Surface-mount Fuses
– Fundamentals
Surface-mount Fuses
Fundamentals
Overview
TE Circuit Protection offers the widest selection of surface-mount
fuses available for addressing a broad range of overcurrent
protection applications. Helping to prevent costly damage and
ng
promote a safe environment for electronic and
electrical
nt
equipment, our single-use chip fuses provide performance stability
to support applications with current ratings from .5A up to 20A.
urrent
TE Circuit Protection also offers the telecom FT600 fuse for
fers
telecommunications applications. This telecom fuse helps comply
ons.
with North American overcurrent
protection requirements,
current
including Telcordia, GR-1089,
TIA-968-A
(formerly FCC Part 68),
and UL60950 3rd edition.
Multi-layer Design for Chip Fuses
hip
The multi-layer design has the benefit of exposing more fuse
he
f
use
element surface area to the
glass-ceramic absorption
material.
absorption
m
te
rial.
o
ma
e
When the fuse elements open, there is more material for the
en,
mate
rial
fo
the
e
h
vaporizing fuse metals to absorb into, resulting in a very
ef
fi
cie
n
t
efficient
orb
n
v
ery
e
i
e
and effective quenching of the
fuse arc.
e
Figure 1 compared the multi-layer design of our SFF fuses
w
ith
ayer design o
f
s
i
g
S
F
F f
uses
with
SF
s
standard glass coated designs. The glass coated designs rely on
s.
g
lass
c
o
ated
d
e
signs
re
ly
s
t
e
d de
s
e
the coating on only one side
of the
fuse
el
em
ent t
o abso
rb
the
e
fuse element to absorb
the
l
m
t
o
r
e
vaporizing fuse material when
it op
ens. Th
e
refore,
t
here is mu
ch
opens. Therefore, there
s
much
p
h
o
e
,
u
less absorption material available to absorb
the fu
se
metals.
The
fuse metals.
ble
t
absorb
h
e
f
u
m
a
s
T
h
e
ab
r
b
b
result can be prolonged arcing and
p
os
sib
le
coating breach.
g
d
possible
s
b
n
bre
ach.
e
ch
h
Figure 2 shows how the absorption characteristics of the
two
orpti
on characteristics
f
he
i
h
r
a
e
r
i
ic
i
c
h
e
designs differ. The multi-layer design indicates a clean separation
desig
n
ind
icates clea sep
ara
tion
g
d a
t
e
an
ea
s
n
with the fuse element evenly diffusing into the surrounding
y diffusin
g
i
nto the surro
unding
u
n
o
o
i
ceramic substrate. In the glass coated design, the element
ass
co
ate
d des
i
gn,
t
e e
lement
o
te
e
s
th
diffusion takes place in a small portion of the
dev
ice
and
is only
l po
rtio
n
f
t
he
device
an
o o
v
e
a
n
absorbed by the glass material
dir
e
tly abo
ve
the
area of failure.
l
directly above
e
rect
re
r
b
F
igur
e
Figure
1
r
G
lass/C
eramic
Glass/Ceramic
C
c
Substrate
Subs
trate
s
e
Multiple Fuse
M
ult
iple
t
Elements
Ele
men
ts
e
n
Substrate
Su
Material
M
Single Fuse Glass
Element Coating
Multi-layer
M
ulti-laye
r
Design
e
Single-layer Glass Coated Design
Sin
Figu
re
Figure
2
u
e
Fault Zones
Zone
11
Multi-layer
Design
Single-layer Glass Coated Design
Single-la
Wire-In-Air Design for 2410SFV Fuses
2410
SFV
Fuses
0
V
r
D
Fuse
The 2410(6125) is a Wire-In-Air SMD
F
use which is very suitable
t
t ti
li ti
for secondary level over current protection applications.
Figure 3 compared our straight wire element design 2410SFV
fuses with normal corrugating wire design fuse. The straight wire
element in air performs consistent fusing and cutting
characteristics together with excellent inrush current
withstanding capability.
Introduced PCB assembly technology into 2410SFV fuses design
and manufacture, we achieved on lead free completely and no
end cap falling off risk comparing with traditional ceramic body
with end cap fuse.
Figure
3
Glass fiber enforced
epoxy body
Straight wire element
Copper terminal
plated with Ni and Tin
Ceramic body
Corrugate wire element
End cap plated with Tin
75
Temperature Derating
A fuse is a temperature sensitive device. Therefore, operating temperature will have an effect on fuse performance and lifetime.
nsitive
f
Operating temperature should be taken into consideration when selecting the fuse current rating. The Thermal Derating Curve for
ould
t
rating. T
a
t
surface mount fuses is presented
in Figure 4.
Use it to determine the derating percentage based on operating temperature and
sented
percenta
ge ba
sed
t
a
apply it to the derated system current.
tem
Figure 4
1206/0603/0402
Series
06/0603/0402
ure
Temperature
Effect on
Current Rating
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
-55
0
110
5
105
0
100
5
95
2410 Series
S
Temper
a
tu
re Effect O
e
er
u
e
Temperature Effect On Current Rating
% De-rating
% De-rating
-35
-15
5
25
45
65
85
5
105
105
5
125
1
5
145
5
0
90
5
85
0
80
5
75
0
70
5
65
0
60
5
55
0
50
-55
-35
-15
-15
1
5
25
45
65
85
105
125
Maximum Operating Temperature (°C)
mum
Tem
peratur
e (
°C)
e
m
em
r
)
Maximum Operating Temperature (°C)
M
axi
mu
Operating
i
mum
m
um
u
Pulse Cycle Derating
Once the I
2
t value for the
a
pplica
ti
on
waveform has been
application
w
aveform has been
ati
a
a
e
h
b
e
n
determined, it must be derated
based
on the number of cycles
erated
based
d
d
t
e
nu
mber
f
cy
cles
n
u
r
e
s
expected over the system lifetime. Since the stress induced by the
ifetim
e.
S
i
nce the str
ss i
ndu
c
ed
b
y t
he
me.
m
.
c
e
t
re
n
r
h
e
current pulse is mechanical
in
natu
,
t
he num
ber
of t
the
al
n
nature, the number
f
times
t
he
a
ure,
m
be
b
e
stress is applied has significant bearing on how much derating
ficant bea
ring
n
how
much
derat
ing
n
t
nt
a
n
g
w
uc
u
c
t
must be applied to the fuse rating. Figure 5 presents the current
e rat
ing.
Figu
re presen
ts the
cur
rent
a
gu
u
re
n
t
s
e
r
e
pulse derating curve for our surface-mount chip fuses up to
su
rfa
ce-mount chip
f
u
ses
u
a
e-
ou
e
u
c
100,000 cycles.
Fi
g
ure
Figure
5
i
e
Surface-mount
Fuse
Pulse Derating Curve
100%
% of Minimum I
2
t
10%
100
1000
10000
100000
Numbe
Number of Pulses
Selecting Surface-mount Fuses
ount
Fus
es
t
s
11
Fuse selection seems straightforward, in that, you pick one which has a current rating just a bit higher than your worstcase system
ghtforward,
highe
operating current. Unfortunately, it’s not that simple. There are derating considerations for operating current and application
temperature. Turn-on and other system operations (like processor speed changes or motor start up) cause current surges or
spikes that also require consideration when selecting a fuse. So selecting the right fuse for your application is not as simple as
knowing the nominal current drawn by the system.
Fuse Selection Flowchart
However, the basic considerations for fuse selection are shown in the flowchart presented in Figure 6. Following this flow chart
will help you select a fuse best suited for your application conditions.
Figure 6
Step 1 –
Determine Steady State
Fuse Current Rating
Apply Standard Steady
State Derating (75%)
[I
fuse
≥
I
sys
/0.75]
Apply
Temperature Derating
[I
fuse
≥
I
sys
/0.75/K
temp
]
Steady State
Fuse Current
Rating
Step 2 –
Determine Pulse
Waveform by
Calculating I
2
t
Step 3 –
Apply Pulse
Cycle Derating
Step 4 –
Apply Pulse
Temperature
Derating
Step 5 –
Apply Derating
for Variance in
the Circuit
Step 6 –
Select Fuse Current
Rating for Pulse
Environment
Step 7 –
Select Fuse Current Rating
(use higher value between Step 1 and Step 6)
Step 8 –
Check Voltage Rating
76
Surface-mount Fuses
– Pulse Tolerant Chip Fuses
Surface-mount Fuses
Pulse Tolerant Chip Fuses
se T l
t Chip F
Pulse Tolerant chip fuses has high inrush current
s
withstand capability and provide overcurrent protection
ovide
on DC power systems. Silver
fusing element, monolithic
er
and multilayer design provides
strong arc suppression
vides
characteristics.
These RoHS-compliant surface-mount devices facilitate
ace-mount
e
the development of more reliable, high performance
performanc
e
c
consumer electronics such as laptops, multimedia
ch
multimed
ia
t
i
ti
m
devices, cell phones, and other portable electronics.
ther
electro
nics
.
o
s
NEW
Benefits
• High inrush current withstanding
c
apa
tand
ing
capability
d
g pability
y
• Ceramic Monolithic structure
ure
• Silver fusing element and
silve
r
termination with
silver
term
ina
tion
e
m
n
a
nickel and tin plating
• Excellent temperature stability
bility
• Strong arc suppression characteristics
Features
• Lead
free
materials
and RoHS
compliant
• Halogen free
(refers
to: Br
900ppm,
Cl
900ppm, Br+Cl 1500ppm)
900
• Monolithic, multilayer
design
•
High-temperature
performance
performanc
• -55°C to +125°C operating temperature range
11
Applications
• Laptops
• Digital cameras
• Cell phones
• Printers
• DVD players
• Portable electronics
• Game systems
• LCD monitors
• Scanners
77
Table FP1 Clear Time Characteristics for Pulse Tolerant Chip Fuses
e
% of rated current
100%
200%
1000%
Clear
time at 25°C
4 hours (min.)
1 seconds (min.)
0.0002 second (min.)
60 seconds (max
.)
(max.)
m
a
ma
max
0.02 seconds
(max
ds
(max.)
s
a
x.)
Table FP2 Typical Electrical Characteristics and Di
me
nsions for
P
uls
e T
oleran Chip Fuses
ectrical
and Dimensions
r
Pulse Tolerant
n
e
n
s
0603 (1608 mm) Pulse Tolerant Chip Fuses
e
s
T
ypica
Typical
El
ectrical
Characteristics
Electrical
Chara
l
a
D
A
Max.
Interrupt Ratings
Voltage
(V
DC
)
32
32
32
32
32
32
32
32
32
Current
(A)
50
50
50
50
50
50
50
50
50
Shape and Dimensions
mm (Inch)
B
P
art Nu
mber
Part Number
u
mb
06
0
3S
060
3SF
P100F/3
2-2
0603SFP100F/32-2
6
3
S
3
2
0603SF
0603SFP150F/32-2
S
FP150F/
3
2-2
F/
/
C
Rat
ed
t
d
Rated
Current
Current
r
e
(A)
1.0
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Nomin
Nominal Nominal
I
2
t
Cold
DC
DCR
2
sec)
†
(A
(Ω)*
0.210
0.101
0.057
0.042
0.030
0.022
0.018
0.014
0.013
0.080
0.11
0.24
0.56
0.72
1.10
2.08
2.63
3.25
0603SF
200F/32-2
0603SFP200F/32-2
S
FP20
2
0
0603S
FP250F/32-2
0603SFP250F/32-2
3S
S
C
D
x
Max
0.51
0.
51
M
n
Min
0.65
5
0.65
Max
0.95
5
A
Min
mm
in
1.45
Max
1.75
Min
0.65
B
Ma
x
a
Max
0.9
5
9
0.95
i
n
Min
0.2
1
2
0.21
0
6
060
06
3SFP300F/32-2
0603SFP300F/32-2
0603SFP350F/32-2
0603SFP400F/32-2
0603SFP450F/32-2
0603SFP500F/32-2
(0.057) (0.069)
(0.03
7)
3
(0.026) (0.037)
(0
08
(
0
.008)
(0.0
20)
0
0
(0.008) (0.020)
(0.02
6) (0.037)
2
0
(0.026) (0.037)
1206 (3216 mm) Pulse Tolerant Chip Fuses
e Toler
ant
Chip
e
t
h
Typica
Typical
Electrical
Chara
Characteristics
D
A
Max.
Interrupt Ratings
Voltage
(V
DC
)
63
63
63
32
32
32
32
32
32
Current
(A)
50
50
50
50
50
50
50
50
50
11
Shape and Dimensions
mm (Inch)
B
Part Number
1206SFP100F/63-2
1206SFP150F/63-2
1206SFP200F/63-2
1206SFP250F/32-2
C
Rated
Current
(A)
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Nominal Nominal
I
2
t
Cold DCR
2
sec)
†
(A
(Ω)*
0.340
0.150
0.090
0.070
0.035
0.029
0.023
0.021
0.017
0.11
0.33
0.80
1.19
1.35
1.84
2.74
3.20
5.50
1206SFP300F/32-2
D
1206SFP350F/32-2
Max
1.80
1206SFP400F/32-2
1206SFP450F/32-2
1206SFP500F/32-2
Min
1.40
A
Min
mm
in
3.00
Max
3.40
Min
0.77
B
Max
1.17
Min
0.26
C
Max
0.76
(0.118) (0.134)
(0.030) (0.046)
(0.010) (0.030)
(0.055) (0.071)
* Measured at 10% of rated current and 25°C ambient temperature.
† Melting I
2
t at 0.001 sec clear time.
78
RoHS Compliant, ELV Compliant
HF
Halogen Free
Surface-mount Fuses
– Pulse Tolerant Chip Fuses
Figure FP1-FP4 Family Performance Curves for Pulse Tolerant Chip Fuses
Figure FP1
0603SFP Average Time Current Curves
1.5
A
1.0
A
3.0
100
10
1
Clear Time (s)
0.1
0.01
0.001
0.0001
1
10
0
100
2. 0
2. 5
C
ur
r
ent (A)
Current (A)
rre
rr
r
A
)
Figure FP2
06
0
3
0603SFP
0603SFP
I
2
T
vs. t
Curves
10,000
5.0A
4.5A
4.0A
3.5A
3.0A
2.5A
2.0A
1.5A
1.0A
100
4.5
A
5.0
A
A
A
A
3.5
A
4.0
A
1000
11
I
2
t (A
2
s)
10
1
0.1
0.01
0.0001
0.001
0.01
0.1
1
10
100
Time (s)
Note:
Curves are nominal
RoHS Compliant, ELV Compliant
HF
Halogen Free
79
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