Approval sheet
WF25R, WF20R, WF10R
±
1%,
±
0.5%,
±
0.25%,
±
0.1%,
±
0.05%
TC25
High Precision Power Thin Film Chip Resistors
Size 2512, 2010, 1210
*Contents in this sheet are subject to change without prior notice.
Page 1 of 7
ASC_WF25_20_10R_V01
Jul.2011
Approval sheet
FEATURE
1. SMD metal film resistor
2. High reliability and stability of +/- 0.5% and below per customer request
3. High performance of TCR: 25 ppm/K and below per customer request
4. High power rating
5. Low current noise
APPLICATION
•
•
•
•
•
Medical equipment
Measuring instrument
Communication device
Computer
Printer
DESCRIPTION
The resistors are constructed in a high grade ceramic body (aluminum oxide). Internal metal electrodes are
added at each end and connected by a resistive layer that is applied to the top surface of the substrate. The
composition of the resistive layer is adjusted to give the approximate resistance required and the value is
trimmed to nominated value within tolerance which controlled by laser trimming of this resistive layer.
The resistive layer is covered with a protective coat. Finally, the two external end terminations are added. For
environmental soldering issue, the outer layer of these end terminations is a Lead-free solder .
Fig 1. Construction of Chip-R WFxxR
Page 2 of 7
ASC_WF25_20_10R_V01
Jul.2011
Approval sheet
QUICK REFERENCE DATA
Item
Series No.
Size code
Resistance Tolerance
Resistance Range
10Ω ~ 1MΩ
( E24 +E192 )
TCR (ppm/°C)
Max. dissipation at T
amb
=70°C
Max. Operation Voltage (DC or RMS)
Max. Overload Voltage (DC or RMS)
Operation temperature
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
1W
200V
400V
WF25R
2512 ( 6432 )
General Specification
WF20R
2010 ( 5025 )
WF10R
1210 ( 3225 )
±1%, ±0.5%, ±0.25%, ±0.1%, ±0.05%
10Ω ~ 1MΩ
( E24 +E192 )
+25 ~ -25 ppm/°C
3/4W
200V
400V
- 55~ +155’C
2/5W
200V
400V
10Ω ~ 1MΩ
( E24 +E192 )
RCWV
=
Rated Power
×
Resistance Value
or Max. RCWV listed above, whichever is lower.
3.
4.
5.
Tolerance
±0.05%
is upon requested
1MΩ to 2 MΩ of WF10R is upon the customer request.
1MΩ to 3 MΩ of WF25R and WF20R is upon the customer request
DIMENSIONS:(unit:mm)
Type
L
W
A
B
t
WF25R
6.35
±
0.10
3.20
±
0.15
0.60
±
0.20
0.50
±
0.20
0.55
±
0.10
WF20R
5.00
±
0.10
2.50
±
0.15
0.60
±
0.20
0.50
±
0.20
0.55
±
0.10
WF10R
3.10
±
0.10
2.60
±
0.15
0.50
±
0.20
0.50
±
0.20
0.55
±
0.10
Protective coat
t
B
A
End termination
Resistive layer
Ceramic Substrate
W T
1001
L
Page 3 of 7
ASC_WF25_20_10R_V01
Jul.2011
Approval sheet
MARKING
4-digits marking for 2512, 2010, 1210 size
For E24/E96 series, each resistor is marked with a four digits code on the protective coating to designate the
nominal resistance value. For non E24/E96 series, no marking is applied!
Example
RESISTANCE
4-digits marking
10Ω
10R0
12Ω
12R0
100Ω
1000
6800Ω
6801
47000Ω
4702
FUNCTIONAL DESCRIPTION
Product characterization
Standard values of nominal resistance are taken from the E24/E192 series for resistors with a tolerance of
±1%, ±0.5%, ±0.25%, ±0.1%.
The values of the E24/E192 series are in accordance with “IEC publication
60063”.
Derating
The power that the resistor can dissipate depends on the operating temperature; see Fig.2
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.
Page 4 of 7
ASC_WF25_20_10R_V01
Jul.2011
Approval sheet
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 within lead-free solder bath. 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 .
WF25
Size code
WF25: 2512
WF20: 2010
WF10: 1210
R
Type code
R: TCR 25ppm
& High power
xxxx
Resistance code
E24 +E192:
3 significant digits followed by
no. of zeros
102Ω
37.4KΩ
220Ω
=1020
=3742
=2200
D
Tolerance
F :
±1.0%
D :
±0.5%
C:
±0.25%
B :
±0.1%
A :
±0.05%
T
Packaging code
T : Reeled
L
Termination code
L
=
Sn base
(lead free)
1. Reeled tape packaging: 8mm width paper taping for WF10R, 12mm width plastic taping for WF25R, WF20R.
4,000pcs/reel for WF25R, WF20R; 5,000pcs/reel for WF10R
Page 5 of 7
ASC_WF25_20_10R_V01
Jul.2011
