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topic 0247

Quantity of ammonia released to air from etching of PCB's

A discussion started in 1996.
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I work at a regulatory agency (Bay Area Air Quality Management District in San Francisco) where we commonly permit PCB etchers since we have jurisdiction over the Silicon Valley. There is little consensus here on the amount of ammonia that would be expected to be emitted during the etching process.

Ideally, as described in Mr. Sedlak's "Ammoniacal Etching of Copper", all of the ammonia would be bound up in the spent etchant. Do you have any idea or know of any reference material that would address how much ammonia would be expected to be emitted in practice?

I would appreciate any guidance you could provide.

Elliot, Julian


There usually is a fairly strong ammonia smell because there is a lot of agitation in these spray etchers, and the ammonia comes off of solution to some degree as ammonia gas just as from a water solution of ammonia used in household cleaning or blueprint development. I think this is a bigger factor than the amount released due to reactions during etching; but without a literature search, I really would have no idea how to quantify either factor, I'm afraid.

Sorry I wasn't able to help, but hopefully one of our readers can.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

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