Nickel-Chromium Alloy Stripper for Flexible Wiring Boards
OwnerKesheng Feng, Nilesh Kapadia +2inventors
InventorsKesheng Feng, Nilesh Kapadia, Steven A. Castaldi, John Ganjei
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Abstract
A nickel-chromium alloy etching composition comprising sulfuric acid, a source of chloride ions, including hydrochloric acid or sodium, potassium or ammonium chloride, and a sulfur compound comprising a sulfur atom with an oxidation state between −2 to +5, such as thiosulfate, sulfide, sulfite, bisulfite, metabisulfite and phosphorus pentasulfide that can efficiently remove nickel-chromium alloy in the presence of copper circuits is disclosed.
Claims22
An etching composition for etching a printed wiring board to remove a nickel-chromium alloy layer, the etching solution comprising:
- a) an acid selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, sulfonic acid, sulfamic acid and combinations of one or more of the foregoing;
- b) a source of halide ions;
- and
- a sulfur compound comprising a sulfur atom with an oxidation state in the range of −2 to +5.
A method of selectively etching a wiring board, wherein the printed wiring board comprises an electrically insulating base material, a metal tie coat layer and a copper layer, the method comprising immersing the flexible wiring board in an etching solution comprising:
- i) an acid selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, sulfonic acid, sulfamic acid and combinations of one or more of the foregoing;
- ii) a source of halide ions;
- and
- iii) a sulfur compound comprising a sulfur atom with an oxidation state in the range of −2 to +5;
- for a period of time and at a temperature sufficient to remove the metal tie coat layer wherein the metal tie coat layer comprises a nickel-chromium alloy and wherein the etch solution etches less than 2 μin of copper.
Dependencies are inferred from the claim text.