IPC-TM-650 EN 2022 试验方法.pdf - 第182页

5.1.7 Allow the boards to extract in this manner for a period of time of 60 ± 5 minutes. 5.1.8 Following the extraction of 5.1.7, remove the bags from the water bath and allow the extract solution to cool for at least 30…

Scope

This

test is used to determine the total ionic con-

tent extractable from on, and absorbed within, the surface of

printed wiring boards (PWBs), for the purposes of process

control. The conductivity of the extract solution is measured

and the results are expressed as sodium chloride equivalence

per unit area.

Applicable Documents

IPC-TM-650

Test

Method 2.3.25, Detection and Measure-

ment of Ionizable Surface Contaminants by Resistivity of Sol-

vent Extract (ROSE)

Test Specimens

The

test specimen may be any unpopulated PWB. The num-

ber of specimens depends on the process control plan or

product drawings/prints.

Apparatus or Material

•

An automated Resistivity of Solvent Extract (ROSE) tester

• Conductivity dip probe with appropriate meter with tem-

perature compensation

• Hydrometer (0.800 - 0.900) for ROSE tester calibration

• Thermometer for ROSE tester calibration

• Clean room (non-ionic) gloves or forceps

• KAPAK™ plastic bags or equivalents (see 6.9)

• Bag sealing equipment

• Water bath, capable of sustaining an 80°C ± 2°C [176°F ±

3.6°F] temperature

• Second water bath capable of sustaining a 25°C ± 1°C

[77°F ± 1.8°F] temperature

• Precision solvent measurement equipment, such as class A

pipettes

• Volumetric glassware

• Plastic ware - high density polyethylene, polymethylpentene

(polypentene) or equivalent.

• Extract solution: 25% v/v deionized water (18 MΩ-cm nomi-

nal resistivity), 75% v/v 2-propanol (electronic or HPLC

grade). No alternative solution or composition is allowed.

• Sodium chloride - reagent grade

• Analytical balance accurate to 0.0001 grams

ARNING: 2-propanol is a flammable material. The 2-propanol /

water mixture is also flammable. Exercise caution when using this

solution.

5 Procedure

5.1 Extraction

NOTE: Throughout

this procedure, do not touch the sample

boards with bare hands. Use the clean room gloves specified

or use clean forceps.

5.1.1

Calculate

the surface area of the PWB using:

Area

(in cm

)

= Length x Width x 2

5.1.2

Prepare

a volume of extract solution specified in 4.

5.1.3

Using

clean room gloves or clean forceps, place the

PWB into virgin KAPAK™ bags. Choose the bag size to give

at least an additional 2.5 cm [1.0 in] on each side of the board

to minimize the amount of extract solution used. Allow at least

an additional 5 cm [2.0 in] above the board top.

5.1.4

Using

a pipette or graduated cylinder, add a volume of

the extract solution into the bag. The amount will depend on

the area of the board surface. This usually varies from 0.8

mL/cm

[5.2

mL/in

]

up to about 3 mL/cm

[19

mL/in

For

example, a 10 cm x 11.5 cm [3.94 in x 4.53 in] board would

require about 100 mL of solution. The amount of solution

should just cover the board completely when most of the air

is forced out of the bag.

5.1.5

Force

most of the air from the bag and heat seal the

bag. This involves contact with a hot metal bar. Take reason-

able precautions to keep extract solution from contacting the

hot bar. Alternatively, the top of the bag may be folded over

and clipped shut.

5.1.6

Place

the bag(s) vertically in a water bath which has

stabilized at 80°C [176°F]. Make sure that the boards do not

float above the water line. Do not allow the water from the

bath to enter the bag or for extract solution to leak out of the

bag.

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.3.25.1

Subject

Ionic

Cleanliness Testing of Bare PWBs

Date

October 2000

Revision

Originating Task Group

Bare Board Cleanliness Assessment Task Group

5-32c

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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5.1.7

Allow

the boards to extract in this manner for a period

of time of 60 ± 5 minutes.

5.1.8

Following the extraction of 5.1.7, remove the bags

from the water bath and allow the extract solution to cool for

at least 30 minutes, with the specimen still in the bag.

5.1.9

Using

clean tongs or forceps, remove the PWB from

the bag.

5.2

Measurement – DIP Probe Method

5.2.1 Calibration of Bridge

This

is essential in this method

because there can be no correlation between resistivity/

conductivity readings and NaCl equivalents without calibra-

tion.

5.2.1.1

Prepare

a standard NaCl solution from a weight of

dry reagent grade NaCl salt dissolved in deionized water to

produce a final diluted concentration of 0.06 g/liter NaCl (5 mL

equals 300 µg NaCl).

5.2.1.2

Place

1 liter of the 2-propanol water solution (at the

calibration temperature of the bridge in use) in a plastic bea-

ker.

NOTE: The 75 % v/v 2-propanol solution must be used in this

calibration. Water cannot be used since it is not the test solu-

tion used in the procedure. The test solution used in this cali-

bration can be recleaned by passing through the DI column

until the required resistivity/conductivity is obtained.

5.2.1.3 From

a 50 mL burette, add to the liter of test solu-

tion, 5 mL of the standard 0.06 g/liter NaCl solution. Stir and

measure resistivity/conductivity.

5.2.1.4

From

a 50 mL burette, add to the liter of test solu-

tion, 20 additional mL of the standard 0.06 g/liter NaCl solu-

tion, for a total of 25 mL. Stir and measure resistivity/

conductivity.

5.2.1.5

From

a 50 mL burette, add to the liter of test solu-

tion, 25 additional mL of the standard 0.06 g/liter NaCl solu-

tion, for a total of 50 mL. Stir and measure resistivity/

conductivity.

5.2.1.6

Plot

a three point nomogram of Conductivity vs.

Solution Concentration (in µg/liter NaCl). See Figure 1 for

example. You should get a linear relationship. Use a best fit

line obtained with a piecewise linear method.

5.2.2

Test Procedure - DIP Probe

NOTE: If

desired, this test can be run at other temperatures;

however, the calibration process must be repeated for the

alternative temperature. This calibration process need only be

done once, providing the conductivity cell has not been

exposed to harsh chemicals which would alter the cell con-

stants. If the conductivity cell is routinely used on harsh

chemical solutions (e.g., plating baths), then the calibration

should be repeated before every test run.

5.2.2.1

Place

the Kapak™ bags containing the extract solu-

tions into the 25°C [77°F] water bath and allow the extract

solutions to reach 25°C [77°F].

5.2.2.2

Insert

the conductivity probe into the Kapak™ bag

containing the room-temperature extract solution. It is impor-

tant that the extract solution be measured at the same tem-

perature used for the calibration solutions. Immerse the probe

to a suitable depth.

NOTE: A ‘‘suitable depth’’ is one which covers the cell elec-

trodes, but not an immersion which covers the wiring. Many

cells are marked with a scribed line which indicates the proper

immersion depth.

5.2.2.3

Gently

agitate the solution. Read the conductivity of

the solution. The time between immersion of the cell and tak-

ing the reading should be the same as used for the calibration

curve. Sufficient time should be allowed for the reading to

come to equilibrium (no change for two minutes).

IPC-2325-1

Figure

1 Nomogram of Conductivity vs. Solution

Concentration

Conductivity

Solution Concentr

ation

in micrograms NaCl/Liter

IPC-TM-650

Number

2.3.25.1

Subject

Ionic

Cleanliness Testing of Bare PWBs

Date

October 2000

Revision

age2of4

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NOTE: Between

measurements, rinse the cell with deionized

water and leave the cell soaking in virgin extract solution.

Never use a dry cell as this is bad technique.

5.2.2.4 Using the linear relationship formed in 5.2.1.6,

determine the concentration of sodium chloride correspond-

ing to the conductivity reading. Use the equation given below

to determine the total micrograms of sodium chloride equiva-

lence per square centimeter (µg NaCl Eq. /cm

)

Using

the nomogram:

Conductivity of Unknown →

Concentration of Unknown

Concentration Volume of Extract Solution

(µg/liter) x (liter)

Extracted

Surface Area (cm

)

µg NaCl Eq./cm

5.2.2.5

the conductivity of the unknown solution is outside

of the bounds represented on the existing nomogram, then

continue the technique used to generate the nomogram (see

5.2.1) until the bounds contain the conductivity of the

unknown solution.

5.3

Measurement – Static ROSE Tester Method

NOTE: This

section was developed using an Omegameter

600SMD with a 10,000 mL cell. Make appropriate changes to

the procedure to accommodate other static ROSE testers.

5.3.1

Perform

a system verification check.

5.3.2 Set

the instrument to an appropriate amount of sol-

vent volume. A target solution level should be 1.5 mL for one

board surface. It is not necessary to cover the spray

jets (if applicable). If the lid is on the test cell, the CO

mixing

minimized.

5.3.3

Enter

the appropriate surface area into the instrument.

5.3.4

allow for the volume of solvent that is to be added,

the instrument setup volume will be set at the minimum vol-

ume (e.g., 2300 mL) plus the volume of solution in the extrac-

tion bag (e.g., 100 mL).

Dwell time or run time: 2 minutes

Pass / Fail Value: None

Begin the test and follow the test prompts.

Remove the cell cover.

5.3.5

Carefully

open the test bag and quickly pour the

extract solution into the test cell. To minimize CO

absorption,

the

addition should be made as quickly as possible and the

cell cover quickly replaced.

5.3.6

The

instrument should very quickly reach equilibrium

(10 -15 seconds) and then should remain essentially

unchanged for the remainder of the two minute run.

5.3.7

Log

the reading in total µg of sodium chloride equiva-

lence per cm

5.3.8

Static ROSE Calculation Example:

Testing a bare board, 10 cm x 20 cm [3.9 in x 7.9 in]

Surface

area is 10 cm x 20 cmx2=400cm

[62

]

Bag

size should be about 15 cm x 30 cm [5.9 in x 12 in] or

larger

Extract solution would be about 620 mL

ROSE volume input to 4620 mL (4000 mL to cover sprays

and 620 mL from extraction)

ROSE tester cell volume set to 4000 mL.

Run time - 2 minutes

5.4

Measurement – Dynamic ROSE Tester Method

5.4.1

Perform

a system verification check.

5.4.2

Program

the instrument with the appropriate surface

area of the board.

5.4.3

Cycle

the instrument to the beginning cleanliness

point.

5.4.4

Carefully

open the test bag and quickly pour the

extract solution into the test cell. To minimize CO

absorption,

the

addition should be made as quickly as possible and the

cell cover quickly replaced.

5.4.5

When

the instrument completes the test, log the read-

ing in total µg of sodium chloride equivalence per cm

Notes

6.1

The

background for this test method may be found in

technical papers:

‘‘Rationale and Methodology for a Modified Resistivity of Sol-

vent Extract Test Method,’’ Philip W. Wittmer, IPC 1995 Fall

Meeting Proceedings, S13-4.

IPC-TM-650

Number

2.3.25.1

Subject

Ionic

Cleanliness Testing of Bare PWBs

Date

October 2000

Revision

age3of4

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