Ammoniacal etching solution and method utilizing same

Claim 2

The solution of claim 1 wherein said ammonium chloride is present in an amount of about 0.2 to 3.0 gram moles.

Claim 3

The solution of claim 3 wherein each said solution contains about 1.0 to 3.0 gram moles of ammonium chloride.

Claim 4

The solution of claim 1 where said inorganic phosphate salt is present in an amount of about 0.05 to 0.5 gram moles.

Claim 5

The solution of claim 5 wherein said phosphate salt is trisodium phosphate.

Claim 6

The solution of claim 1 wherein X is chlorine and n is 3 so that said haloacetate is the trichloracetate.

Claim 7

The solution of claim 1 wherein said promoter provides a combination of ions of at least one of iodine and bromine and ions of at least one of gold, silver, mercury, platinum, palladium and rhodium.

Claim 8

The solution of claim 1 wherein said promoter provides a combination of iodide and mercuric ions.

Claim 9

An aqueous ammoniacal etching solution for the etching of metals selected from the group consisting of copper, zinc, cadmium, aluminum and alloys in which one of these metals comprises the major portion thereof, and consisting essentially of, on a per liter basis at makeup, ammonium trichloracetate; ammonium hydroxide; about 0.1 to 0.6 gram mole of a soluble cupric compound selected from the group consisting of cupric trichloroacetate, cupric chloride, cupric acetate, cupric hydroxide, the ammonia complexes of such compounds, and mixtures thereof; 0.2 to 4.0 gram moles of ammonium chloride; 0.0 to 0.5 gram mole of soluble phosphate salts having the formula M3PO4 where M is NH4 or an alkali metal; and an effective amount of a promoter selected from the group consisting of soluble inorganic iodide and bromide salts, soluble noble metal salts and oxides, and mixtures thereof, said solution having a pH value of about 7.5 to 11.0, the total ammonium ion in said soluTion at makeup being 2.5 - 10.0 gram moles and the total trichloroacetate radical in said solution at makeup being about 0.5 - 2.0 gram moles.

Claim 10

The solution of claim 10 wherein said ammonium chloride provides chloride ion in an amount of about 0.2 to 2.0 gram moles.

Claim 11

The solution of claim 11 wherein said ammonium chloride is present in an amount of about 1.25 to 2.0 gram moles.

Claim 12

The solution of claim 12 wherein said phosphate salt is present and provided by addition of about 0.05 to 0.5 gram mole of trisodium phosphate.

Claim 13

The solution of claim 10 wherein said promoter is an iodide salt.

Claim 14

The solution of claim 10 wherein said promoter is a mercuric salt or oxide.

Claim 15

The solution of claim 10 wherein said promoter provides a combination of iodide and mercuric ions.

Claim 16

The solution of claim 10 wherein said pH is about 8.0 -10.5.

Claim 17

In a method of etching a metal surface the steps comprising: (a) preparing an aqueous ammoniacal solution consisting essentially of, on a per liter basis at makeup, ammonium haloacetate of the formula CXnH(3 n)COONH4 wherein X represents a substituent selected from the group consisting of chlorine, bromine and iodine, and wherein n is an integer of 1 to 3; ammonium hydroxide; up to 4.0 gram moles of ammonium chloride; up to about 0.5 gram of soluble phosphate salt having the formula M3PO4 where M is NH4 or an alkali metal; up to saturation of a soluble cupric compound selected from the group consisting of cupric haloacetate wherein the haloacetate corresponds to the above formula, cupric chloride, cupric acetate, cupric hydroxide, the ammonia complexes of such compounds, and mixtures thereof; and an effective amount of promoter selected from the group consisting of soluble inorganic iodide and bromide salts, soluble noble metal salts and oxides, and mixtures thereof, the total ammonium ion in said solution at makeup being about 0.5 - 2.0 gram moles and the total haloacetate radical in said solution at makeup being about 0.5 - 2.0 gram moles; (b) maintaining said solution at a pH of about 7.5 to 11.0 and at a temperature of at least about 100* Fahrenheit; (c) contacting the metallic surface of a workpiece with said solution for a period of time sufficient to produce the desired etching of said surface, the metal of said surface being susceptible to attack by said ammoniacal solution and selected from the group consisting of copper, zinc, cadmium, aluminum, and alloys in which one of these metals comprises the major portion thereof, and (d) removing any residue of said solution from said surface.

Claim 18

The method of claim 18 wherein said solution is maintained at a pH value of about 8.0 to 11.0 and at a temperature of about 110* to 130* Fahrenheit.

Claim 19

The method of claim 18 wherein said step of contacting said metal surface is effected by spraying said solution upon said surface, and wherein the periof of contact of any finite portion of said solution is less than about 1 second.

Claim 20

The method of claim 20 wherein said promoter consists essentially of a salt or oxide of a noble metal selected from the class consisting of gold, silver, mercury, platinum, palladium and rhodium.

Claim 21

The method of claim 18 wherein said metallic surface has a tin/lead alloy resist pattern thereover, and wherein said phosphate salt is present in an amount of 0.05 to 0.5 gram mole.

Claim 22

The method of claim 18 wherein said solution is employed over an extended period of time to etch the metallic surface of a multiplicity of workpieces by contact therewith, and wherein, after said solution contains about 2.0 gram moles per liter of the metal of said surface dissolved therein, said method includes the additional step of (e) removing a portion of said solution and replacing said portion with approximately the same volume of a fresh solution containing a quantity of ammonium chloride dissolved therein sufficient to maintain about a 2.0 to 4.0 molar concentration of chloride ion in said solution.

Claim 23

The method of claim 23 wherein said fresh solution also contains a quantity of said promoter sufficient to maintain the concentration thereof effective, and a quantity of ammonium hydroxide sufficient to adjust the pH of said solution to about 10.0.