Approval sheet
WK25S WK20S WK10S WK12S WK08S
±
5%,
±
10%,
±
20%
Thick Film Power Surge Chip Resistors
Size 2512 , 2010 , 1210, 1206 , 0805
*Contents in this sheet are subject to change without prior notice.
Page 1 of 7
ASC_WKxxS_V02
Apr.- 2012
Approval sheet
FEATURE
1. Power rating and compact size
2. High reliability and stability
3. Reduced size of final equipment
4. High anti-surge protection
5. Halogen free
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. Construction of Chip-R WKxxS
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ASC_WKxxS_V02
Apr.- 2012
Approval sheet
QUICK REFERENCE DATA
Item
Series No.
Size code
Resistance Tolerance
Resistance Range
TCR (ppm/°C)
Max. dissipation at
T
amb
=70°C
Max. Operation Voltage
(DC or RMS)
Max. Overload Voltage
(DC or RMS)
Climatic category (IEC
60068)
Note :
1.
2.
This is the maximum voltage that may be continuously supplied to the resistor element, see “IEC publication
60115-8”
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.
General Specification
WK25S
2512(6432 )
WK20S
2010 (5025)
WK10S
1210 (3225)
±5% ±10% ±20%
(E24)
0.27Ω ~ 22MΩ
±
200 ppm /°C
1W
200V
400V
3/4W
200V
400V
1/3W
200V
400V
55/155/56
1/4W
200V
400V
1/8W
150V
300V
WK12S
1206 ( 3216 )
WK08S
0805 (2012)
MECHANICAL DATA(unit : mm)
Symbol
L
W
T
Tt
Tb
WK25S
6.30±0.15
3.20±0.15
0.55±0.15
0.30±0.15
0.60±0.20
WK20S
5.00±0.15
2.50±0.15
0.55±0.15
0.30±0.15
0.60±0.20
WK10S
3.20±0.15
2.50±0.15
0.55±0.15
0.30±0.20
0.50±0.25
WK12S
3.20±0.15
1.60±0.15
0.55±0.10
0.30±0.20
0.50±0.25
WK08S
2.00
±
0.10
1.25
±
0.10
0.55
±
0.10
0.30
±
0.20
0.40
±
0.20
Page 3 of 7
ASC_WKxxS_V02
Apr.- 2012
Approval sheet
MARKING
1. Each resistor is marked with a three-digit code on the protective coating to designate the nominal
resistance value.
Single purse limiting power chart
De-rating curve
The power that the resistor can dissipate depends on the operating temperature; see Fig.2
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ASC_WKxxS_V02
Apr.- 2012
Approval sheet
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
CATALOGUE NUMBERS
The resistors have a catalogue number starting with .
WK25
Size code
WK25 : 2512
WK20 : 2010
WK10 : 1210
WK12 : 1206
WK08 : 0805
S
Type code
S
: surge
472_
Resistance code
E24 : 3 significant digits followed
by no. of zeros and a blank
472 = 4K7
J
Tolerance
J:
±5%
K:
±10%
M:
±20%
T
Packaging code
T : 7” Reeled taping
L
Termination code
L
=
Sn base (lead
free)
Page 5 of 7
ASC_WKxxS_V02
Apr.- 2012
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