NTC thermistors for
temperature measurement
Leadless NTCs
Series/Type:
Date:
B57220K
March 2013
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information contained therein without EPCOS' prior express consent is prohibited.
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Temperature measurement and compensation
Leadless NTCs
B57220K
K220
Applications
Temperature measurement and
compensation
Features
Front surfaces silver-plated
For clamp contacting
UL approval (E69802)
Options
Alternative resistance ratings, rated
temperatures and resistance tolerances
available on request.
Delivery mode
Bulk
Dimensional drawing
∅d
= 2.9
±0.3
mm
th = 1.3
±0.3
mm
Approx. weight 50 mg
General technical data
Climatic category
Max. power
Resistance tolerance
Rated temperature
Dissipation factor
Thermal cooling time constant
Heat capacity
(IEC 60068-1)
(at 25
°C)
55/250/21
180
±5
20
approx. 2.5
approx. 12
approx. 30
(in air)
(in air)
P
25
∆R
R
/R
R
T
R
δ
th1)
τ
c1)
C
th1)
mW
%
°C
mW/K
s
mJ/K
Electrical specification and ordering codes
R
20
Ω
2.5 k
R
25
Ω
2056.9
No. of R/T
characteristic
1008
B
25/100
K
3560
±1.5%
Ordering code
B57220K0212A003
1) Depends on mounting situation
Please read
Cautions and warnings
and
Important notes
at the end of this document.
Page 2 of 17
Temperature measurement and compensation
Leadless NTCs
B57220K
K220
Reliability data
Test
Storage in
dry heat
Standard
IEC
60068-2-2
Test conditions
∆R
25
/R
25
(typical)
< 3%
Remarks
No visible
damage
Storage in damp
heat, steady state
Rapid temperature
cycling
Endurance
Long-term stability
(empirical value)
Note
Storage at upper
category temperature
T: 250
°C
t: 1000 h
IEC
Temperature of air: 40
°C
60068-2-78 Relative humidity of air: 93%
Duration: 21 days
IEC
Lower test temperature: 55
°C
60068-2-14 Upper test temperature: 155
°C
Number of cycles: 100
P
max
: 180 mW
t: 1000 h
Temperature: 70
°C
t: 10000 h
< 3%
No visible
damage
No visible
damage
No visible
damage
No visible
damage
< 3%
< 3%
< 5%
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.
Please read
Cautions and warnings
and
Important notes
at the end of this document.
Page 3 of 17
Temperature measurement and compensation
Leadless NTCs
B57220K
K220
Mounting instructions
1
1.1
Soldering
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
Bath temperature
Soldering time
Distance from thermistor
max. 260
°C
max. 4 s
min. 6 mm
Iron soldering
max. 360
°C
max. 2 s
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
Please read
Cautions and warnings
and
Important notes
at the end of this document.
Page 5 of 17
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