Page 1 of 7 WR18-20-25X(W) Ver.11 April.-2010
WR18X(W), WR20X(W), WR25X(W)
±
±±
±1%, ±
±±
±5%
Power chip resistors
Size 1218,2010,2512
Customer :
Approval No :
Issue Date :
Customer Approval :
Page 2 of 7 WR18-20-25X(W) Ver.11 April.-2010
FEATURE
1. High power rating and compact size
2. High reliability and stability
3. Reduced size of final equipment
4. LoHS compliant and Lead free products
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. Consctruction of 2512, 2010 Chip-R
Fig 2. Construction of a 1218 Chip-R
Page 3 of 7 WR18-20-25X(W) Ver.11 April.-2010
QUICK REFERENCE DATA
Item General Specification
Series No. WR18X(W) WR20X(W) WR25X(W)
Size code 1218(3248) 2010 ( 5025 ), 2512(6432)
Resistance Tolerance ±5% (E24); ±1% (E24+E96)
Resistance Range 1Ω ~ 10MΩ, Jumper (0Ω)
± 100 ppm/°C ± 100 ppm/°C ± 100 ppm/°C TCR (ppm/°C) : 10Ω≤ Rn < 1MΩ
1Ω≤ Rn < 9.76Ω& 1MΩ≤ Rn < 10MΩ ± 200 ppm/°C ± 300 ppm/°C ± 300 ppm/°C
Max. dissipation at T
amb
=70°C 1W 0.5 W 1W
Max. Operation Voltage (DC or RMS) 200V 200V 250V
Max. Overload Voltage (DC or RMS) 400V 400V 500V
Climatic category (IEC 60068) 55/155/56
Test conditions for jumper ( 0 ohm )
Type
WR18X(W) WR20X(W) WR25X(W)
Power Rating At 70C
1 W 1/2 W 1 W
Resistance
Max. 50mR Max. 50mR Max. 50mR
Rated Current
4.5 A 3.2 A 4.5 A
Peak Current
11 A 8 A 11 A
Operating Temperature
-55C ~ 155C -55C ~ 155C -55C ~ 155C
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)
TYPE WR18X(W)
WR20X(W)
WR25X(W)
L 3.05±0.15 5.00±0.20 6.40±0.20
W 4.60±0.20 2.50±0.20 3.20±0.20
T 0.55±0.10 0.55±0.10 0.60±0.10
Tt 0.45±0.25 0.65±0.25 0.65±0.25
Tb 0.50±0.25 0.60±0.25 0.90±0.25
Page 4 of 7 WR18-20-25X(W) Ver.11 April.-2010
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
0000 = 0Ω
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.3
Figure 3. Maximum dissipation in percentage of rated power
as a function of the ambient temperature.
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 5 of 7 WR18-20-25X(W) Ver.11 April.-2010
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 4.
Fig 4. Infrared soldering profile for Chip Resistors
CATALOGUE NUMBERS
The resistors have a catalogue number starting with .
WR20 X 472_ J T L
Size code
WR25 : 2512
WR20 : 2010
WR18: 1218
Type code
X : Normal
W : 1% For <10Ω
and >1MΩ
Resistance code
E24 : 2 significant digits followed
by no. of zeros and a blank
4.7Ω =4R7_
10Ω =100_
220Ω =221_
Jumper =000_
(“_” means a blank)
E96 : 3 significant digits followed
by no. of zeros
102Ω =1020
37.4KΩ =3742
Tolerance
J : ±5%
F : ±1%
P : Jumper
Packaging code
T : 7” Reel taping
(T:1218 10” Reel)
Termination code
L = Sn base (lead
free)
TEST AND REQUIREMENTS(JIS C 5201-1 : 1998)
Page 6 of 7 WR18-20-25X(W) Ver.11 April.-2010
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(T.C.R)
Clause 4.8
Natural resistance change per change in degree centigrade.
( )
6
121
12 10×
−
−
ttR RR
(ppm/°C) t
1
: 20°C+5°C-1°C
R
1
: Resistance at reference temperature
R
2
: Resistance at test temperature
Refer to
“QUICK REFERENCE
DATA”
Short time overload
(S.T.O.L) Clause
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. ±(2%+0.1Ω)
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. ±(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. ±(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 strength
Clause 4.33 Resistors mounted on a 90mm glass epoxy resin PCB(FR4);
bending : 2 mm, once for 10 seconds ∆R/R max. ±(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
Page 7 of 7 WR18-20-25X(W) Ver.11 April.-2010
PACKAGING
Plastic Tape specifications (unit :mm)
Type A B W F E
WR18 4.90±0.20 3.55±0.30
WR20 5.50±0.20 2.80±0.20
WR25 6.90±0.20 3.60±0.20
12.00±0.30 5.50±0.10 1.75±0.10
Type P1 P0 ΦD T
WR18 8.00±0.10 1.30±0.20
WR20
WR25 4.00±0.10 4.00±0.10
1.0 0.0
50.1
+
−
Φ
MAX1.2
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
WR20, WR25 by plastic tape taping 4,000 pcs per reel.
WR18 by plastic tape taping 3,000 pcs per reel
