IPC-TM-650 EN 2022 试验方法.pdf - 第460页

• 10 dB Attenuator HP8491B • Programmable Power Meter HP436A • Power Sensor HP8484A with 70 to 10 dBm range • IEEE 488 (GPIB) cables • Controlling computer with GPIB interface The above equipment is connected as explaine…

3.0

Test Specimen

Specimen

length corresponds to an

available fixture length L. Longer L values enable lower mini-

mum resonant frequencies to be achieved. L is also the length

dimension of the copper plates described in 5.0. Four types of

specimens can be used for this method, as shown in Figure

3.1

Type A

Two

25.4 mm wide by L long cards etched free

of copper cladding. These are placed on either side of a cen-

ter strip of smooth copper foil of specified thickness and width

and will be assembled between 25.4 mm wide by L long cop-

per foil cards.

3.2

Type B

One

25.4 mm wide by L long card with clad

copper on one side and copper etched off the other side, and

a second card of matching size with clad copper on one side

and copper etched off the other side except for a centered

strip of specified width extending to both ends of the card.

The copper free surface of the first card is assembled against

the etched strip of the other to form the stripline resonator.

3.3

Type C

Two

25.4 mm wide by L long cards with clad

copper on one side and copper etched off the other side

except for a centered strip of specified width extending to

both ends of the card. The etched strip surfaces of both cards

face together to form the stripline resonator.

3.4

Type D

Oversize

cards similar to type B are bonded

together with a selected bonding film and then trimmed to size

to form the stripline resonator assembly. This could be a test

coupon cut from a bonded stripline circuit board assembly.

For types B, C, and D, the specimen card should first be pre-

pared with about 5 mm or more excess length. Wide pressure

sensitive adhesive (PSA) tape can be used to mask the

ground plane side, and a narrow PSA tape can be used to

mask for the centered strip before etching off exposed cop-

per. Trimming the excess length after etching removes any

undercut areas at the ends. Trimming to length should be

done in a way that leaves the end surfaces with sharp edges

and no conductor edge distortion or smears over that surface.

Sanding specimens clamped between paper-phenolic lami-

nate drill-entry boards is an advised method for finishing the

end surfaces.

Type A specimens with untreated smooth copper foil will pro-

vide the most accurate values for tan δ, but will tend to have

a low bias on ε

Type C eliminates all clamped interfaces with

the air layer between the dielectric and the conductor to give

the most accurate ε

value

but, with the copper surfaces

treated for adhesion, tends to have a high bias on dissipation

factor. Type D gives a good measure of practical performance

in an application.

4.0

Suggested Electronic Apparatus

The

principal com-

ponents required for the test setup consist of the test fixture

described in 5.0 combined with the components described in

4.1, Figure 2, Type A and Type B, or preferably with the sys-

tem in 4.2, Figure 2, Type C.

4.1

A Test Setup for Computer Automation of Data

This

requires

a microwave signal source, an accurate means of

measuring the signal frequency, an accurate means for

detecting power level, and an accurate method of determin-

ing frequency values above and below the resonant frequency

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

specimen.

4.1.1

The

following components or equivalent, properly

interconnected, can be used most effectively with a computer

control program for automated testing.

• Sweep Frequency Generator Mainframe HP8350B

• RF Plug-In, 0.01 to 20 GHz HP83592A

• Power Splitter HP11667A

• Automatic Frequency Counter HP5343A

• Source Synchronizer HP5344A

Obtained as an interconnected assembly with the counter.

• Coaxial cables and adapters

IPC-125551-1

Figure

1 Exploded End Views of Stacked Specimen

Types A, B, C and D (See 3.0) with Copper Foil Thickness

Exaggerated and Including the Copper Plates (See 5.1.2)

and Steel Bars (See 5.1.1) of the Fixture

IPC-TM-650

Number

2.5.5.5.1

Subject

Stripline

Test for Complex Relative Permittivity of Circuit Board

Materials to 14 GHz

Date

3/98

Revision

age2of11

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•

10 dB Attenuator HP8491B

• Programmable Power Meter HP436A

• Power Sensor HP8484A with 70 to 10 dBm range

• IEEE 488 (GPIB) cables

• Controlling computer with GPIB interface

The above equipment is connected as explained in 4.1.1.1

through 4.1.1.3, and as illustrated in Figure 2, Type A.

4.1.1.1

RF Connections

The

power splitter connects

directly to the RF plug-in output. One output of the splitter

connects by RF cable to the counter input. The other output

is connected by RF cable to the attenuator which connects to

one of the test fixture probe lines.

4.1.1.2

Control Connections

Connections

between

counter and synchronizer are provided as specified by the

manufacturer. The FM output from the synchronizer connects

by BNC to the FM input on the sweeper. GPIB cables connect

in parallel to the sweeper, synchronizer, power meter, and

computer interface.

4.1.1.3

Other Connections

The

power sensor is con-

nected to the other probe of the fixture, and its special cable

connects into the power meter.

4.1.2

The

microwave signal source must be capable of pro-

viding 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 output that falls within a 0.1 dB range. When the

source is set for a particular frequency, the output must be

capable of remaining 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

0.05% or less and an accuracy of 0.08% or less. An error of

+8 MHz in measurement of a resonant frequency near 10 GHz

for a material 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 equation 5 in 7.2.

4.1.3

synthesized CW generator can be used to replace

the sweeper, plug-in, power splitter, connector, and source

synchronizer for the simpler set-up shown in Figure 2, Type B.

4.2

Automated Network Analyzer for the Test Setup

The

instrumentation described in 4.1 may be replaced with

either a scalar or vector network analyzer, with test cables

connected to the test fixture of 5.0 as the device under test

(DUT), as shown in Figure 2, Type A. Examples of automated

network analyzers known to be suitable include the Hewlett-

Packard 8510 vector network analyzer or the Wiltron Model

561 scalar network analyzer. These or equivalent may be

used.

IPC-125551-1

Figure

2 Schematic Drawings of Instrumentation

Setups Suitable for Measurements of Permittivity

IPC-TM-650

Number

2.5.5.5.1

Subject

Stripline

Test for Complex Relative Permittivity of Circuit Board

Materials to 14 GHz

Date

3/98

Revision

age3of11

电子技术应用　　　　　　　ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ

Such

instruments may be operated either manually or under

computer control with suitable programming to locate the

resonant frequency and the frequencies above and below

resonance where transmitted power is 3 dB below that at

resonance. Network analyzers have several advantages over

the instrumentation described in 4.1. Data collection is rapid

and may be continuously refreshed with averaging. The log

magnitude response curve for ratio of transmitted to incident

power (the S21 parameter) as dB versus frequency is visible

on a screen for easy verification of a valid resonance. A large

number of dB, frequency data points near the resonance, are

readily available for optional use of non-linear regression

analysis techniques to determine the frequency and Q values

with statistically better degrees of uncertainty than those

attainable by the three point (f

and f

)

method in either

section 6.2 or 6.3.

5.0

Test Fixture

5.1 Fixture Parts for Clamping

is the selected length for

the specimen. A fixture may include hardware for more than

one value of L. Suggested L values are 50.8, 76.2, 152.4, and

304.8 mm. Since the fundamental resonant frequency and its

harmonics are inversely proportional to the value of L for a

given ε

the selection of an L value determines the low fre-

quency at which the material may be measured for ε

and

tan

δ. Figure 1 shows the end views of a series of specimen con-

figurations and includes the parts for clamping.

5.1.1

For

each L value, two ground tool steel clamping bars

25.4 mm x 28.58 mm x (L-6.35), as shown in Figure 3. These

are intended to provide uniformly distributed force along the

length of the specimen, transferred through part 5.1.2. A rec-

ommended practice is to provide these with a small diameter

threaded rod, such as #4-40, centered on each end and

extending about 20 mm to serve as a means for attaching the

probe assembly of 5.2 used in 6.1.5 or the alignment jig of

5.1.3 used in 6.1.1.

5.1.2

For

each L value, two pure copper ground plates 25.4

mm x 9.52 mm x L with all edges sharp as in Figure 4. These

provide at the ends a copper surface perpendicular to the

specimen length direction, which serves as a contact area

over a range of specimen thicknesses for making ground con-

tinuity to the coaxial probe. When these are clamped with

5.1.1 as described in 6.1.1, the inside corners at each end

between the outer face of 5.1.2 and the end surface of 5.1.1

form reference locations equidistant from the center line of the

stripline resonator element that are used by the probe assem-

bly 5.2 to align the coaxial probe with that center line.

5.1.3

stacking alignment jig as used in 6.1.1 of an appro-

priate design. Figure 5 shows a suggested design.

5.1.4

low profile mechanical force gage with 4.45 kN

compression capacity such as a Dillon Model U, PN 30482-

0053, available from Dillon Quality Plus, Inc., 1140-T Avenida

Acaso, Camarillo, CA 993012. One is needed for each of part

5.1.5.

5.1.5

clamping arrangement with 5.1.4 properly mounted

in the line of force and with alignment parts for assuring the

line of force is properly located through the stack assembled

IPC-25551-3

Figure

3 Three View Drawing of a Steel Clamping Bar

(See 5.1.1) Cut to Length for the 50.8 mm L Value

(Extended #4-40 Threaded Rod Both Ends is Not Shown)

IPC-25551-4

Figure

4 Three View Drawing of a Copper Ground Plate

(See 5.1.2) for the 50.8 mm L Value

IPC-TM-650

Number

2.5.5.5.1

Subject

Stripline

Test for Complex Relative Permittivity of Circuit Board

Materials to 14 GHz

Date

3/98

Revision

age4of11

电子技术应用　　　　　　　ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ