Page 48 - Chip Scale Review Sep Oct_2022-digital

with the die on the substrate. This
way, thick copper wires or ribbons
c a n b e w e d g e b o n d e d w i t h ou t
breaking the die (Figure 2b). The
benefits of copper wire bonding and
DTS are discussed in the second
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part of the article.
Phase formation
The phase formation and bonding
m e c h a n i s m of ou r n e w c o p p e r-
b o n d i n g t e c h no l o g y o n S i 3 N 4
cer a m ics were cha r acter i zed by
s ca n n i n g e l e c t r o n m i c r osc o p y
(SEM) as shown in Figure 3. The
actual bonding mechanism is based
on the reaction between the active
m e t a l (t i t a n i u m) a n d t h e Si 3 N 4
c e r a m i c , fo r m i ng a s t a bl e Ti N
Figure 3: Typical Condura .ultra microstructure measured by SEM.
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layer. Because there is no silver
Silver pressure sintering can also plates, with ou r Die Top System i n t h e C o n d u r a ®.u l t r a s y s t e m ,
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be used for advanced die frontside ( DTS ). It consists of a thi n Cu typical Ag- and Cu-rich phases are
interconnections as reported with plate (t y pically 50µm) with pre- eliminated, which are known from
t h e a t t a c h m e n t of m e t a l cl i p s , applied sinter paste, that is picked the standard AMB technology as
f le x i ble p r i n t e d c i r c u it b o a r d s from a carrier to be placed on top of using high Ag-containing brazing
(PCBs), or copper plates. We chose the die using a standard die bonder f iller metal pastes. Nevertheless,
to develop the last one, i.e., copper and then pressure-sintered together the bonding mechanism towards the
Si 3 N 4 ceramic via a TiN reaction
layer is similar.

Thermal shock performance
S i 3 N 4 - b a s e d A M B s u b s t r a t e s
m e e t t h e h i g h e s t r e q u i r e m e n t s
i n t e r m s of t h e r m a l sho c k t e s t
(TST) performance because of the
ceramic’s mechanical robustness.
To a s s e s s r e s i s t a n c e v s . t h e
t he r mome cha n ical st re ss of ou r
copper bonding technology on Si 3 N 4
For over a decade, Technic’s Elevate ceramics, thermal shock tests were
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Chemistry has risen to meet the perfor med using an inter nal test
2
greatest challenges of our industry layout (30.6x29mm with 0.5mm Cu
with innovation, expertise, exceptional on 0.32mm ceramic) as shown in
analytical support, and the best Figure 4. The status of the copper-
customer service in the industry. bonded substrates before testing was
characterized by scanning acous-tic
microscopy (SAM) and is shown in
• Electroplating Solutions for Figure 4a. The red color indicates
Copper an etched isolation groove that is
Nickel & Tin part of the used test layout. In case
Precious Metals of delam i nat ion bet ween copper
• Photoresist Strippers and braze metal/ceramic because
• Metal Etchants of thermal shock, the red-colored
• Post Etch Residue Removers isolation groove will broaden in the
SAM picture.
The integrity of the substrates was
reassessed by SAM after 3,000 and
5,000 cycles of thermal shock. The
results are shown in Figure 4b and
illustrate no major broadening of the
Learn more at www.technic.com

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