IPC-TM-650 EN 2022 试验方法.pdf - 第668页

In addition, there shall be at least two unprocessed control coupons for comparison purposes (Table 1, Sample Group F). 5.2.1 Positive, permanent and noncontaminating identifica- tion of test specimens is of paramount im…

Scope

This

test method is to characterize fluxes by

determining the degradation of electrical insulation resistance

of rigid printed wiring board specimens after exposure to the

specified flux. This test is carried out at high humidity and heat

conditions.

Applicable Documents

IPC-B-24

Surface

Insulation Resistance Test Board

IPC-A-600

Acceptability

of Printed Boards

IPC

J-STD-004

Requirements

for Soldering Fluxes

IPC-9201

Surface

Insulation Resistance Handbook

Test Specimen

minimum of 10 ml of liquid flux, a rep-

resentative container of solder paste, cored wire, paste flux, or

extracted solder preform flux. The reflow/extraction process

should be carried out in accordance with IPC J-STD-004.

3.1

Comb Patterns

Use

the IPC-B-24 test pattern (see

Figure 1), which consists of four comb patterns per coupon.

Each individual comb has 0.4 mm lines and 0.5 mm spacing.

The metallization shall be unpreserved bare copper.

3.2

Laminat

The

laminate material for this test shall be

FR-4 epoxy-glass.

Apparatus

4.1

clean test chamber capable of programming and

recording an environment of 25 +10/-2 °C [77 + 18/-3 °F] to

at least 85 ± 2 °C [185 ± 3.6 °F] and 20% ± 5% to 85% ± 2%

relative humidity. A salt solution and desiccator may be used

to maintain humidity if a tight temperature control is main-

tained on the chamber.

4.2

power supply capable of producing a standing bias

potential of 45-50 volts DC with a tolerance of ± 10%.

4.3

resistance meter capable of reading high resistance

(10

ohms)

with a test voltage of 100 volts, or an ammeter

capable of reading 10

-10

amps

in combination with 100 volts

DC power supply.

4.4

Three

2000 ml beakers.

4.5

Exhaust

ventilation hood.

4.6

Metal

tongs.

4.7 Soft

bristle brush.

4.8

Deionized

or distilled water (2 megohm-cm minimum

resistivity recommended).

4.9

Drying

oven capable of maintaining at least 50 °C

[122 °F].

Procedure

5.1 Test Conditions

All

fluxes will be tested at 85 ± 2 °C,

[185 ± 3.6 °F], 85 ± 2% relative humidity for 168 hours.

5.2

Specimen Preparation

There

shall be three test cou-

pons for each liquid flux to be tested in the cleaned state

(Table 1, Sample Group A). When testing liquid fluxes which

are intended to remain in the uncleaned state, six test cou-

pons are required. Three uncleaned test coupons shall be

soldered pattern side down (Table 1, Sample Group B) and

three shall be soldered pattern side up (Table 1, Sample

Group C).

Solder paste coupons shall be reflowed pattern side up and

either cleaned (Table 1, Sample Group D) or not cleaned

(Table 1, Sample Group E).

IPC-2633-1

Figure

1 Test Pattern from IPC-B-24

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.6.3.3

Subject

Surface

Insulation Resistance, Fluxes

Date

06/04

Revision

Originating Task Group

Flux Specifications Task Group, (5-24a)

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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ELECTRONICS INDUSTRIES

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addition, there shall be at least two unprocessed control

coupons for comparison purposes (Table 1, Sample Group F).

5.2.1

Positive,

permanent and noncontaminating identifica-

tion of test specimens is of paramount importance. (For

example, a vibrating scribe.) Permanent ink may be used on

the back side of the test coupon if areas beneath conductors

are avoided.

5.2.2

Visually

inspect the test specimens for any obvious

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

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

men should be discarded.

5.2.3

Clean

each test or control coupon with deionized or

distilled water and scrub with a soft bristle brush for a mini-

mum of 30 seconds. Spray rinse thoroughly with deionized or

distilled water. Rinse the cleaned area thoroughly with fresh

2-propanol.

An alternative cleaning method is to place the test coupon in

an ionic contamination tester containing 75% 2-propanol,

25% deionized water and process the solution until all ionics

have been removed.

During the remainder of the specimen preparation, handle test

specimens by the edges only, and use noncontaminating rub-

ber gloves.

5.2.4

Dry

the cleaned boards for two hours at 50 °C

[122 °F].

5.2.5 If

boards are to be stored before treatment, place the

boards in Kapak® bags or other contamination-free contain-

ers (do not heat seal) in a desiccator.

5.3

Sample Preparation

Flux

application and soldering.

5.3.1

Liquid Flux or Flux Extract

Coat

the test pattern

with a thin coating of the liquid flux or flux extract under test.

5.3.1.1

Preheat

the flux coated test coupon using the tem-

perature profile recommended by the vendor. If no profile is

available, preheat the test coupon in an oven set at a tem-

perature such that the test coupon reaches a temperature of

140 °C [284 °F] in 30 to 45 seconds.

5.3.1.2 Immediately

expose the test coupon to solder by

floating the fluxed comb patterns of the test specimen face

down on the solder pot at 245-260 °C [473-500 °F] for4±1

seconds. Be sure that all dross is removed from the solder pot

surface just before contact with the specimen.

5.3.1.3

Alternatively,

the specimen can be wave soldered

face down at 245-260 °C [473-500 °F] and a conveyor speed

with a contact time of3±1seconds.

5.3.1.4

For

fluxes to be tested in the uncleaned state, a

second set of test patterns shall be fluxed and floated pattern

up on the solder pot or passed pattern up over the solder

wave.

5.3.2 Solder Paste or Paste Flux

Stencil

print the solder

paste or paste flux onto the comb pattern using a 0.15 mm

[0.00591 in] (6 mil) thick stencil (the IPC-A-24 artwork con-

tains the stencil design).

5.3.2.1

The

samples shall be run through a reflow soldering

process using the temperature profile recommended by the

vendor.

5.3.3

Cored Wire

Using

a clean fine-tip soldering iron

apply the cored wire to the comb patterns being careful not to

bridge the conductors. The iron temperature should be as

specified by the cored wire vendor.

5.4

Cleaning of Samples

5.4.1

After

exposure to flux and solder, samples to be

tested in an uncleaned state shall be tested as outlined in 5.5

through 5.6.1.

5.4.2

After

exposure to flux and solder, samples to be

tested in the cleaned state shall be cleaned using one of the

able 1 Coupons for SIR Testing

Sample

Group

Flux/

Solder

Clean

Number of

Coupons

Yes Yes 3

B Yes No 3

C Yes No 3

D Yes Yes 3

E Yes No 3

FNoNo2

= Pattern down/cleaned

B = Pattern down/not cleaned

C = Pattern up/not cleaned

D = Solder paste/reflow/cleaned

E = Solder paste/reflow/not cleaned

F = Control (precleaned, unprocessed)

IPC-TM-650

Number

2.6.3.3

Subject

Surface

Insulation Resistance, Fluxes

Date

06/04

Revision

age2of4

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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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