WF25S, WF20S, WF12S, WF08S, WF06S
±5%, ±10%, ±20%
Power Surge Chip Resistors
Size 2512 , 2010 , 1206 , 0805 , 0603
Page 1 of 7
WFxxS_V07
Jan.2011
FEATURE
1. Power rating and compact size
2. High reliability and stability
3. Reduced size of final equipment
4. Surge protection
APPLICATION
•
Power supply
•
Measurement instrument
•
Automotive industry
•
Medical or Military equipment
DESCRIPTION
The resistors are constructed in a high grade ceramic body (aluminum oxide). Internal electrodes are added at
each end and connected by a resistive paste that is applied to the top surface of the substrate. The composition
of the paste is adjusted to request resistance to nominal value within tolerance which controlled by printing
process in this resistive layer.
The resistive layer is covered with a protective coat. Finally, the two external end terminations are added. For
ease of soldering the outer layer of these end terminations is a Tin (Pb free) alloy.
Fig 1. Consctruction of Chip-R
Page 2 of 7
WFxxS_V07
Jan.2011
QUICK REFERENCE DATA
Item
General Specification
Series No.
WF25S
WF20S
WF12S
WF08S
WF06S
Size code
2512(6432 )
2010 (5025)
1206 ( 3216 )
0805 (2012)
0603 (1608)
±5% ±10% ±20% (E24)
Resistance Tolerance
Resistance Range
1Ω ~ 1MΩ
± 100 ppm /°C
TCR (ppm/°C)
Max. dissipation at
Tamb=70°C
1W
1/2W
1/4W
1/8W
1/10 W
Max. Operation Voltage
(DC or RMS)
200V
200V
200V
150V
50V
Max. Overload Voltage
(DC or RMS)
400V
400V
400V
300V
100V
Climatic category (IEC
60068)
55/155/56
Note :
1.
This is the maximum voltage that may be continuously supplied to the resistor element, see “IEC publication
60115-8”
2.
Max. Operation Voltage : So called RCWV (Rated Continuous Working Voltage) is determined by
RCWV = Rated Power × Resistance Value or Max. RCWV listed above, whichever is lower.
MECHANICAL DATA(unit : mm)
Symbol
WF25S
WF20S
WF12S
WF08S
WF06S
L
6.30±0.20
5.00±0.20
3.10±0.15
2.00±0.15
1.60 ± 0.10
W
3.10±0.20
2.50±0.20
1.60±0.15
1.20±0.15
0.80 ± 0.10
T
0.60±0.15
0.60±0.10
0.55±0.10
0.50±0.10
0.45 ± 0.15
Tt
0.60±0.25
0.60±0.25
0.50±0.25
0.40±0.20
0.30 ± 0.15
Tb
0.60±0.25
0.60±0.25
0.50±0.25
0.40±0.20
0.30 ± 0.10
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WFxxS_V07
Jan.2011
MARKING
1. Each resistor is marked with a three-digit code on the protective coating to designate the nominal
resistance value.
2. Surge Resistor is prints underline on three-digit code for identification
Example:
472
472 = 4700Ω
Surge Performance
WFxxS series
10000
1000
Peak power
(Watt)
2512
2010
100
1206
0805
10
0603
1 .001
1ms
.01
.1
10ms
100ms
1
1s
Surge duration
De-rating curve
The power that the resistor can dissipate depends on the operating temperature; see Fig.2
Page 4 of 7
WFxxS_V07
Jan.2011
MOUNTING
Due to their rectangular shapes and small tolerances, Surface Mountable Resistors are suitable for handling by
automatic placement systems.
Chip placement can be on ceramic substrates and printed-circuit boards (PCBs).
Electrical connection to the circuit is by individual soldering condition.
The end terminations guarantee a reliable contact.
SOLDERING CONDITION
The robust construction of chip
resistors allows them to be completely
immersed in a solder bath of 260°C for
10 seconds. Therefore, it is possible to
mount Surface Mount Resistors on one
side of a PCB and other discrete
components on the reverse (mixed
PCBs).
Surface Mount Resistors are tested for
solderability at 235°C during 2 seconds.
The test condition for no leaching is
260°C for 30 seconds. Typical
examples of soldering processes that
provide reliable joints without any
damage are given in Fig 3.
Fig 3. Infrared soldering profile for Chip Resistors WFxxS
CATALOGUE NUMBERS
The resistors have a catalogue number starting with .
WF20
S
Size code
Type code
Resistance code
Tolerance
Packaging code
Termination code
WF25 : 2512
S : surge
E24 : 3 significant digits followed
by no. of zeros and a blank
J: ±5%
T : 7” Reeled taping
L = Sn base (lead
free)
WF20 : 2010
WF12 : 1206
472_
472 = 4K7
J
K: ±10%
T
L
M: ±20%
WF08 : 0805
WF06 : 0603
Page 5 of 7
WFxxS_V07
Jan.2011
TEST AND REQUIREMENTS(JIS C 5201-1 : 1998)
TEST
Temperature
Coefficient of
Resistance(T.C.R)
Clause 4.8
PROCEDURE
Natural resistance change per change in degree centigrade.
R2 − R1
× 106
R1 (t2 − t1 )
(ppm/°C)
REQUIREMENT
Refer to “QUICK REFERENCE
DATA”
t1 : 20°C+5°C-1°C
R1 : Resistance at reference temperature
R2 : Resistance at test temperature
Short time overload
(S.T.O.L)
Clause 4.13
Permanent resistance change after a 5second application of ∆R/R max. ±(1%+0.1Ω)
a voltage 2.5 times RCWV or the maximum overload voltage
specified in the above list, whichever is less.
Resistance to
soldering heat(R.S.H)
Clause 4.18
Un-mounted chips completely immersed for 10±1second in a no visible damage
solder bath at 260℃±5ºC
∆ R/R max. ±(1%+0.05Ω)
Solderability Clause
Clause 4.17
Un-mounted chips completely immersed for 2±0.5second in good tinning (>95% covered)
a solder bath at 235℃±5℃
no visible damage
Temperature cycling
30 minutes at -55°C±3°C, 2~3 minutes at 20°C+5°C-1°C, 30
minutes at +155°C±3°C, 2~3 minutes at 20°C+5°C-1°C, total
5 cycles
Clause 4.19
Load life (endurance)
Clause 4.25
no visible damage
∆R/R max. ±(1%+0.05Ω)
70±2ºC, 1000 hours, loaded with RCWV or Vmax,1.5 hours ∆R/R max. ±(3%+0.1Ω)
on and 0.5 hours off
Clause 4.24
1000 hours, at rated continuous working voltage in humidity ∆R/R max. ±(3%+0.1Ω)
chamber controller at 40°C±2°C and 90~95% relative
humidity, 1.5hours on and 0.5 hours off
Bending strength
Clause 4.33
Resistors mounted on a 90mm glass epoxy resin PCB(FR4); ∆R/R max. ±(1%+0.05Ω)
bending : 2 mm, once for 10 seconds
Adhesion
Pressurizing force: 5N, Test time: 10±1sec.
No remarkable damage or
removal of the terminations
Insulation Resistance
Apply the maximum overload voltage (DC) for 1minute
R≧10GΩ
Clause 4.6
Dielectric Withstand
Apply the maximum overload voltage (AC) for 1 minute
No breakdown or flashover
Load life in Humidity
Clause 4.32
Voltage
Clause 4.7
Page 6 of 7
WFxxS_V07
Jan.2011
PACKAGING
Plastic Tape specifications (unit :mm)
Series No.
A
B
WF25S
6.70±0.20
3.50±0.20
WF20S
5.50±0.20
2.80±0.20
WF12S
3.57±0.20
2.00±0.20
WF08S
2.40±0.20
1.65±0.20
WF06S
1.90±0.20
1.10±0.20
Series No.
P1
P0
W
F
E
12.00±0.30
5.50±0.05
1.75±0.10
8.00±0.30
3.50±0.05
1.75±0.10
ΦD
T
WF25S
Max. 1.2
WF20S
WF12S
4.00±0.10
Φ1.50 +−00..10
4.00±0.10
Max. 1.0
WF08S
0.65±0.05
WF06S
Reel dimensions
Reel / Tape
7” reel for 8mm tape
7” reel for 12mm tape
A
B
C
Φ178.0±2.0
Φ60.0±1.0
13.0±0.2
D
9.00±0.50
12.4±1.00
Taping quantity
-1206 0805 0603 Chip resistors 5,000 pcs per reel.
-2010 2512 Chip resistors 4,000 pcs per reel.
Page 7 of 7
WFxxS_V07
Jan.2011
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