Patent ID: 6943102
Filing Date: 2005-09-13
Classification: H01L,H05K

Abstract:
1. A method for fabricating a printed board including interconnections and a plurality of solder bumps formed on a substrate, the method comprising the steps of: providing a substrate on which interconnections and a plurality of pads in a predetermined pattern are formed; providing a solder bump transfer sheet having a plurality of solder bumps placed to correspond to the predetermined pattern of said plurality of pads; and transferring said plurality of solder bumps of said solder bump transfer sheet to said plurality of pads on said substrate, wherein said solder bump transfer sheet is produced by a method comprising the steps of: forming on the surface of a stainless steel sheet a chromium oxide layer as an outermost surface wherein the chromium oxide layer contains substantially no iron oxide formed during formation of the chromium oxide layer; and forming a plurality of solder bumps placed in a predetermined pattern on said chromium oxide layer, wherein said stainless steel sheet has a conductive surface, said chromium oxide layer being formed on said conductive surface, and said plurality of solder bumps are formed by electroplating, said chromium oxide layer is formed by a process including a step of thermally oxidizing the conductive surface of said stainless steel sheet, and said step of forming a plurality of solder bumps comprises the steps of: forming a resist layer on said chromium oxide layer, the resist layer having a plurality of openings formed in said predetermined pattern; depositing solder on portions of said chromium oxide layer exposed in said plurality of openings of said resist layer by electroplating; and prior to said step of depositing solder by electroplating, washing the outermost surface of said stainless steel sheet with an acid aqueous solution.