Flameproof Power

Metal Film Resistors

MF-S Series

Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com

Issue C · 01.06

Welwyn Components

148

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.

b

6

6

c

1.4 mm

Figure 1

Packaging

The preferred method of packaging is taped and ammo

packed, see figure 1 for critical dimensions.

Alternative packaging is available by special request.

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.

Flammability

The resistors will not burn or emit incandescent particles

under any condition of applied temperature or power

overload.

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).

Terminations

Material

Solder-coated copper wire.

Strength

The terminations meet the requirements of

IEC 68.2.21

Solderability

The terminations meet the requirements of

IEC 115-1, Clause 4.17.3.2

Maximum

Load: 1000 hours at 70˚C

5

%

R

Shelf life: 12 months at room temperature

1

%

R

Derating from rated power at 70˚C

C

˚

5

5

1

t

a

o

r

e

z

%

R

Climatic

1

%

R

Climatic category

40/125/56

Temperature rapid change

5

.

0

%

R

Resistance to solder heat

5

.

0

%

R

Performance Data

Type

MF1S

MF2S

MF3S

Large ammo pack

5000

2500

2500

1000

Standard Quantities Per Package

c

b

e

p

y

T

52

5

MF1S

52

5

MF2S

52

5

MF3S

67

10

Issue D · 01.07