Balls everywhere

[palindrome]

Hello

This is something I am losing my mind over. I got a well known solder wire from well known supplier. Lead free.

I try to solder e.g. a connector and what I find is that solder is bubbling and shooting tiny solder balls all over the PCB. Sometimes the bubbling pulls out the connector pin with it, which means I have to desolder and try again with a new one.

When I looked at forums, people recommend soldering at 350C with that solder, but I tried anything from 230C upwards. At 230C there is no bubbling, but it takes forever to solder. Bubbles start at 250C.

I tried to preheat the PCB and connector using heatgun. Cleaning everything with isopropyl alcohol. Adding flux.
I tried different soldering stations, it makes no difference.
I tried different soldering times. I can usually minimise it by touching the solder for split second, wait for cool down and redo until joint looks okay, but I am worried I might create cold solder joints this way as well.

It is tedious to look under microscope to find and remove the balls and I had a nightmare on several occasions where I pictured missed ball dislodged during transport an landed on power supply pins then causing product to short.
I also use a thick brush to remove them, but I know it still can miss some.

It happens the most with large connectors (3.96mm). Once the bubble bursts there are also little craters in the joint and surface looks rough. Something with 2.54mm pitch is usually okay, but still an odd ball shoots out.

I used that solder before and don't remember it being this bad. Do I have a bad batch?

Is it common?

Should I try other solder brands?

Thanks!



 

[Analog Kid]

Lead-free: yuck!
Do you have to use lead-free? Some RoHS requirement? Leaded solder works so much better. (If you can find it.)

[Whales]

> This is something I am losing my mind over. I got a well known solder wire from well known supplier. Lead free.

What part number?

It sounds like your issue is with the flux, not the alloy.  Leaded and lead-free alloys all come with a variety of fluxes & flux-versus-metal ratios. 

I made the mistake of buying some cheap name-brand solder from Element14 a few years ago.  It was cheap because no-one wanted it, flux was extremely aggressive and the smoke made me want to hurl.  I now stick with cheaper lead-free with standard rosin core from a local supplier, it works wonders for general purpose work and I have not had to use leaded in years.

[ahsrabrifat]

Contaminants like dirt, oils, or residues on the PCB or connector can cause bubbling. Clean the surface with Isopropyl alcohol. Use a new solder spool and fresh connectors.

[inse]

I have seen bubbling solder joints as well, usually at older PCBs but no ball ejection yet.
Old resin boards tend to bubble a lot.
I don‘t know whether the PCB substrate is disintegrating under heat or whether moisture is evaporating.
You could give a try and dry the boards in the oven at >100C for some time

[Psi]

Yeah, sounds like you may have the wrong type of solder.

Maybe acid core, maybe something else.

Is it brand new solder or something you inherited from someone's dad? 

If it's old then it's also possible, i guess, that moisture has got into the flux core and is causing issues.  I know with solder paste water or isopropanol contamination causes small explosions (instant boiling) that throws solder balls all over the place.

[Siwastaja]

What solder exactly (brand and part number)?

Is it possible that boards have been stored in humid conditions for a long time? Does the solder bubble similarly if you solder e.g. wires together outside of PCB?

[Solder_Junkie]

I have been soldering for over 50 years and not come across a problem using either lead or lead free solder. The only issue I have had where solder balls are created is when using solder paste and a hot air soldering station... by the way, in the main it is easier to solder using a soldering iron than it is to use hot air...

FWIW, I use Weller solder, Multicore and own brand from Rapid Electronics. https://www.rapidonline.com/

SJ

[Haenk]

Is that solder with a core or do you use flux and solder without core? Which diameter, how fast do you feed?
Iron or hot air?
I'd stick to major brand name solder with flux core, that usually works very good.

Unfortunately very few data given to pinpoint the problem.

[Konkedout]

Hi, emordnilaP

Sorry I just had to say that.    If anyone does not know what I am talking about, please see:

 https://en.wikipedia.org/wiki/Palindrome

[palindrome]

Thank you for your comments!

The solder I've been using is Kester K100LD 3.3%/275 wire 0.031

What high quality lead free solder would you recommend trying instead?

It's for typical through hole parts (caps, resistors, connectors).

[Solder_Junkie]

That Kester stuff should be OK, although I haven't used that brand myself. My Weller soldering station is generally set to 370 C, perhaps a little more for lead free, although I rarely use lead free as it has no advantage to me as a hobby constructor. I only use lead free if replacing a part on a commercial board that used lead free in the first place.

SJ

[mtwieg]

I've encountered solder wire "spattering" in the past (I think it was a kester wire, not sure which one though), though typically it happened only when initially applying the wire to a molten joint, not afterwards. Are you applying flux/rosin besides what's already contained in the wire?

The spatter is not due to the solder itself, but the flux or other impurities (especially solvents like water) outgassing as they boil rapidly. There's not much you can do about it with technique AFAIK. I would look for another wire with a different flux type, or a lower flux content.

I've seen claims that multi-core solder wire (where flux is added as multiple smaller cores instead of one big one) mitigates spatter, but can't attest to that myself.

[palindrome]

No, I generally don't apply additional flux.

However, I had an issue where I had something resembling cold solder joint, but on the outside it looked perfect. After cutting out the leg and looking through microscope I saw a film around the joint, where solder didn't actually adhere to it. Pretty strange. To solder this particular parts I'd clean both legs and the PCB with isopropyl alcohol and apply generous amount of Amtech flux. That seems to be doing the job, but on the other hand feels a bit ridiculous.

Now, the bubbling occurs regardless if I clean the pcb or use extra flux beside what is in the wire.

When using large tip, I also see a bubble forming on the tip and when it bursts it shoots large solder ball and flux.

[Whales]

Thankyou for the solder model.  You're on their highest flux percentage (3.3%) for the 275 product range which could be a contributing factor.

However...

> When using large tip, I also see a bubble forming on the tip and when it bursts it shoots large solder ball and flux.

Interesting.

Do you have a thermocouple handy?  Could you try measuring your tip temperature and compare it with what you think the temperature is set to?  I normally put a blob on solder on the tip when doing this (but someone might point out if this is wrong or not).

I have encountered solder dangerously exploding before (safety goggles territory) when my iron has been too hot.  I assume it's because of the flux creating gases way too fast.

[SteveThackery]

Yes, I'm beginning to wonder if there's a problem with the temperature control. It could well be too hot.

[Psi]

A video would shed some light on the issue. Can your phone take a macro video you can upload to youtube or goggle drive and post a link?

[palindrome]

I'll see if I could come up with PCB that won't reveal my secret project 

That said, I bought Edsyn SAC8250-3 and tried it on 350C. There was bubbling, but not as dramatic and it did shoot one small ball. What was even weirder it was emitting thick white smoke that covered adjacent pins, components and PCB itself.
However, I soldered two PCBs with it and it didn't pull any pin out of its plastic guard.
Joints looked smooth until they cooled then had white rough residue all over them.
The solder also flowed nicely into the pad.
edit: at 320C it was better, but still joints were looking very much white.

Second was Weller WSW SAC M1. This was was bubbling like crazy, but not much smoke. There were craters in the joints. Joints were never coming smooth. I didn't notice any balls (yet).
edit: okay, under microscope I saw dozens of tiny solder balls, so that's even worse.

I am using JBC DDE soldering station.

edit:
maybe indeed problem is too much flux for this application. Now how do I find solder wire with low flux. Stores typically don't allow sorting by flux content. It has to be no clean.

[Whales]

> What was even weirder it was emitting thick white smoke that covered adjacent pins, components and PCB itself.

That'd be their flux.  Was it hard to clean off?


> Joints looked smooth until they cooled then had white rough residue all over them. [...]  joints were looking very much white.

The current lead free that I'm using at home (Sn99.3 Cu0.7) leaves shiny joints.  At work I use SAC solder (eg SAC305 3% silver 0.5% copper) which looks shiny whilst hot, but then suddenly goes dull when solidifying. 

SAC is supposed to be mechanically better (even more so than leaded solders sometimes), but the dull joints are aesthetically dissatisfying.  (I want shiny joints, screw the materials science!  Also it makes them easier to inspect)


> 320C [...] 350C

Be wary that soldering iron temperatures are famously misleading and inconsistent.  For example: I do almost all of my lead-free soldering with my iron set to "300degC".

(1) Dials on stations are only roughly labelled. (easily +/- 50degC)
(2) Temperature sensors are only approximate (easily +/- 50degC)  (on both expensive & cheap setups)
(3) The temperature probe is often not in the tip itself (easily +/- 50degC)  (on both expensive & cheap setups)

The real question is whether or not you're getting the joint itself to a useful temperature.  You can only judge that by feel.  The temperature numbers you're giving us don't mean anything because the actual joints you are making could be anything from 230degC to 450degC.

I recommend backing your iron down to find the temperature where solder joints just barely melt, then turn it up from there until it's comfortable to use.  Treat the temperature knob/dial/buttons as an accelerator pedal, not a numeric control.


> Now how do I find solder wire with low flux. Stores typically don't allow sorting by flux content.

If they don't label the product with a part number you can research then you're SOL. 

Higher rosin contents are easier to use, so I suspect they will be popular to stock, but it might also be a case of the ordering personnel simply not knowing this is something that matters.


>  It has to be no clean.

Have you tried rosin fluxes?  If you have the chance then I'd suggest trying some rosin fluxes too, the residues are inert (they just look more obvious than no-clean's residues) and can be cleaned off reasonably easily (whereas many people claim "no-clean" means "can't clean").  YMMV.


> under microscope I saw dozens of tiny solder balls, so that's even worse.

They're probably stuck on with the flux residue too.  You might need to add a washing step.  (Which also ties in with my last point, which might make things easier)

Are there just a few balls or too many?  Dozens doesn't sound too bad, but I don't know if that was for a whole board (fine) or just a single joint (yuck!).  There will always be some amount of solder balls regardless of solder alloy;  for handwork I either choose to accept the residue & balls (personals repairs) or clean both off (stuff that's safety critical, fine pitch patrts or for other people).   Usually it's a compromise where I only clean some key spots, I am far too lazy to do more than that.