IPC-TM-650 EN 2022 试验方法.pdf - 第671页

1 Scope This test method is used to determine the mois- ture and insulation resistance of applied conformal coating under prescribed conditions of temperature and humidity. Raw material qualification testing is performed…

between

two electrified conductors. Both of these conditions

must be eliminated for proper testing.

6.2

IPC-B-24 test board artwork and electronic data is avail-

able from IPC.

6.3

Safety

Observe all appropriate precautions on MSDS

for chemicals involved in this test method.

IPC-TM-650

Number

2.6.3.3

Subject

Surface

Insulation Resistance, Fluxes

Date

06/04

Revision

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Scope

This

test method is used to determine the mois-

ture and insulation resistance of applied conformal coating

under prescribed conditions of temperature and humidity.

Raw material qualification testing is performed on designated

comb patterns.

Applicable Documents

IPC-CC-830

Qualification

and Performance of Electrical Insu-

lating Compound for Printed Board Assemblies

J-STD-004

Requirements

for Soldering Fluxes

IPC-A-600

Acceptability

of Printed Boards

Test Specimens

3.1 Class 1, 2 and 3

Five

IPC-B-25A boards (See Figure 1)

using the D comb patterns, one uncoated and four coated

with conformal coating according to the coating suppliers

recommendations.

Apparatus

4.1 Chamber

clean chamber capable of programming

and recording an environment of 25 ± 5°C [77° ± 9°F] to at

least 65 ± 2°C [149° ± 3.6°F] and 90-98% relative humidity.

Power Supply Capable of producing a standing bias potential

of 100 VDC with a tolerance of ± 10%.

4.3

Resistance Meter

Capable

of reading high resistance

(10

ohms

or greater), with a test voltage of 100VDC.

4.4

Oven

Capable

of maintaining at least 120°C [248°F].

4.5

Timer

4.6 Solder Pot

4.7 Tongs

4.8 Soldering Iron

4.9 Flux

Water

white rosin (R or RMA) with halide content

less than 0.5%, i.e., type Symbol A and B or ROL0 and ROL1

according to J-STD-004.

Test

5.1 Ambient Conditions

25°,

+2°, -5°C [77°, +3.6°, -9°F].

40-50% relative humidity.

5.2

Test Conditions

25°

to 65° ± 2°C [77° to 149° ±

3.6°F], with 90, -5, +3% relative humidity, 50VDC bias,

cycling, 6

⁄

days.

5.3

Specimen Preparation

5.3.1

Positive,

permanent and noncontaminating identifica-

tion of the test specimens is of paramount importance.

5.3.2

Visually

inspect the test specimens for any obvious

defects, as described in the IPC-A-600. If there is any doubt

about the overall quality of any test specimen, the test speci-

men should be discarded.

IPC-2634-1

Figure

1 IPC-B-25A Test Board (Test Points on D Pattern

Are Identiﬁed)

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.6.3.4

(Supersedes

2.6.3.4 and 2.6.3.1C for Conformal

Coating Test)

Subject

Moisture and Insulation Resistance –

Conformal Coating

Date

07/03

Revision

Originating Task Group

Conformal Coating Task Group (5-33a)

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.

age1of2

ASSOCIA

TION CONNECTING

ELECTRONICS INDUSTRIES

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5.3.3

One

uncoated specimen subjected to the same pro-

cessing (except coating) as the coated specimens shall be

supplied with each lot of samples as a test control.

5.4

Electrical Connections

5.4.1

Solder a single strand PTFE insulated wire, using the

flux specified in 4.9, to each pad of the D comb pattern.

These wires will be used to connect each pad of the desig-

nated comb pattern to polarization and insulation resistance

testing. When soldering the wires onto the pads care should

be taken to ensure that the flux does not splatter onto the

combs. A simple off-contact shield fixture should be used to

protect the test patterns from the flux spitting during solder-

ing.

Note: An alternate method is to use gold plated alligator clips.

5.5

Soldering Flux Removal

The

flux shall not be

removed. If the flux has contaminated the comb pattern on

the control, the sample shall be discarded and a new one

used. It cannot be cleaned because it will not represent the

cleaning process that was used prior to conformal coating

application.

5.6

Specimen Handling

For

the remainder of the test, the

surface of the test specimens either uncoated or coated with

conformal coating should not be handled or exposed to any

other contaminating influence.

5.7

Procedure

5.7.1

Condition

the specimens at 50 ± 2°C [122 ± 3.6°F]

with no added humidity, for a period of 24 hours.

5.7.2

Testing

5.7.2.1

Allow

the specimens to cool. Measure and record

the initial insulation resistance measurements at ambient labo-

ratory conditions. Apply 100 VDC on the specimen’s test

points with the resistance meter and take the reading after

one minute. On the D comb pattern, test points 1, 3 and 5 are

connected to the positive terminal and test points 2 and 4 are

connected to the negative terminal of the resistance meter.

5.7.2.2

Place

specimens in a chamber, in the vertical posi-

tion and under a condensation drip shield. Each chamber load

shall contain at least one uncoated board that is representa-

tive of the cleaning process used prior to conformal coating

application for each lot tested.

5.7.2.3

chambers door and apply a 50 VDC polariz-

ing bias to all test patterns. Electrical connections to speci-

mens shall be made so that electrical polarization voltage and

the test voltage of the same polarity are connected to the

same terminal.

5.7.2.4 Expose

test specimens to 20 cycles of temperature

and humidity. Polarizing voltage shall be maintained through-

out the entire 20-cycle period. Humidity shall be maintained at

85% minimum through the cycles except that when going to

low temperature in Step c below, the humidity may drop to

80% minimum.

One cycle is as follows:

a. Start test at 25°C [77°F] and raise the temperature to 65°C

[149°F] over a time span of 1.75 ± 0.75 hours.

b. Maintain temperature at 65°C [149°F] for 3, +0.5, -0 hours

c. Lower the temperature from 65°C [149°F] to 25°C [77°F]

over 1.75 ± 0.5 hours

Note: There shall be no delay between cycles.

5.7.3

Measurement/Evaluation

5.7.3.1

Disconnect

50 VDC polarizing voltage source before

taking the insulation resistance measurements. Insulation

resistance shall be read as specified in 5.7.2.1.

5.7.3.2 Measure

and record the resistance at the first,

fourth, seventh and tenth cycle, between the 2nd and 3rd

hour of the high phase of each cycle. These measurements

are to be conducted without opening the chamber.

5.7.3.3

Upon

completion of the 20 cycles, the test comb

patterns shall be maintained at 25° ± 2°C [77° ± 3.6°F] rela-

tive humidity of 50 ± 5% for 24 hours.

5.7.3.4

After

the 24-hour stabilization, the insulation resis-

tance shall be measurements as previously stated in section

5.7.2.1.

5.7.3.5

The

comb patterns will be examined for appearance

and dielectric withstanding voltage in accordance with IPC-

CC-830.

IPC-TM-650

Number

2.6.3.4

Subject

Moisture

and Insulation Resistance –

Conformal Coating

Date

07/03

Revision

age2of2

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