Page 54 - Chip Scale Review_March April_2022-digital

Figure 5: An SAT image of the metal interconnects
area for a PS PBM/Cu-Sn bonded stack.

Figure 6: Wafer-level Maszara bond strength test.
scanning acoustic tomography (SAT) to
inspect the bonding quality. Figure 5
shows a magnified view of the SAT image
focused on the metal interconnects area,
which demonstrates a good bond line
quality with no voids on both the PS PBM
interfaces (light gray area) and the metal-
to-metal contacts (dark gray area).
Bond strength. Silicon wafers
coated with the PS PBM were bonded
together to evaluate the bond strength
of the polymeric bonding material. The
bonding was carried out at 150°C, 8kN,
for 15min. The temperature used for
bonding the PS PBM itself is much lower
than the temperature for PS PBM/Cu-Sn
hybrid bonding because there is no metal
annealing required. Actually, the PS
PBM can be bonded at <100°C, or even
room temperature. A detailed study will
be published in a separate paper at the
Electronic Components and Technology
Conference (ECTC) later this year.
The bond strength was evaluated with a
Maszara razor blade test at wafer-level [5-
6] with the PS PBM in a fully-cured state
before bonding. The test is performed
E-Tec Interconnect AG, Mr. Pablo Rodriguez, Lengnau Switzerland by inserting a razor blade between the
Phone : +41 32 654 15 50, E-mail: p.rodriguez@e-tec.com bonded PS PBM wafer pairs, and then
measuring the resulting crack length via
visual or infrared inspection. Figure 6

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