IPC-TM-650 EN 2022 试验方法.pdf - 第670页

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 precauti…

procedures

listed below. The cleaning parameters shall be

reported in the Qualification Test Report of J-STD-004.

5.4.2.1

The

samples to be cleaned shall be cleaned with an

appropriate environmentally safe solvent or aqueous cleaning

medium. The use of a commercial in-line or batch cleaner is

preferred. If this is not available, the following laboratory clean-

ing process shall be followed.

5.4.2.2

Samples

shall be cleaned within 30 minutes or less

after soldering. For solvent or aqueous detergent cleaning,

three 2000 ml beakers each containing 1000 ml of solvent

shall be used such that one beaker serves as the primary

cleaning stage and the other two are used for rinsing pur-

poses. Each test coupon shall be agitated in each beaker for

one minute. In the case of aqueous detergent, one beaker

shall contain the cleaning agent and the remaining beakers

shall contain deionized water for rinsing purposes. Beaker

solutions shall be used to clean or rinse a maximum of three

specimens before the solutions are replaced. After the clean-

ing procedure, dry the samples for two hours at 50 °C

[122 °F]. Following cleaning and drying, the specimens shall

be tested as outlined in 5.5 through 5.6.1.

5.5

Preparation of Samples for Chamber

Visually

inspect

all combs and discard (or replace, if possible) any

combs with bridging of conductors or visible (at 10-30X with

backlighting) metallic debris between conductors. Shield the

comb patterns during soldering of the connection points. Use

water white rosin to solder Teflon®-insulated wires to the con-

nection points of the specimens. Do not attempt to remove

the flux residues. Connectors may be used in lieu of soldering

wires but are not recommended. In the event of a dispute, the

samples with soldered wires shall be used as a referee.

5.5.1

Place

the specimens in the environmental chamber in

a vertical position such that the air flow is parallel to the direc-

tion of the board in the chamber. Set the chamber tempera-

ture at 85 ± 2°C [185 ± 3.6 °F] and humidity at 20% RH and

allow the oven to stabilize at this temperature for three hours.

Then slowly ramp the humidity to 85 ± 2% over a minimum 15

minute period. Allow the specimens to come to equilibrium for

at least one hour before applying the bias voltage to begin the

test. If a salt solution and desiccator are used for humidity,

specimens shall be held for 24 hours before beginning the

test.

5.5.2 Connect

the 45-50v DC voltage source to the speci-

men test points to apply the bias voltage to all specimens.

Placea1MΩ current limiting resistor in series with each test

point.

5.6

Measurements

shall be made with test

specimens in the chamber under the test conditions of tem-

perature and humidity at 24, 96 and 168 hours. To take these

measurements, the 45 - 50v DC bias voltage source must be

removed from the test specimen and a test voltage of -100v

DC shall be applied. (Test voltage polarity is opposite the bias

polarity.)

5.7

Evaluation

5.7.1

Each

comb pattern on each test specimen shall be

evaluated by the insulation resistance values obtained at 96

and 168 hours. If the control coupon readings are less than

1000 megohms, a new set of test coupons shall be obtained

and the entire test repeated. The reading at 24 hours may fall

below the required value provided that it recovers by 96

hours.

5.7.2

Any

reason for deleting values (scratches, condensa-

tion, bridged conductors, outlying points, etc.) must be noted.

Deletion of results for more than two combs shall require the

test to be repeated.

5.7.3

All

specimens shall also be examined under a 10x to

30x microscope using backlighting within 24 hours of com-

pleting the testing. If the coupons are to be held longer, they

shall be placed in Kapak® or other noncontaminating con-

tainer and stored in a desiccator. All samples must be evalu-

ated within seven days. If dendritic growth is observed, it shall

be determined if the dendrite spans 25% or more of the origi-

nal spacing. This latter condition will constitute a failure. It

should be determined whether dendritic growth is due to con-

densation from the chamber (see 6.1). Visible discoloration,

corrosion, or dendritic growth shall be reported.

Notes

6.1

condensation occurs on the test specimens in the

environmental chamber while the samples are under voltage,

dendritic growth will occur. This can be caused by a lack of

sufficient control of the humidification of the chamber. Water

spotting may also be observed in some chambers where the

air flow is from back to front. In this case, water condensation

on the cooler chamber window can be blown around the

chamber as microdroplets that deposit on test specimens and

cause dendritic growth if the spots bridge the distance

IPC-TM-650

Number

2.6.3.3

Subject

Surface

Insulation Resistance, Fluxes

Date

06/04

Revision

age3of4

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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

age4of4

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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.

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