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Strange reaction with Selective Solder alloy

Strange reaction with Selective Solder alloy

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A while back, we had a yellow coating showing up on some sol... - Apr 05, 2022 by ProcEng1

Here are the nozzles that soaked, but didn't get tinned. Si... - Apr 05, 2022 by ProcEng1

Datasheet says that post solder cleaning is required.I assum... - Apr 05, 2022 by Evtimov

This flux is used to clean nozzles. It's not applied direct... - Apr 05, 2022 by ProcEng1

Try adipic acid to clean your nozzles. It is a powder and ca... - Apr 05, 2022 by Stephen

I had the same looking coating on solder joints when we used... - Apr 06, 2022 by bukas

Why not just switch back to Superior 75? Why switch in the ... - Apr 06, 2022 by dontfeedphils

Because it was recommended by the machine manufacturer. Sup... - Apr 06, 2022 by ProcEng1

I spoke with a Tech at Superior Flux. He confirmed that Sup... - Apr 06, 2022 by ProcEng1

I just got the acid powder. How exactly do you use it? ... - Apr 06, 2022 by ProcEng1

ProcEng1

#87793

Strange reaction with Selective Solder alloy | 5 April, 2022

A while back, we had a yellow coating showing up on some solder joints at Selective Solder (LEAD alloy). I contacted the company for our machine and he looked into it. One change we had made not too long before is we switched from Superior 75 to Superior 515 flux for cleaning nozzles. But that doesn't really explain how the yellow stuff got on the board.

Now the problem has cropped up again. We had a few boards showing a yellow substance on the joints roughly 24 hours after soldering. We also did a big cleaning and re-tinning of nozzles, which involves soaking them in the Superior flux and then re-tinning them. Some of the soaked nozzles didn't get tinned yesterday, and they also show signs of yellow. The LEAD FREE nozzles did not. So I am thinking that the Superior 515 is somehow reacting to the LEAD alloy. Has anyone experienced this or can shed some light on it?

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ProcEng1

#87794

Strange reaction with Selective Solder alloy | 5 April, 2022

Here are the nozzles that soaked, but didn't get tinned.

Since the solder joints also had yellow, I am wondering if the contamination is lingering in the solder pot, and getting on the joints. The Superior is never applied to a board. In the board photo, there is also yellow on the SMT joints, which are not being soldered at Selective.

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Evtimov

#87795

Strange reaction with Selective Solder alloy | 5 April, 2022

Datasheet says that post solder cleaning is required.I assume this will completely go away after cleaning. Water based water soluble fluxes often leave nasty residues.

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ProcEng1

#87798

Strange reaction with Selective Solder alloy | 5 April, 2022

This flux is used to clean nozzles. It's not applied directly to the board.

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Stephen

#87799

Strange reaction with Selective Solder alloy | 5 April, 2022

Try adipic acid to clean your nozzles. It is a powder and can be awkward to work with as a result. But you might end up preferring it.

Also look where the substance is not. There are two PTH joints without it. And that chip cap is closer to the PTH than the resistor but the cap doesn't have the substance. It almost looks like the board was set down on something that had a puddle. Or transferred over something with gunk on it.

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bukas

#87800

Strange reaction with Selective Solder alloy | 6 April, 2022

I had the same looking coating on solder joints when we used rosin in IPA. after switching to water based no clean it never happened again.

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dontfeedphils

#87801

Strange reaction with Selective Solder alloy | 6 April, 2022

Why not just switch back to Superior 75? Why switch in the first place?

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ProcEng1

#87802

Strange reaction with Selective Solder alloy | 6 April, 2022

Because it was recommended by the machine manufacturer. Sup 75 is also very corrosive. It basically ruins any tools that touch it if they aren't cleaned properly.

I am ordering some of that powder to try.

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ProcEng1

#87804

Strange reaction with Selective Solder alloy | 6 April, 2022

I spoke with a Tech at Superior Flux. He confirmed that Superior 515 will absoluteley turn yellow at room temp. Hydrobromic Acid in the flux, as it binds the hydrogen gases off and the bromine turns yellow.

What is weird, is that Tin Bromide is yellow. Lead bromide is white. My SN100 solder doesn't turn yellow, but the 63/37 alloy turns yellow. I'm sure there is a rabbit hole of chemistry that explains why the 37% tin turns yellow, but 100% tin doesn't.

Also, I am pretty sure that the new operator probably had some Superior on their fingers when handling the board. So that is also being addressed with training.

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ProcEng1

#87805

Strange reaction with Selective Solder alloy | 6 April, 2022

I just got the acid powder. How exactly do you use it?

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