Littelfuse MHS Varistor Series Manual de usuario descargar pdf (Pagina 3)

Revised: December 16, 2013

Varistor Products

MHS Series

MHS Varistor Series

Surface Mount Multilayer Varistors (MLVs) > MHS Series

Speciﬁcations are subject to change without notice.

Please refer to www.littelfuse.com/series/MHS.html for current information.

Lead (Pb) Soldering Recommendations

The principal techniques used for the soldering of



and Wave soldering. Typical proﬁles are shown on the right.

The recommended solder for the MHS suppressor is





Wave soldering is the most strenuous of the processes.

To avoid the possibility of generating stresses due to

thermal shock, a preheat stage in the soldering process

is recommended, and the peak temperature of the solder

process should be rigidly controlled.

When using a reﬂow process, care should be taken to

ensure that the MHS chip is not subjected to a thermal

gradient steeper than 4 degrees per second; the ideal

gradient being 2 degrees per second. During the soldering

process, preheating to within 100 degrees of the solder's

peak temperature is essential to minimize thermal shock.



still necessary to ensure that any further thermal shocks



printed circuit boards being removed from the solder

process and subjected to cleaning solvents at room

temperature. The boards must be allowed to cool gradually



230

5.0 6.0 7. 0

MAXIMUM TEMPERATURE 260˚C

20 - 40 SECONDS WITHIN 5˚C

PREHEAT ZONE

RAMP RATE

<3˚C/s

60 - 150 SEC

> 217˚C

FIGURE 7. LEAD-FREE RE-FLOW PROFILE

230

5.0 6.0 7. 0

MAXIMUM TEMPERATURE 260˚C

20 - 40 SECONDS WITHIN 5˚C

PREHEAT ZONE

RAMP RATE

<3˚C/s

60 - 150 SEC

> 217˚C

FIGURE 7. LEAD-FREE RE-FLOW PROFILE

Reﬂow Solder Proﬁle

Wave Solder Proﬁle

Device Characteristics



transient voltage suppressor approaches a linear (ohmic)

relationship and shows a temperature dependent effect.

At or below the maximum working voltage, the suppressor

is in a high resistance model (approaching 10

Ω at its

maximum rated working voltage). Leakage currents at

maximum rated voltage are below 100µµA;

for 0402 size below 20µµA.

100%

-9

-8

SUPPRESSOR CURRENT (A

)

10%

-7

-6

-5

-4

-3

-2

25 50 75 100

125

SUPPRESSOR VOLTAGE IN PERCENT OF

NOM

VALUE AT 25

C (%)

FIGURE 10. TYPICAL TEMPERATURE DEPENDANCE OF THE CHARACTERISTIC

CURVE IN THE LEAKAGE REGION

Typical Temperature Dependance of the Characteristic



Speed of Response

The Multilayer Suppressor is a leadless device. Its response

time is not limited by the parasitic lead inductances found

in other surface mount packages. The response time of the





in “real world” applications, the associated circuit wiring

is often the greatest factor effecting speed of response.

Therefore, transient suppressor placement within a circuit

can be considered important in certain instances.

GRAINS

DEPLETION

FIRED CERAMIC

DIELECTRIC

REGION

METAL

ELECTRODES

DEPLETION

REGION

METAL END

TERMINATION

FIGURE 11. MULTILAYER INTERNAL CONSTRUCTION

Multilayer Internal Construction

Figure 5

Figure 6

Figure 7

Figure 8

1 2 3 4 5

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