IPC-TM-650 EN 2022 试验方法.pdf - 第437页

Height of base plate from step to top edge Height of clamp block and specimen Height from launcher body to resonator center line Width of clamp block and specimen Horizontal center line distance between probe lines Probe…

The

test pattern card shall have a permittivity equal to the

nominal value of the type being tested with a tolerance of ±

2.5% of the nominal value (measured by stacking sufficient

plies to the total thickness requirement of a specimen as

above. Use a photo resist and etching method capable of

reproducing circuit dimensions with ± 0.025 mm tolerance. All

copper shall be removed from the other side of the test pat-

tern card. See 9.7, Note, for special treatment of ceramic-

PTFE substrate types.

The pattern card of Figure 4 is 68.6 mm wide by 55.4 mm

high and is designed for the fixture hardware in Figure 5

through Figure 14. The length is cut so that when the pattern

card is clamped for the lap joint with the striplines on the base

card, the resonator is centered in the 51 mm high area above

the base plates of the fixture. For materials with permittivity

values higher than the nominal 2.50 shown in Table 1, please

see 5.2 for a discussion of recommended fixture modifica-

tions.

Probe line widths are based on ground plane spacing taken

as twice the nominal thickness of the two specimens plus

thickness of the pattern card and its 0.034 mm copper foil

pattern and computed as if the stripline were centered

between ground planes

(1,3)

Chamfer

values are based on published design curves

(2)

The

length of the four node resonator is given in Table 1.

Resonators of lower node values for the purpose of measur-

ing ∆L according to 6.1, will be proportionately shorter with

the probe lengths modified so that the gap is the same.

The values for conductor loss, 1/Q

in Table 1 are calculated

from known properties of copper, the test frequency, the cal-

culated characteristic impedance of the section of stripline

comprising the resonator, and its cross-sectional geometry

using published formulas

(1)

The values shown are usually

biased low giving a high bias to loss tangent results, because

conductor actually used may not have a smooth surface and

may include oxides, microvoids, or other sources of higher

resistivity.

5.2

Fixture Modifications for High Permittivity Materi-

als

Modification

of the fixture design of Figure 5 through Fig-

ure 14 and pattern card dimensions in Figure 4 are recom-

mended to overcome problems experienced with extraneous

transmissions and resonances at frequencies near the desired

resonant peak.

5.2.1 Replace

the coax-stripline launcher shown in Figure 7.

The part suggested has a tab width of 1.27 mm and may be

replaced with Omni-Spectra Part No. 2070-5029-02, or

equivalent, intended for 1.57 mm ground plane spacing and

with a tab width of 0.635 mm. A further acceptable alternative

is to redesign the base plates to accept another type of

coaxial fitting such as a flange mount jack, which can be

modified to provide a smooth, low-reflection transition from

3.0 mm semirigid cable with Z

50 Ohm, low permittivity

insulation into stripline with Z

50 Ohm, and high permittiv-

ity insulation in the fixture.

5.2.2

the stripline launcher in 5.2.1 is used, the edge at

the step to accommodate the launcher body on the base

plate should be machined with a slight undercut for an acute

included angle of about 80°. This, combined with a means to

press the launcher body axially against the edge, will assure a

well-defined ground connection from coax to stripline. A

poorly defined ground connection with ground current path

length varying or longer than that of the signal conductor has

been found to give rise to scattering, reflections, and reso-

nances in the open ended probe line that are evident as extra-

neous fixture transmissions that may distort the resonant peak

to be measured.

5.2.3

Omit

the conductor lap joints but keep the extended

base cards in the fixture assembly. See figures 13 and 14.

With high permittivity materials, the lap joint also gives rise to

unwanted scattering, reflections, and resonances in the open-

ended probe line, as discussed in 5.2.2. For this purpose the

resonator pattern card will have a longer vertical dimension to

extend down to the launcher pin replacing the spacer board

in Figure 13. It should still center the resonator in the clamp-

ing block area. The base dielectric boards will be etched free

of metal. The ground plane foils will also extend down to the

launcher.

The feature of extending the base dielectric boards upward

above the base plates is to be retained as a means to prevent

premature damage to the resonator pattern card with

repeated loading and unloading of the fixture. The base plate

with the deeper step will be on the side toward which the

resonator pattern faces to avoid straining the offset launcher

tab during assembly.

5.2.4

Scale

down the fixture dimensions to move remaining

probe line resonances away from the resonant frequency of

interest. For ε

10.5 material, the following dimensions were

found effective.

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

age4of25

电子技术应用　　　　　　　ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ

Height

of base plate from step to top edge

Height of clamp block and specimen

Height from launcher body to resonator

center line

Width of clamp block and specimen

Horizontal center line distance between

probe lines

Probe length from launch to gap

8.53

25.4

21.23

55.9

30.5

25.81

5.2.5 Thinner

copper cladding (weight Q) for the resonator

pattern card is recommended as mentioned in 5.1. If weight

Q is used, the embedding process discussed in note 9.7 can

be avoided. Experience has indicated that this reduction in

thickness has not impaired the loss tangent values obtained

by the method.

5.3

Older Fixture Design

older acceptable alternate

test fixture design is shown in Figure 15. This is included since

fixtures of this type are in service at various laboratories. Com-

pared to 5.1, fixtures of this design depend on ambient con-

ditions for temperature control. Changing resonator test pat-

tern cards is less convenient.

5.4

Temperature Control

is a well-known fact that PTFE

and composites containing it show a room temperature tran-

sition in the crystalline structure that produces a step-like

change in the permittivity. This temperature region should be

avoided.

Normally, control of ambient temperature is adequate for rou-

tine measurements. A means other than ambient temperature

to control fixture temperature facilitates collecting data on the

variation of permittivity with temperature. With the test fixture

of 5.1., use 6 mm inside diameter tubing for circulating fluid to

control temperature. The following items are needed to com-

plete the temperature control system.

5.4.1

Laboratory

Immersion Heating Bath/Circulator, such

as Haake Model D1, Lauda Model MT, or equivalent and a

small capacity bath. The Immersion Heating Bath/Circulator

shall be connected to the clamping blocks in series with a

return line to the bath.

5.4.2

Two

fine diameter thermocouple probes with leads

and suitable instrumentation for readout or recording of tem-

perature. A digital thermometer, such as Ohmega Model DSS

115 or equivalent, is used for monitoring temperature.

6.0

Measuring Procedure

6.1 Preparation for Testing

The

actual length of the reso-

nator element shall be determined by an optical comparator or

other means capable of accuracy to 0.005 mm or smaller.

Unless otherwise specified, specimens shall be stored before

testing at 23°C + 1-5°C/50% ± 5% relative humidity (RH). The

referee minimum storage time is 16 hours. Shorter times may

be used if they can be shown to yield equivalent test results.

If electronic equipment, as listed in 4.2, is used, it shall be

turned on at least one half hour before use to allow warm-up

and stabilization. The automatic frequency counter listed in

4.2 is provided with temperature control of the clock crystal

that operates even when the power switch is off. Care should

able 1 Dimensions for Stripline Test Pattern Cards in Millimeters

Nom. ε

Nom.

Thk.

Pattern

Card

Thk.

Probe

Width

Chamfer

X, Y

Probe

Gap

Resonator

Width

Resonator

Length 4

Node

1/Q

Conductor

Loss

2.20

1.59 0.22 2.74 3.05 2.54 6.35 38.1 0.00055

2.33 1.59 0.22 2.67 2.92 2.54 6.35 38.1 0.00055

2.50 1.59 0.22 2.49 2.79 2.54 6.35 38.1 0.00055

3.0 1.59 0.22 2.13 2.41 2.54 5.08 31.8 0.00058

3.5 1.59 0.22 1.85 2.16 2.54 5.08 31.8 0.00058

4.0 1.59 0.22 1.62 1.93 2.54 5.08 31.8 0.00058

4.5 1.59 0.22 1.45 1.73 2.54 5.08 31.8 0.00058

6.0 1.59 0.22 1.07 1.30 2.29 3.81 25.4 0.00062

6.0 1.27 0.22 0.86 1.07 2.29 3.81 25.4 0.00072

10.5 1.27 0.22 0.41 0.54 2.03 2.54 17.3 0.00079

Standard

clamp force for all the above is 4.45 ± 0.22 kN

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

age5of25

电子技术应用　　　　　　　ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ

taken to assure that power is continuously supplied to this

unit to avoid a longer warm-up time. Other equipment using

vacuum tube devices will require a longer warm-up time as

specified in the manufacturer’s literature.

The temperature of the test fixture shall be in the range of

22°C to 24°C, unless otherwise specified. If this standard

temperature is to be used and the temperature of the fixture

is to be controlled by the ambient conditions in the testing

laboratory, then the laboratory shall be maintained at 22°C to

24°C and the fixture shall be stored in the laboratory for at

least 24 hours prior to use.

If non-standard temperature is specified and the fixture of 4.1

is used with the temperature control apparatus described in

4.2, then the rest of this paragraph applies. Prior to making

electrical measurements, the circulator is started and adjusted

to within 1°C of the desired test temperature. The time

required for stabilization depends on the specific temperature

control apparatus in use, the size of the circulation bath tank,

and the temperature selected. Additional stabilization time will

be required for each specimen to come to the set temperature

after it has been clamped in the fixture.

The test fixture containing the test specimens shall be placed

in the clamping fixture and the specified force of 4.45 ± 0.22

kN is applied through the calibrated force gauge to the 1290

area

centered directly over the resonant circuit as shown

in the assembly of Figure 12, Figure 13, or Figure 15.

6.2

Manual Measurement of the Specimen

The

follow-

ing procedure is applicable where equipment as described in

4.1 is available. The equipment of 4.2 could also be operated

manually. The stripline resonator formed by the fixture pattern

card and ground planes with the specimen cards inserted is

referred to as a cavity. The sweep oscillator is referred to here

as the sweeper.

6.2.1

Determination of Cavity Resonant Frequency

The

resonant

frequency of the circuit shall be found by scanning

the sweeper over the expected transmission range of the test

resonator. The sweeper shall be precisely adjusted to the fre-

quency that produces a maximum reading of the SWR Meter

No. 1. The frequency meter shall then be adjusted for a mini-

mum reading of the SWR Meter No. 2. Record the resonant

frequency. The input selector of the SWR Meter No. 1 should

be set for low impedance input for proper square law detec-

tion.

6.2.2

Determination of Cavity Half-Power Points

With

the

incident signal having been set to maximum resonator

transmission, adjust the gain of the SWR Meter No. 1 until the

meter reads 0 dB. The frequency of the sweeper shall then be

adjusted to give 3 dB readings both above and below the

maximum transmission frequency. Measure each frequency

with the frequency meter and record the results:

• f1: above the maximum transmission frequency

• f2: below the maximum transmission frequency

6.3

Automated Measurement of the Specimen

For

automated system to be used in performing the measure-

ment, computer software is needed that will collect paired

values of frequency and transmitted power. From this data,

the frequency for maximum power transmission and the fre-

quencies of the half power points are determined. The com-

puter program may optionally include computation of permit-

tivity and loss tangent as described in 7.0. Results and

collected data may be displayed on the screen, stored in a

disk file, sent to a printer, or any combination of these.

In one possible mode of operation with the equipment

described in 4.2, the following sequence of steps is performed

as many times as necessary to get enough data to complete

the test procedure. The computer is designated as the con-

troller on the GPIB.

6.3.1

The

computer sets the sweeper to a selected carrier

wave frequency without an AM or FM audio signal to a desired

output power level, such as 10 dBm.

6.3.2

The

same frequency is given to the synchronizer with

instructions to lock the frequency of the sweeper to the speci-

fied value.

6.3.3

The

computer checks the synchronizer for status until

the status value drops to zero, indicating the frequency is

locked.

6.3.4

The

power meter reading is obtained by the computer.

Since it takes a finite amount of time for the power sensor to

stabilize, either a delay is used or the reading may be taken

repeatedly until consecutive readings meet a given require-

ment for stability.

6.4

Use of the Network Analyzer for Measurement of

the Specimen

automated network analyzer may be

used either by operating the front panel controls manually or

under computer control with suitable specialized software.

The fixture with the specimen is connected by test cables and

adapters as a device under test. Set up the instrument so the

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

age6of25

电子技术应用　　　　　　　ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ