the tip do you mean with the copper brush material, or clean it via some other method additionally? I do have some tip cleaner in a round tin that seems to turn a bit like liquid when I drag the tip through it. I'll try that and if it doesn't remove the extra, I'll try to get a picture.

author: Shock
author_rank: Super Contributor
timestamp: August 03, 2020, 09:07:05 am
content: For cleaning the trick is to always leave a good coating of solder on the tip when it's not in use. Cover the entire tinned area, it protects it from becoming oxidized itself and burning a layer of flux and other residues directly onto the exposed surface. I'll clean and tin the tips I've used prior to powering off the station.Right before soldering you clean the solder off (brass wool is fine) and expose the bare tip. Unless drag soldering or using a little solder to create a thermal link/bridge to the target you should be aiming to feed solder into the joint rather than the tip. Between joints you can clean the tip again by adding a little solder to the tip and then clean it off. When the tip goes into the stand for any prolonged period you tin it with solder again but leave that coating on to protect it.The sponge can be used with some distilled water but what tends to happen is if you are not completely retinning and cleaning the tip often it will oxidize up over time. Tip rejuvenator will have some harsh flux in it so you typically want to avoid it if possible and attempt to tin and clean the tip several times just with solder and the brass wool. You can tell if regular cleaning by that above method is working as the tip will wet more easily each time. If there is a patch of the tinned portion of the tip that is impossible to wet with solder you know you have a problem.

author: tooki
author_rank: Super Contributor
timestamp: August 03, 2020, 10:02:23 am
content: Quote from: Shock on August 03, 2020, 09:07:05 amI know this is what you’re supposed to do with regular rosin/resin/other non-water-soluble flux solder, and indeed it’s what I do, and my tips last forever.What I don’t know, and I’m hoping you do, is: is it safe to do this with water soluble solders that can leave a hygroscopic flux residue on the tip? I would think there’s a chance it could cause damage to any part of the tip not actively covered by solder (e.g. the non-tinnable plating right next to the tinnable area, where the flux tends to accumulate).Quote from: alank2 on August 02, 2020, 09:05:53 pmCould it be large ground or power planes sucking away all the heat?Quote from: alank2 on August 03, 2020, 12:55:59 amKester is good.But you mention above that you’re using the type with water soluble flux. Is your external flux (the flux pen) also the water-soluble type? AFAIK you don’t want to be mixing water-soluble and non-water-soluble fluxes (like no-clean or rosin).From your other threads, I infer that (like me), you’re not yet a highly experienced electronics professional. As such, I’dstronglyrecommend avoiding water-soluble fluxes, as they place exacting, uncompromising demands on your post-soldering cleaning processes, and are also categorically prohibited for certain types of joints (stranded wire being the big one, but also any other component where flux can wick up into somewhere that’s hard or impossible to clean reliably). Use rosin flux if you plan to perform post-soldering solvent cleaning, or no-clean if you don’t. (No-clean fluxes are designed to be left on, but are harder to remove when you do want to remove them.)Wha I honestly don’t know much about are the very few water-soluble no-clean fluxes like Chipquik sells. It seems to be rosin that’s modified to make it water-soluble.Note when using external flux for hand soldering:alwaysperform thorough post-soldering cleaning, as many fluxes that are designed to be safe to leave onare only safe once they’ve been fully heated to soldering temperatures, which isn’t the case with hand soldering, where flux that has been only slightly warmed spreads beyond the joint and never reaches soldering temperatures.Quote from: alank2 on August 03, 2020, 12:55:59 amHe means cleaning the tip in brass wool or damp sponge.(Above that, in his same reply, he also mentions cleaning a joint after tinning the joint, then re-fluxing the joint before reflowing.)Quote from: alank2 on August 03, 2020, 12:55:59 amFYI, tip cleaners in the little round tins are basically for rejuvenating tips that have become resistant to tinning due to heavy oxides. They’re not so much intended for lightly dragging across the surface as they are for plunging the tip in and keeping it there so the aggressive flux in it can really work its way with the oxides, upon which the solder in the tip cleaner can attach and wet it right away. Note that after successfully using such a tip rejuvenator, you’re supposed to clean off the tip thoroughly (to remove its aggressive flux residues) and immediately re-tin using your regular solder. You do not want those flux residues hanging out on the tip for extended periods. And frankly, you don’t even really want them in your brass wool where they can re-contaminate the tip, so I prefer to wipe that off with a folded-up paper towel (even better, if you have it, is some Kimwipes) before re-tinning with my regular rosin or no-clean solder.If you can, get a picturebeforeusing the tip rejuvenator tin.

author: Shock
author_rank: Super Contributor
timestamp: August 03, 2020, 11:36:23 am
content: Quote from: tooki on August 03, 2020, 10:02:23 amWhat I do is wipe the tip from the handle side forward this seems to reduce the flux build up. Pushing the tip into the brass wool I think tends to push crud up the tip where it gets baked on. Over time from there it starts to creep down the tinned part of the tip and becomes hard to remove. The abrasive nature of the brass wool should keep that to a minimum.

author: tooki
author_rank: Super Contributor
timestamp: August 03, 2020, 02:20:29 pm
content: Quote from: Shock on August 03, 2020, 11:36:23 amYes, during normal use. But my question was specifically with regards to applying solder for tip protection when powering off. Is water-soluble flux safe then? (Since the flux isn’t getting wiped off at all.)

author: alank2
author_rank: Super Contributor
timestamp: August 03, 2020, 02:56:43 pm
content: I'll try to get a picture later and post it up.

author: Shock
author_rank: Super Contributor
timestamp: August 03, 2020, 07:23:20 pm
content: Quote from: tooki on August 03, 2020, 02:20:29 pmSome fluxes are going to be worse than others. If you don't aggressively over clean your tips and keep them something like the right hand image but well coated with solder over the tinned portion then I don't see how hydroscopic flux will cause much of an issue.If you do over clean especially with brass wool you can wear the protective chrome/nickel layer on the unused portion of the tip. It's another reason why I prefer to wipe the tip on the brass wool (especially odd shaped tips) rather than jab into it. But that is just my personal preference, some people will do that and flick solder all over the place.

author: alank2
author_rank: Super Contributor
timestamp: August 05, 2020, 01:23:04 am
content: I seemed to be able to clean it off a bit and it looks like it is just bent!