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Gold Pads Soldering problem

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#38447

Gold Pads Soldering problem | 14 December, 2005

Not all but some new boards we have had solder joint problems, for example some of the pads refuse to solder at all and the solder paste ends up attched only to the leg, reworking makes no difference and a variety of fluxes have failed. How can some high volume production boards work fine and these prototypes fail so badly. Can anyone offer an explanation?

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RDR

#38459

Gold Pads Soldering problem | 14 December, 2005

See "black pad" and determine if that's what you have.

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#38469

Gold Pads Soldering problem | 14 December, 2005

Heavens to Murgatroyd, we agree with Russ that "black pad" could be the cause of your solderability problem, but oxidized nickel is an additional explanation.

While its often easy for assembler to jump this conclusion, it sounds like you've been blanked by your board fabricator.

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#38477

Gold Pads Soldering problem | 15 December, 2005

SNAGGLETOOTH HOLDS HIS HANDS UP, HAVING JUST REACHED THE EDGE OF HIS OWN IGNORNACE. I just read up on black pads - http://www.emsnow.com/npps/story.cfm?ID=9784 when i checked the joints under the microscope they were a light grey slightly discoloured with what looked like gold, maybe about 10% did not solder at all and i had real problems fixing them, but its sounds like "Porous gold" where the nickel spreads and then oxidises to prevent any soldering on that pad. Also when i have checked the PCB specification it shows no surface layer type? Any ideas on how to fix these after reflow as these are always prototype PCB�s and i have deadlines, no chance to reclamate the PCB�s MUST DELIVE on time....

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#38484

Gold Pads Soldering problem | 15 December, 2005

Snaggie

Oxidized nickel is very tough to solder. Using the typical fluxes that are in everyone's fireproof storage cabinet [that they've been sampled by very nice saletypes] is like bringing a knife to a gun fight. Recognize that the flux you want is going to be nasty. So, it will have to be cleaned.

Search the fine SMTnet Archives for more.

Talk to your flux supplier for recommendations.

What do you mean when you say "Also when i have checked the PCB specification it shows no surface layer type?"?

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#38514

Gold Pads Soldering problem | 16 December, 2005

i would assume when the PCB planner and customer would specify what "surface layer type"they want but this section is always empty but i have found that out yesterday that we only use ENIG and not FLASH GOLD, which is good to know........ but it seems it is almost like "pissing in the wind" trying to get these pads to solder at all not just to a good level... but i will research some better solder fluxes....would reflowing the boards again with dispensed solder paste with added flux work better?

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JAX

#38520

Gold Pads Soldering problem | 16 December, 2005

Try paste flux instead.... oh yeah.. clean it as soon as it comes out of reflow.

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