IPC-TM-650 EN 2022 试验方法-- - 第431页

IPC-TM-650 Number Subject Date Revision Page 3 of 4 2.5.5.3 Permittivity (Dielectric Constant) and Loss Tangent (Dissipation Factor) of Materials (Two Fluid Cell Method) 12/87 C 5.4.2 Record the capacitance of the air fi…

IPC-TM-650

Number

Subject Date

Revision

Page 2 of 4

2.5.5.3

Permittivity

(Dielectric

Constant)

and

Loss

Tangent

(Dissipation

Factor)

of

Materials

(Two

Fluid

Cell

Method)

12/87

C

4.3

Test

Leads

2

RG

58/U

coax

cables

approximately

304.8

mm

[1

2

in]

long

with

suitable

connectors

for

the

bridge.

One

lead

shall

have

a

banana

plug

(high

lead)

and

the

low

lead

should

have

a

GR8743

at

the

cell

end.

(Note:

The

use

of

a

G874-QBJA3

4

instead

of

the

standard

GR874

will

permit

a

BNC5

connector

to

be

used

for

the

cell

connection

of

the

low

lead,

reducing

the

chances

of

damaging

the

874

connector.)

4.4

Flask

with

stopper

(for

silicone

fluid

storage).

4.5

Beaker

for

cell

overflow.

4.6

Funnel.

4.7

Filter

paper

(coarse).

4.8

1

Centistoke

Dow

Corning

200

Fluid

(500

ml

minimum).

Note:

Fluid

must

be

at

the

same

ambient

temperature

as

the

test

cell

and

should

be

stored

in

close

proximity

to

the

test

cell.

4.9

Forceps

or

large

tweezers.

5.0

Procedure

5.1

Conditioning

All

materials

which

are

affected

by

mois¬

ture,

including

all

reinforced

laminates

and

most

films,

should

be

conditioned

at

23℃

±

2

℃

50

±

5%

RH

for

a

minimum

of

24

hours

prior

to

testing.

If

required

by

the

specification,

specimens

may

be

tested

after

humidity

or

water

immersion

or

tested

after

desiccation.

5.2

Test

Conditions

For

ambient

temperature

tests

the

temperature

should

be

23℃

±

2

℃.

Note:

Variation

should

not

exceed

1

during

the

test.

Ambi¬

ent

humidity

is

not

critical

for

most

materials.

The

exception

is

very

thin,

very

hydroscopic

material

such

as

polyimide

film,

where

moisture

content

may

be

well

over

1

%.

Such

material

must

be

tested

at

the

desired

humidity

since

the

dielectric

constant

will

increase

measurably

with

moisture

content

and

changes

may

occur

very

rapidly

after

removal

from

a

con¬

trolled

environment.

For

materials

which

experience

glass

transitions

in

the

room

temperature

region,

e.g.,

PTFE,

some

acrylics,

the

temperature

should

be

23℃

±

1

℃.

5.3

Set

Up

5.3.1

Open

the

electrode

on

the

cell.

Blow

out

the

cell

using

clean

compressed

air

to

remove

any

dust

or

silicone

fluid.

5.3.2

Warm

up

the

bridge

for

at

least

the

minimum

amount

of

time

recommended

by

the

manufacturer.

5.3.3

Attach

the

low

lead

to

the

guarded

electrode

of

the

cell

and

the

bridge.

5.3.4

Attach

the

high

lead

to

the

bridge

and

place

the

banana

plug

in

the

vicinity

of,

but

not

touching,

the

banana

plug

jack

of

the

test

cell.

Note:

Be

certain

the

shielding

on

the

high

lead

does

not

con¬

tact

the

banana

plug.

5.3.5

Set

the

bridge

up

on

appropriate

ranges:

Capacitance:

200

pf

(or

1

00

pf)

Conductance:

microsiemens

0-2

PTFE

and

very

low

loss

material.

0-20

Epoxy

and

other

moderate

loss

materials.

0-200

Some

phenolic

and

very

high

loss

materials.

Note:

For

very

thick

specimens

>3.18

mm

[>0.125

in]

the

0

to

20

pf

range

can

often

be

used,

increasing

the

precision

of

the

measurement.

All

values

must

be

obtained

on

the

same

range

for

both

capacitance

and

conductance.

5.3.6

Set

the

cell

spacing

on

the

LD-3

to

approximately

125%

of

the

material

thickness

0.51

mm

minimum

to

7.62

[0.020

in

minimum

to

0.3

in]

Note:

The

spacing

may

be

as

little

as

1

0%

or

as

much

as

50%

greater

than

specimen

thick¬

ness

without

a

significant

effect

on

results.

5.3.7

Zero

the

bridge

for

both

capacitance

and

conduc¬

tance.

5.4

Measurement

5.4.1

Connect

the

banana

plug

of

the

high

lead

to

the

cell.

3.

GR874

•―

Catalogue

#874-9414

Gilbert

Engineering,

Glendale,

AZ,

(602)

245-1050

4.

G874-QBJA

—

Catalogue

#874

QBJA

Gilbert

Engineering,

Glendale,

AZ

5.

BNC

—

Catalogue

#999-225

Amphenol

IPC-TM-650

Number

Subject Date

Revision

Page 3 of 4

2.5.5.3

Permittivity

(Dielectric

Constant)

and

Loss

Tangent

(Dissipation

Factor)

of

Materials

(Two

Fluid

Cell

Method)

12/87

C

5.4.2

Record

the

capacitance

of

the

air

filled

cell

as

g

to

the

nearest

.01

pf

(or

nearest

.001

pf

if

the

0-20

pf

scale

is

used).

5.4.3

Remove

the

specimen

from

the

humidity

controlled

environment.

5.4.4

Insert

the

first

specimen

to

be

tested

with

the

marked

corner

remaining

in

the

upper

left

and

the

right

side

of

the

test

specimen

against

one

side

of

the

test

cell.

Note:

This

will

ensure

that

subsequent

measurements

are

taken

using

the

same

area

of

the

specimen.

5.4.5

Read

and

record

the

value

of

capacitance

with

the

specimen

in

the

cell

as

C3.

5.4.6

Remove

the

first

specimen

and

obtain

C3

for

any

other

specimens

to

be

measured

with

same

cell

spacing.

5.4.7

After

removing

the

last

specimen

from

the

cell,

fill

the

cell

with

Dow

Corning

200

Fluid

using

the

funnel

and

a

filter

to

remove

any

small

particles

from

the

fluid

and

collect

any

excess

fluid

from

the

overflow

pipe

on

the

cell

with

the

small

beaker.

5.4.8

Allow

a

few

seconds

for

the

temperature

of

the

cell

and

fluid

to

equilibrate

and

record

the

capacitance

of

the

liq¬

uid

filled

cell

as

C2.

Note:

If

the

capacitance

is

drifting

consistently

in

one

direc¬

tion,

the

fluid

is

not

at

equilibrium.

5.4.9

Record

the

conductance

of

the

fluid

filled

as

cell

.

Note:

The

value

obtained

will

vary

somewhat

with

cell

spacing

and

humidity

but

should

not

exceed

500

microsiemen

(200

microsiemen

if

low

loss

material,

with

a

loss

tangent

under

.001

is

being

tested).

Values

beyond

this

are

generally

indica¬

tive

of

problems

with

the

leads,

contamination

of

the

fluid

or

bridge

error

and

must

be

corrected

if

correct

dissipation

fac¬

tor

is

to

be

determined.

5.4.10

Insert

the

first

specimen

in

the

fluid

filled

cell

exactly

as

in

the

dry

reading

and

record

the

value

of

the

capacitance

as

C4

and

the

value

of

the

conductance

as

G2-

Note:

Values

should

stabilize

within

a

few

seconds

after

speci¬

men

insertion.

If

they

do

not

there

is

very

likely

air

trapped

in

the

cell.

This

is

quite

common

if

multiple

thin

specimens

are

used

to

form

one

test

specimen.

If

this

occurs

presoaking

the

specimen

with

fluid

before

immersion

and

inserting

one

ply

at

a

time

should

eliminate

the

problem.

5.4.11

Remove

the

first

specimen

and

insert

each

subse¬

quent

specimen

in

the

same

order

as

the

dry

values

were

obtained

and

record

the

C4

and

G2

values

for

each.

5.4.12

After

the

last

specimen

is

measured

and

removed

from

fluid,

check

and

record

the

values

of

the

capacitance

and

conductance.

Note:

If

the

level

of

the

fluid

with

the

specimen

removed

does

not

cover

the

electrodes,

fill

the

cell

before

checking

the

final

values.

This

check

on

C2

will

be

used

to

verify

the

amount

of

influence

that

changes

in

ambient

temperature

have

had

on

the

values

obtained.

6

.0

Calculation

6.1

Calculate

the

value

of

the

permittivity

(dielectric

constant)

of

each

specimen

tested

using

the

equation:

Round

the

value

obtained

to

the

nearest

.01.

ci/

1

.00058

/L

(C3-C1) (C2-C1)

C4

(

+

(03-01)04-(04-02)

03

6.2

Calculate

the

value

of

the

loss

tangent

(dissipation

fac¬

tor)

of

each

specimen

tested

using

the

equation:

=

6.2832

C4

+

(

C4-C2

)

(

6.2832

C4

-

6.2832

C2)

Round

the

value

to

the

nearest

.0001

.

Note:

Values

should

be

calculated

using

a

computer

and

must

not

be

rounded

prematurely.

6.3

If

the

value

of

C2

changed

during

the

course

of

the

mea¬

surements,

use

the

final

values

of

C2

and

G2>

the

value

of

，

and

the

values

on

the

last

specimen

for

C3

and

C4

to

recalcu¬

late

the

DK

and

Df

of

the

final

specimen.

If

the

difference

in

DK

values

is

significant,

the

temperature

of

the

cell

must

be

con¬

trolled

more

precisely

during

the

measurement

period.

6.4

Calculate

the

average

permittivity

(dielectric

constant)

(if

more

than

one

specimen

was

tested).

6.5

Calculate

the

average

loss

tangent

(dissipation

factor)

(if

more

than

one

specimen

was

tested).

7

.0

Report

Figure 1

IPC-TM-650

Number

Subject Date

Revision

Page 4 of 4

12/87

2.5.5.3

Permittivity

(Dielectric

Constant)

and

Loss

Tangent

(Dissipation

Factor)

of

Materials

(Two

Fluid

Cell

Method)

7.1

Report

the

minimum,

maximum

and

average

values

of

the

permittivity

(dielectric

constant).

7.2

Report

the

average

value

of

the

loss

tangent

(dissipation

factor).

7.3

Report

the

specimen

preconditioning,

e.g.,

C-24/23/50.

7.4

Report

the

actual

test

conditions

for

temperature

and

humidity.

7.5

Report

if

the

specimen

was

built

up.

7.6

Report

the

approximate

cell

spacing.

7.7

Report

any

anomalies

in

the

test

or

variations

from

the

prescribed

procedures

or

tolerances.