The fine copper pillar is a relatively small package compared to other interconnect types, thereby providing a significant advantage for the flip chip packaging industry. Furthermore, the technology has a low cost, which makes it a good choice for low-end flip chip applications. As a result, the fine pitch copper pillar is gaining in popularity as a key interconnect in this space. It is an excellent choice for interconnecting memories, microprocessors, and analog circuits. However, the fine pitch Cu pillar is not without its limitations. For example, the copper pillar has to be formed on the pads of a bottom-FET wafer. This means that the pillar will be a primary load transfer link between the die and substrate. Therefore, it is important to consider the proper wetting procedure for the copper pillar.

The copper pillar has two main parts: the pillar and the liner. The pillar is a metal plate that is formed on the surface of a copper plate. The pillar may have a copper or gold cap. It is important to consider the proper wetting procedure to ensure a good result. In general, the copper pillar will have a higher stress rating than the pillar made from pure nickel. This effect can be counteracted by adding layers of Ni and Cu. In addition, the pillar may have an aluminum or gold cap to improve its wetting properties.

The liner may be formed over the upper portion of a dielectric layer 60. The liner may also be formed directly over metal interconnects. The liner may also be formed in the form of a photoresist material. The corresponding jig may be used for this method of assembly. This method is a good fit for the fine pitch copper pillar since it is a good way to ensure an accurate placement of the pillar. The liner may also be a good way to improve the overall stress rating of the pillar.

The copper pillar may be the main load transfer link between the die and substrate, but it is not the only way to connect the two. Another way is by combining the two technologies. For example, a fine pitch copper pillar can be coupled to a bottom-FET die and a top-FET die using the aforementioned technologies. It is also possible to integrate the pillar into the substrate itself. This allows for a large number of interconnects per unit area of Silicon.