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WF12K, WF08K, WF06K, WF04K
±
±±
±1.0%, 0.5%, ±
±±
±0.25%, ±
±±
±0.1%
TC50
High Precision Thick Film chip resistors
Size 1206, 0805, 0603, 0402
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FEATURE
1. SMD Thick film resistor
2. High reliability and stability
3. High performance of TCR: 50 ppm/K
4. High precision
5. RoHS compliant & Lead free
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. Consctruction of Chip-R WFxxK
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QUICK REFERENCE DATA
Item General Specification
Series No. WF12K WF08K WF06K WF04K
Size code 1206 ( 3216 ) 0805 ( 2012 ) 0603 ( 1608 ) 0402 ( 1005 )
Resistance Tolerance ±
±±
±1.0%, ±
±±
±0.5%, ±
±±
±0.25%, ±
±±
±0.1%
Resistance Range 10Ω
ΩΩ
Ω ~ 1MΩ
ΩΩ
Ω
( E24 +E96 ) 100Ω
ΩΩ
Ω ~ 1MΩ
ΩΩ
Ω
( E24 +E96 )
TCR (ppm/°C) ±
±±
± 50 ppm/°
°°
°C
Max. dissipation at T
amb
=70°C 1/4W 1/8W 1/10W 1/16W
Max. Operation Voltage (DC or RMS) 200V 150V 50V 50V
Max. Overload Voltage (DC or RMS) 400V 300V 100V 100V
Climatic category 55/125/56
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.
DIMENSIONS(unit : mm)
Type
WF12K WF08K WF06K WF04K
L
3.10 ±
±±
± 0.10 2.00 ±
±±
± 0.10 1.60 ±
±±
± 0.10 1.00 ±
±±
± 0.05
W
1.60 ±
±±
± 0.10 1.25 ±
±±
± 0.10 0.80 ±
±±
± 0.10 0.50 ±
±±
± 0.05
A
0.50 ±
±±
± 0.20 0.40 ±
±±
± 0.20 0.30 ±
±±
± 0.10 0.20 ±
±±
± 0.10
B
0.45 ±
±±
± 0.20 0.40 ±
±±
± 0.20 0.30 ±
±±
± 0.15 0.25 ±
±±
± 0.10
t
0.60 ±
±±
± 0.15 0.50 ±
±±
± 0.15 0.45 ±
±±
± 0.10 0.35 ±
±±
± 0.05
Protective coat
Resistive layer
End termination
Ceramic Substrate
t
B
A
T
W
L
1001
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MARKING
3-digits marking for 0603 size
WFxxK has same marking rule as commodity ±1%.
3-digits marking（±1% : 0603）
Nominal resistance Description
1.E-24 series As 0603 WR06X ±5%.
2.E-96 series The 1st two digit codes are referring to the CODE on the table, the 3rd code is the index of resistance
value :
Y=10
-2
，X=10
-1
，A=10
0
，B=10
1
，C=10
2
，D=10
3
，E=10
4
，F=10
5
EX : 17.8Ω=25X，178Ω=25A，1K78 =25B
17K8=25C， 178K=25D， 1M78=25E
3. Remark There is no marking for the items are not under E-24 and E-96 series
CODE
R_value
CODE
R_value
CODE
R_Value
CODE
R_value
CODE
R_value
CODE
R_value
CODE
R_value
CODE
R_value
01 100
13 133
25 178
37 237
49 316
61 422
73 562
85 750
02 102
14 137
26 182
38 243
50 324
62 432
74 576
86 768
03 105
15 140
27 187
39 249
51 332
63 442
75 590
87 787
04 107
16 143
28 191
40 255
52 340
64 453
76 604
88 806
05 110
17 147
29 196
41 261
53 348
65 464
77 619
89 825
06 113
18 150
30 200
42 267
54 357
66 475
78 634
90 845
07 115
19 154
31 205
43 274
55 365
67 487
79 649
91 866
08 118
20 158
32 210
44 280
56 374
68 499
80 665
92 887
09 121
21 162
33 215
45 287
57 383
69 511
81 681
93 909
10 124
22 165
34 221
46 294
58 392
70 523
82 698
94 931
11 127
23 169
35 226
47 301
59 402
71 536
83 715
95 953
12 130
24 174
36 232
48 309
60 412
72 549
84 732
96 976
4-digits marking for 1206, 0805 size
Each resistor is marked with a four digits code on the protective coating to designate the nominal resistance
value of E24+E96. For values below 97Ω6 the R is used as a digit. For values of 100Ω or greater, the first 3
digits are significant, the fourth digit indicates the number of multiple to follow.
Example
RESISTANCE 10Ω 12Ω 100Ω 6800Ω 47000Ω
4-digits marking 10R0 12R0 1000 6801 4702
No marking code for 0402 size
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FUNCTIONAL DESCRIPTION
Product characterization
Standard values of nominal resistance are taken from the E24 & E96 series for resistors with a tolerance of
±1.0%, ±0.5%, ±0.25%, ±0.1%. The values of the E24/E96 series are in accordance with “IEC publication
60063”.
Derating
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
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.
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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 .
WF08 K xxxx D T L
Size code
WF12: 1206
WF08: 0805
WF06: 0603
WF04: 0402
Type code
TCR 50ppm
Resistance code
E24 +E192:
R is first code followed by
3 significant digits.
E24: 39R0=>39R0
820R =>8200
E96: 49R9 =>49R9
499R =>4990
Tolerance
F : ±1.0%
D : ±0.5%
C: ±0.25%
B : ±0.1%
Packaging
code
T : Reeled
Termination
code
L : lead free
1. Reeled tape packaging: 8mm width paper taping.
5,000pcs/reel for WF12, WF08, WF06;
10,000pcs/reel for WF04.
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TEST AND REQUIREMENTS(JIS C 5201-1 : 1998)
REQUIREMENT
TEST PROCEDURE Resistor
DC resistance
Clause 4.5 DC resistance values measured
<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
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. ±(0.5%+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 +125 °C±3°C,
2~3 minutes at 20°C+5°C-1°C, total 5
continuous cycles
no visible damage
∆R/R max. ±(0.5%+0.05Ω)
Load life (endurance)
Clause 4.25 70±2ºC, 1000 hours, loaded with RCWV or
Vmax,1.5 hours on and 0.5 hours off ∆R/R max. ±(1.0%+0.05Ω)
Load life in Humidity
Clause 4.24 1000 hours, at rated continuous working voltage 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. ±(1.0%+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. ±(0.5%+0.05Ω)
Adhision
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
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PACKAGING
Paper Tape specifications (unit :mm)
FP0
D
Series No. A B W D E
WF12 3.60±0.20 2.00±0.20 8.00±0.30 3.50±0.20 1.75±0.10
WF08 2.40±0.20 1.65±0.20 8.00±0.30 3.50±0.20 1.75±0.10
WF06 1.90±0.20 1.10±0.20 8.00±0.30 3.50±0.20 1.75±0.10
WF04 1.20±0.10 0.7±0.10 8.00±0.20 3.50±0.05 1.75±0.10
Series No. F P0 ΦD T
WF12 4.00±0.10 4.00±0.10
1.0 0.0
50.1
+
−
Φ
Max. 1.0
WF08 4.00±0.10 4.00±0.10
1.0 0.0
50.1
+
−
Φ
Max. 1.0
WF06 4.00±0.10 4.00±0.10
1.0 0.0
50.1
+
−
Φ
0.65±0.05
WF04 2.00±0.10 4.00±0.10
1.0 0.0
50.1
+
−
Φ
0.40±0.05
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 5,000 pcs per reel ( WF12, WF08, WF06 )
- Chip resistors 10,000 pcs per reel ( WF04 )
