Page 24 - Chip Scale Review Sep Oct_2022-digital

size of a reticle. Flip-chip bonding of extra
large compound die on a substrate will
become increasingly difficult as the size of
compound die increases. A compound die
consists of different-sized and thickness
silicon dies and an EMC. The CTE values
of silicon and EMC materials have a
considerably wide range, therefore, die
warpage will be compounded due to the
differing degrees of expansion of the silicon
and EMC materials.
Design of a die attach tool to handle
an extra large compound is essential in
ensuring good bondability and yield as
follows (Figure 11): 1) Ensures temperature
Figure 9: Die shift compensation by Nucleus FOWLP die bonder: a) before die shift compensation; and b) after uniformity for a large heater for handling
die shift compensation. SOURCE: ASMPT the extra large compound die; 2) Ensures
warpage control by mechanical means; 3)
A customized tooling design follows the
characteristics of a particular compound
die; and 4) Enables analysis of potential
die crack/stress issues when handling a
compound die from pick-up to attachment
on the substrate
Summary
To enable heterogeneous integrations
during the development of advanced
packaging, a technique requiring high-
precision die attach is necessary. The rising
requirements of advanced packaging – in
Figure 10: Wafer substrate warpage on a vacuum chuck. SOURCE: ASMPT
tandem with the development of advanced
nodes – have raised the bar for high-
precision die attach capabilities. In the
new era of advanced packaging, selecting
a dependable and long-term partner in
equipment development to accomplish the
arduous demands of advanced packaging
development should be a top project goal.

References
1. “Technology Roadmap – Front-
end Manufacturing vs. Advanced
Packaging,” Yole Group, 2020.
2. J. H. Lau, et al., “Fan-out wafer-
level packaging for heterogeneous
integration,” IEEE Trans. on Comp.,
Figure 11: a) Compound die in a 2.5D package; and b) warpage scan image. SOURCE: ASMPT Packaging and Mfg. Tech., vol. 8,
decreases as a result of advanced node TCB” is currently under development and no. 9, pp. 1544-1560, Sept. 2018, doi:
10.1109/TCPMT.2018.2848649.
development, there are technical issues in it can be a solution for the above issues. 3. M. Li, et al., “Characterizations of
removing all flux from beneath a die after Large compound die handling issue. fan-out wafer-level packaging,” Inter.
die attachment via TCB. If flux residue When the development trend of 2.5D Symp. on Microelectronics. Vol. 2017,
remains beneath a die and is transferred packaging is toward including more chiplets No. 1, International Microelectronics
to subsequent processes, the final yield in the same package, the compound die size Assembly and Packaging Soc., 2017.
will be reduced. The method of “flux-less increases to three, or even four times, the

Biography
Percy Lam is Sales Manager at ASMPT Limited, Hong Kong, with responsibilities of product management
and business development in the Advanced Packaging Technology Equipment sector. Areas covered are
die attach solutions for FOWLP/PLP, with a focus on promoting package assembly equipment solutions
for heterogeneous integration applications. He graduated from the Chinese U. of Hong Kong, majoring in
Electronic Engineering. Email: percy.lam@asmpt.com

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