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Wave soldering problem - strange colour of the solder

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#46661

Wave soldering problem - strange colour of the solder | 15 January, 2007

Hi all,

Last week I have noticed, that solder changed colour in our Soltec wave soldering machine. I am using normal 62Sn37Pb alloy and it's colour changed to violet/darkblue with gold areas. I know that gold colour means that, there is to much Cu in the solder. At the end of the week I received results of the solder sample analysis and it looks like there is about 0.1%CU in the solder. Solder with this level of Cu should be still ok. From the moment it started I noticed, that there is lower wave height on every recipe. I can see the difference in solderability and density of the solder too.

Is there any way to fix the solder without replacement of the whole solder in the solder pot? If any of You had similar experience, please let me know.

Best Regards Adam

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#46676

Wave soldering problem - strange colour of the solder | 15 January, 2007

Check the temp of your pot. It may be getting cooler if you can notice a difference in pump height and density. You may have lost a heater element or two. You can adjust your pot chemestry, but why would you want to if your solder sample came back OK?

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greg york

#46683

Wave soldering problem - strange colour of the solder | 15 January, 2007

are you using composite pallets in the wave or oil/wax around the pump impellar? cheers greg

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#46698

Wave soldering problem - strange colour of the solder | 16 January, 2007

I have checked pot temperature in different parts of solder pot and it looks like it is correct (250C). I have also lowered solder pot temperature and removed copper from the surface of the solder pot (operation repeated couple times). There is still much difference in density of solder and wave settings had to be increased about 20-30 rpm for every single recipe to archieve previous wave level.

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#46700

Wave soldering problem - strange colour of the solder | 16 January, 2007

We are using composite pallets for our boards.

Regards Adam

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greg york

#46720

Wave soldering problem - strange colour of the solder | 16 January, 2007

Try to process the composite pallet through the wave without any flux and view volume of smoke and if any residue is deposited in the wave when it exits. My guess is that the pallets are releasing some binders that are high boiling and this in turn causes the solder to thicken and clogs up the baffles feeding the wave. Is also seen by producing a gold/yellow dross and a spongy silvery dross. Hope it helps Cheers Greg York

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greg york

#46721

Wave soldering problem - strange colour of the solder | 16 January, 2007

Sorry that answer never really gave you the reason and ways to resolve. Reason - most composite pallets are only good up to 180C so thermal excursions at 250 or even 270c lead free kill them. Try to stay on top of cleaning as well and some pallet material are good up to 300C with a coating of PTFE for good measure. So worth finding out if this is not helping your situation by putting it over the wave to view the amount/type of residue deposited in the solder pot Thanks Greg York

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jimmyjames

#46829

Wave soldering problem - strange colour of the solder | 19 January, 2007

You guys are all joking right?! There aren't any contaminates in your solder, the different colors on the surface are completely normal and even expected.

The top layer of solder oxidizes and the structure of the surface resembles crystals, refracting light into different colors. Just like a rainbow effect you see on a piece of steel that has been heated to red hot and then allowed to cool slowly. Even if you clean the surface to a mirror finish, after only a couple minutes you can see it start to "dis-color" from light gold to blues and purple (depending on the angle at which light hits it and you view it from.

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#46831

Wave soldering problem - strange colour of the solder | 19 January, 2007

I thought the same thing but he did mention density. I threw out the color thing immediately - which is normal. But to NOTICE a density proble with set programs seem aby-normal. Unless one our maintenance guys got a hold of your machine for a PM. Then everything changes.

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RDR

#46836

Wave soldering problem - strange colour of the solder | 19 January, 2007

Even the level of solder in the pot can have effect on your wave height. backflow gate may have been tweaked a bit, that affects wave height, many many things affect the proper RPM required for the correct wave height. Pot may be a little lower than it was in the machine before from a PM or a cleaning, i would say raise rpm by 30 and move on

Russ

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Al Coholic

#46841

Wave soldering problem - strange colour of the solder | 19 January, 2007

Add solder.

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#46864

Wave soldering problem - strange colour of the solder | 22 January, 2007

Thx guys, I'll check everything you mentioned, including solder pot, and solder feeder sensors.

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