Method for forming packaging of flip-chip semiconductor

Abstract

A method of forming a flip-chip semiconductor package, the main steps of which are: providing an oxidized (220) copper leadframe and a semiconductor chip having copper pillars extending from die pads and having solder balls on the free ends of the copper pillars, The solder balls are coated (225) with flux. The semiconductor chip is placed ( 230 ) on the oxidized copper lead frame with solder balls adjacent to portions on the oxide layer and aligned with interconnect locations on the lead frame. When reflowing (235), the flux adjacent to the portion of the oxide layer selectively removes the portion of the oxide layer from the interconnect location. In addition, the solder balls become molten and bond to the oxide-cleaved surface of the interconnect location. The remaining portion of the oxide layer that has not been removed advantageously provides a passivation layer that advantageously contains molten solder and prevents molten solder from flowing away from the interconnect location.

Description

technical field [0001] The present invention relates to the formation of flip chip semiconductor packages on leadframes, and more particularly, to the formation of flip chip semiconductor packages on bare copper leadframes. Background technique [0002] In semiconductor packaging, it is quite sensitive and difficult to handle packaging semiconductor chips into packages with external connections. Packaging makes semiconductor chips easier to handle and also allows external circuits to be easily connected thereto. [0003] A known method of semiconductor packaging is to use plated lead frames. A leadframe is a patterned sheet of metal, typically copper that has been plated with silver, nickel or palladium. Plating is necessary to prevent oxidation of the copper, to provide a surface to which solder will bond, or when wire connections are used, gold or aluminum can be bonded. The pattern of metal sheets provides the leadframe that forms the semiconductor package. [0004] G...

AI Technical Summary

Problems solved by technology

A second consideration is that interconnects with reduced solder volume cannot support the semiconductor chip flatly

However, to a large extent, copper leadframes also suffer from the same drawbacks discussed above as plated leadframes, in addition, when the copper is exposed, it tends to oxidize and the solder does not bond well to the copper oxide

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