53

In specifying capacitance change with temperature for Class

2 materials, EIA expresses the capacitance change over an

operating temperature range by a 3 symbol code. The first

symbol represents the cold temperature end of the temper-

ature range, the second represents the upper limit of the

operating temperature range and the third symbol repre-

sents the capacitance change allowed over the

operating temperature range. Table 1 provides a detailed

explanation of the EIA system.

Effects of Voltage – Variations in voltage have little effect

on Class 1 dielectric but does affect the capacitance and

dissipation factor of Class 2 dielectrics. The application of

DC voltage reduces both the capacitance and dissipation

factor while the application of an AC voltage within a

reasonable range tends to increase both capacitance and

dissipation factor readings. If a high enough AC voltage is

applied, eventually it will reduce capacitance just as a DC

voltage will. Figure 2 shows the effects of AC voltage.

Capacitor specifications specify the AC voltage at which to

measure (normally 0.5 or 1 VAC) and application of the

wrong voltage can cause spurious readings. Figure 3 gives

the voltage coefficient of dissipation factor for various AC

voltages at 1 kilohertz. Applications of different frequencies

will affect the percentage changes versus voltages.

Typical effect of the application of DC voltage is shown in

Figure 4. The voltage coefficient is more pronounced for

higher K dielectrics. These figures are shown for room tem-

perature conditions. The combination characteristic known

as voltage temperature limits which shows the effects of

rated voltage over the operating temperature range is

shown in Figure 5 for the military BX characteristic.

General Description

Figure 2

50

40

30

20

10

0

12.5

25

37.5

50

Volts AC at 1.0 KHz

Cap. Change vs. A.C. Volts

X7R

Figure 3

Curve 3 - 25 VDC Rated Capacitor

Curve 2 - 50 VDC Rated Capacitor

Curve 1 - 100 VDC Rated Capacitor

Curve 3

Curve 2

Curve 1

.5

1.0

1.5

2.0

2.5

AC Measurement Volts at 1.0 KHz

10.0

8.0

6.0

4.0

2.0

0

D.F. vs. A.C. Measurement Volts

X7R

EIA CODE

Percent Capacity Change Over Temperature Range

RS198

Temperature Range

X7

-55°C to +125°C

X5

-55°C to +85°C

Y5

-30°C to +85°C

Z5

+10°C to +85°C

Code

Percent Capacity Change

D±3.3%

E±4.7%

F±7.5%

P±10%

R±15%

S±22%

T

+22%, -33%

U

+22%, - 56%

V

+22%, -82%

MIL CODE

Symbol

Temperature Range

A

-55°C to +85°C

B

-55°C to +125°C

C

-55°C to +150°C

Symbol

Cap. Change

Cap. Change

Zero Volts

Rated Volts

R

+15%, -15%

+15%, -40%

W

+22%, -56%

+22%, -66%

X

+15%, -15%

+15%, -25%

Y

+30%, -70%

+30%, -80%

Z

+20%, -20%

+20%, -30%

Table 1: EIA and MIL Temperature Stable and General

Application Codes

EXAMPLE – A capacitor is desired with the capacitance value at 25°C

to increase no more than 7.5% or decrease no more than 7.5% from

-30°C to +85°C. EIA Code will be Y5F.

Temperature characteristic is specified by combining range and

change symbols, for example BR or AW. Specification slash sheets

indicate the characteristic applicable to a given style of capacitor.