摘要:
In some embodiments, to increase the height-to-pitch ratio of a solder connection that connects different structures with one or more solder balls, only a portion (510) of a solder ball's (140) surface is melted when the connection is formed on one structure (110) and/or when the connection is being attached to another structure (HOB). The structure (110) may be an integrated circuit, an interposer, a rigid or flexible wiring substrate, a printed circuit board, some other packaging substrate, or an integrated circuit package. In some embodiments, solder balls (140.1, 140.2) are joined by an intermediate solder ball (140i), upon melting of the latter only. Any of the solder balls (140, 140i) may have a non-solder central core (140C) coated by solder shell (140S). Some of the molten or softened solder may be squeezed out, to form a "squeeze-out" region (520, 520A, 520B, 520.1, 520.2). In some embodiments, a solder connection (210) such as discussed above, on a structure (110A), may be surrounded by a dielectric layer (1210), and may be recessed in a hole (1230) in that layer (1210), to help in aligning a post (1240) of a structure (HOB) with the connection (210) during attachment of the structures (110A, HOB). The dielectric layer (1210) may be formed by moulding. The dielectric layer may comprise a number of layers (1210.1, 1210.2), "shaved" (partially removed) to expose the solder connection (210). Alternatively, the recessed solder connections (210) may be formed using a sublimating or vapourisable material (1250), placed on top of the solder (210) before formation of the dielectric layer (1210) or coating solder balls (140); in the latter case, the solder (140C) sinks within the dielectric material (1210) upon removal of the material (1250) and subsequent reflow. In some embodiments, the solder connections (210) may also be formed in openings (2220) in a dielectric layer (2210) (photoimageable polymer or inorganic) by solder paste printing and/or solder ball jet placement followed by reflow to let the solder sink to the bottom of the openings (2220), with possible repetition of the process and possible use of different solders in the different steps. The solder connections (210, 210.1, 210.2) may be used for bonding one or more structures (HOB, HOC) (e.g. an integrated circuit die or wafer, a packaging substrate or a package) to a structure (110A) (a wiring substrate) on which a die (HOB) is flip-chip connected. The solder connections (210, 210.1, 210.2) may differ from each other, in particular in height, which can be used for attaching a structure (HOB) with posts (1240) of different heights or for attaching two structures (HOB, HOC) in the case of a stepped form of the dielectric layer, one of the structures (HOC) being possibly placed higher than the other structure (HOB). In some embodiments, the structure (HOA) may be removed after bonding to the structures (HOB, HOC) and a redistribution layer (3210) may be formed to provide connecting lines (3220) connecting the solder connections (210) to contact pads (120R) and possibly interconnecting between the solder connections (210) and/or between the contact pads (120R).