Flameproof Power
Metal Film Resistors
MF-S Series
Construction
The resistance element is a precisely controlled thin film of
metal alloy on a high purity ceramic core, protected by a
cement coating applied so that terminations remain
completely clear.
This permits a well defined body length, (clean lead to clean
lead dimension L).
Welwyn Components
Marking
MF Series resistors are colour coded with 5 bands for 1%
tolerance or 4 bands for other tolerances. IEC 62 colours
are used.
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 incandescent 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
Performance Data
Maximum
Load: 1000 hours at 70˚C
Shelf life: 12 months at room temperature
Derating from rated power at 70˚C
Climatic
Climatic category
Temperature rapid change
Resistance to solder heat
R%
R%
R%
R%
R%
R%
5
1
zero at 155˚ C
1
40/125/56
0.5
0.5
Application Notes
1. If the resistors are to dissipate full rate power, it is
recommended that the terminations should not be
soldered closer than 4mm from the body.
2. Due to operating temperature limitations imposed by some
pcb materials, derating may be necessary. An estimate of
the temperature rise to be expected can be calculated
using the thermal impedance figures given under Electrical
Data.
3. Lead Formed resistors can also be supplied. Standard
options of Lancet, Radial and Goalpost forming are shown
in lead Form Information section.
Packaging
The preferred method of packaging is taped and ammo
packed, see figure 1 for critical dimensions.
Alternative packaging is available by special request.
Figure 1
c
f
1
6
b
Body location f
1
– f
2
f
2
6
1.4 mm
Standard Quantities Per Package
Type
Large ammo pack
MF
1
/
2
S
5000
MF1S
2500
MF2S
2500
MF3S
1000
Type
MF
1
/
2
S
MF1S
MF2S
MF3S
b
52
52
52
67
c
5
5
5
10
© 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
148
Issue D 01.07
Issue C · 01.06
WELWYN [ WELWYN COMPONENTS LIMITED ]
