IPC-TM-650 EN 2022 试验方法.pdf - 第657页

IPC-263-01 Figure 1 Moisture and Insulation Resistance T est Graph IPC-263-2 Figure 2 Insulation Resistance Coupon E (See T able 7-3), mm [in] IPC-TM-650 Number 2.6.3 Subject Moisture and Insulation Resistance, Printed B…

5.1.8

Specimen

preparation for METHOD B is now com-

pleted, continue the procedure with 5.2.

5.1.9

METHOD A - Application of Conformal Coating.

Continuation of Sample Preparation

Apply

coating to the

appropriate area of the test specimen, in a manner concurrent

with user’s production techniques or as specified by the coat-

ing supplier.

5.1.10

After

the application of coating, the test specimens

are to be cured, as specified by the coating supplier.

5.1.11

After

curing, stabilize to ambient temperature.

5.2

Test

5.2.1

Take

the initial insulation resistance measurements at

laboratory ambient temperature. Apply the voltage specified in

the procurement documentation on the test specimen’s test

points as specified in 5.2.2 with the resistance meter, and

take the reading after measurement stabilization.

5.2.2

Test

points on the test specimens shall be connected

in a manner that will allow adjacent conductor patterns, both

between conductor layers and on the same conductor layer,

to alternate between the positive (+) and negative (–) terminals

of the power supply or resistance meter.

5.2.3

Place

test specimens in chamber in a vertical position

and under a condensation drip shield. Connect the DC volt-

age source to the test specimen test points as indicated in

5.2.2. Apply a 100 ± 10 volts DC polarization voltage to all test

specimens.

5.2.4

Expose

test specimens to one of the following speci-

fied test conditions: (See 6.4.)

(a) Class1–35°C±5°C[95°F±9°F], 85% to 93% rela-

tive humidity, for four days (static).

(b) Class2–50°C±5°C[122 °F ± 9 °F], 85% to 93% rela-

tive humidity, for seven days (static).

+5/-2 °C [77 °F +9/-4 °F] to 65 °C ± 2 °C [ 149 °F ± 4 °F],

85% to 93% relative humidity, 160 hours total.

5.2.4.1

Temperature cycling

The

following constitutes

one complete cycle (for the Class 3 Test Condition).

(a) Start test at 25 °C +5/-2 °C [77 °F +9/-4 °F], and raise

temperature at 65 °C ± 2 °C [149 °F ± 4 °F], over a time

span of 150 minutes ± 5 minutes.

(b) Maintain temperature at 65 °C ± 2 °C [149 °F ± 4 °F] over

a time span of 180 minutes ± 5 minutes.

25 °C +5/-2 °C [77 °F +9/-4 °F] over a time span of 150

minutes ± 5 minutes.

There shall be no delay between cycles. Polarizing voltage

shall be maintained throughout the 20 cycle period. The

humidity may drop a minimum of 80% relative humidity when

going from high to low temperature. See Figure 1 for a graphi-

cal illustration of temperature cycling.

5.3

Measurement

5.3.1

Disconnect

100 volts DC polarized voltage source

before taking any insulation resistance measurement. Insula-

tion resistance shall be read as specified in 5.2.1. Voltage

polarity for measurement should be identical to that of the

polarizing voltage.

5.3.2

Final

resistance measurements shall be made after

removal of specimen from the chamber, and after one hour

and before two hours stabilization at laboratory ambient tem-

peratures.

Any reasons for deleting values, e.g., scratches, condensa-

tion, bridged conductors, etc., must be noted.

5.4

Evaluation

5.4.1

Each

test specimen shall be evaluated for insulation

resistance quality for its class, following and/or during the ini-

tial, wet and/or dry conditions, as applicable.

5.4.2

After

completion of all electrical testing, the test speci-

mens shall be examined for evidence of mealing, blistering,

delamination, or other forms of degradation, following 24 hour

stabilization at laboratory ambient temperatures.

6 Notes

6.1

Test Pattern Examples

6.1.1 ‘‘Y’’ Patterns

There

are a variety of ‘‘Y’’ test patterns

(also referred to as ‘‘E’’ test coupons) in various specifications

within the industry. See Figure 2 for an illustration of ‘‘Y’’ pat-

tern test coupons.

IPC-TM-650

Number

2.6.3

Subject

Moisture

and Insulation Resistance, Printed Boards

Date

05/04

Revision

age2of4

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IPC-263-01

Figure

1 Moisture and Insulation Resistance Test Graph

IPC-263-2

Figure

2 Insulation Resistance Coupon E (See Table 7-3), mm [in]

IPC-TM-650

Number

2.6.3

Subject

Moisture

and Insulation Resistance, Printed Boards

Date

05/04

Revision

age3of4

电子技术应用　　　　　　　ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ

6.1.2

Comb Patterns

Various

‘‘comb patterns’’ can be

properly tested following the procedures in this document.

The test points for comb patterns such as in Figure 3 are 1 to

2, 2 to 3, 3 to 4, and 4 to 5. Test points 1-3-5 are connected

to the positive (+) terminal, and test points 2-4 are connected

to the negative (–) terminals of the resistance meter.

6.1.3

Production Board Testing

Occasionally,

production

boards must be tested in lieu of test patterns. When this is

required, one must use good judgment and select adjacent

conductors for wiring terminal lands for testing, because con-

ductor spacing and placement can affect test results.

6.2 Documented alternative cleaning procedures may be

implemented. As an example, if there is a concern that scrub-

bing will adversely affect test results, e.g., when the test

specimens have very fine spacing and/or are plated with soft

metals (tin/lead, gold, etc.).

6.3 If

printed boards are to be stored before coating, place

the boards in a dry noncontaminating environment.

6.4

Performance

specifications should specify the method

of test specimen preparation, test condition class, and any

deviations to this test method.

6.5

The

test chamber should be constructed out of materi-

als that will not corrode or add ionic contamination to the test

environment.

IPC-263-3

Figure

3 Typical ‘‘Comb Pattern’’ (from IPC-B-25A)

IPC-TM-650

Number

2.6.3

Subject

Moisture

and Insulation Resistance, Printed Boards

Date

05/04

Revision

age4of4

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