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Etching Aluminum for Brazing

2004

We make heat transfer plates, primarily for the electronics industry. A representative unit is composed of two machined plates, typically in the range of 1/4-inch to 7/8-inch thick; 12-24 inches wide x 18-36 inches long. After the plates are machined we apply a thin layer (.003 thick) of aluminum brazing foil between the plates, and then run them through our brazing ovens to seal the coolant channels and make a single cooling plate.

MY QUESTION: I would like to review and optimize the etching process we are currently using to clean/prepare the aluminum surfaces, to assure the highest quality braze. We are currently using a nitric acid and hydrofluoric acid mixture. Can somebody please comment on our choice of acids, and what mixture ratio might be best?

Thank you!

Steve Hogseth
Custom Machining - Chippewa Falls, Wisconsin, USA

Steve, what is the percentage of Nitric/ H.F acid you are presently using ? Have you tried Phosphoric acid?

Brian J
precision engineering - Geelong, Australia
2004