Page 1 of 7 WF25P/20P/12P_V09 Mar.2011
WF25P, WF20P, WF12P
±
±±
±1%, ±
±±
±5% 1Ω ~ 1MΩ
Thick Film High Power Chip Resistors
Size 2512 2W, 2010 1W, 1206 1/2W
Page 2 of 7 WF25P/20P/12P_V09 Mar.2011
FEATURE
1. High power rating and compact size
2. High reliability and stability
3. Reduced size of final equipment
4. RoHS compliant and Lead free products
5. Flame Retardant
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 a Tin (lead free) alloy.
Fig 1. Construction of Chip-R
Page 3 of 7 WF25P/20P/12P_V09 Mar.2011
QUICK REFERENCE DATA
Item General Specification
Series No. WF25P WF20P WF12P
Size code 2512 (6432) 2010 (5025) 1206 (3216)
Resistance Tolerance ±1%, ±5%
Resistance Range 0Ω,1Ω ~ 1MΩ
TCR (ppm/°C) ±100
Max. dissipation at T
amb
=70°C 2 W 1 W 1/2 W
Max. Operation Voltage (DC or RMS) 300V 200V 200V
Max. Overload Voltage (DC or RMS) 500V 400V 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.
3. 2W loading with total solder-pad and trace size of 300 mm
2
4. Lead free product is upon customer requested.
5. 0
Ω maximum resistance Rmax < 20mΩ and rated current < 4Amp
MECHANICAL DATA
Unit: mm
Symbol
WF25P WF20P WF12P
L 6.30 ± 0.20
5.00 ± 0.20
3.10 ± 0.15
W 3.10 ± 0.20 2.50 ± 0.20
1.60 ± 0.15
T 0.60 ± 0.15
0.60 ± 0.10
0.55 ± 0.10
Tt 0.60 ± 0.25
0.60 ± 0.25
0.50 ± 0.25
Tb 1.80 ± 0.25
0.60 ± 0.25
0.50 ± 0.25
102
Page 4 of 7 WF25P/20P/12P_V09 Mar.2011
Recommended Solder Pad Dimensions
D
W
L
MARKING
Each resistor is marked with a four-digit (WF25P;WF20P,WF12P ±1%) and three-digit
(WF25P,WF20P,WF12P ±5%) code on the protective coating to designate the nominal resistance value.
Example:
102 = 1kΩ
16R0 = 16Ω
FUNCTIONAL DESCRIPTION
Product characterization
Standard values of nominal resistance are taken from the E96 & E24 series for resistors with a tolerance of
±5% & ±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
Figure 2
Maximum dissipation in percentage of rated power as a
function of the ambient temperature
Type W
D L
WF25P 3.7
mm
2.45
mm
7.6
mm
102
16R0
16R0 16R0
16R0
Page 5 of 7 WF25P/20P/12P_V09 Mar.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
CATALOGUE NUMBERS
T
he resistors have a catalogue number starting with .
WF25 P 102 J T L
Size code
WF25 : 2512
WF20 : 2010
WF12 : 1206
Type code
P :Power
2512 size=2 watt
2010 size=1 watt
1206 size=0.5 watt
Resistance code
5% E24: 2 significant digits
followed by No. of zeros
e.g.:
3ohm =3R0
10ohm =100
56Kohm =563
1% E24+E96:3 significant
digits
followed by No. of zeros
100Ω =1000
37.4KΩ =3742
Tolerance
J : ±5%
F : ±1%
P :
Jumper
Packaging
code
T : 7” Reel
taping
Termination
code
L = Sn base
(lead free)
Tape packaging WF12 : 8mm width paper taping 5,000pcs per reel.
WF25；WF20:
12mm width plastic taping 4,000pcs per reel.
Page 6 of 7 WF25P/20P/12P_V09 Mar.2011
TEST AND REQUIREMENTS
Basic specification : JIS C 5201-1 : 1998
TEST PROCEDURE REQUIREMENT
Clause 4.8
Temperature Coefficient
of Resistance (TCR )
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
Refer to quick reference data for T.C.R
specification
Clause 4.13
Short time overload 5.0× Rated power or Max. Overload Voltage for 5 sec.
Measure resistance after 30 minutes.. ∆R/R max. J:≦ ±(2%+0.1Ω)
F:≦ ±(1%+0.05Ω)
Clause 4.18
Resistance to soldering
heat
Un-mounted chips completely immersed for 10±1second
in a SAC solder bath at 260℃±5ºC No visible damage
∆R/R max. J:≦ ±(1%+0.1Ω)
F:≦ ±(0.5%+0.05Ω)
Clause 4.17
Solderability 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
Clause 4.18
Leach Test Un-mounted chips completely immersed for 60±1second
in a solder bath at 260 ±5℃ ℃ Ditto
Clause 4.19
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 continuous cycles
No visible damage
∆R/R max. J ≦±(1%+0.1Ω)
F ≦±(0.5%+0.05Ω)
Clause 4.25
Load life (endurance) 1000 +48/-0 hours, loaded with RCWV or Vmax
in
chamber controller 70±2ºC, 1.5 hours on and 0.5 hours
off
No visible damage
∆R/R max. J ≦±(3%+0.1Ω)
F ≦±(1%+0.05Ω)
Clause 4.24
Load life in Humidity 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
No visible damage
∆R/R max. J ≦±(3%+0.1Ω)
F ≦±(1%+0.05Ω)
Clause 4.33
Bending strength Resistors mounted on a 90mm glass epoxy resin
PCB(FR4); bending : 2 mm(2512;2010) 3mm(1206),
once for 10 seconds
No visible damage
∆R/R max. J ≦±(1%+0.1Ω)
F ≦±(0.5%+0.05Ω)
Clause 4.32
Adhesion 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
Page 7 of 7 WF25P/20P/12P_V09 Mar.2011
PACKAGING
Paper Tape(WF12P) & Plastic Tape(WF25P;WF20P) specifications (unit :mm)
Series No. A B W F E
WF25P 6.90±0.20 3.60±0.20
WF20P 5.50±0.20 2.80±0.20 12.00±0.30 5.50±0.10 1.75±0.10
WF12P 3.60±0.20 2.00±0.20 8.00±0.30 3.50±0.20 1.75±0.10
Series No. P1 P0 ΦD T
WF25P
WF20P Max. 1.2
WF12P
4.00±0.10 4.00±0.10
1.0 0.0
50.1
+
−
Φ
Max. 1.0
Reel dimensions
(unit : mm)
Reel / Tape A B C D
7” reel for 12mm tape 12.4±1.0
7” reel for 8mm tape Φ178.0±2.0 Φ60.0±1.0 13.0±0.2 9.0±0.5
