Approval sheet
Page 1 of 7 ASC_WF25-20H_V05 Oct.-2011
WF25H, WF20H
±
±±
±0.1%, ±
±±
±0.5%
Thick Film Power High Precision Resistors
Size 2512, 2010
*Contents in this sheet are subject to change without prior notice.
Approval sheet
Page 2 of 7 ASC_WF25-20H_V05 Oct.-2011
FEATURE
1. High power rating and compact size
2. High reliability and stability
3. Reduced size of final equipment
4. High precision of resistance
APPLICATION
• Power supply
• PDA
• Digital meter
• Computer
• Automotives
• Battery charger
• DC-DC power converter
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 paste that is applied to the top surface of the substrate. The
composition of the paste 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
ease of soldering the outer layer of these end terminations is Tin (lead free) alloy.
Fig 1. Construction of Chip-R
Approval sheet
Page 3 of 7 ASC_WF25-20H_V05 Oct.-2011
QUICK REFERENCE DATA
Item General Specification
Series No. WF25H WF20H
Size code 2512 ( 6432 ) 2010 ( 5025 )
Resistance Tolerance ±0.5% ; ±0.1% (E24+E96)
Resistance Range 1Ω ~ 10MΩ,
± 200 ppm/°C TCR (ppm/°C) 1Ω ≤ Rn ≤ 10Ω
10Ω < Rn ≤ 10MΩ ± 100 ppm/°C
Max. dissipation at T
amb
=70°C 1 W 0.5W
Max. Operation Voltage (DC or RMS) 250V 200V
Max. Overload Voltage (DC or RMS) 500V 400V
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
ValueResistancePower RatedRCWV ×=
or Max. RCWV listed above, whichever is lower.
MECHANICAL DATA(unit : mm)
Symbol 2512 2010
L 6.40±0.20 5.00±0.20
W 3.20±0.20 2.50±0.20
T 0.60±0.10 0.55±0.10
Tt 0.65±0.25 0.65±0.25
Tb 0.90±0.25 0.60±0.25
MARKING
Each resistor is marked with a four-digit code on the protective coating to designate the nominal resistance
value.
Example:
1R00 = 1Ω
1001 = 1000Ω
Approval sheet
Page 4 of 7 ASC_WF25-20H_V05 Oct.-2011
FUNCTIONAL DESCRIPTION
Product characterization
Standard values of nominal resistance are taken from the E96 & E24 series for resistors with a tolerance of
±0.5% & ±0.1%. The values of the E24/E96 series are in accordance with “IEC publication 60063”.
Derating curve
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.
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
Approval sheet
Page 5 of 7 ASC_WF25-20H_V05 Oct.-2011
CATALOGUE NUMBERS
The resistors have a catalogue number starting with :
WF25 H 1000 B T L
Size code
WF25 : 2512
WF20 : 2010
Type code
H : Thick film,
High precision
Resistance code
E24+E96 : 3 significant
digits followed by no. of zeros
102Ω =1020
37.4KΩ =3742
Tolerance
B : ±0.1%
D : ±0.5%
Packaging code
T : 7” Reel taping
Termination code
L = Sn base
(lead free)
TEST AND REQUIREMENTS(JIS C 5201-1 : 1998)
Essentially all tests are carried out according to the schedule of IEC publication 115-8, category LCT/UCT/56 (rated
temperature range : Lower Category Temperature, Upper Category Temperature; damp heat, long term, 56 days). The
testing also meets the requirements specified by EIA, EIAJ and JIS.
The tests are carried out in accordance with IEC publication 68, "Recommended basic climatic and mechanical robustness
testing procedure for electronic components" and under standard atmospheric conditions according to IEC 60068-1,
subclause 5.3. Unless otherwise specified, the following value supplied :
Temperature: 15°C to 35°C.
Relative humidity: 45% to 75%.
Air pressure: 86kPa to 106 kPa (860 mbar to 1060 mbar).
All soldering tests are performed with midly activated flux.
TEST PROCEDURE REQUIREMENT
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
( TCR )
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
Test temperature –55 ~ +155°C
1Ω ≤ Rn < 9.76Ω, ± 300 ppm/°C
10Ω ≤ Rn < 1MΩ, ± 200 ppm/°C
1MΩ ≤ Rn < 10MΩ, ± 300 ppm/°C
Approval sheet
Page 6 of 7 ASC_WF25-20H_V05 Oct.-2011
TEST PROCEDURE REQUIREMENT
Short time
overload ( STOL )
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. ±(1%+0.05Ω)
Resistance to
soldering heat
Clause 4.17
Un-mounted chips 10±1 seconds, in a SAC solder bath at
260±5ºC no visible damage
∆ R/R max. ±(1%+0.05Ω)
Solderability
Clause 4.18
Un-mounted chips completely immersed for 2±0.5 sec. in a
SAC solder bath at 235±5ºC good tinning (>95% covered)
no visible damage
Temperature
cycling
Clause 4.19
1. 30 minutes at -55°C±3°C,
2. 2~3 minutes at 20°C+5°C-1°C,
3. 30 minutes at +155°±3°C,
4. 2~3 minutes at 20°C+5°C-1°C,
Total 5 continuous cycles
no visible damage
∆R/R max. ±(1%+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. ±(3%+0.1Ω)
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. ±(3%+0.1Ω)
Bending and
Termination
strength
Clause 4.33
Resistors mounted on a 90mm glass epoxy resin PCB(FR4);
bending : 2 mm, once for 10 seconds
Pulling test : 500grams
∆R/R max. ±(1%+0.05Ω)
Insulation
Resistance
Clause 4.6
Apply the maximum overload voltage (DC) for 1minutes R≧10GΩ
Dielectric Withstand
Voltage
Clause 4.7
Apply the maximum overload voltage (AC) for 1 minutes No breakdown or flashover
Approval sheet
Page 7 of 7 ASC_WF25-20H_V05 Oct.-2011
PACKAGING
Plastic tape specifications (unit :mm)
Type A B W F E
2512 6.90±0.20 3.60±0.20 12.00±0.30 5.50±0.1 1.75±0.10
2010 5.50±0.20 2.80±0.20 12.00±0.30 5.50±0.1 1.75±0.10
Type P1 P0 ΦD T
2512 4.00±0.10 4.00±0.10
1.0 0.0
50.1
+
−
Φ
Max. 1.2
2010 4.00±0.10 4.00±0.10
1.0 0.0
50.1
+
−
Φ
Max. 1.2
Reel dimensions
Symbol A B C D
(unit : mm) Φ178.0±2.0 Φ60.0±1.0 13.0±0.2 14.0±0.2
Taping quantity
- Chip resistors 4,000 pcs per reel.
