120

www .littelfuse .com

Varistor Products

CA Varistor Series

High Energy Industrial Disc

Passivation Layer

The standard CA Series is supplied with passivation layer around the

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

the dimensional drawing. The CA Series is also available without a

passivation layer for applications where the customer provides a suitable

encapsulation or potting material as recommended below.

(See Ordering Information.)

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 standard CA Series is supplied with sintered silver electrodes on

CA32 devices and arc-sprayed copper-over-aluminum electrodes for CA40

and CA60 series. CA40 parts are also available with sintered silver elec-

trode, see “Ordering information.” In general, when discs are stacked to

attain a specific operating voltage or energy capability, the copper finish is

typically chosen. Likewise, the copper finish is used with high temperature

lead attach soldering operations (wave solder). 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 13.

Stacking and Contact Pressure

Recommendations

When applications require the stacking of Littelfuse CA 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

dependent upon diameter size and is given in the following table.

MODEL

NUMBER

SIZE

(mm)

TYPICAL DISC

WEIGHT (GRAMS)

V131CA32

V131CA40

32

40

9

21

V151CA32

V151CA40

32

40

11

23

V251CA32

V251CA40

V251CA60

32

40

60

8

17

39

V271CA32

V271CA40

V271CA60

32

40

60

10

18

42

V321CA32

32

11

V321CA40

40

22

V321CA60

60

50

V421CA32

32

15

V421CA40

40

28

V421CA60

60

66

V481CA32

32

16

V481CA40

40

31

V481CA60

60

71

V511CA32

32

18

V511CA40

40

35

V511CA60

60

80

V571CA32

32

20

V571CA40

40

38

V571CA60

60

88

V661CA32

32

23

V661CA40

40

44

V661CA60

60

101

V751CA32

32

26

V751CA40

40

51

V751CA60

60

116

V881CA60

60

141

V112CA60

V142CA60

V172CA60

V202CA60

V242CA60

V282CA60

60

60

60

60

60

60

178

220

265

317

377

450

250

200

150

100

50

0

0

100

200

300

400

500

600

700

800

900

TIME (SEC)

FIGURE 13. TYPICAL BELT OVEN TEMPERATURE PROFILE

MODEL SIZE (mm)

MAXIMUM PRESSURE

32

40

60