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

B57964S

Leaded NTC thermistors, lead spacing 2.5 mm

S964

Page 14 of 26

Please read Cautions and warnings and

Important notes at the end of this document.