Use of electrolytic plating to control solder wetting
AssigneeInternational Business Machines Corporation
InventorsCharles L. Arvin, Brian M. Erwin, Eric D. Perfecto, Wolfgang Sauter
Life of this patent
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Abstract
A method including forming a copper pillar, electroplating a metal layer on a top surface and a sidewall of the copper pillar, and electroplating a metal cap above the top surface of the copper pillar in direct contact with the metal layer. The method further including forming an intermetallic by heating the metal layer and the copper pillar in a non-reducing environment, the intermetallic including elements of both the copper pillar and the metal layer, where molten solder will wet to the metal cap and will not wet to the intermetallic.
Claims19
A method comprising:
- forming a copper pillar;
- electroplating a metal layer on a top surface and a sidewall of the copper pillar;
- electroplating a metal cap above the top surface of the copper pillar in direct contact with the metal layer, wherein the metal cap is less than 1 μm;
- and
- forming an intermetallic by heating the metal layer and the copper pillar in a non-reducing environment, the intermetallic comprising elements of both the copper pillar and the metal layer, wherein the intermetallic comprises one of:
- only Cu3Sn;
- only Cu3Sn and SnO2;
- and only tin, Cu3Sn, and SnO2,
- wherein molten solder will wet to the metal cap and will not wet to the intermetallic.
(canceled)
A method comprising:
- forming a copper pillar;
- forming a solder bump directly on a top surface of the copper pillar by electroplating a solder cap and reflowing the solder cap to form the solder bump;
- electroplating a metal layer on a top surface of the solder bump and on a sidewall of the copper pillar, wherein the metal layer comprises tin and is less than 1 μm;
- and
- forming an intermetallic from a first portion of the metal layer in contact with the sidewall of the copper pillar by heating the metal layer and the copper pillar in a non-reducing environment, the intermetallic comprising elements of both the copper pillar and the metal layer, a second portion of the metal layer in contact with the solder bump remains unreacted, wherein forming the intermetallic includes:
- converting a portion of the metal layer in direct contact with the copper pillar to Cu3Sn;
- and
- oxidizing an outermost portion of the metal layer to forming SnO2, wherein the intermetallic comprises one of:
- only Cu3Sn;
- only Cu3Sn and SnO2;
- and only tin, Cu3Sn, and SnO2.
(canceled)
(canceled)
A method comprising:
- forming a copper pillar;
- electroplating a first metal layer on a top surface and a sidewall of the copper pillar;
- electroplating a second metal layer on top of the first metal layer, wherein the second metal layer is less than 1 μm;
- and
- forming an intermetallic by heating the first metal layer and the copper pillar in a non-reducing environment, the intermetallic comprising elements of both the copper pillar and the metal layer, wherein the intermetallic comprises one of:
- only Cu3Sn;
- only Cu3Sn and SnO2;
- and only tin, Cu3Sn, and SnO2
- wherein molten solder will wet to the second metal layer.
Dependencies are inferred from the claim text.