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Blue Haze ( Not the same as Purple Haze)

#21401

Blue Haze ( Not the same as Purple Haze) | 3 September, 2002

My customer is finding a blue haze on some SMT pads after processing, kind of looks like a water spot on the surface of solder joints. It requires 20x mag and very good lighting to see. We have done 2 different ionic tests and the boards pass to class 3. We attempted to remove with mild solvents to perform chemical analysis and it does not come off with alcohol. We have not gone to destructive testing as of yet. Thought I might get someone here that has seen something similar. We are running a water soluble process, Kester paste, washed in a batch washer (DI water with Aimterge). Anyone have any clues?

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#21403

Blue Haze ( Not the same as Purple Haze) | 3 September, 2002

Naw, alcohol and solvents won't do dip.

Hold-off on: * Destructive testing. [Athough this will convince you to move on to other things.] * Rework of the solder connections. [Although this will correct the problem.]

Consider investigating your aqueous cleaning solution concentration. Some saponifiers are very basic (pH of 10-11) and they literally "etch" the solder joints if saponifier/water solution is not balanced. We have seen several instances of "blue" solder joints that are really oxidized due to the cleaning solution etching action. We found these to be reliable solder connections.

As a side note: The 'blue' you see is actually a diffusion of light by the tin oxide on the surface of your solder connection.

"Squze me while kiss the sky."

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#21404

Blue Haze ( Not the same as Purple Haze) | 4 September, 2002

Thanks Dave

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#21409

Blue Haze ( Not the same as Purple Haze) | 4 September, 2002

Thank you for not mispronouncing that phrase ala Wayne's World. We here in the Seattle area are sensitive to that stuff, ya know?

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