A process of forming an aperture in a metallic sheet including the steps of:a) defining at least one feature in a sheet of metallic material;b) laser drilling the at least one feature but not entirely removing it from the metallic sheet, the at least one feature being partially filled by metallic material which has melted and resolidified; and thenc) chemically etching the metallic sheet and the melted and resolidified metallic material wherein the etchant attacks and at least partially dissolves the melted and resolidified metallic material, weakening the bond of the melted and resolidified metallic material to the metallic sheet.