IPC-TM-650 EN 2022 试验方法.pdf - 第432页

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/…

5.4.2

Record

the capacitance of the air filled cell as C

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 C

5.4.6

Remove

the first specimen and obtain C

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 C

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 G

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 C

and

the value of the conductance as G

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 C

and

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 C

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:

DK =

1.00058

(C3−C1)(C2−C1) C4

(C3−C1) C4 −(C4−C2) C3

Round

the value obtained to the nearest .01.

6.2

Calculate

the value of the loss tangent (dissipation fac-

tor) of each specimen tested using the equation:

DF =

6.2832

* .99942 C1−C4

C4−C2

6.2832

−

6.2832

Round

the value to the nearest .0001.

Note: Values should be calculated using a computer and must

not be rounded prematurely.

6.3

the value of C

changed

during the course of the mea-

surements, use the final values of C

and

the value of C

and

the values on the last specimen for C

and

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

IPC-TM-650

Number

2.5.5.3

Subject

Permittivity

(Dielectric Constant) and Loss Tangent (Dissipation

Factor) of Materials (Two Fluid Cell Method)

Date

12/87

Revision

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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.

IPC-2553-1

Figure

IPC-TM-650

Number

2.5.5.3

Subject

Permittivity

(Dielectric Constant) and Loss Tangent (Dissipation

Factor) of Materials (Two Fluid Cell Method)

Date

12/87

Revision

age4of4

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1.0

Scope

1.1 Summary

This

method is intended for the rapid mea-

surement of the X-band (8.00 to 12.40 GHz) apparent relative

stripline permittivity (see 9.1) and loss tangent of metal clad

substrates. Measurements are made under stripline condi-

tions using a resonant element pattern card, which is sepa-

rated from the ground planes by sheets of the material to be

tested. Further information about this method may be found in

ASTM D3380-75.

1.2

Definitions

Terms

used in this method include:

Complex Relative Permittivity The values for relative per-

mittivity and dissipation factor considered as a complex num-

ber.

Permittivity Dielectric constant (see IPC-T-50) or relative per-

mittivity. The symbol used in this document is ε

’orκ’ are

sometimes used.

Relative Permittivity A dimensionless ratio of absolute per-

mittivity of a dielectric to the absolute permittivity of a vacuum.

Loss Tangent Dissipation factor (see IPC-T-50), dielectric

loss tangent. The symbol used in this document is tan δ (see

9.2).

1.3

Limitations

The

following limitations in the method

should be noted. Users are cautioned against assuming the

method yields permittivity and loss tangent values that directly

correspond to applications. The value of the method is for

assuring consistency of product, thus reproducibility of results

in fabricated boards.

1.3.1

The

measured effective permittivity for the resonator

element can differ from that observed in an application.

Where the application is in stripline and the line width to

groundplane spacing is less than that of the resonator ele-

ment in the test, the application will exhibit a greater compo-

nent of the electric field in the X, Y plane. Heterogeneous

dielectric composites are anisotropic to some degree, result-

ing in a higher observed ε

for

narrower lines.

Microstrip lines in an application may also differ from the test

in the fraction of substrate electric field component in the X, Y

plane.

Bonded stripline assemblies have air excluded between

boards, thus tend to show greater ε

values.

1.3.2

High

degrees of anisotropy of some composites can

result in an increased degree of coupling of the resonant ele-

ment, resulting in a falsely lower Q value. If a correction is not

applied either mathematically as in 7.2.2 or by deviating from

the probe gaps specified for the test pattern, an upward bias

in the calculated loss tangent will result.

1.3.3

The

sensitivity of the method to differences in ε

specimens

is impaired by the fact that the resonator pattern

card remains as part of the fixture and at the same time con-

stitutes a significant part of the dielectric involved in measure-

ments.

1.3.4

The

method does not lend itself to use of stable ref-

eree specimens of known electric properties traceable to The

National Institute of Standards and Technology (NIST).

2.0

Applicable Documents

2.1 IPC

IPC-T-50

Terms

and Definitions

IPC-MF-150

Metal

foil for Printed Wiring Application

IPC-TM-650

Method

2.3.7.1, Cupric Chloride Etching

IPC-TM-650

Method

2.5.5.3, Permittivity (Dielectric Con-

stant) and Loss Tangent (Dissipation Factor) of Materials (Two

Fluid Cell Method)

ASTM

D3380-75

Standard

Method of Test for Permittivity

(Dielectric Constant) and Dissipation Factor of Plastic-Based

Microwave Circuit Substrates

3.0

Test Specimen

All

metal cladding shall be removed

from the material to be tested by any standard etching pro-

cess, including rinsing and drying; however, IPC-TM-650,

Method 2.3.7.1, shall be used as a referee procedure. The

test specimen shall consist of a set of two sheets (or two

packets of sheets) of a preferred size of at least 51 mm x 69

mm.

3.1 A

smaller size may be used if it has been shown not to

affect results. The minimum vertical dimension must extend

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.5.5.5

Subject

Stripline

Test for Permittivity and Loss Tangent

(Dielectric Constant and Dissipation Factor) at X-Band

Date

3/98

Revision

Originating

Task Group

High Speed/High Frequency Test Methods

Subcommittee (D-24)

Material

in this Test Methods Manual was voluntarily established by Technical Committees of the IPC. This material is advisory only

and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this

material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement.

Equipment referenced is for the convenience of the user and does not imply endorsement by the IPC.

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