Metal stripping additive, composition containing the same, and method for stripping metal by using the composition

A method for stripping metal, comprising the following steps:

• contacting an electronic element to be processed with a metal stripping composition;
• wherein said metal stripping composition, comprising:
• 40 to 60% (v/v) of nitric acid;
• and
• 40 to 60% (v/v) of a metal stripping additive;
• wherein said metal stripping additive, comprising:
• 10 to 40 wt % of phosphate, wherein said phosphate is monobasic potassium phosphate, dipotassium hydrogen phosphate, or a combination thereof;
• 3 to 15 wt % of carbonate, wherein said carbonate is sodium bicarbonate, potassium bicarbonate, sodium carbonate, or a combination thereof;
• 5 to 15 wt % of a component selected from at least one of citric acid or a derivative thereof, oxalate or a derivative thereof, or malate or a derivative thereof, wherein said citric acid or a derivative thereof is citric acid monohydrate, trisodium citrate monohydrate, or a combination thereof;
• and
• 5 to 30 wt % of a component selected from at least one of sodium hypochlorite or a derivative thereof, or pyridinesulfonic acid or a derivative thereof;
• wherein said metal is gold, copper, nickel, tin, palladium, or a combination thereof;
• wherein said composition has no harm to an object made of silver, stainless steel, titanium, plastic, or a combination thereof;
• and
• wherein said electronic element is a central processing unit, a printed circuit board, a memory, a flip chip, a mobile phone, or a combination thereof.