IPC-TM-650 EN 2022 试验方法.pdf - 第433页

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 m…

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.

age1of25

ASSOCIA

TION CONNECTING

ELECTRONICS INDUSTRIES

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from

the base boards to the top of the 25.4 mm x 51 mm area

to which clamping pressure is applied. The minimum horizon-

tal dimension must be enough to extend at least 6.5 mm

beyond the center line of the vertical portion of the probe line

on either side. For the pattern card of Figure 4 and fixture of

Figure 12, these minimums are 38.1 mm x 68.6 mm. For the

smaller size, the clamp force in 6.1 or Table 1 is not changed

because the effective area over which the force is applied is

not reduced. The test fixture is designed to accommodate a

total specimen thickness of either 3.18 mm ± 0.22 mm or

2.54 mm ± 0.18 mm from an even number of layers.

NOTE: Testing of built-up specimens introduces error, which

can exceed 5% due to air gaps. Exact correlation factors and

techniques must be agreed upon or other methods of test

used. The 1 MHz method of IPC-TM-650, Method 2.5.5.3,

can be used with a correction factor based on tests of

samples of the nominal thickness of Table 1 using both tech-

niques.

With some material types not based on woven fabric rein-

forcement, it is possible to machine specimens to achieve the

nominal thickness for test.

4.0

Suggested Electronic Apparatus

The

principal com-

ponents required for the test setup consist of the test fixture

described in 5.0, a microwave signal source, an accurate

means of measuring the signal frequency, an accurate means

for detecting power level, and an accurate method of deter-

mining frequency values above and below the resonant fre-

quency at the half-power level for the test fixture loaded with

the specimen.

The microwave signal source must be capable of providing an

accurate signal. During the required time period and range of

frequency needed to make a permittivity and loss tangent

measurement, the source must provide a leveled power out-

put that falls within a 0.1 dB range. When the source is set for

a particular frequency, the output must be capable of remain-

ing within 5 MHz of the set value for the time required to make

a measurement.

The means for measuring frequency shall have a resolution of

5 MHz or less and an accuracy of 8 MHz or less. An error of

+8 MHz in measurement of a resonant frequency for a mate-

rial with nominal permittivity of 2.50 represents a -0.004 error

in permittivity.

The means for detecting the power level shall have a resolu-

tion of 0.1 dB or less and be capable of comparing power

levels withina3dBrange with an accuracy of 0.1 dB. An error

of 0.1 dB in estimating half power frequency points can result

in an error in the loss tangent of about 0.0001 for a material

with 2.5 permittivity. See 7.2, equation 5.

4.1

Manual Test Setup

The

method of determining the

half-power points depends partly on the type of signal source

used. If the power input to the test fixture is maintained con-

stant as the frequency is varied, then an SWR meter may be

used to determine the half-power points at the output of the

test fixture. This may be accomplished by using a leveled

sweep generator or by using a tunable klystron (at a consid-

erable savings) and manually adjusting the power input to the

test fixture to a prescribed level by use of a variable attenua-

tor. A typical equipment list is shown below. Equivalent makes

and models of equipment may be substituted where it can be

shown that equivalent results are obtained. For example, if a

leveling system is not used and the power output of the

source varies widely with frequency, a ratiometer may be sub-

stituted for the two SWR meters. If only permittivity is desired,

it is not necessary to level the input.

The following equipment, or equivalent, may be used.

• Sweep Frequency Generator H.P. 8350B or 8620C

• X-Band Frequency Plug in Unit H.P. 83545A or 86251A

• Frequency Meter H.P. X532B

• Crystal Detector (2) H.P. 423B (Neg)

• Matched Load Resistor for one Crystal Detector H.P.

11523A, opt. 001

• SWR Meter (2) H.P. 415E

• Directional Coupler HP 779D

• 10 dB Attenuator H.P. 8491B

• 8.9 kN Dillon Force Gauge, Compression Model X, Part

Number 381612301, with ± 1% full scale accuracy

• Vise or press that is able to exert controlled 4.45 kN force

on the test fixture and that opens at least 127 mm to accept

the force gauge and test fixture

• Semi-rigid Coaxial Cable and Connectors

• Waveguide to Coaxial Adapters (2) H.P. X281A

• The measuring equipment shall be connected as shown on

Figure 1.

4.2

A Test Setup for Computer Automation of Data

The

following

components or equivalent, properly interconnected,

can be used most effectively with a computer control program

for automated testing.

IPC-TM-650

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

age2of25

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