IPC-TM-650 EN 2022 试验方法.pdf - 第572页

4.7 Large beaker or pan filled with ambient temperature dis- tilled water. 4.8 Rack for supporting and separating specimens in the 50 ° C water bath. 4.9 Lint free paper towels. 5.0 Procedure 5.1 Preconditioning Unless o…

1.0

Scope

This

method describes a technique for evaluat-

ing the ability of an insulating material to resist electrical break-

down perpendicular to the plane of the material when sub-

jected to short term, high voltages at standard AC power

frequencies of 50-60 Hz.

1.1

Applicability and Use of Data

This

method may be

used on material of any thickness up to approximately 0.125

inch, however, for material over 0.020 inch, other methods

such as dielectric breakdown are normally used to character-

ize a material’s electrical integrity. Results of this test may be

drastically affected by moisture content, and results obtained

using different preconditioning may not be comparable.

This method uses an oil medium to prevent flashover on a

small specimen and results may not be comparable to tests

run in air. Values obtained using this method should not be

used for predicting the insulating ability of ultra thin metal clad

laminates.

The values determined by this method generally decrease with

increasing specimen thickness for otherwise identical material.

This method is based on the techniques described in ASTM

D149.

2.0

Applicable Document

ASTM D149

Standard

Test Method for Dielectric Breakdown

Voltage and Dielectric Strength of Solid Electrical Insulating

Materials at Commercial Power Frequencies

3.0

Test Specimens

3.1 Number

Three

specimens shall be prepared unless

otherwise specified.

3.2

Form

Specimens

should be 4.0 inch ± 1.0 inch X 4.0 ±

1.0 inch; however, size is not critical as long as no flashover

occurs around the edges.

3.3

Location

Specimens

shall be cut by any convenient

means from both edges

and

the center of the laminate

(except no specimen shall be taken closer than 1 inch from

the edge of full size sheets).

3.4

Foil Clad Material

Foil

clad materials shall have all

metal cladding removed by etching and should be thoroughly

cleaned prior to conditioning or testing.

3.5

Uncured Material

Uncured

material must be fully

cured. Under normal conditions, two ply lamination is recom-

rnended for comparison of prepreg material. Single ply lami-

nates are recommended for cover lays and similar products

designed for single ply usage.

4.0

Apparatus/Materials

4.1

High

voltage breakdown tester, 25 KV, minimum with an

adequate current rating

a motorized control capable of 500

volts per second rate of rise and a meter capable of indicating

breakdown voltage within 5% over the entire range of actual

breakdown voltages (generally 1 KV to 20 KV).

4.2

Oil

tank filled with insulating oil

4.3

Electrode

test set 2 inch diameter electrodes with 1/4

inch radius on the edge of the electrodes and 50 g. ± 2g.

load applied by the weight of upper electrode (in air).

4.4

Two

high voltage test leads (leads rated in excess of the

tester voltage capability are recommended).

4.5

Micrometer

capable of resolving at least 0.0001 inch.

Note: For accurate measurement of material under 0.005 inch

test accuracy may be severely limited by the ability to measure

the specimen accurately.

4.6

Constant

temperature water bath, capable of maintain-

ing 50°C ± 2°C, filled with distilled water.

Edges: For a reinforced laminate the specimens shall be from opposite edges of the reinforcement.

2. Current capacity: 40 milliamps is normally satisfactory.

3. Insulating oil: Shell Dial AX Insulating Oil has been found suitable for breakdowns up to 100 KV.

The

Institute for Interconnecting and Packaging Electronic Circuits

2215 Sanders Road • Northbrook, IL 60062

IPC-TM-650

TEST

METHODS MANUAL

Number

2.5.6.2

Subject

Electric

Strength of Printed Wiring Material

Date

8/97

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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4.7

Large

beaker or pan filled with ambient temperature dis-

tilled water.

4.8

Rack

for supporting and separating specimens in the

50°C water bath.

4.9

Lint

free paper towels.

5.0

Procedure

5.1 Preconditioning

Unless

otherwise specified, the

specimen shall be conditioned for 48 hours (+2 hours –0

hours) in distilled water maintained at 50°C ± 2°C.

Following this the specimen shall be immersed in the ambient

temperature distilled water for 30 minutes minimum, 4 hours

maximum, to achieve temperature equilibrium without signifi-

cant changes in moisture content.

5.2

Test Conditions

The

test should be performed at

ambient temperature, 23°C ± 5°C. Relative humidity is not

significant as the tests are performed under oil.

5.3

Equipment Set Up

5.3.1

Set

the high voltage tester in accordance with the

manufacturer’s instructions so that the voltage range will be

adequate for the material being tested.

5.3.2

Set

up the control for testing using a 500 volt per sec-

ond rate of rise.

5.3.3

Attach

the leads (if not permanently wired) such that

the high lead is connected to one electrode and the ground

lead is connected to the other electrode.

5.4

Test

5.4.1

Remove

a preconditioned specimen from the ambient

temperature water and wipe dry with a lint free paper towel.

5.4.2

Determine

and record the thickness of the specimen

at four locations 1 inch from the edge at the midpoint of each

side.

5.4.3 Insert

the specimen into the test fixture centering it to

reduce chances of flashover.

5.4.4

Operate

the tester such that the voltage is applied with

a 500 volts per second increase and observe the point at

which the tester indicates a breakdown.

5.4.5 Record the breakdown voltage to the nearest .1 KV

for values over 10 KV and to at least the nearest 5% for all

lower values.

5.4.6

Remove

the specimen from the oil medium and verify

that a breakdown has occurred. If none is apparent reinsert

the specimen, carefully centering it, and retest as in 5.4.4 and

5.4.5. Note: If flashover occurs, either a larger specimen or

new oil must be used.

4.7

Test

the remaining two specimens as in 5.4.1 through

5.4.6.

6.0

Calculations

6.1

Calculate

the average thickness for each specimen from

the four individual values measured.

6.2

Determine

the electric strength in volts per mil for each

specimen by dividing the breakdown voltage expressed in

kilovolts by the thickness express in inches.

ES =

6.8 KV

.005

inch

1000 V

inch

1000

mils

= 1360 v/mil

6.3

Determine

the average electric strength by averaging the

individual values for each specimen. Round the average to the

nearest 10 volts/mil.

6.4

any specimen falls below the specification minimum,

calculate the percentage of the requirement:

min =

Lowest

Value

Spec

Value

X 100%

e.g. Value = 670 volts per mil

Specification = 750 volts per mil

min =

670

750

100% = .893 X 100% = .89 X 100% = 89%

7.0

Report

7.1

Report

the average value for electric strength in volts per

mil to the nearest 10 volts per mil.

IPC-TM-650

Number

2.5.6.2

Subject

Electric

Strength of Printed Wiring Material

Date

8/97

Revision

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7.2

Report

the minimum value in percent of requirement if it

is below the requirement for average electric strength.

7.3

Report the actual thickness range of the material tested

including the minimum and maximum individual thickness

measurements.

7.4

Report

any anomalies in the test or any variations from

the prescribed procedures or tolerances.

8.0 Notes

8.1 This

test method may be modified to an air medium to

predict performance in normal environments more accurately,

however, unless the electrode is effectively guarded, the

breakdown will generally occur in air.

8.2

For

testing the effect of copper foil on clad laminate

under 0.005 inch it is suggested that two inch circular elec-

trodes be left on the 4 inch X 4 inch specimen by etching. The

ground electrode may be slightly larger to assure registration.

8.3

For

materials which are compressible, a standard pres-

sure of 25 PSI is to be used for determining specimen thick-

ness.

IPC-TM-650

Number

2.5.6.2

Subject

Electric

Strength of Printed Wiring Material

Date

8/97

Revision

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