324
S. Lee
Single head, high accuracy <+/-2μm
Multi heads, low accuracy <+/-10μm
(a)
(b)
… … … …
Fig. 10.69 Schematic of hybrid assembly process: a pre-alignment placement and b post TCB
the overall cost of TCB technology. Specifically, an optimized high bond force is
necessary for the micro-bumps on the die to penetrate the highly viscous NCF and
contact the substrate or interposer pads, consequently guaranteeing good wetting and
no fillers entrapment. An alternative approach for improving the throughput of TCB
process, 3D stacking process TCB using epoxy flux can be considered as a good
alternative building blocks. This chapter also reviewed 2.5/3D research using noclean flux with TCB to guide how to develop assembly process through systematic
DOEs.
Figure 10.69 illustrates a concept of hybrid process for attaching die using a
high accuracy TCB tool in less than a second. This method would guarantee a high
placement accuracy and save process time by reflowing of multiple, pre-aligned die
using a TCB block head. The hybrid assembly process could overcome the throughput
challenge while still taking advantage of NCF [84]. Such a TCB assembly concept
would help move the industry toward a process that can deliver advanced assemblies
at a cost competitive position.
In addition, this chapter highlighted the interactive effects between process, material, and equipment. A few leading companies that have driven both material and
equipment for 3D packaging are conducting research and development (R/D) on
the synergistic effects between materials, processes, and equipment to improve 3D
TSV technology including TCB. Academia is recommended to investigate the fundamentals aspects of all three fields to answer technical challenges resulting from the
intrinsic characteristics of TCB—e.g., the very fast heating and cooling rates. For
example, academia could advise industry on methods to reduce temperature gradients
within the package during TCB bonding, thus possibly lowering the peak temperature
that would reduce the bonding cycle time. Comprehensive studies would examine
orientation and size of solder grains under reflow condition given the uni-directional
heat flux from head to stage as the special topic addresses in this chapter. This chapter
described some of the fundamental aspects of materials technology and process for
TCB technology to enable high-throughput, low-cost of 3D assembly processes as a
stepping-stone from the conventional 2D technology.
Acknowledgements The editors would like to thank Paul Vianco from Sandia National Laboratory,
Yonghao Xiu and Yuying Wei from Intel Corporation for their critical review of this Chapter.
S. Lee
Single head, high accuracy <+/-2μm
Multi heads, low accuracy <+/-10μm
(a)
(b)
… … … …
Fig. 10.69 Schematic of hybrid assembly process: a pre-alignment placement and b post TCB
the overall cost of TCB technology. Specifically, an optimized high bond force is
necessary for the micro-bumps on the die to penetrate the highly viscous NCF and
contact the substrate or interposer pads, consequently guaranteeing good wetting and
no fillers entrapment. An alternative approach for improving the throughput of TCB
process, 3D stacking process TCB using epoxy flux can be considered as a good
alternative building blocks. This chapter also reviewed 2.5/3D research using noclean flux with TCB to guide how to develop assembly process through systematic
DOEs.
Figure 10.69 illustrates a concept of hybrid process for attaching die using a
high accuracy TCB tool in less than a second. This method would guarantee a high
placement accuracy and save process time by reflowing of multiple, pre-aligned die
using a TCB block head. The hybrid assembly process could overcome the throughput
challenge while still taking advantage of NCF [84]. Such a TCB assembly concept
would help move the industry toward a process that can deliver advanced assemblies
at a cost competitive position.
In addition, this chapter highlighted the interactive effects between process, material, and equipment. A few leading companies that have driven both material and
equipment for 3D packaging are conducting research and development (R/D) on
the synergistic effects between materials, processes, and equipment to improve 3D
TSV technology including TCB. Academia is recommended to investigate the fundamentals aspects of all three fields to answer technical challenges resulting from the
intrinsic characteristics of TCB—e.g., the very fast heating and cooling rates. For
example, academia could advise industry on methods to reduce temperature gradients
within the package during TCB bonding, thus possibly lowering the peak temperature
that would reduce the bonding cycle time. Comprehensive studies would examine
orientation and size of solder grains under reflow condition given the uni-directional
heat flux from head to stage as the special topic addresses in this chapter. This chapter
described some of the fundamental aspects of materials technology and process for
TCB technology to enable high-throughput, low-cost of 3D assembly processes as a
stepping-stone from the conventional 2D technology.
Acknowledgements The editors would like to thank Paul Vianco from Sandia National Laboratory,
Yonghao Xiu and Yuying Wei from Intel Corporation for their critical review of this Chapter.