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Varistor Products

NA Varistor Series

Passivation Layer

The standard NA Series is supplied with passivation layer around the

outside perimeter of the disc forming an electrical insulator as detailed in

the dimensional drawing.

Encapsulated Recommendations

After lead attachment, the disc/lead assembly may be coated or

encapsulated in a package to provide electrical insulation and isolation

from environmental contamination as required by the application.

Coating/Filler materials for containers may include silicones,

polyurethanes, and some epoxy resins. Two examples of acceptable

polyurethanes are Dexter Hysol (US7013, parts A and B) and Rhenatech

(resin 4714, hardener 4900), or their equivalents. Materials containing

halogens, sulfides, or alkalines are not recommended.

Electrode Metallization

The NA Series is supplied with a sintered silver metallization for the

electrode finish. The silver metallization is typically used for solder reflow

lead attach operations (I-R, Vapour-Phase).

The recommended temperature profile of a belt-fed convection oven is

shown in Figure 6.

Stacking and Contact Pressure

Recommendations

When applications require the stacking of Littelfuse NA discs or when

electrical connection is made by pressure contacts, the minimum pres-

sure applied to the disc electrode surface should be 2.2kGs (5 pounds).

The maximum recommended pressure applied to the disc electrode is

Packaging and Shipping

The NA Series is supplied in bulk for shipment. Discs are packaged in

compartmentalized cartons to protect from scratching or edge-chipping

during shipment.

250

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100

50

0

0

100

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900

TIME (SEC)

FIGURE 6. TYPICAL BELT OVEN TEMPERATURE PROFILE

Ordering Information

VARISTOR DESIGNATOR

DISC SIZE (mm)

SERIES DESIGNATOR

V 25 1 NA 34

High Energy Industrial Square Disc