Fusible Nickel
Film Resistors
FN Series
Welwyn Components
•
Predictable fusing characteristics
•
Constant current fusing
•
Flameproof
Electrical Data
FN4
Power rating at 70°C
Resistance range
TCR
Resistance tolerance*
Standard values
Thermal impedance
Ambient temperature range
°C/watt
°C
watts
ohms
ppm/°C
%
0.4
0R1 to 20R
See Figure 1
5, 10, 20
E24 preferred
215
-55 to 155
* Below 1R, 10 and 20% only.
Physical Data
Dimensions (mm) & Weight (g)
PCB
mounting
Type
FN4
L Max
6.2
D Max
2.5
f min
21.0
d nom
0.6
centres
10.2
Min.
bend
radius
0.6
Wt.
nom
0.3
d
D
L
f
Construction
The nickel film is deposited on a high purity ceramic rod. End
caps are force fitted and termination wires welded to the
caps. The resistive film is adjusted to the required value by a
helical cut; finally the flame retardant lacquer protection is
applied to the resistor body and the resistor is marked with an
indelible ink.
Marking
Resistors are colour coded with five bands. Four of the bands
are used to indicate value and tolerance, with IEC 62 colours
being used. A fifth black band denotes constant current
fusibility.
Solvent Resistance
The body protection and marking are resistant to all normal
industrial cleaning solvents suitable for printed circuits.
Terminations
Material
Strength
Solder-coated copper wire.
The terminations meet the requirements of
IEC 68.2.21
Flammability
The resistors will not burn or emit encandescent particles
under any condition of applied temperature or power
overload.
Solderability
The terminations meet the requirements of
IEC 115-1, Clause 4.17.3.2
General Note
Welwyn Components reserves the right to make changes in product specification without notice or liability.
All information is subject to Welwyn’s own data and is considered accurate at time of going to print.
A subsidiary of
TT electronics plc
Issue B · 03.02
© Welwyn Components Limited
· Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com
168
Fusible Nickel
Film Resistors
FN Series
Welwyn Components
Performance Data
Maximum
Load: 1000 hours at 70°C
Shelf life: 12 months at room temperature
Derating from rated power at 70°C
Long term damp heat
Resistance to solder heat
Fusing characteristics
∆R%
∆R%
∆R%
∆R%
1
0.5
zero at 155°C
1
0.5
See Figure 2
Packaging
All FN resistors are supplied tape packed ready for loading on
to automatic sequencing and insertion machines.
Component wires will not protrude beyond the outside edge
of the tapes.
Alternative packaging available by request.
A detailed Packaging Data Sheet is available upon request.
Lead Formed resistors can also be supplied. Standard options
of Lancet, Radial and Goalpost forming are shown in Lead
Form Information section
Fusing
After fusing the final resistance value will be
≥10
times the
initial value.
Standard Quantities Per Package
Type
Large ammo pack
FN4
5000
5
f
1
6
52
f
2
6
Body location f
1
– f
2
≤
1.4 mm
© Welwyn Components Limited
Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com
Issue B · 03.02
169
Fusible Nickel
Film Resistors
FN Series
Welwyn Components
Ordering Procedure
Example: FN4 at 0.33 ohms and 10% tolerance in ammo pack box of 5000 pieces -
FN4
–
R33 K
I
Type
Value (use IEC62 code)
Tolerance (use IEC62 code)
J
K
M
5%
10%
20%
Packing
I
Ammo
5000/box
Standard
© Welwyn Components Limited
Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com
Issue B · 03.02
169
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