Approval sheet
WF25P, WF20P, WF12P
±
1%,
±
5% 1
~ 1M
Thick Film High Power Chip Resistors
Size 2512 2W, 2010 1W, 1206 1/2W
*Contents in this sheet are subject to change without prior notice.
Page 1 of 7
ASC_WF25-20-12P_V10
Jul.2011
Approval sheet
FEATURE
1.
2.
3.
4.
5.
High power rating and compact size
High reliability and stability
Reduced size of final equipment
RoHS compliant and Lead free products
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
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ASC_WF25-20-12P_V10
Jul.2011
Approval sheet
QUICK REFERENCE DATA
Item
Series No.
Size code
Resistance Tolerance
Resistance Range
TCR (ppm/°C)
Max. dissipation at T
amb
=70°C
Max. Operation Voltage (DC or RMS)
Max. Overload Voltage (DC or RMS)
Climatic category (IEC 60068)
Note :
1.
2.
This is the maximum voltage that may be continuously supplied to the resistor element, see “IEC publication
60115-8”
Max. Operation Voltage : So called RCWV (Rated Continuous Working Voltage) is determined by
General Specification
WF25P
2512 (6432)
WF20P
2010 (5025)
±1%, ±5%
0 ,1Ω ~ 1MΩ
±100
2W
300V
500V
1W
200V
400V
55/155/56
1/2 W
200V
400V
WF12P
1206 (3216)
RCWV
=
Rated Power
×
Resistance Value
or Max. RCWV listed above, whichever is lower.
3.
2W loading with total solder-pad and trace size of 300 mm
2
4.
0Ω maximum resistance Rmax < 20mΩ
TEST CONDITION FOR JUMPER (0
Ω
)
Item
Power Rating At 70°C
Resistance
Rated Current
Peak Current
Operating Temperature
10A
25A
WF25P
2W
WF20P
1W
Max. 20mΩ
7A
17.5A
-55 ~ +155°C
5A
12.5A
WF12P
1/2W
MECHANICAL DATA
Unit: mm
Symbol
L
W
T
WF25P
6.30
±
0.20
3.10
±
0.20
0.60
±
0.15
0.60
±
0.25
1.80
±
0.25
WF20P
5.00
±
0.20
2.50
±
0.20
0.60
±
0.10
0.60
±
0.25
0.60
±
0.25
WF12P
3.10
±
0.15
1.60
±
0.15
0.55
±
0.10
0.50
±
0.25
0.50
±
0.25
102
Tt
Tb
Page 3 of 7
ASC_WF25-20-12P_V10
Jul.2011
Approval sheet
Recommended Solder Pad Dimensions
D
W
Type
WF25P
L
W
3.7
mm
D
2.45
mm
L
7.6
mm
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
16R0
102
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
Page 4 of 7
ASC_WF25-20-12P_V10
Jul.2011
Approval sheet
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
Size code
WF25
WF20
WF12
: 2512
: 2010
: 1206
P
Type code
P :Power
2512 size=2 watt
2010 size=1 watt
1206 size=0.5 watt
102
Resistance code
5% E24:
2 significant digits
followed by No. of zeros
e.g.:
3ohm
10ohm
1%
digits
=3R0
=100
J
Tolerance
J :
±5%
F :
±1%
P :
Jumper
T
Packaging
code
T : 7” Reel
taping
L
Termination
code
L
=
Sn base
(lead free)
56Kohm
=563
E24+E96:3
significant
followed by No. of zeros
100Ω
37.4KΩ
=1000
=3742
Tape packaging
WF12 : 8mm width paper taping 5,000pcs per reel.
WF25；WF20:
12mm width plastic taping 4,000pcs per reel.
Page 5 of 7
ASC_WF25-20-12P_V10
Jul.2011
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