NTC thermistors for
temperature measurement
Leaded NTC thermistors,
lead spacing 2.5 mm
Series/Type: B57891S
Date: March 2013
© EPCOS AG 2013. Reproduction, publication and dissemination of this publication, enclosures hereto and the
information contained therein without EPCOS' prior express consent is prohibited.
Applications
Temperature measurement and
compensation
Features
Favorable price/ performance ratio
Rugged design, epoxy resin encapsulation
Leads: copper-clad Fe wire, tinned
UL approval (E69802)
Options
Lead spacing 5 mm available on request
Delivery mode
Bulk (standard), cardboard tape, reeled or in
Ammo pack on request
Dimensional drawing
Dimensions in mm
Approx. weight 0.2 g
General technical data
Climatic category (IEC 60068-1) 55/155/56
Max. power (at 25 °C) P25 200 mW
Resistance tolerance ∆RR/RR±1, ±3, ±5 %
Rated temperature TR25 °C
Dissipation factor (in air) δth approx. 4 mW/K
Thermal cooling time constant (in air) τcapprox. 15 s
Heat capacity Cth approx. 60 mJ/K
Electrical specification and ordering codes
R25
ΩNo. of R/T
characteristic
B25/100
K
Ordering code
+ = Resistance tolerance
F = ±1%
H = ±3%
J = ±5%
2.2 k 1008 3560 ±1.5% B57891S0222+008
5 k 2003 3980 ±1% B57891S0502+008
10 k 4901 3950 ±1% B57891S0103+008
20 k 2904 4300 ±1% B57891S0203+008
100 k 4003 4450 ±1% B57891S0104+008
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 2 of 26Please read Cautions and warnings and
Important notes at the end of this document.
Reliability data
Test Standard Test conditions ∆R25/R25
(typical)
Remarks
Storage in
dry heat
IEC
60068-2-2
Storage at upper
category temperature
T: 155 °C
t: 1000 h
< 3% No visible
damage
Storage in damp
heat, steady state
IEC
60068-2-78
Temperature of air: 40 °C
Relative humidity of air: 93%
Duration: 56 days
< 1% No visible
damage
Rapid temperature
cycling
IEC
60068-2-14
Lower test temperature: 55 °C
Upper test temperature: 155 °C
Number of cycles: 100
< 2% No visible
damage
Endurance Pmax: 200 mW
t: 1000 h
< 3% No visible
damage
Long-term stability
(empirical value)
Temperature: 70 °C
t: 10000 h
< 3% No visible
damage
Note
Contact of NTC thermistors with any liquids and solvents shall be prevented. It must be
ensured that no water enters the NTC thermistors (e.g. through plug terminals).
Avoid dewing and condensation unless thermistor is specified for these conditions.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 3 of 26Please read Cautions and warnings and
Important notes at the end of this document.
R/T characteristics
R/T No. 1008 2003 2904
T (°C) B25/100 = 3560 K B25/100 = 3980 K B25/100 = 4300 K
RT/R25 α(%/K) RT/R25 α(%/K) RT/R25 α(%/K)
55.0 53.104 6.1 97.578 7.5 121.46 7.4
50.0 39.318 6.0 67.65 7.2 84.439 7.2
45.0 29.325 5.8 47.538 7.0 59.243 7.1
40.0 22.03 5.7 33.831 6.7 41.938 6.9
35.0 16.666 5.5 24.359 6.5 29.947 6.7
30.0 12.696 5.4 17.753 6.3 21.567 6.6
25.0 9.7251 5.2 13.067 6.0 15.641 6.3
20.0 7.5171 5.1 9.7228 5.8 11.466 6.2
15.0 5.8353 4.9 7.3006 5.6 8.451 6.0
10.0 4.5686 4.8 5.5361 5.5 6.2927 5.9
5.0 3.605 4.7 4.2332 5.3 4.7077 5.7
0.0 2.8665 4.5 3.266 5.1 3.5563 5.5
5.0 2.2907 4.4 2.5392 5.0 2.7119 5.3
10.0 1.8438 4.3 1.9902 4.8 2.086 5.1
15.0 1.492 4.1 1.5709 4.7 1.6204 5.0
20.0 1.2154 4.0 1.2492 4.5 1.2683 4.8
25.0 1.0000 3.9 1.0000 4.4 1.0000 4.7
30.0 0.82976 3.8 0.80575 4.3 0.7942 4.6
35.0 0.68635 3.7 0.65326 4.1 0.63268 4.5
40.0 0.57103 3.6 0.5329 4.0 0.5074 4.3
45.0 0.48015 3.5 0.43715 3.9 0.41026 4.2
50.0 0.40545 3.4 0.36064 3.8 0.33363 4.1
55.0 0.3417 3.3 0.29908 3.7 0.27243 4.0
60.0 0.28952 3.2 0.24932 3.6 0.2237 3.9
65.0 0.24714 3.1 0.20886 3.5 0.18459 3.8
70.0 0.21183 3.1 0.17578 3.4 0.15305 3.7
75.0 0.18194 3.0 0.14863 3.3 0.12755 3.6
80.0 0.1568 2.9 0.12621 3.2 0.10677 3.5
85.0 0.13592 2.8 0.10763 3.1 0.089928 3.4
90.0 0.11822 2.8 0.092159 3.1 0.076068 3.3
95.0 0.1034 2.7 0.079225 3.0 0.064524 3.3
100.0 0.090741 2.6 0.068356 2.9 0.054941 3.2
105.0 0.079642 2.6 0.059247 2.8 0.047003 3.1
110.0 0.070102 2.5 0.051531 2.8 0.040358 3.0
115.0 0.061889 2.4 0.044921 2.7 0.034743 3.0
120.0 0.054785 2.4 0.039282 2.7 0.030007 2.9
125.0 0.048706 2.3 0.034387 2.6 0.026006 2.8
130.0 0.043415 2.3 0.030186 2.5 0.022609 2.8
135.0 0.038722 2.2 0.02665 2.5 0.01972 2.7
140.0 0.034615 2.2 0.023594 2.4 0.017251 2.6
145.0 0.031048 2.1 0.020931 2.4 0.015139 2.6
150.0 0.02791 2.1 0.018616 2.3 0.013321 2.5
155.0 0.025193 2.0 0.016612 2.3 0.011754 2.5
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 4 of 26Please read Cautions and warnings and
Important notes at the end of this document.
R/T No. 1008 2003 2904
T (°C) B25/100 = 3560 K B25/100 = 3980 K B25/100 = 4300 K
RT/R25 α(%/K) RT/R25 α(%/K) RT/R25 α(%/K)
160.0 0.02279 2.0
165.0 0.020667 2.0
170.0 0.01878 1.9
175.0 0.01709 1.9
180.0 0.015582 1.8
185.0 0.014227 1.8
190.0 0.013012 1.8
195.0 0.011934 1.7
200.0 0.010964 1.7
205.0 0.0101 1.7
210.0 0.0093191 1.6
215.0 0.0085949 1.6
220.0 0.0079384 1.6
225.0 0.0073411 1.5
230.0 0.006798 1.5
235.0 0.0063087 1.5
240.0 0.0058623 1.5
245.0 0.0054487 1.4
250.0 0.0050705 1.4
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 5 of 26Please read Cautions and warnings and
Important notes at the end of this document.
R/T characteristics
R/T No. 4003 4901
T (°C) B25/100 = 4450 K B25/100 = 3950 K
RT/R25 α(%/K) RT/R25 α(%/K)
55.0 103.81 6.8 87.89 7.1
50.0 73.707 6.7 61.759 6.9
45.0 52.723 6.6 43.934 6.7
40.0 37.988 6.5 31.618 6.5
35.0 27.565 6.4 23.006 6.3
30.0 20.142 6.2 16.915 6.1
25.0 14.801 6.1 12.555 5.9
20.0 10.976 5.9 9.4143 5.7
15.0 8.1744 5.8 7.1172 5.5
10.0 6.1407 5.7 5.4308 5.4
5.0 4.6331 5.5 4.1505 5.2
0.0 3.5243 5.4 3.2014 5.0
5.0 2.6995 5.3 2.5011 4.9
10.0 2.0831 5.1 1.9691 4.7
15.0 1.6189 5.0 1.5618 4.6
20.0 1.2666 4.9 1.2474 4.5
25.0 1.0000 4.7 1.0000 4.3
30.0 0.78351 4.6 0.808 4.2
35.0 0.62372 4.5 0.6569 4.1
40.0 0.49937 4.4 0.5372 4.0
45.0 0.40218 4.3 0.44235 3.9
50.0 0.32557 4.2 0.3661 3.8
55.0 0.26402 4.1 0.30393 3.7
60.0 0.21527 4.0 0.25359 3.6
65.0 0.17693 3.9 0.21283 3.5
70.0 0.14616 3.8 0.17942 3.4
75.0 0.12097 3.7 0.15183 3.3
80.0 0.10053 3.7 0.12901 3.2
85.0 0.083761 3.6 0.11002 3.1
90.0 0.070039 3.5 0.094179 3.1
95.0 0.058937 3.4 0.080896 3.0
100.0 0.049777 3.4 0.069722 2.9
105.0 0.042146 3.3 0.060397 2.9
110.0 0.035803 3.2 0.052493 2.8
115.0 0.030504 3.2 0.045733 2.7
120.0 0.026067 3.1 0.039963 2.7
125.0 0.022332 3.0 0.035059 2.6
130.0 0.019186 3.0 0.030844 2.6
135.0 0.016515 2.9 0.027192 2.5
140.0 0.014253 2.9 0.024034 2.4
145.0 0.012367 2.8 0.021285 2.4
150.0 0.010758 2.8 0.018895 2.4
155.0 0.0093933 2.7 0.016813 2.3
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 6 of 26Please read Cautions and warnings and
Important notes at the end of this document.
1) ≤0.2 mm over 10 sprocket holes.
Taping and packing
1 Taping of SMD NTC thermistors
1.1 Cardboard tape for case size 0402 and 0603 (taping to IEC 60286-3)
Dimensions (mm)
Case size
0402
(8-mm tape)
Case size
0603
(8-mm tape)
Tolerance
A0×B00.60 ×1.15 0.95 ×1.80 ±0.2
T20.70 1.10
T 0.60 0.90 max.
D01.50 1.50 ±0.10
P04.00 4.00 ±0.101)
P22.00 2.00 ±0.05
P12.00 4.00 ±0.10
W 8.00 8.00 ±0.30
E 1.75 1.75 ±0.10
F 3.50 3.50 ±0.05
G 0.75 0.75 min.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 7 of 26Please read Cautions and warnings and
Important notes at the end of this document.
2) ≤0.2 mm over 10 sprocket holes.
1.2 Blister tape for case size 0805 and 1206 (taping to IEC 60286-3)
Dimensions (mm)
Case size
0805
(8-mm tape)
Case size
1206
(8-mm tape)
Tolerance
A0×B01.60 ×2.40 1.90 ×3.50 ±0.2
K01.40 1.40 max.
T22.5 2.5 max.
D01.50 1.50 +0.10/–0
D11.00 1.00 min.
P04.00 4.00 ±0.102)
P22.00 2.00 ±0.05
P14.00 4.00 ±0.10
W 8.00 8.00 ±0.30
E 1.75 1.75 ±0.10
F 3.50 3.50 ±0.05
G 0.75 0.75 min.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 8 of 26Please read Cautions and warnings and
Important notes at the end of this document.
3) Chip thickness depends on the resistance value.
1.3 Reel packing
Packing survey
Case
size
Chip
thick-
ness3)
8-mm tape Reel dimensions Packing units
mm mm pcs./reel
Blister Card-
board
A Tol. W1 Tol. W2 180-mm
reel
330-mm
reel
0402 0.5 x 180 3/+0 8.4 +1.5/0 14.4 max. 10000
0603 0.8 x 180 3/+0 8.4 +1.5/0 14.4 max. 4000
330 ±2.0 12.4 +1.5/0 18.4 max. 16000
0805 0.8 x 180 3/+0 8.4 +1.5/0 14.4 max. 4000 16000
1.2 x 330 ±2.0 12.4 +1.5/0 18.4 max. 3000 12000
1206 0.8 x 180 2/+0 8.4 +1.5/0 14.4 max. 4000
1.2 x 180 2/+0 8.4 +1.5/0 14.4 max. 2000
2 Packing codes
The last two digits of the complete ordering code state the packing mode:
Last two digits
60 SMD Cardboard tape 180-mm reel packing
62 SMD Blister tape 180-mm reel packing
70 SMD Cardboard tape 330-mm reel packing
72 SMD Blister tape 330-mm reel packing
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 9 of 26Please read Cautions and warnings and
Important notes at the end of this document.
3 Taping of radial leaded NTC thermistors
Dimensions and tolerances
Lead spacing F = 2.5 mm and 5.0 mm (taping to IEC 60286-2)
Dimensions (mm)
Lead
spacing
2.5 mm
Lead
spacing
5 mm
Tolerance of
lead spacing
2.5/5 mm
Remarks
w 11.0 11.5 max.
th 5.0 6.0 max.
d 0.5/0.6 0.5/0.6 ±0.05
P012.7 12.7 ±0.3 ±1 mm / 20 sprocket holes
P15.1 3.85 ±0.7
F 2.5 5.0 +0.6/0.1
∆h 0 0 ±2.0 measured at top of component body
∆p 0 0 ±1.3
W 18.0 18.0 ±0.5
W05.5 5.5 min. peel-off force ≥5 N
W19.0 9.0 +0.75/0.5
W23.0 3.0 max.
H 18.0 18.0 +2.0/0
H016.0 16.0 ±0.5
H132.2 32.2 max.
D04.0 4.0 ±0.2
t 0.9 0.9 max. without wires
L 11.0 11.0 max.
L14.0 4.0 max.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 10 of 26Please read Cautions and warnings and
Important notes at the end of this document.
Types of packing
Ammo packing
Ammo
type
xyz
I 80 240 210
Packing unit: 1000 - 2000 pcs./reel
Reel packing
Packing unit: 1000 - 2000 pcs./reel
Reel dimensions (in mm)
Reel type d f n w
I 360 max. 31 ±1 approx. 45 54 max.
II 500 max. 23 ±1 approx. 59 72 max.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 11 of 26Please read Cautions and warnings and
Important notes at the end of this document.
Cassette packing
Packing unit: 1000 - 2000 pcs./cassette
Bulk packing
The components are packed in cardboard boxes, the size of which depends on the order quantity.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 12 of 26Please read Cautions and warnings and
Important notes at the end of this document.
4 Packing codes
The last two digits of the complete ordering code state the packing mode:
Last two digits
00, 01, 02, 03,04,
05, 06, 07, 08 Bulk
40 Bulk
45 Bulk
50 Radial leads, kinked Cardboard tape Cassette packing
51 Radial leads, kinked Cardboard tape 360 or 500-mm reel packing
52 Radial leads, straight Cardboard tape Cassette packing
53 Radial leads, straight Cardboard tape 360 or 500-mm reel packing
54 Radial leads, kinked Cardboard tape AMMO packing
55 Radial leads, straight Cardboard tape AMMO packing
(If no packing code is indicated, this corresponds to 40)
Example 1: B57164K0102J000 Bulk
B57164K0102J052 Cardboard tape, cassette packing
Example 2: B57881S0103F002 Bulk
B57881S0103F251 Cardboard tape, reel packing
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 13 of 26Please read Cautions and warnings and
Important notes at the end of this document.
Mounting instructions
1 Soldering
1.1 Leaded NTC thermistors
Leaded thermistors comply with the solderability requirements specified by CECC.
When soldering, care must be taken that the NTC thermistors are not damaged by excessive
heat. The following maximum temperatures, maximum time spans and minimum distances have
to be observed:
Dip soldering Iron soldering
Bath temperature max. 260 °C max. 360 °C
Soldering time max. 4 s max. 2 s
Distance from thermistor min. 6 mm min. 6 mm
Under more severe soldering conditions the resistance may change.
1.2 Leadless NTC thermistors
In case of NTC thermistors without leads, soldering is restricted to devices which are provided
with a solderable metallization. The temperature shock caused by the application of hot solder
may produce fine cracks in the ceramic, resulting in changes in resistance.
To prevent leaching of the metallization, solder with silver additives or with a low tin content
should be used. In addition, soldering methods should be employed which permit short soldering
times.
1.3 SMD NTC thermistors
SMD NTC thermistors can be provided with a nickel barrier termination or on special request with
silver-palladium termination. The usage of mild, non-activated fluxes for soldering is recommend-
ed as well as a proper cleaning of the PCB.
Nickel barrier termination
The nickel barrier layer of the silver/nickel/tin termination (see figure 1) prevents leaching of the
silver base metalization layer. This allows great flexibility in the selection of soldering parameters.
The tin prevents the nickel layer from oxidizing and thus ensures better wetting by the solder. The
nickel barrier termination is suitable for all commonly-used soldering methods.
Note: SMD NTCs with AgPd termination are not approved for lead-free soldering.
Figure 1
SMD NTC thermistors, structure of nickel barrier
termination
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 14 of 26Please read Cautions and warnings and
Important notes at the end of this document.
1.3.1 Solderability (test to IEC 60068-2-58)
Preconditioning: Immersion into flux F-SW 32.
Evaluation criterion: Wetting of soldering areas ≥95%.
Solder Bath temperature (°C) Dwell time (s)
SnPb 60/40 215 ±3 3 ±0.3
SnAg (3.0 ... 4.0), Cu (0.5 ... 0.9) 245 ±3 3 ±0.3
1.3.2 Resistance to soldering heat (test to IEC 60068-2-58)
Preconditioning: Immersion into flux F-SW 32.
Evaluation criterion: Leaching of side edges ≤1/3.
Solder Bath temperature (°C) Dwell time (s)
SnPb 60/40 260 ±5 10 ±1
SnAg (3.0 ... 4.0), Cu (0.5 ... 0.9) 260 ±5 10 ±1
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 15 of 26Please read Cautions and warnings and
Important notes at the end of this document.
Wave soldering
Temperature characteristic at component terminal with dual wave soldering
Solder joint profiles for silver/nickel/tin terminations
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 16 of 26Please read Cautions and warnings and
Important notes at the end of this document.
Reflow soldering
Recommended temperature characteristic for reflow soldering following JEDEC J-STD-020D
Profile feature Sn-Pb eutectic assembly Pb-free assembly
Preheat and soak
- Temperature min Tsmin 100 °C 150 °C
- Temperature max Tsmax 150 °C 200 °C
- Time tsmin to tsmax 60 ... 120 s 60 ... 180 s
Average ramp-up rate Tsmax to Tp3°C/ s max. 3 °C/ s max.
Liquidous temperature TL183 °C 217 °C
Time at liquidous tL60 ... 150 s 60 ... 150 s
Peak package body temperature Tp1) 220 °C ... 235 °C2) 245 °C ... 260 °C2)
Time (tP)3) within 5 °C of specified
classification temperature (Tc)20 s3) 30 s3)
Average ramp-down rate Tpto Tsmax 6°C/ s max. 6 °C/ s max.
Time 25 °C to peak temperature maximum 6 min maximum 8 min
1) Tolerance for peak profile temperature (TP) is defined as a supplier minimum and a user maximum.
2) Depending on package thickness. For details please refer to JEDEC J-STD-020D.
3) Tolerance for time at peak profile temperature (tP) is defined as a supplier minimum and a user maximum.
Note: All temperatures refer to topside of the package, measured on the package body surface.
Number of reflow cycles: 3
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 17 of 26Please read Cautions and warnings and
Important notes at the end of this document.
Solder joint profiles for silver/nickel/tin terminations
1.3.3 Recommended geometry of solder pads
Recommended maximum dimensions (mm)
Case size
inch/mm
ABC
0402/1005 0.6 0.6 1.7
0603/1608 1.0 1.0 3.0
0805/2012 1.3 1.2 3.4
1206/3216 1.8 1.2 4.5
1.3.4 Notes
Iron soldering should be avoided, hot air methods are recommended for repair purposes.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 18 of 26Please read Cautions and warnings and
Important notes at the end of this document.
2 Conductive adhesion
An alternative to soldering is the gluing of thermistors with conductive adhesives. The benefit of
this method is that it involves no thermal stress. The adhesives used must be chemically inert.
3 Clamp contacting
Pressure contacting by means of clamps is particularly suitable for applications involving frequent
switching and high turn-on powers.
4 Robustness of terminations (leaded types)
The leads meet the requirements of IEC 60068-2-21. They may not be bent closer than 4 mm
from the solder joint on the thermistor body or from the point at which they leave the feed-
throughs. During bending, any mechanical stress at the outlet of the leads must be removed. The
bending radius should be at least 0.75 mm.
Tensile strength: Test Ua1:
Leads ∅ ≤0.25 mm = 1.0 N
0.25 < ∅ ≤0.35 mm = 2.5 N
0.35 < ∅ ≤0.50 mm = 5.0 N
0.50 < ∅ ≤0.80 mm = 10.0 N
0.80 < ∅ ≤1.25 mm = 20.0 N
Bending strength: Test Ub:
Two 90°-bends in opposite directions at a weight of 0.25 kg.
Torsional strength: Test Uc: severity 2
The lead is bent by 90°at a distance of 6 to 6.5 mm from the thermistor body.
The bending radius of the leads should be approx. 0.75 mm. Two torsions of
180°each (severity 2).
When subjecting leads to mechanical stress, the following should be observed:
Tensile stress on leads
During mounting and operation tensile forces on the leads are to be avoided.
Bending of leads
Bending of the leads directly on the thermistor body is not permissible.
A lead may be bent at a minimum distance of twice the wire's diameter +2 mm from the solder
joint on the thermistor body. During bending the wire must be mechanically relieved at its outlet.
The bending radius should be at least 0.75 mm.
Twisting of leads
The twisting (torsion) by 180°of a lead bent by 90°is permissible at 6 mm from the bottom of the
thermistor body.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 19 of 26Please read Cautions and warnings and
Important notes at the end of this document.
5 Sealing and potting
When thermistors are sealed, potted or overmolded, there must be no mechanical stress caused
by thermal expansion during the production process (curing / overmolding process) and during
later operation. The upper category temperature of the thermistor must not be exceeded. Ensure
that the materials used (sealing / potting compound and plastic material) are chemically neutral.
6 Cleaning
Washing processes may damage the product due to the possible static or cyclic mechanical
loads (e.g. ultrasonic cleaning). They may cause cracks to develop on the product and its parts,
which might lead to reduced reliability or lifetime.
7 Storage
In order to maintain their solderability, thermistors must be stored in a non-corrosive atmosphere.
Humidity, temperature and container materials are critical factors.
Do not store SMDs where they are exposed to heat or direct sunlight. Otherwise, the packing ma-
terial may be deformed or SMDs may stick together, causing problems during mounting. After
opening the factory seals, such as polyvinyl-sealed packages, use the SMDs as soon as possible.
The components should be left in the original packing. Touching the metallization of unsoldered
thermistors may change their soldering properties.
Storage temperature: 25 °Cupto45°C
Relative humidity (without condensation): ≤75% annual mean
<95%, maximum 30 days per annum
Solder the thermistors listed in this data book after shipment from EPCOS within the time speci-
fied:
SMDs with nickel barrier termination: 12 months
SMDs with AgPd termination: 6 months
Leaded components: 24 months
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 20 of 26Please read Cautions and warnings and
Important notes at the end of this document.
8 Placement and orientation of SMD NTC thermistors on PCB
a) Component placement
It is recommended that the PC board
should be held by means of some
adequate supporting pins such as
shown left to prevent the SMDs from
being damaged or cracked.
b) Cracks
When placing a component near an
area which is apt to bend or a grid
groove on the PC board, it is advisable
to have both electrodes subjected to
uniform stress, or to position the
component's electrodes at right angles
to the grid groove or bending line (see
c) Component orientation).
c) Component orientation
Choose a mounting position that
minimizes the stress imposed on the
chip during flexing or bending of the
board.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 21 of 26Please read Cautions and warnings and
Important notes at the end of this document.
Cautions and warnings
See "Important notes".
Storage
Store thermistors only in original packaging. Do not open the package prior to storage.
Storage conditions in original packaging: storage temperature 25 °C ... +45 °C, relative
humidity ≤75% annual mean, <95% maximum 30 days per annum, dew precipitation is
inadmissible.
Do not store thermistors where they are exposed to heat or direct sunlight. Otherwise, the
packing material may be deformed or components may stick together, causing problems during
mounting.
Avoid contamination of thermistor surface during storage, handling and processing.
Avoid storage of thermistors in harmful environments like corrosive gases (SOx, Cl etc).
Use the components as soon as possible after opening the factory seals, i.e. the
polyvinyl-sealed packages.
Solder thermistors within the time specified after shipment from EPCOS.
For leaded components this is 24 months, for SMD components with nickel barrier termination
12 months, for SMD components with AgPd termination 6 months.
Handling
NTC thermistors must not be dropped. Chip-offs or any other damage must not be caused
during handling of NTCs.
Do not touch components with bare hands. Gloves are recommended.
Avoid contamination of thermistor surface during handling.
Washing processes may damage the product due to the possible static or cyclic mechanical
loads (e.g. ultrasonic cleaning). They may cause cracks to develop on the product and its parts,
which might lead to reduced reliability or lifetime.
Bending / twisting leads
A lead (wire) may be bent at a minimum distance of twice the wire’s diameter plus 4 mm from
the component head or housing. When bending ensure the wire is mechanically relieved at the
component head or housing. The bending radius should be at least 0.75 mm.
Twisting (torsion) by 180°of a lead bent by 90°is permissible at 6 mm from the bottom of the
thermistor body.
Soldering
Use resin-type flux or non-activated flux.
Insufficient preheating may cause ceramic cracks.
Rapid cooling by dipping in solvent is not recommended.
Complete removal of flux is recommended.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 22 of 26Please read Cautions and warnings and
Important notes at the end of this document.
Mounting
Ensure that no thermo-mechanical stress occurs due to production processes (curing or
overmolding processes) when thermistors are sealed, potted or overmolded or during their
subsequent operation. The maximum temperature of the thermistor must not be exceeded.
Ensure that the materials used (sealing/potting compound and plastic material) are chemically
neutral.
Electrodes/contacts must not be scratched or damaged before/during/after the mounting
process.
Contacts and housing used for assembly with the thermistor must be clean before mounting.
Ensure that adjacent materials are designed for operation at temperatures comparable to the
surface temperature of the thermistor. Be sure that surrounding parts and materials can
withstand the temperature.
Avoid contamination of the thermistor surface during processing.
The connections of sensors (e.g. cable end, wire end, plug terminal) may only be exposed to
an environment with normal atmospheric conditions.
Tensile forces on cables or leads must be avoided during mounting and operation.
Bending or twisting of cables or leads directly on the thermistor body is not permissible.
Avoid using chemical substances as mounting aids. It must be ensured that no water or other
liquids enter the NTC thermistors (e.g. through plug terminals). In particular, water based
substances (e.g. soap suds) must not be used as mounting aids for sensors.
Operation
Use thermistors only within the specified operating temperature range.
Use thermistors only within the specified power range.
Environmental conditions must not harm the thermistors. Only use the thermistors under
normal atmospheric conditions or within the specified conditions.
Contact of NTC thermistors with any liquids and solvents shall be prevented. It must be
ensured that no water enters the NTC thermistors (e.g. through plug terminals). For
measurement purposes (checking the specified resistance vs. temperature), the component
must not be immersed in water but in suitable liquids (e.g. Galden).
Avoid dewing and condensation unless thermistor is specified for these conditions.
Bending or twisting of cables and/or wires is not permissible during operation of the sensor in
the application.
Be sure to provide an appropriate fail-safe function to prevent secondary product damage
caused by malfunction.
This listing does not claim to be complete, but merely reflects the experience of EPCOS AG.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 23 of 26Please read Cautions and warnings and
Important notes at the end of this document.
Symbols and terms
Symbol English German
A Area Fläche
AWG American Wire Gauge Amerikanische Norm für Drahtquerschnitte
B B value B-Wert
B25/100 B value determined by resistance
measurement at 25 °C and 100 °C
B-Wert, ermittelt durch Widerstands-
messungen bei 25 °C und 100 °C
Cth Heat capacitance Wärmekapazität
I Current Strom
N Number (integer) Anzahl (ganzzahliger Wert)
P25 Maximum power at 25 °C Maximale Leistung bei 25 °C
Pdiss Power dissipation Verlustleistung
Pel Electrical power Elektrische Leistung
Pmax Maximum power within stated
temperature range
Maximale Leistung im
angegebenenTemperaturbereich
∆RB/RBResistance tolerance caused by
spread of B value
Widerstandstoleranz, die durch die
Streuung des B-Wertes verursacht wird
Rins Insulation resistance Isolationswiderstand
RPParallel resistance Parallelwiderstand
RRRated resistance Nennwiderstand
∆RR/RRResistance tolerance Widerstandstoleranz
RSSeries resistance Serienwiderstand
RTResistance at temperature T
(e.g. R25 = resistance at 25 °C)
Widerstand bei Temperatur T
(z.B. R25 = Widerstand bei 25 °C)
T Temperature Temperatur
∆T Temperature tolerance Temperaturtoleranz
t Time Zeit
TAAmbient temperature Umgebungstemperatur
Tmax Upper category temperature Obere Grenztemperatur
(Kategorietemperatur)
Tmin Lower category temperature Untere Grenztemperatur
(Kategorietemperatur)
Top Operating temperature Betriebstemperatur
TRRated temperature Nenntemperatur
Tsurf Surface temperature Oberflächentemperatur
V Voltage Spannung
Vins Insulation test voltage Isolationsprüfspannung
Vop Operating voltage Betriebsspannung
Vtest Test voltage Prüfspannung
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 24 of 26Please read Cautions and warnings and
Important notes at the end of this document.
Symbol English German
αTemperature coefficient Temperaturkoeffizient
∆Tolerance, change Toleranz, Änderung
δth Dissipation factor Wärmeleitwert
τcThermal cooling time constant Thermische Abkühlzeitkonstante
τaThermal time constant Thermische Zeitkonstante
Abbreviations / Notes
Symbol English German
Surface-mounted devices Oberflächenmontierbares Bauelement
* To be replaced by a number in ordering
codes, type designations etc.
Platzhalter für Zahl im Bestellnummern-
code oder für die Typenbezeichnung.
+ To be replaced by a letter. Platzhalter für einen Buchstaben.
All dimensions are given in mm. Alle Maße sind in mm angegeben.
The commas used in numerical values
denote decimal points.
Verwendete Kommas in Zahlenwerten
bezeichnen Dezimalpunkte.
Temperature measurement and compensation B57891S
Leaded NTC thermistors, lead spacing 2.5 mm S891
Page 25 of 26Please read Cautions and warnings and
Important notes at the end of this document.
The following applies to all products named in this publication:
1. Some parts of this publication contain statements about the suitability of our products for
certain areas of application. These statements are based on our knowledge of typical re-
quirements that are often placed on our products in the areas of application concerned. We
nevertheless expressly point out that such statements cannot be regarded as binding
statements about the suitability of our products for a particular customer application.
As a rule, EPCOS is either unfamiliar with individual customer applications or less familiar
with them than the customers themselves. For these reasons, it is always ultimately incum-
bent on the customer to check and decide whether an EPCOS product with the properties de-
scribed in the product specification is suitable for use in a particular customer application.
2. We also point out that in individual cases, a malfunction of electronic components or
failure before the end of their usual service life cannot be completely ruled out in the
current state of the art, even if they are operated as specified. In customer applications
requiring a very high level of operational safety and especially in customer applications in
which the malfunction or failure of an electronic component could endanger human life or
health (e.g. in accident prevention or lifesaving systems), it must therefore be ensured by
means of suitable design of the customer application or other action taken by the customer
(e.g. installation of protective circuitry or redundancy) that no injury or damage is sustained by
third parties in the event of malfunction or failure of an electronic component.
3. The warnings, cautions and product-specific notes must be observed.
4. In order to satisfy certain technical requirements, some of the products described in this
publication may contain substances subject to restrictions in certain jurisdictions (e.g.
because they are classed as hazardous). Useful information on this will be found in our Ma-
terial Data Sheets on the Internet (www.epcos.com/material). Should you have any more de-
tailed questions, please contact our sales offices.
5. We constantly strive to improve our products. Consequently, the products described in this
publication may change from time to time. The same is true of the corresponding product
specifications. Please check therefore to what extent product descriptions and specifications
contained in this publication are still applicable before or when you place an order. We also
reserve the right to discontinue production and delivery of products. Consequently, we
cannot guarantee that all products named in this publication will always be available. The
aforementioned does not apply in the case of individual agreements deviating from the fore-
going for customer-specific products.
6. Unless otherwise agreed in individual contracts, all orders are subject to the current ver-
sion of the "General Terms of Delivery for Products and Services in the Electrical In-
dustry" published by the German Electrical and Electronics Industry Association
(ZVEI).
7. The trade names EPCOS, BAOKE, Alu-X, CeraDiode, CeraLink, CSMP, CSSP, CTVS,
DeltaCap, DigiSiMic, DSSP, FilterCap, FormFit, MiniBlue, MiniCell, MKD, MKK, MLSC,
MotorCap, PCC, PhaseCap, PhaseCube, PhaseMod, PhiCap, SIFERRIT, SIFI, SIKOREL,
SilverCap, SIMDAD, SiMic, SIMID, SineFormer, SIOV, SIP5D, SIP5K, ThermoFuse,
WindCap are trademarks registered or pending in Europe and in other countries. Further
information will be found on the Internet at www.epcos.com/trademarks.
Important notes
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