<s>
Wire	B-Algorithm
bonding	I-Algorithm
is	O
the	O
method	O
of	O
making	O
interconnections	O
between	O
an	O
integrated	O
circuit	O
(	O
IC	O
)	O
or	O
other	O
semiconductor	O
device	O
and	O
its	O
packaging	B-Algorithm
during	O
semiconductor	B-Architecture
device	I-Architecture
fabrication	I-Architecture
.	O
</s>
<s>
Although	O
less	O
common	O
,	O
wire	B-Algorithm
bonding	I-Algorithm
can	O
be	O
used	O
to	O
connect	O
an	O
IC	O
to	O
other	O
electronics	O
or	O
to	O
connect	O
from	O
one	O
printed	O
circuit	O
board	O
(	O
PCB	O
)	O
to	O
another	O
.	O
</s>
<s>
Wire	B-Algorithm
bonding	I-Algorithm
is	O
generally	O
considered	O
the	O
most	O
cost-effective	O
and	O
flexible	O
interconnect	O
technology	O
and	O
is	O
used	O
to	O
assemble	O
the	O
vast	O
majority	O
of	O
semiconductor	O
packages	O
.	O
</s>
<s>
Wire	B-Algorithm
bonding	I-Algorithm
can	O
be	O
used	O
at	O
frequencies	O
above	O
100GHz	O
.	O
</s>
<s>
The	O
wire	B-Algorithm
bonding	I-Algorithm
industry	O
is	O
transitioning	O
from	O
gold	O
to	O
copper	O
.	O
</s>
<s>
By	O
2015	O
,	O
it	O
is	O
expected	O
that	O
more	O
than	O
a	O
third	O
of	O
all	O
wire	B-Algorithm
bonding	I-Algorithm
machines	O
in	O
use	O
will	O
be	O
set	O
up	O
for	O
copper	O
.	O
</s>
<s>
Copper	O
wire	O
has	O
become	O
one	O
of	O
the	O
preferred	O
materials	O
for	O
wire	B-Algorithm
bonding	I-Algorithm
interconnects	O
in	O
many	O
semiconductor	O
and	O
microelectronic	O
applications	O
.	O
</s>
<s>
Copper	O
is	O
used	O
for	O
fine	O
wire	O
ball	B-Algorithm
bonding	I-Algorithm
in	O
sizes	O
from	O
up	O
to	O
.	O
</s>
<s>
Copper	O
wire	O
up	O
to	O
can	O
be	O
successfully	O
wedge	B-Algorithm
bonded	I-Algorithm
.	O
</s>
<s>
Special	O
packaging	B-Algorithm
is	O
required	O
in	O
order	O
to	O
protect	O
copper	O
wire	O
and	O
achieve	O
a	O
longer	O
shelf	O
life	O
.	O
</s>
<s>
During	O
the	O
fabrication	B-Architecture
of	O
wire	B-Algorithm
bonds	I-Algorithm
,	O
copper	O
wire	O
,	O
as	O
well	O
as	O
its	O
plated	O
varieties	O
,	O
must	O
be	O
worked	O
in	O
the	O
presence	O
of	O
forming	O
gas	O
[	O
95%	O
nitrogen	O
and	O
5%	O
hydrogen ]	O
or	O
a	O
similar	O
anoxic	O
gas	O
in	O
order	O
to	O
prevent	O
corrosion	O
.	O
</s>
<s>
Pure	O
gold	O
wire	O
doped	O
with	O
controlled	O
amounts	O
of	O
beryllium	O
and	O
other	O
elements	O
is	O
normally	O
used	O
for	O
ball	B-Algorithm
bonding	I-Algorithm
.	O
</s>
<s>
This	O
process	O
brings	O
together	O
the	O
two	O
materials	O
that	O
are	O
to	O
be	O
bonded	O
using	O
heat	O
,	O
pressure	O
and	O
ultrasonic	B-Application
energy	O
referred	O
to	O
as	O
thermosonic	B-Algorithm
bonding	I-Algorithm
.	O
</s>
<s>
The	O
most	O
common	O
approach	O
in	O
thermosonic	B-Algorithm
bonding	I-Algorithm
is	O
to	O
ball-bond	O
to	O
the	O
chip	O
,	O
then	O
stitch-bond	O
to	O
the	O
substrate	O
.	O
</s>
<s>
Junction	O
size	O
,	O
bond	O
strength	O
and	O
conductivity	O
requirements	O
typically	O
determine	O
the	O
most	O
suitable	O
wire	O
size	O
for	O
a	O
specific	O
wire	B-Algorithm
bonding	I-Algorithm
application	O
.	O
</s>
<s>
All-aluminum	O
systems	O
in	O
semiconductor	B-Architecture
fabrication	I-Architecture
eliminate	O
the	O
"	O
purple	O
plague	O
"	O
(	O
brittle	O
gold-aluminum	O
intermetallic	O
compound	O
)	O
sometimes	O
associated	O
with	O
pure	O
gold	O
bonding	O
wire	O
.	O
</s>
<s>
Aluminum	O
is	O
particularly	O
suitable	O
for	O
thermosonic	B-Algorithm
bonding	I-Algorithm
.	O
</s>
<s>
The	O
main	O
classes	O
of	O
wire	B-Algorithm
bonding	I-Algorithm
:	O
</s>
<s>
Ball	B-Algorithm
bonding	I-Algorithm
usually	O
is	O
restricted	O
to	O
gold	O
and	O
copper	O
wire	O
and	O
usually	O
requires	O
heat	O
.	O
</s>
<s>
For	O
wedge	B-Algorithm
bonding	I-Algorithm
,	O
only	O
gold	O
wire	O
requires	O
heat	O
.	O
</s>
<s>
Wedge	B-Algorithm
bonding	I-Algorithm
can	O
use	O
large	O
diameter	O
wires	O
or	O
wire	O
ribbons	O
for	O
power	O
electronics	O
application	O
.	O
</s>
<s>
Ball	B-Algorithm
bonding	I-Algorithm
is	O
limited	O
to	O
small	O
diameter	O
wires	O
,	O
suitable	O
for	O
interconnect	O
application	O
.	O
</s>
<s>
In	O
either	O
type	O
of	O
wire	B-Algorithm
bonding	I-Algorithm
,	O
the	O
wire	O
is	O
attached	O
at	O
both	O
ends	O
using	O
a	O
combination	O
of	O
downward	O
pressure	O
,	O
ultrasonic	B-Application
energy	O
,	O
and	O
in	O
some	O
cases	O
heat	O
,	O
to	O
make	O
a	O
weld	O
.	O
</s>
<s>
The	O
correct	O
combination	O
of	O
temperature	O
and	O
ultrasonic	B-Application
energy	O
is	O
used	O
in	O
order	O
to	O
maximize	O
the	O
reliability	O
and	O
strength	O
of	O
a	O
wire	B-Algorithm
bond	I-Algorithm
.	O
</s>
<s>
If	O
heat	O
and	O
ultrasonic	B-Application
energy	O
is	O
used	O
,	O
the	O
process	O
is	O
called	O
thermosonic	B-Algorithm
bonding	I-Algorithm
.	O
</s>
<s>
In	O
wedge	B-Algorithm
bonding	I-Algorithm
,	O
the	O
wire	O
must	O
be	O
drawn	O
in	O
a	O
straight	O
line	O
according	O
to	O
the	O
first	O
bond	O
.	O
</s>
<s>
Ball	B-Algorithm
bonding	I-Algorithm
,	O
however	O
,	O
creates	O
its	O
first	O
bond	O
in	O
a	O
ball	O
shape	O
with	O
the	O
wire	O
sticking	O
out	O
at	O
the	O
top	O
,	O
having	O
no	O
directional	O
preference	O
.	O
</s>
<s>
There	O
are	O
multiple	O
challenges	O
when	O
it	O
comes	O
to	O
wire	B-Algorithm
bond	I-Algorithm
manufacturing	O
and	O
reliability	O
.	O
</s>
<s>
Much	O
work	O
has	O
been	O
done	O
to	O
characterize	O
various	O
metal	O
systems	O
,	O
review	O
critical	O
manufacturing	O
parameters	O
,	O
and	O
identify	O
typical	O
reliability	O
issues	O
that	O
occur	O
in	O
wire	B-Algorithm
bonding	I-Algorithm
.	O
</s>
<s>
For	O
example	O
,	O
a	O
high	O
current	O
device	O
for	O
a	O
space	O
application	O
might	O
require	O
a	O
large	O
diameter	O
aluminum	O
wire	B-Algorithm
bond	I-Algorithm
in	O
a	O
hermetically	O
sealed	O
ceramic	O
package	O
.	O
</s>
<s>
If	O
cost	O
is	O
a	O
large	O
constraint	O
,	O
then	O
avoiding	O
gold	O
wire	B-Algorithm
bonds	I-Algorithm
may	O
be	O
a	O
necessity	O
.	O
</s>
<s>
Some	O
recent	O
work	O
has	O
been	O
done	O
to	O
look	O
at	O
copper	O
wire	B-Algorithm
bonds	I-Algorithm
in	O
automotive	O
applications	O
.	O
</s>
<s>
Parameters	O
such	O
bond	O
force	O
,	O
ultrasonic	B-Application
energy	O
,	O
temperature	O
,	O
and	O
loop	O
geometry	O
,	O
to	O
name	O
a	O
few	O
,	O
can	O
have	O
a	O
significant	O
effect	O
on	O
bond	O
quality	O
.	O
</s>
<s>
There	O
are	O
various	O
wire	B-Algorithm
bonding	I-Algorithm
techniques	O
(	O
thermosonic	B-Algorithm
bonding	I-Algorithm
,	O
ultrasonic	B-Application
bonding	O
,	O
thermocompression	B-Algorithm
bonding	I-Algorithm
)	O
and	O
types	O
of	O
wire	B-Algorithm
bonds	I-Algorithm
(	O
ball	B-Algorithm
bonding	I-Algorithm
,	O
wedge	B-Algorithm
bonding	I-Algorithm
)	O
that	O
affect	O
susceptibility	O
to	O
manufacturing	O
defects	O
and	O
reliability	O
issues	O
.	O
</s>
<s>
A	O
combination	O
of	O
wire	B-Algorithm
bond	I-Algorithm
pull/shear	O
testing	O
,	O
nondestructive	O
testing	O
,	O
and	O
destructive	O
physical	O
analysis	O
(	O
DPA	O
)	O
can	O
be	O
used	O
to	O
screen	O
manufacturing	O
and	O
quality	O
issues	O
.	O
</s>
<s>
While	O
wirebond	B-Algorithm
manufacturing	O
tends	O
to	O
focus	O
on	O
bond	O
quality	O
,	O
it	O
often	O
does	O
not	O
account	O
for	O
wearout	O
mechanisms	O
related	O
to	O
wire	B-Algorithm
bond	I-Algorithm
reliability	O
.	O
</s>
<s>
Common	O
examples	O
of	O
environments	O
that	O
lead	O
to	O
wire	B-Algorithm
bond	I-Algorithm
failures	O
include	O
elevated	O
temperature	O
,	O
humidity	O
,	O
and	O
temperature	O
cycling	O
.	O
</s>
<s>
This	O
not	O
a	O
problem	O
in	O
metal	O
systems	O
where	O
the	O
wire	B-Algorithm
bond	I-Algorithm
and	O
bond	O
pad	O
are	O
the	O
same	O
material	O
such	O
as	O
Al-Al	O
.	O
</s>
<s>
Additionally	O
,	O
diffusion	O
related	O
issues	O
,	O
such	O
as	O
Kirkendall	O
voiding	O
and	O
Horsting	O
voiding	O
,	O
can	O
also	O
lead	O
to	O
wire	B-Algorithm
bond	I-Algorithm
failures	O
.	O
</s>
<s>
Under	O
temperature	O
cycling	O
,	O
thermomechanical	O
stress	O
is	O
generated	O
in	O
the	O
wire	B-Algorithm
bond	I-Algorithm
as	O
a	O
result	O
of	O
coefficient	O
of	O
thermal	O
expansion	O
(	O
CTE	O
)	O
mismatch	O
between	O
the	O
epoxy	O
molding	O
compound	O
(	O
EMC	O
)	O
,	O
the	O
leadframe	B-Algorithm
,	O
the	O
die	O
,	O
the	O
die	O
adhesive	O
,	O
and	O
the	O
wire	B-Algorithm
bond	I-Algorithm
.	O
</s>
<s>
This	O
leads	O
to	O
low	O
cycle	O
fatigue	O
due	O
to	O
shear	O
or	O
tensile	O
stresses	O
in	O
the	O
wire	B-Algorithm
bond	I-Algorithm
.	O
</s>
<s>
Various	O
fatigue	O
models	O
have	O
been	O
used	O
to	O
predict	O
the	O
fatigue	O
life	O
of	O
wire	B-Algorithm
bonds	I-Algorithm
under	O
such	O
conditions	O
.	O
</s>
<s>
Proper	O
understanding	O
of	O
the	O
use	O
environment	O
and	O
metal	O
systems	O
are	O
often	O
the	O
most	O
important	O
factors	O
for	O
increasing	O
wire	B-Algorithm
bond	I-Algorithm
reliability	O
.	O
</s>
<s>
While	O
there	O
are	O
some	O
wire	B-Algorithm
bond	I-Algorithm
pull	O
and	O
shear	O
testing	O
techniques	O
,	O
these	O
tend	O
to	O
be	O
applicable	O
for	O
manufacturing	O
quality	O
rather	O
than	O
reliability	O
.	O
</s>
