Summary:Unlike a pure copper pillar, a nickel or nickel alloy pillar improves the performance of a device by...
Unlike a pure copper pillar, a nickel or nickel alloy pillar improves the performance of a device by spreading electrical current better than copper. This results in less shorting between the connections of a device. Additionally, a nickel or nickel alloy pillar may have a gold cap that enhances solder wetting. The thickness of the nickel or nickel alloy pillar helps to prevent the flow of solder onto the sidewalls of the copper pillar, which can lead to bridging and shorting.
Thermo-compression bonding is a method for bonding copper pillar interconnects. It is widely used in fine-pitch copper pillar assemblies. It provides a reliable bonding process that is suitable for mass production. Thermo-compression bonding uses a non-conductive paste underfill. The main benefit of this process is its ability to be applied to a variety of materials. It is suitable for both high-k and low-k materials and is particularly well-suited for high-density I/O applications.
In conventional copper pillar structures, the copper plate is deposited on a liner. The photoresist material is then processed to form an opening. The opening is aligned with a nickel or nickel alloy pillar, and the pillar is deposited in contact with the layer. This step, which takes about 15 minutes, reduces the overall stress of the pillar by adding a layer of Ni and Cu. It also produces a uniform protective coating.
The copper pillar has several advantages, such as its superior electromigration performance, and its superior pitch. However, a copper pillar-based solder connector is expensive to manufacture. It is difficult to prevent the flow of solder from wetting the sidewalls of the pillar, which can lead to bridging or shorting. A modified surface, such as an oxide or nitride layer, can help. It is also possible to fabricate a pillar without a solder layer.
The copper pillar is the primary load transfer link between a die and a substrate. This load transfer link is particularly important in fine-pitch semiconductor structures, which involve the use of vertical pillars. In addition, the nickel or nickel alloy pillar can be fabricated on the copper layer. This reduces device shorting between the connections and makes it possible to fabricate denser pitch interconnects.
The main technical parameters:
1, accuracy level: 2 ~ 4000A; 0.5: 5000 ~ 10000A; 1 level.
2, the ambient conditions: -40 ~ +60 ℃, relative humidity ≤ 95% (35 ℃).
3, overload performance: rated current 120%, 2 hours.
4, the voltage drop: 50mV60mV70mV100mV
5, the load under the heat: temperature stability tends to change, the rated current 50A the following does not exceed 80 ℃; rated current 50A or more does not exceed 120 ℃.
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