Page 49 - Chip Scale Review Sep Oct_2022-digital

Figure 5: Peel test sample after completion of the
peel test. A dark color remains on the peel strip and
®
Figure 4: SAM pictures of 20 individual Condura .ultra test layouts before and after thermal shock tests: a) 0 on the substrate, which indicates Si 3 N 4 has been
cycles; b) 3,000 cycles; and c) 5,000 cycles. The test conditions and further details are mentioned in the text. pulled out. The small rectangle indicates the position
No major degradation is visible after 5,000 cycles. for the EDS spectroscopy mapping seen in Figure 6.
isolation grooves between the initial
stat us of the subst rates with the
copper-bonding technology and after
completing the cycling, proving that
no delamination between the ceramic
a n d t h e b r a z e m e t a l o c c u r r e d .
This indicates that copper-bonded
technology can fully leverage the
mechanical robustness of the Si 3 N 4
ceramics, the same as Ag-containing
AMB technology.

Copper peel strength
T h e c o p p e r p e e l s t r e ng t h
characterizes the adhesion strength of
the copper (Cu) foil to the ceramic. A
simple peel test is used in which a Cu
peel strip (10mm wide x 0.3mm thick)
is brazed onto a piece of 0.32mm
thick Si 3 N 4 ceramic using our copper-
bonded technology. The Cu is peeled
off and the force is measured.
Closer inspection of the failure
mode of the peel sample can provide
va lu a ble i n fo r m a t io n a b out t he
bonding quality. Figure 5 shows
t h e p e e l e d - o f f C u s t r i p a f t e r
the peel test (right side) and the
remaining substrate counter par t.
A dark color on the peel strip and
on the counterpart is visible, which
indicates pulling out Si 3 N 4 particles
from the ceramic substrate. This

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