Varistor Products

©2010 Littelfuse, Inc.

Revision: June 28, 2010

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

components in surface mount technology are IR Re-flow

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

The recommended solder for the MHS suppressor is

a 62/36/2 (Sn/Pb/Ag), 60/40 (Sn/Pb) or 63/37 (Sn/Pb).

Littelfuse also recommends an RMA solder flux.

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.

Once the soldering process has been completed, it is

still necessary to ensure that any further thermal shocks

are avoided. One possible cause of thermal shock is hot

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

to less than 50ºC before cleaning.

230

Reflow Solder Profile

Wave Solder Profile

Device Characteristics

At low current levels, the V-I curve of the multilayer

transient voltage suppressor approaches a linear (ohmic)

relationship and shows a temperature dependent effect.

At or below the maximum working voltage, the suppressor

maximum rated working voltage). Leakage currents at

maximum rated voltage are below 100

μA, typically 25μA;

for 0402 size below 20

μA, typically 5μA.

100%

1E-9

1E-8

SUPPRESSOR CURRENT (ADC)

10%

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

25

50

75

100

125oC

o

o

o

o

Typical Temperature Dependance of the Characteristic

Curve in the Leakage Region

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 Z

than 1ns and the MLE can clamp very fast dV/dT events

such as ESD. Additionally, 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

Multilayer Internal Construction

Figure 5

Figure 6

Figure 7

Figure 8