IPC-TM-650 EN 2022 试验方法.pdf - 第576页

5.4.3 Test to Breakdown, Step-by-Step Test An initial voltage shall be applied equal to 50 of the breakdown voltage in the short-time test, adjusted as shown in Table 1. The voltage shall then be increased in equal incre…

opposing

cylindrical rods 6.4 mm in diameter, with edges

rounded to a radius of 0.75 mm. The upper movable elec-

trodes shall weigh 45.35g ± 2g. When 6.4 mm electrodes are

used, it is advisable that they be surrounded by guard elec-

trodes or shrouds.

4.5.1

The

dielectric strength of an insulating material varies

with the thickness of the material and the area and geometry

of the test electrodes, and these should be specified in the

specification. Tests made with different electrodes are not

comparable. Where materials are made up into forms of uni-

form thickness, such as sheets and plates, tests shall be

made upon that thickness of material. In other cases, a thick-

ness of the test specimen and diameter and shape of the

electrode have been selected, which are compatible with con-

venience of testing.

4.6

Equipment Testing Apparatus

4.6.1 For Tests Made in Air

Use

may be made of any well

designed oven of sufficient size to hold the test equipment. It

should be provided with some means of circulating air so that

approximately constant temperature is maintained around the

test specimen and with a thermometer or thermocouple for

measuring the temperature as near the point of test as prac-

ticable to the nearest 1°C.

4.6.2

For Test Under Oil

Use

may be made of an oil bath,

provided with some means for circulating the oil so that the

temperature is substantially uniform around the test speci-

mens and with a thermometer or thermocouple for measuring

the temperature as near the point of test as practicable to the

nearest 1°C.

Procedure

5.1 Test Medium

The

medium to be used in the tests

should be specified in the specification. In general, it is prefer-

able to test materials in the medium, whether air or oil, in

which they are to be used. Where conditions of use are not

well defined, materials should be tested in air up to the point

where the breakdown is so high that an excessive amount of

material is required to prevent flashover to excessive burning

of the surface. For specimens having a high breakdown, such

as the thicker and highgrade materials, it is usually necessary

to make dielectric strength tests under oil: however; it should

be understood that breakdown values obtained under oil are

not comparable with those obtained in air.

5.2

Preparing Specimens

5.2.1

the preparation of test specimens, care shall be

taken to have the surfaces adjacent to the electrodes parallel

and as plane and smooth as the material permits. The dielec-

tric strength of an insulating material varies with the thickness

of the test specimen. Therefore, tests on specimens of differ-

ent thicknesses are not comparable. The thickness used shall

be the average thickness of the sample measured as specified

in the specification involved.

5.2.2

The

dielectric strength of most insulating materials var-

ies with temperature and humidity. The test coiditions to be

used should be specified in the specification. Usually it is

desirable to determine the dielectric behavior of a material

over the range of temperature and humidity to which it is likely

to be subjected in use. When required, materials may be con-

ditioned in a suitably controlled chamber. The test specimen

shall be kept in the chamber long enough to reach a uniform

temperature and humidity prior to testing. When required, the

dielectric strength tests shall be made on the specimen while

still in the conditioning chamber. For purpose of tests, a high-

voltage conductor may be conveniently carried into the cham-

ber through an insulating bushing.

5.3

Positioning and Care of Electrodes

Electrodes

shall

be held truly coaxial. Where electrodes have flat test faces, the

latter shall be parallel to each other. The test faces shall be

kept smooth and polished and free from pitting.

5.4

Application of Voltage

5.4.1 Test for Specified Minimum Requirement

The

voltage

shall be applied and increased at a uniform rate from

zero to the value specified in the material specification and

shall be held at the value for the specified time. Unless other-

wise specified, the rate of rise per second shall be 5% of the

specified voltage. Note that this test is to check for ability to

withstand a specified voltage and not to determine the break-

down value.

5.4.2

Test to Breakdown, Short-time Test

The

voltage

shall be increased from zero to breakdown at a uniform rate.

The rate of rise shall be 0.5 or 1.0 kilovolts per second.

depending on the total test time required and the voltage-time

characteristic of the material. The rate of rise of voltage should

be specified in the material specification.

IPC-TM-650

Number

2.5.6.3

Subject

Dielectric

Breakdown Voltage and Dielectric Strength

Date

10/86

Revision

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5.4.3

Test to Breakdown, Step-by-Step Test

initial

voltage shall be applied equal to 50 of the breakdown voltage

in the short-time test, adjusted as shown in Table 1.

The voltage shall then be increased in equal increments as

stated in the various material specifications, the voltage being

held at each step for a definite time as stated in the specifica-

tions. The change from each step to the next higher shall be

made as rapidly as possible and the time of change included

in the succeeding test interval.

5.4.4

Test to Breakdown, Slow-Rate-of-Test

initial

voltage shall be applied equal to approximately 50% of the

breakdown voltage in the short time test, unless otherwise

specified. The voltage shall then be increased at a uniform

rate up to the point of breakdown. Unless otherwise specified,

the rate should be chosen to give approximately the same

voltage-time exposure of the test specimen, as provided in

the step-by-step test.

5.4.5

Determining Rate of Rise of Voltage

The

rate of

voltage rise may be calculated from measurements of time

required to raise the voltage between two prescribed values.

When motordriven regulating equipment is used, the speed-

control rheostat may be calibrated in terms of voltage rise for

any particular test transformer.

5.5

Number of Tests

Unless

otherwise specified, five tests

shall be made. If the average deviation from the mean

exceeds 10% or if any individual test deviates more than 15%

from the mean, five additional tests shall be made.

5.6

Report

The

report shall include the following data:

1. The average thickness of the sample

2. Breakdown voltage at each puncture

3. Volts per mil for each puncture

4. The average, maximum, and minimum volts per 0.0075

mm for each sample

5. The temperature of the surrounding medium should be

recorded

6. The RH% of the surrounding air

7. The conditioning treatment

8. The duration of the test

9. In the step-by-step test, the value of the initially applied

voltage and the voltage increment

10. In the slow rate of rise test, the value of the initially applied

voltage and the rate of rise of the voltage

11. The size and type of electrodes

12. The test medium (air or type of oil)

6 Notes

Due

to the high voltage used in this test method,

extreme caution should be exercised.

able 1 Application of Initial Voltage

Breakdown

voltage by

short-time method

Adjust 50% of breakdown

voltage to nearest

kilovolts or less 1.0 kilovolt (unless

otherwise speciﬁed)

Over 25 to 50 kilovolts.

inclusive

2.0 kilovolts

Over 50 to 100 kilovolts,

inclusive

5.0 kilovolts

Over 100 kilovolts 10.0 kilovolts

IPC-TM-650

Number

2.5.6.3

Subject

Dielectric

Breakdown Voltage and Dielectric Strength

Date

10/86

Revision

age3of3

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Scope

The

dielectric withstanding voltage test (also

called high-potential, over potential, voltage breakdown, or

dielectric strength test) consists of the application of a voltage

higher than rated voltage for a specific time between mutually

isolated portions of a PCB or between isolated portions and

ground. This is used to prove that the PCB can operate safely

at its rated voltage and withstand momentary over potentials

due to switching, surges, and other similar phenomena.

Although this test is often called a voltage breakdown or

dielectric strength test, it is not intended that this test cause

insulation breakdown or that it be used for detecting corona,

rather it serves to determine whether insulating materials

and/or conductor spacings are adequate.

Applicable Documents

None

Test Specimen

The

test specimen shall be comprised of

a minimum of two conductor lines per conductive layer, suffi-

cient to allow a voltage to be applied between adjacent con-

ductor patterns both between conductive layers and on the

same conductive layer (see 6.1).

Apparatus or Material

4.1

A high voltage source capable of supplying the specified

voltage with a tolerance of ± 5% (see 6.2).

4.2

voltage measuring device with an accuracy of 5%. If

leakage current measuring capability is required, the device

shall be capable of detecting the leakage current to within 5%

of the requirement.

4.3

Soft

bristle brush

4.4 Deionized

or distilled water (2 megohm-cm minimum

resistivity recommended)

4.5

Isopropyl

alcohol

4.6

Drying

oven

Procedure

5.1 Specimen Preparation

(see

6.3)

5.1.1

Positive,

permanent, and noncontaminating identifica-

tion of test specimen is of paramount importance.

5.1.2 Visually

inspect the test specimens for any obvious

defects, as described in the applicable performance specifica-

tion. If there is any doubt about the overall quality of any test

specimen, the test specimen should be replaced and this

replacement noted.

5.1.3

Solder

single stranded (to simulate discrete compo-

nent axial leads) polytetrafluroethylene (PTFE) insulated wires

in each of the connection points of the test specimens. These

wires will be used to connect the test patterns of the test

specimens to the high voltage source.

5.1.4

Wet

test lead terminals with deionized or distilled

water and scrub with a soft bristle brush for a minimum of 30

seconds. During the remainder of the test specimen prepara-

tion, handle test specimens by the edges only (see 6.4).

5.1.5

Spray

rinse thoroughly with deionized or distilled

water. Hold test specimen at an approximate 30° angle and

spray from top to bottom.

5.1.6

Wet

test lead terminals with clean isopropyl alcohol

and agitate for a minimum of 30 seconds. Scrub with a soft

bristle brush to remove flux residue.

5.1.7

Rinse

cleaned area thoroughly with fresh isopropyl

alcohol.

5.1.8

Dry

test specimens in a drying oven for a minimum of

three hours at an oven temperature of between 49 °C to

60 °C (120 °F to 140 °F).

5.1.9

Allow

the test specimens to cool to room temperature.

(see 6.5)

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.5.7

Subject

Dielectric

Withstanding Voltage, PCB

Date

05/04

Revision

Originating Task Group

Rigid Printed Board Performance Task Group

(D-33a)

Material

in this Test Methods Manual was voluntarily established by Technical Committees of 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 IPC.

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