Dross or Dark Green Mud Found in HAL machine

Are they applying a dross reducing powder, like what you would use in a Wave solder pot?

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Hello !

I got exp only with leadfree HASL, but maybe the same problems apply. Also, the leaded HASL has probably lower process temperature.

This could be copper, which has settled to the tank bottom. With leadfree, the copper is removed from molten solution by reducing temperature and letting it settle about 4 hours. Copper sinks to the bottom and is lifted out with metal sieve.

There is always copper in HASL as the copper from PCB goes into solution. I dont know, how fast it solves into leaded HASL but in leadfree, temperatures are high and the copper migration is remarkable.

Also, the green color may suggest it as copper dross oxide will be probably green.

So I would check following

1) remove all clean solder from solderpot 2) clean the solderpot and all fixtures (this is a messy job and is probably overlooked) 3) put the solder back and melt. Check, if the mixer (solder pump) is correctly operating. 4) take a sample and order metallurgical analysis. Nowadays, even the scrapyards have portable device that can do it 5) check if its manuf specified limits 6) if too much copper, let the copper sink to the bottom. I cant say the correct temp for leaded alloy, ask the manufacturer

And also 1) maybe the pre-cleaning unit and flux application is bad (too much flux or PCBs not rinsed well after acid cleaning)

2) is the soldermask OK after HASL ?

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