How to avoid solder spikes when disengaging iron?

[lpc32]

What's the solution to "solder spikes", like the left side of the switch below? Swiping sideways just makes the spikes more angled. Is it a question of flux? Tip contamination?

[IanB]

A combination of insufficient flux and keeping the iron on the joint for too long. Once the flux is used up the molten solder will form a "skin" of oxide on the surface that will drag and cause the spikes when you move the iron away.

Apply flux from a flux dispenser before soldering and try to complete all joints within 2-3 seconds.

[lpc32]

I think the joint above was about 1 second. Though it worked well enough for thruhole, maybe the flux is dodgy.

[Dongulus]

Some suggestions that might help:

• Wipe off excess solder form your iron's tip.
• Melt the solder by heating the pad, not directly with the tip.
• Pull the tip away from the joint faster.
• Use less solder.

[Old_Tech]

Excessive time has exhausted the flux.  Remove excess solder, and add a little flux (which can be from new solder).
Remove the iron a little earlier.

[T3sl4co1l]

Temperature needs to be just high enough that the joint remains liquid as you pull away from it; any extra evaporates, pushes or decomposes flux.

I prefer paste flux over anything from a pen or solvent; seems to me, the (petroleum jelly and/or PEG?) base is more persistent, which improves coverage (film formation), even though it's not a chemically active component.

Tim

[Mechatrommer]

Temperature needs to be just high enough that the joint remains liquid as you pull away from it; any extra evaporates, pushes or decomposes flux.

flux evaporates well before the joint melts. atm of melting joints is already an extra for the flux... well, i have better solution to this than all but i want to keep it to myself to avoid controversial discussion.

[David_AVD]

My guess is the iron is not hot enough.  About 375°C should be fine for general PCB work with leaded solder.

[Monkeh]

Temperature needs to be just high enough that the joint remains liquid as you pull away from it; any extra evaporates, pushes or decomposes flux.

flux evaporates well before the joint melts. atm of melting joints is already an extra for the flux... well, i have better solution to this than all but i want to keep it to myself to avoid controversial discussion.

Then why open your mouth?

If you have something to contribute, get on with it.

[Kjelt]

My guess is the iron is not hot enough.  About 375°C should be fine for general PCB work with leaded solder.

That's pretty hot, more for leadfree solder. 
I rarely go beyond 350 but it all depends on the solder iron, the tipsize and the size of the solderjoint. With my new Weller WXMP iron that will heat instantaneously I solder with ease normal through holes at 330°C.  Remember that the melting point of leaded solder starts at 188 °C.

[mzzj]

I have noticed that cheap no-name solders have increased tendency for this. Sometimes part of the roll is like a snot and rest of it works fine.  Could be impurities or alloying being way off from normal 63/37? I feel like there is already a small difference between 63/37 and 60/40 solders.

[lpc32]

Wow, lots of ideas. Thanks.

• Melt the solder by heating the pad, not directly with the tip.

Not sure it was possible in the above case, it's too small.

I'll try next time more/different flux (my Kester pen was MIA ), higher temperature, and different solder (the one above was some unknown solder from the 90s).

[nanofrog]

I'll try next time more/different flux (my Kester pen was MIA ), higher temperature, and different solder (the one above was some unknown solder from the 90s).

Given the age, try cutting a few inches of solder wire off to get to fresher flux, and see if that doesn't improve matters a bit.

[Rasz]

just squirt some flux on the board in addition to whats in the solder core

[lpc32]

Thanks.

[WarSim]

Short answer get better. 
More helpful answer the process is complicated.  The principals are temperature, time and purity. 
Clean surfaces, because any surface can not be cleaned perfectly outside a vacuum, but mechanical cleaning should always be the first step.  To help we used exclusion techniques with helpers like IPI, Oil, Paste, nitrogen, freon, flux, etc.  first reason for solder spikes.  Contamination can create a skin on the solder that will follow the heat gradation. 
Correct temperature.  This issue is not simply setting a soldering iron temp and go.  The factors include source temp, source thermal mass, target thermal mass, iron tip contamination, tip thermal resistance, solder specification.  The good soldering irons manufactures will publish their specifications and characteristics of each of their tips as new.  All the good solder manufactures will publish their solders specifications and characteristics.   Every other factor is compensated for by best practices.  Above I said a tip as new because as the tip is used thermal cycling, contamination and abuse the tip will age, for this we have cleaners, thinners and vacuum ovens.  If a tip is cared for they can last for over a decade with nominal use (low volume assembly)  and almost a year with continuous use (high volume factories with multiple shifts).  The full solder data sheets are a wealth of knowledge covering irons, solder pots, wave solder etc.  They use to include a lot of helpful best practice information but about 25 years ago they stopped due to a deluge of opinion claiming to know more about solder fundamentals than the manufactures.  If you can find it try to find the "best practices" manual for the solder you are using.  I accept for a fact 3M and Kester know the solder they make.  If you follow the proper solder storage practices solder can be stored for decades.  For example some of the special alloy solders I have used was over 25 years old.  If not properly stored here are some rules of thumb.  If the solder is corroded don't use it if you have a choice.  If you don't clean, characterized, correct and compensate.  If flux cored and the solder was not properly solder balled cut off 1/4" for every day it was stored for every 10C above 15C.  Of course this rule will vary with the type of flux.  The next reasons for solder spikes.  Solder is worked it must be within the manufactures thermal band.  Too low you can cause a spike caused by thermal gradation, will likely also cause a cold solder joint.  Temp too high can cause wasting of the alloy components.  Not all solder is simply just lead and tin.  Extreme overheating with cause a detectable reddish hue.  Spiking in this situation is caused by the solder trying to wet the hottest point.  For proper extraction the target thermal mass must be able to keep the solder in range long enough to wet after solder tip removal. 
Time is primarily dwell time.  And dwell time is the most common technique to compensate for many of the above factors.  Infinite heat sources, infinite thermal masses and zero thermal resistances don't exist.  Too short bad joints too long damaged components, extremely too long lifted pads and wasted solder. 
There are many solder techniques out there.  Just please don't join the groups using the worst techniques I have seen.  I call them the solder flickers and flux Bridgers.  Yes it is exactly as it sounds.   Solder flickers try to avoid spikes and ripples by rapidly tapping the joint causing little balls of molten solder to be flicked everywhere.  Flux bridgers use a steady stream of flux to create and maintain the thermal bridge.  Even with extractors causes plumes of toxic white smoke.  Both insisted they where the only ones who knew how to solder correctly, yes It did cost both their position. 
Hope this helps, I was purposely vague in areas to avoid the technique wars.  In the end it is about getting good results without damage to the components or the people doing it.  Missle/space grade soldering has been drilled into me for decades, but I accept not every solder joint needs to be perfect. After how many companies inspect every joint with X-ray and microscope, very few.  I just isn't required for most soldering. 
Sorry got a bit longer than intended. 


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[lpc32]

Thanks, WarSim.

What do you mean by "solder balled"?

[WarSim]

When your done tap the solder to a cooling iron to form a ball of solder at the end of the solder.  This seals the end so the flux core will age as slow as possible.  When you buy a new roll of solder the manufacture should have done this to each end of the solder.  If you buy a hobby roll and this isn't done, keep in mind the solder could be pre-aged for you. 


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[lpc32]

Won't the end be sealed anyway due to normal use?

[WarSim]

It is actually less likely than expected to be completely sealed. 
The seal is poorest when mechanically separated. 
When in use the seal is very dependant on soldering practices and style.  For example if you need to increase iron temp to compensate for target thermal mass.  The flux could still be off-gassing when the solder end solidifies.  This leaves vulcanization voids which break the seal.  To keep this from happening the iron needs to be lower than normal soldering temp.  That is why I said to the solder ball with a cooling iron. 
Remember this is academic if you do not need long solder life.  A gel core under normal use should still last 2yrs.  Good tip maintenance would use up at least 1/2" before soldering begins, so flux aging at the end would have little effect. 


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