IPC-TM-650 EN 2022 试验方法.pdf - 第429页

1.0 Scope 1.1 Purpose This method is suitable for determining the volume permittivity, (dielectric constant) and loss tangent (dis- sipation factor) of insulating materials at 1 MHz. It is not dependent on either direct …

5.3.2

Dissipation Factor

The

dissipation factor value is

read directly from the digital display.

5.4

Report

The

report shall contain the following:

1. Measurement of effective thickness of specimens tested.

2. Capacitance values of the specimens tested.

3. Calculated dielectric constants and averaged measure-

ment.

4. Dissipation factor values and averaged measurement.

6.0 Notes

6.1

The

dielectric constant is defined as the ratio of the

capacitance with the test material between the two plates to

the capacitance of air between two plates.

6.2

The

dissipation factor of a dielectric material is the rela-

tionship between the permittivity (capacitance of material) and

conductivity (ability to conduct or the reciprocal of the electri-

cal resistivity) measured at a given frequency.

IPC-2552-1

Figure

1 Special Test Fixture for Dielectric Constant and Dissipation Factor Measurements

IPC-TM-650

Number

2.5.5.2

Subject

Dielectric

Constant and Dissipation Factor of Printed Wiring

Board Material—Clip Method

Date

12/87

Revision

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1.0

Scope

1.1 Purpose

This

method is suitable for determining the

volume permittivity, (dielectric constant) and loss tangent (dis-

sipation factor) of insulating materials at 1 MHz. It is not

dependent on either direct or indirect measurement of speci-

men thickness and therefore is very useful for thin films and

laminates but may also be used on specimens up to approxi-

mately 6.35 mm [0.25 in] thick.

It is useful for all ranges of permittivity and for loss tangent as

low as 0.0005 providing the range and accuracy of the bridge

used are adequate.

1.2

Description of Method

The

two fluid method utilizes

air as one fluid and a suitable liquid, normally Dow 200 1.0CS

silicone fluid, as the second. Using an established value for

the permittivity of air, the values for the permittivity of the fluid

and the sample may easily be calculated. The cell spacing is

fixed during all readings but does not need to be known accu-

rately for the series of readings required. Since specimens do

not require any electrodes to be applied and since many

specimens can be measured at one time without changing

any spacings or machine settings, the method is not only very

accurate but very rapid.

The method has been used for measurement of PTFE and

epoxy glass laminates and flexible films, e.g., polyimide.

Reproducibility lab to lab is excellent for permittivity provided

minimal precautions are observed and bridge accuracy is

appropriate. On most materials, the effects of small changes

in moisture or temperature are larger than any error due to the

method. Lab to lab correlation on stable material such as

PTFE have shown results to be consistently within 0.005 or

(0.20%).

2.0

Applicable Document

3.0 Test Specimens

3.1 Number

Unless

otherwise specified in the material

specification, one specimen is adequate for materials which

are uniform, e.g., unreinforced plastics. For woven reinforced

materials where resin content may vary, at least 2 specimens,

representing the thinnest and thickest part of the sample,

should be tested. For material with random reinforcement, a

minimum of three specimens from the edge and center of the

sheet are recommended to characterize variation within the

sheet.

3.2

Form

Individual

specimens shall be 81.3 mm ± 1.3 mm

x 81.3 to 101.6 mm [3.2 in ± 0.05 in x 3.2 in to 4.0 in] x thick-

ness.

For materials under 0.254 mm [0.010 in], individual specimens

should be stacked to a minimum of 0.381 mm [0.015 in] to

maximize accuracy. Thinner specimen buildups may be used

if the correlation with the 0.381 mm [0.015 in] specimen is

within the required accuracy for the particular equipment, cell

spacing and material being tested.

3.3

Foil Clad Materials

All

foil clad materials shall have the

metal cladding completely removed by etching and shall be

rinsed and dried prior to conditioning.

3.4

Marking

Mark

each specimen in the upper left corner

with an engraving pencil or an ink which is not soluble in the

Dow Corning 200 fluid.

4.0

Apparatus/Materials

4.1

MHz Capacitance Bridge with 0-200 (or 0-100) pf

range.

4.2

Cell

Balsbaugh

LD-3

equivalent (see Figure 1) three

terminal cell. Note: For accuracy of 1% or better, room tem-

perature must not vary more than 1°C during measurements.

Temperature control is necessary if laboratory variation

exceeds these limits.

Capacitance Bridge—Suggested is Boonton 76A automatic capacitance bridge. This model has adequate capacitance range and adequate conductance resolu-

tion (0.001 microsiemen) to permit measurement of dissipation factors down to approximately 0.0005. Other bridges, e.g., Boonton 75D, are also adequate for

low loss materials and some other bridges may be suitable for higher loss materials, such as epoxy where dissipation factors exceed 0.01 and resolution of 0.01

microsiemen or even 0.1 microsiemen may be adequate.

2. Balsbaugh LD-3 Gillian and Co,, Watertown, MA, (617) 624-5688 or Zincast Corporation, 44 Homestead Ave., Stanford, CT 06902, (203) 359-0109

The

Institute for Interconnecting and Packaging Electronic Circuits

2215 Sanders Road • Northbrook, IL 60062

IPC-TM-650

TEST

METHODS MANUAL

Number

2.5.5.3

Subject

Permittivity

(Dielectric Constant) and Loss Tangent

(Dissipation Factor) of Materials (Two Fluid Cell

Method)

Date

12/87

Revision

Originating Task Group

N/A

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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4.3

Test Leads

RG 58/U coax cables approximately

304.8 mm [12 in] long with suitable connectors for the bridge.

One lead shall have a banana plug (high lead) and the low lead

should have a GR874

the cell end. (Note: The use of a

G874-QBJA

instead

of the standard GR874 will permit a

BNC

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

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°C ± 2°C50±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°C ± 2°C.

Note: Variation should not exceed 1°C 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°C ± 1°C.

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 100 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 10% 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.

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

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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