<s>
Flat	B-Algorithm
no-leads	I-Algorithm
packages	I-Algorithm
such	O
as	O
quad-flat	O
no-leads	O
(	O
QFN	B-Algorithm
)	O
and	O
dual-flat	O
no-leads	O
(	O
DFN	O
)	O
physically	O
and	O
electrically	O
connect	O
integrated	O
circuits	O
to	O
printed	O
circuit	O
boards	O
.	O
</s>
<s>
Flat	O
no-leads	O
,	O
also	O
known	O
as	O
micro	O
leadframe	B-Algorithm
(	O
MLF	O
)	O
and	O
SON	O
(	O
small-outline	O
no	O
leads	O
)	O
,	O
is	O
a	O
surface-mount	O
technology	O
,	O
one	O
of	O
several	O
package	B-Algorithm
technologies	O
that	O
connect	O
ICs	O
to	O
the	O
surfaces	O
of	O
PCBs	O
without	O
through-holes	B-Algorithm
.	O
</s>
<s>
Flat	O
no-lead	O
is	O
a	O
near	O
chip	B-Algorithm
scale	I-Algorithm
plastic	O
encapsulated	O
package	B-Algorithm
made	O
with	O
a	O
planar	O
copper	O
lead	B-Algorithm
frame	I-Algorithm
substrate	O
.	O
</s>
<s>
Perimeter	O
lands	O
on	O
the	O
package	B-Algorithm
bottom	O
provide	O
electrical	O
connections	O
to	O
the	O
PCB	O
.	O
</s>
<s>
The	O
QFN	B-Algorithm
package	B-Algorithm
is	O
similar	O
to	O
the	O
quad-flat	B-Algorithm
package	I-Algorithm
(	O
QFP	B-Algorithm
)	O
,	O
and	O
a	O
ball	B-Algorithm
grid	I-Algorithm
array	I-Algorithm
(	O
BGA	O
)	O
.	O
</s>
<s>
The	O
figure	O
shows	O
the	O
cross	O
section	O
of	O
a	O
flat	O
no-lead	O
package	B-Algorithm
with	O
a	O
lead	B-Algorithm
frame	I-Algorithm
and	O
wire	B-Algorithm
bonding	I-Algorithm
.	O
</s>
<s>
In	O
punch	O
singulation	O
,	O
a	O
single	O
package	B-Algorithm
is	O
moulded	O
into	O
shape	O
.	O
</s>
<s>
The	O
lead	B-Algorithm
frame	I-Algorithm
is	O
made	O
of	O
copper	O
alloy	O
and	O
a	O
thermally	O
conductive	O
adhesive	O
is	O
used	O
for	O
attaching	O
the	O
silicon	O
die	O
to	O
the	O
thermal	O
pad	O
.	O
</s>
<s>
The	O
silicon	O
die	O
is	O
electrically	O
connected	O
to	O
the	O
lead	B-Algorithm
frame	I-Algorithm
by	O
1	O
–	O
2thou	O
diameter	O
gold	B-Algorithm
wires	I-Algorithm
.	O
</s>
<s>
The	O
pads	O
of	O
a	O
saw-singulated	O
package	B-Algorithm
can	O
either	O
be	O
completely	O
under	O
the	O
package	B-Algorithm
,	O
or	O
they	O
can	O
fold	O
around	O
the	O
edge	O
of	O
the	O
package	B-Algorithm
.	O
</s>
<s>
Two	O
types	O
of	O
QFN	B-Algorithm
packages	O
are	O
common	O
:	O
air-cavity	O
QFNs	B-Algorithm
,	O
with	O
an	O
air	O
cavity	O
designed	O
into	O
the	O
package	B-Algorithm
,	O
and	O
plastic-moulded	O
QFNs	B-Algorithm
with	O
air	O
in	O
the	O
package	B-Algorithm
minimized	O
.	O
</s>
<s>
Less-expensive	O
plastic-moulded	O
QFNs	B-Algorithm
are	O
usually	O
limited	O
to	O
applications	O
up	O
to	O
~	O
2	O
–	O
3GHz	O
.	O
</s>
<s>
It	O
is	O
usually	O
composed	O
of	O
just	O
2	O
parts	O
,	O
a	O
plastic	O
compound	O
and	O
copper	O
lead	B-Algorithm
frame	I-Algorithm
,	O
and	O
does	O
not	O
come	O
with	O
a	O
lid	O
.	O
</s>
<s>
In	O
contrast	O
,	O
the	O
air-cavity	O
QFN	B-Algorithm
is	O
usually	O
made	O
up	O
of	O
three	O
parts	O
;	O
a	O
copper	O
leadframe	B-Algorithm
,	O
plastic-moulded	O
body	O
(	O
open	O
,	O
and	O
not	O
sealed	O
)	O
,	O
and	O
either	O
a	O
ceramic	O
or	O
plastic	O
lid	O
.	O
</s>
<s>
QFN	B-Algorithm
packages	O
can	O
have	O
a	O
single	O
row	O
of	O
contacts	O
or	O
a	O
double	O
row	O
of	O
contacts	O
.	O
</s>
<s>
This	O
package	B-Algorithm
offers	O
a	O
variety	O
of	O
benefits	O
including	O
reduced	O
lead	O
inductance	O
,	O
a	O
small	O
sized	O
"	O
near	O
chip	B-Algorithm
scale	I-Algorithm
"	O
footprint	O
,	O
thin	O
profile	O
and	O
low	O
weight	O
.	O
</s>
<s>
These	O
features	O
make	O
the	O
QFN	B-Algorithm
an	O
ideal	O
choice	O
for	O
many	O
new	O
applications	O
where	O
size	O
,	O
weight	O
,	O
thermal	O
and	O
electrical	O
performance	O
are	O
important	O
.	O
</s>
<s>
This	O
has	O
been	O
the	O
case	O
with	O
QFN	B-Algorithm
packages	O
,	O
especially	O
when	O
it	O
comes	O
to	O
adoption	O
by	O
new	O
non-consumer	O
electronic	O
OEMs	O
.	O
</s>
<s>
Some	O
key	O
QFN	B-Algorithm
design	O
considerations	O
are	O
pad	O
and	O
stencil	O
design	O
.	O
</s>
<s>
This	O
does	O
have	O
the	O
potential	O
to	O
affect	O
the	O
thermal	O
and	O
electrical	O
performance	O
of	O
the	O
joints	O
,	O
so	O
it	O
can	O
be	O
helpful	O
to	O
consult	O
the	O
package	B-Algorithm
manufacturer	O
for	O
optimal	O
performance	O
parameters	O
.	O
</s>
<s>
Stencil	O
design	O
is	O
another	O
key	O
parameter	O
in	O
QFN	B-Algorithm
design	O
process	O
.	O
</s>
<s>
For	O
larger	O
QFN	B-Algorithm
components	O
,	O
moisture	O
absorption	O
during	O
solder	O
reflow	O
can	O
be	O
a	O
concern	O
.	O
</s>
<s>
If	O
there	O
is	O
a	O
large	O
amount	O
of	O
moisture	O
absorption	O
into	O
the	O
package	B-Algorithm
then	O
heating	O
during	O
reflow	O
can	O
lead	O
to	O
excessive	O
component	O
warpage	O
.	O
</s>
<s>
Several	O
other	O
issues	O
with	O
QFN	B-Algorithm
manufacturing	O
include	O
:	O
part	O
floating	O
due	O
to	O
excessive	O
solder	O
paste	O
under	O
the	O
center	O
thermal	O
pad	O
,	O
large	O
solder	O
voiding	O
,	O
poor	O
reworkable	O
characteristics	O
,	O
and	O
optimization	O
of	O
the	O
solder	O
reflow	O
profile	O
.	O
</s>
<s>
It	O
can	O
therefore	O
be	O
challenging	O
to	O
integrate	O
component	O
package	B-Algorithm
families	O
,	O
such	O
as	O
the	O
QFN	B-Algorithm
,	O
into	O
high	O
reliability	O
environments	O
.	O
</s>
<s>
QFN	B-Algorithm
components	O
are	O
known	O
to	O
be	O
susceptible	O
to	O
solder	O
fatigue	O
issues	O
,	O
especially	O
thermomechanical	O
fatigue	O
due	O
to	O
thermal	O
cycling	O
.	O
</s>
<s>
The	O
significantly	O
lower	O
standoff	O
in	O
QFN	B-Algorithm
packages	O
can	O
lead	O
to	O
higher	O
thermomechanical	O
strains	O
due	O
to	O
coefficient	O
of	O
thermal	O
expansion	O
(	O
CTE	O
)	O
mismatch	O
as	O
compared	O
to	O
leaded	O
packages	O
.	O
</s>
<s>
For	O
example	O
,	O
under	O
accelerated	O
thermal	O
cycling	O
conditions	O
between	O
-40	O
°C	O
to	O
125°C	O
,	O
various	O
quad	B-Algorithm
flat	I-Algorithm
package	I-Algorithm
(	O
QFP	B-Algorithm
)	O
components	O
can	O
last	O
over	O
10,000	O
thermal	O
cycles	O
whereas	O
QFN	B-Algorithm
components	O
tend	O
to	O
fail	O
at	O
around	O
1,000	O
-3	O
,	O
000	O
cycles	O
.	O
</s>
<s>
package	B-Algorithm
to	O
PCB	O
substrate	O
)	O
.	O
</s>
<s>
As	O
a	O
result	O
there	O
has	O
been	O
much	O
experimental	O
testing	O
and	O
finite	B-Application
element	I-Application
analysis	I-Application
across	O
various	O
QFN	B-Algorithm
package	B-Algorithm
variants	O
to	O
characterize	O
their	O
reliability	O
and	O
solder	O
fatigue	O
behavior	O
.	O
</s>
<s>
proposed	O
a	O
semi-analytical	O
model	O
to	O
assess	O
the	O
reliability	O
QFN	B-Algorithm
solder	O
joints	O
under	O
thermal	O
cycling	O
.	O
</s>
<s>
This	O
model	O
generates	O
effective	O
mechanical	O
properties	O
for	O
the	O
QFN	B-Algorithm
package	B-Algorithm
,	O
and	O
calculates	O
the	O
shear	O
stress	O
and	O
strain	O
using	O
a	O
model	O
proposed	O
by	O
Chen	O
and	O
Nelson	O
.	O
</s>
<s>
The	O
QFN	B-Algorithm
package	B-Algorithm
is	O
similar	O
to	O
the	O
quad	B-Algorithm
flat	I-Algorithm
package	I-Algorithm
,	O
but	O
the	O
leads	O
do	O
not	O
extend	O
out	O
from	O
the	O
package	B-Algorithm
sides	O
.	O
</s>
<s>
It	O
is	O
hence	O
difficult	O
to	O
hand-solder	O
a	O
QFN	B-Algorithm
package	B-Algorithm
,	O
inspect	O
solder	O
joint	O
quality	O
,	O
or	O
probe	O
lead(s )	O
.	O
</s>
<s>
Different	O
manufacturers	O
use	O
different	O
names	O
for	O
this	O
package	B-Algorithm
:	O
ML	O
(	O
micro-leadframe	O
)	O
versus	O
FN	O
(	O
flat	O
no-lead	O
)	O
,	O
in	O
addition	O
there	O
are	O
versions	O
with	O
pads	O
on	O
all	O
four	O
sides	O
(	O
quad	O
)	O
and	O
pads	O
on	O
just	O
two	O
sides	O
(	O
dual	O
)	O
,	O
thickness	O
varying	O
between	O
0.9	O
–	O
1.0mm	O
for	O
normal	O
packages	O
and	O
0.4mm	O
for	O
extremely	O
thin	O
.	O
</s>
<s>
Micro	O
lead	B-Algorithm
frame	I-Algorithm
package	B-Algorithm
(	O
MLP	O
)	O
is	O
a	O
family	O
of	O
integrated	O
circuit	O
QFN	B-Algorithm
packages	O
,	O
used	O
in	O
surface	O
mounted	O
electronic	O
circuits	O
designs	O
.	O
</s>
<s>
These	O
package	B-Algorithm
generally	O
have	O
an	O
exposed	O
die	O
attach	O
pad	O
to	O
improve	O
thermal	O
performance	O
.	O
</s>
<s>
This	O
package	B-Algorithm
is	O
similar	O
to	O
chip	B-Algorithm
scale	I-Algorithm
packages	I-Algorithm
(	O
CSP	B-Algorithm
)	O
in	O
construction	O
.	O
</s>
<s>
MLPD	O
are	O
designed	O
to	O
provide	O
a	O
footprint-compatible	O
replacement	O
for	O
small-outline	B-Algorithm
integrated	I-Algorithm
circuit	I-Algorithm
(	O
SOIC	O
)	O
packages	O
.	O
</s>
<s>
Micro	O
lead	B-Algorithm
frame	I-Algorithm
(	O
MLF	O
)	O
is	O
a	O
near	O
CSP	B-Algorithm
plastic	O
encapsulated	O
package	B-Algorithm
with	O
a	O
copper	O
leadframe	B-Algorithm
substrate	O
.	O
</s>
<s>
This	O
package	B-Algorithm
uses	O
perimeter	O
lands	O
on	O
the	O
bottom	O
of	O
the	O
package	B-Algorithm
to	O
provide	O
electrical	O
contact	O
to	O
the	O
printed	O
circuit	O
board	O
.	O
</s>
<s>
The	O
die	O
attach	O
paddle	O
is	O
exposed	O
on	O
the	O
bottom	O
of	O
the	O
package	B-Algorithm
surface	O
to	O
provide	O
an	O
efficient	O
heat	O
path	O
when	O
soldered	O
directly	O
to	O
the	O
circuit	O
board	O
.	O
</s>
<s>
A	O
more	O
recent	O
design	O
variation	O
which	O
allows	O
for	O
higher	O
density	O
connections	O
is	O
the	O
dual	O
row	O
micro	O
lead	B-Algorithm
frame	I-Algorithm
(	O
DRMLF	O
)	O
package	B-Algorithm
.	O
</s>
<s>
This	O
is	O
an	O
MLF	O
package	B-Algorithm
with	O
two	O
rows	O
of	O
lands	O
for	O
devices	O
requiring	O
up	O
to	O
164	O
I/O	O
.	O
</s>
