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Unsoldered gold pads on unleaded wave solder process

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#66576

Unsoldered gold pads on unleaded wave solder process | 13 June, 2012

We have a problem with our Unleaded wave solder machine only randomly soldering some pads. I have looked at the flux level and that appears fine aswell as cheking the preheat and solder height in the bath. The probelm is not exclusive to one perticular type of PCB but all the problems appear to be on PCB's which have gold pads. I have also cleaned up a PCB with IPA and one with acatone to see if its contamination on the pads. This had little or no effect.

Wave solder machine is JT NSM450 Flux is BLT 10-75-30 Solder is BLT SAC/P/03/07 Any help would be greeatly appriciated.

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#66579

Unsoldered gold pads on unleaded wave solder process | 13 June, 2012

Sorry, but I don't have a quick and easy answer. Before jumping the 'black pad shark,' tell us more about your boards ... * Is the gold still on the pads after soldering? * Can you make the pads take solder using a soldering iron? * Does this happen to all boards? Or just every so often? * Are all of these boards from a single source? Or are they from multiple suppliers? * What is the 'actual' plating on top of the copper on the boards? * How are the boards packaged from your supplier? * How are boards stored after receipt from the supplier?

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#66580

Unsoldered gold pads on unleaded wave solder process | 13 June, 2012

It is possible that there is nickel contamination in the gold. Depending on your plating board vendors put nickel down first. The plating also could be to thin. Dave had a good suggestion in trying to solder the pad with a Iron that will tell a lot.

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#66585

Unsoldered gold pads on unleaded wave solder process | 14 June, 2012

Yes pads are still gold after the wave soldering process even if you wave solder a pcb several times. I have tried soldering using an iron and the solder takes to the pad as you would expect. This happens on all boards of this type and all boards are from single source packaged in sealed bubble wrap. PCB's are stored on shelves in the main assembly area. The plating on the PCB is copper with an Electroless Nickel Gold Immersion finish.

Thanks for the help so far

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#66591

Unsoldered gold pads on unleaded wave solder process | 14 June, 2012

That you can get good solder flow when hand soldering seems to indicate that the temperature of your solder pot is too low.

Still, I'm uneasy that you see gold on the pads after passing the board across the solder pot. Gold is so thin with ENIG. So if the gold did not dissolve into the solder, something is wrong.

Here's where I'd take this: * Get your board fabricator involved. ** Can they duplicate your problem? ** Is there a film, maybe something organic on top of the gold? ** Is something causing the gold to dewet? * Understand your materials better. Check the composition of the solder in your pot. * Check your process control. Make sure you're hitting the temperature values that you should be measuring for your solder and flux.

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#66601

Unsoldered gold pads on unleaded wave solder process | 15 June, 2012

Good info above from davef Solder pot contamination seems likely, are you using any dross reducers or additives that might be reacting with this particluar batch of PWBs? 'hege

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#66608

Unsoldered gold pads on unleaded wave solder process | 18 June, 2012

Measured the pot temprature independantly from the software (268C/514F from moving wave). We are using Dross Inhibiter Tin/P Regenerator from BLT. Monthly sample checks are carried out on the solder bath and are all within limits. It will be hard to get our board fabricator involved as I deal with just production support and not design/fabrication etc which is on another site. I have also looked at the tempratures of the preheat and they appear normal after running a profile PCB through.

Thanks for the help

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#66642

Unsoldered gold pads on unleaded wave solder process | 21 June, 2012

It's possible that if the nickel on your board was skip plated by your fab that you would get the symptoms that you describe.

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#66643

Unsoldered gold pads on unleaded wave solder process | 22 June, 2012

Are you spray fluxing ? If so, check that you are getting flux onto the whole pcb uniformly.... That BLT flux is a water based material, are you getting rid of all the water in the preheat before you get to the wave ( can you hear any spitting as the pcb travels into the wave ?) Any water spitting will interfere with the solder flow over the surface and cause solder skips.

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#66644

Unsoldered gold pads on unleaded wave solder process | 22 June, 2012

Spray fluxing yes but have checked the uniformity by using a fluxometer. Also have put boards through with only flux and preheat. no wave up to see if the carrier is being burnt off.

I will look into the skip plating issue.

Thanks again

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