Approval sheet
Page 1 of 7 ASC_WF25_20_10U_V02 Nov.2011
WF25U, WF20U, WF10U,
±
±±
±1%, ±
±±
±0.5%, ±
±±
±0.25%, ±
±±
±0.1%, ±
±±
±0.05%
TC25
High Precision Thin Film Chip Resistors
Size 2512, 2010, 1210
*Contents in this sheet are subject to change without prior notice.
Approval sheet
Page 2 of 7 ASC_WF25_20_10U_V02 Nov.2011
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. Low current noise
5. +/-0.05% is upon the customer request.
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 WFxxU
Approval sheet
Page 3 of 7 ASC_WF25_20_10U_V02 Nov.2011
QUICK REFERENCE DATA
Item General Specification
Series No. WF25U WF20U WF10U
Size code 2512 ( 6432 ) 2010 ( 5025 ) 1210 ( 3225 )
Resistance Tolerance ±1%, ±0.5%, ±0.25%, ±0.1%, ±0.05%
Resistance Range 10Ω ~ 1MΩ
( E24 +E192 )
10Ω ~ 1MΩ
( E24 +E192 )
10Ω ~ 1MΩ
( E24 +E192 )
TCR (ppm/°C) +25 ~ -25 ppm/°C
Max. dissipation at T
amb
=70°C 3/4W 1/2W 1/4W
Max. Operation Voltage (DC or RMS) 200V 200V 200V
Max. Overload Voltage (DC or RMS) 400V 400V 400V
Operation temperature - 55~ +155’C
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
Value
Resistance
Power
Rated
×
=
or Max. RCWV listed above, whichever is lower.
3. 1MΩ to 2 MΩ of WF10U is upon the customer request.
4. 1MΩ to 3 MΩ of WF25U and WF20U is upon the customer request
DIMENSIONS:( unit:mm)
Type
WF25U WF20U WF10U
L
6.35 ±
±±
± 0.10 5.00 ±
±±
± 0.10 3.10 ±
±±
± 0.10
W
3.20 ±
±±
± 0.15 2.50 ±
±±
± 0.15 2.60 ±
±±
± 0.15
A
0.60 ±
±±
± 0.20 0.60 ±
±±
± 0.20 0.50 ±
±±
± 0.20
B
0.50 ±
±±
± 0.20 0.50 ±
±±
± 0.20 0.50 ±
±±
± 0.20
t
0.55 ±
±±
± 0.10 0.55 ±
±±
± 0.10 0.55 ±
±±
± 0.10
Protective coat
Resistive layer
End termination
Ceramic Substrate
t
B
A
T
W
L
1001
Approval sheet
Page 4 of 7 ASC_WF25_20_10U_V02 Nov.2011
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 10Ω 12Ω 100Ω 6800Ω 47000Ω
4-digits marking 10R0 12R0 1000 6801 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%, ±0.05%. 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.
Approval sheet
Page 5 of 7 ASC_WF25_20_10U_V02 Nov.2011
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.
CATALOGUE NUMBERS
The resistors have a catalogue number starting with .
WF25 U xxxx D T
L
Size code
WF25: 2512
WF20: 2010
WF10: 1210
Type code
U: TCR 25ppm
Resistance code
E192+E24:
3 significant digits followed
by no. of zeros
102Ω =1020
37.4KΩ =3742
220Ω =2200
Tolerance
F : ±1.0%
D : ±0.5%
C: ±0.25%
B : ±0.1%
A : ±0.05%
Packaging code
T : Reeled
Termination code
L = Sn base
(lead free)
1. Reeled tape packaging: 8mm width paper taping for WF10U, 12mm width plastic taping for WF25U, WF20U
4,000pcs/reel for WF25U, WF20U; 5,000pcs/reel for WF10U
Approval sheet
Page 6 of 7 ASC_WF25_20_10U_V02 Nov.2011
TEST AND REQUIREMENTS (JIS C 5201-1 : 1998)
REQUIREMENT
TEST PROCEDURE Resistor
DC resistance
Clause 4.5 DC resistance values measured at the test voltages specified below :
<10Ω@0.1V, <100Ω@0.3V, <1KΩ@1.0V,
<10KΩ@3V, <100KΩ@10V,<1MΩ@25V, <10MΩ@30V
Within the specified tolerance
Temperature Coefficient
of Resistance(T.C.R)
Clause 4.8
Natural resistance change per change in degree centigrade.
( )
6
121
12 10×
−
−
ttR RR
(ppm/°C)
R
1
: Resistance at reference temperature
R
2
: Resistance at test temperature
t
1
: 20°C+5°C-1°C
t2 : 125°C+5°C-1°C or -55°C+5°C-1°C
Refer to
“QUICK REFERENCE DATA”
Short time overload
(S.T.O.L)
Clause 4.13
Permanent resistance change after a 5second application of a voltage
2.5 times RCWV or the maximum overload voltage specified in the
above list, whichever is less.
∆R/R max. ±(0.5%+0.05Ω)
Resistance to soldering
heat(R.S.H)
Clause 4.18
Un-mounted chips completely immersed for 10±1second in a SAC
solder bath at 260℃±5ºC no visible damage
∆ R/R max. ±(0.1%+0.05Ω)
Solderability
Clause 4.17
Un-mounted chips completely immersed for 2±0.5 second in a SAC
solder bath at 235℃±5℃ good tinning (>95% covered)
no visible damage
Temperature cycling
Clause 4.19 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 continuous
cycles
no visible damage
∆R/R max. ±(0.25%+0.05Ω)
Load life (endurance)
Clause 4.25 1000 +48/-0 hours, loaded with RCWV or Vmax in chamber controller
70±2ºC, 1.5 hours on and 0.5 hours off ∆R/R max. ±(0.5%+0.05Ω)
Load life in Humidity
Clause 4.24 1000 +48/-0 hours, loaded with RCWV or Vmax in humidity chamber
controller at 40°C±2°C and 90~95% relative humidity, 1.5hours on
and 0.5 hours off
∆R/R max. ±(0.5%+0.05Ω)
Bending strength
Clause 4.33 Resistors mounted on a 90mm glass epoxy resin PCB(FR4);
bending : 3 mm, once for 10 seconds. ∆R/R max. ±(0.1%+0.05Ω)
Adhesion
Clause 4.32 Pressurizing force: 5N, Test time: 10±1sec. No remarkable damage or
removal of the terminations.
Insulation Resistance
Clause 4.6 Apply the maximum overload voltage (DC) for 1minute R≧10GΩ
Dielectric Withstand
Voltage
Clause 4.7
Apply the maximum overload voltage (AC) for 1 minute No breakdown or flashover
Approval sheet
Page 7 of 7 ASC_WF25_20_10U_V02 Nov.2011
PACKAGING
Paper Tape specifications (unit :mm)
Series No. A B W F E
WF25 6.90±0.20 3.60±0.20 12.00±0.30 5.50±0.10 1.75±0.10
WF20 5.50±0.20 2.80±0.20 12.00±0.30 5.50±0.10 1.75±0.10
WF10 3.60±0.20 3.00±0.20 8.00±0.30 3.50±0.20 1.75±0.10
Series No. P1 P0 ΦD T
WF25 4.00±0.10 4.00±0.10
1.0 0.0
50.1
+
−
Φ
MAX1.2
WF20 4.00±0.10 4.00±0.10
1.0 0.0
50.1
+
−
Φ
MAX1.2
WF10 4.00±0.10 4.00±0.10
1.0 0.0
50.1
+
−
Φ
Max. 1.0
Reel dimensions
A
B
C
D
Symbol A B C D
(unit : mm) Φ178.0±2.0 Φ60.0±1.0 13.0±0.2 9.0±0.5
Taping quantity
- Chip resistors 4,000 pcs per reel ( WF25U, WF20U )
- Chip resistors 5,000 pcs per reel ( WF10U )