IPC-TM-650 EN 2022 试验方法--.pdf - 第178页

4.4 Tes t Procedure 4.4.1 Carefully preclean all plasticware with deionized water (16 M Ω -cm resistivity minimum) followed by a final rinse with the extraction test solution. 4.4.2 Determine the surface area per Section…

extraction solution before measuring the resistivity of the com-

posite sample.

4.2 Test Equipment and Chemicals

4.2.1

Miscellaneous laboratory ware (e.g., beakers, funnels,

storage bottles and graduated cylinders). This plastic ware

can be high density polyethylene, polymethylpentene (poly-

pentene), polypropylene or equivalent. Glassware cannot be

used because it has been shown to contribute ionic contami-

nation in a short time with this 2-propanol/DI water solution.

4.2.2

Conductivity bridge or equivalent conductivity probe

and temperature compensated liquid conductivity cell appara-

tus capable of measuring specific resistivities within a range

covering at least 100 kΩ-cm to 20 MΩ-cm.

4.2.3

Deionization column. Up to 100% solvent compatible

mixed bed or equivalent.

Some of these columns are color dyed. This dye will

interfere with test results. Make certain that the column used

has no dye.

4.2.4

Electronic Grade 2-Propanol (isopropyl alcohol) or

99.5% purity minimum

4.2.5

Deionized water (DI water), preferably above 16

MΩ-cm water resistivity

It is critical to always use wash solution with the same

composition of 2-propanol/DI water for all comparative data

discussions.

4.2.6

Wash solution composed of 75 ± 2% v/v 2-propanol/

DI water or 50 ± 2% v/v 2-propanol/DI water. This wash solu-

tion must be deionized to a resistance equal to or greater than

16 MΩ-cm (conductivity less than 0.0625 µS/cm). If stored,

this wash solution must be freshly deionized prior to use. Typi-

cal resistivity of 25 MΩ-cm (conductivity of 0.04 µS/cm) can

be achieved. Measurement of the 2-propanol/DI water solu-

tion should be performed using a calibrated hydrometer. The

default extract solution composition is 75 ± 2% v/v

2-propanol/DI water.

4.3 Calibration of Bridge

This is essential in the manual

method because there can be no correlation between

resistivity/conductivity readings and NaCl equivalents without

calibration. All future specification requirements are to be

stated in maximum micrograms of NaCl equivalent per square

centimeter (µg NaCl Eq./cm

Ensure that a proper cell constant value is considered

in any conductivity calculations. Check the specific conductiv-

ity bridge manufacturer’s manual for this detail.

4.3.1

Prepare or purchase (these standard solutions are

available from equipment vendors, as well as many of the

chemical companies) a standard NaCl solution from a weight

of ACS reagent grade NaCl salt dissolved in deionized water

(16 MΩ-cm resistivity minimum) to produce a final diluted con-

centration of 0.06 g/liter NaCl (5 mL contains 300 µg NaCl).

It is recommended that dry NaCl be used for this solu-

tion. A recommended drying exposure is one hour at 105 °C

or higher.

4.3.2

Place one liter of the 2-propanol/DI water solution (at

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

beaker.

The 75%/25% v/v or 50%/50% v/v 2-propanol/DI

water solution must be used in this calibration. Water cannot

be used since it is not the test solution used in the procedure.

The test solution used in this calibration should be made fresh

daily.

4.3.3

From a 50 mL burette, add to the liter of test solution,

5 mL of the standard 0.06 g/liter NaCl solution. Stir and mea-

sure resistivity/conductivity.

If the resistivity is measured, convert to conductivity by

take the reciprocal, prior to plotting the data.

4.3.4

From a 50 mL burette, add to the liter of test solution,

20 additional mL of the standard 0.06 g/liter NaCl solution, for

a total of 25 mL. Stir and measure resistivity/conductivity.

4.3.5

From a 50 mL burette, add to the liter of test solution,

25 additional mL of the standard 0.06 g/liter NaCl solution, for

a total of 50 mL. Stir and measure resistivity/conductivity.

4.3.6

Plot a three-point nomogram of Conductivity vs.

µg/liter of NaCl. A linear relationship is expected with the use

of a linear regression best fit line through the data points. If a

multi-range meter is used the curve should not be extended

beyond the maximum reading of the meter for that range,

unless linearity is proven by additional points obtained by add-

ing more standard salt solution. The nomogram will never

cross the zero point of conductivity.

An R

value of 0.99 should be expected before the

instrument would be considered calibrated.

Number

2.3.25

Subject

Detection and Measurement of Ionizable Surface Contaminants by

Resistivity of Solvent Extract (ROSE)

Date

11/12

Revision

IPC-TM-650

—

Note:

Page

4.4 Test Procedure

4.4.1

Carefully preclean all plasticware with deionized water

(16 MΩ-cm resistivity minimum) followed by a final rinse with

the extraction test solution.

4.4.2

Determine the surface area per Section 3.

4.4.3

Suspend the test specimen within an appropriately

sized funnel positioned over a graduated cylinder. Use clean

gloves when handling the samples to be tested.

4.4.4

Prepare the extraction solution volume using a general

ratio of no more than 10 mL: 1 cm

of area. Direct a fine

stream of freshly-deionized test solution on both sides of the

specimen, covering all board and component surfaces. Con-

tinue this process, slowly collecting the extraction solution.

The volume collected is not critical, but the total collected vol-

ume must be exactly recorded. A volume correction is made

in the calculation.

4.4.5

Pour the final measured volume into a plastic ware

beaker, stir and measure the resistivity/conductivity with either

a bridge probe or equivalent conductivity probe.

4.4.6

The resistivity/conductivity readings can be used to

convert the µg NaCl equivalent as follows:

1. Locate where the resistivity or conductivity intersects the

calibration curve on the X-axis (see Figure 1).

2. Extend a vertical line from the point of intersection to the

x-axis. Read and record µg/liter NaCl (M).

3. Multiply the concentration in µg/liter NaCl by the total liters

of test solution used (V). This result indicates the total µg of

NaCl equivalents removed from the printed wiring board

(T).

T = M x V

Where:

T = the numerical value of the total amount of NaCl equiva-

lents removed from the printed board, expressed in micro-

gram (µg);

M = the numerical value of the NaCl concentration of test

solution, expressed in microgram per liter (µg/L);

V = the numerical value of the total volume of test solution,

expressed in liter (L)

4. Divide the micrograms of NaCl equivalents by the area of

the printed wiring board or assembly (A). This yields the

conductivity factor in µg NaCl Eq./cm

T/A = µg NaCl Eq./cm

If samples read over the highest standard the sample

should be diluted by a known factor, retested and calculations

adjusted accordingly.

5 Dynamic Extraction Method

5.1 Description

In the dynamic method, a purified

2-propanol/DI water mixture is circulated into and out of a test

tank chamber containing the sample being tested. The mix-

ture exiting the test tank is passed through a conductivity cell

which measures the conductivity continuously. These conduc-

tivity values are integrated over the time of the extraction. The

mixture is then pumped through a resin deionization column

before it is recirculated back into the test tank. As ionic mate-

rials are extracted from the samples and then pumped out of

the cell, the conductivity of the solution will change dynami-

cally until all of the extractable ionic material has been

removed.

5.2 Test Equipment

Dynamic conductivity measurement

system includes a test tank, a temperature compensated con-

ductivity cell, ion exchange columns and a metering pump

connected together in a recirculating loop as described in 5.1.

The conductivity readings are integrated over the time of the

measurement by electronic integration. The equipment may

have the capability of heating the 2-propanol/DI water mixture

IPC-2325d-1

Number

2.3.25

Subject

Detection and Measurement of Ionizable Surface Contaminants by

Resistivity of Solvent Extract (ROSE)

Date

11/12

Revision

IPC-TM-650

Solution

Concentration

micrograms

NaCI/Liter

Note:

Figure

Nomogram

Conductivity

Solution

Concentration

Page

to accelerate extraction of ionic soils from poorly accessible

places such as under surface mounted components.

5.3 Procedure

5.3.1 Solvent Systems

Industry has established two differ-

ent standard test solutions that are used worldwide:

75 % / 25 %, nominal v/v 2-propanol/DI water

50 % / 25 %, nominal v/v 2-propanol/DI water

Select the solution required by the specification (e.g., industry

standards, engineering drawing specifications, contract docu-

mentation, etc.).

5.3.2

Determine the surface area per Section 3.

5.3.3 Calibration

Once the fluid in the system has estab-

lished a stable level of conductivity, a precise quantity of a

sodium chloride calibration solution is injected into the test

solution in the test tank. This is done according to the calibra-

tion instructions provided by the manufacturer of the equip-

ment.

System calibration should be verified daily, when used.

5.3.4 Testing

Once the system has been calibrated or veri-

fied in accordance with 5.3.3, immerse the test specimen into

the sample tank. The test time should be in accordance with

the monitoring plan criteria (set time or auto-shutoff). Use

clean gloves when handling the samples to be tested. Finger

dirt contains ionic soils which may contribute to false read-

ings. During the course of the measurement, the conductivity

will rise from the initial baseline level and then gradually return.

When it has returned to the baseline level, no additional ionic

material can be removed and the measurement is complete.

5.4 Interpretation of Test Data

The number obtained

from this type of measurement indicates the total amount of

ionic material extracted from the entire sample in terms of

equivalent amounts of sodium chloride (assuming the calibra-

tion was done with sodium chloride). This should be divided

by the total surface area of the sample from which the ions

were extracted to determine the surface ionic density of the

original sample.

The following parameters must be

specified:

a) Solvent composition

b) Solvent volume for static method or flow rate for dynamic

method

c) Test temperature

d) Calibration of system

e) Sample area calculation

f) Test time

g) Equipment type and model number

The actual surface ionic density is most commonly calculated

by programming the area into the instrument’s microproces-

sor system. The total ionic amount will then be automatically

divided by the area to indicate surface ionic density in terms

of micrograms of sodium chloride equivalence per unit of sur-

face area (µg NaCl eq./cm

6 Static Extraction Method

6.1 Description

In the static extraction method, a mea-

sured volume of freshly deionized 2-propanol/DI water mixture

is introduced into the test tank and its resistivity (or conductiv-

ity) measured continuously while the 2-propanol/DI water mix-

ture is agitated. Once the system has been calibrated or veri-

fied in accordance with 6.3.3 and solution has been run

through the ion exchange columns, the test specimen is

immersed into the tank. The test time should be in accor-

dance with the monitoring plan criteria (set time or auto-

shutoff). Care must be taken not to handle the sample or any

of the appliances used to insert it into the tank. Finger dirt

contains ionic soils which may contribute to spurious read-

ings. During the course of the measurement, the conductivity

will rise from the initial baseline and then level off. When it has

stabilized and no additional ionic material can be removed

then the measurement is complete. After the test is completed

the solvent mixture is passed through ion exchange columns

to remove ionic materials and regenerate the 2-propanol/DI

water solvent mixture to its original high resistivity level for fur-

ther tests.

6.2 Test Equipment

A static conductivity measurement

system includes a test tank, a temperature-compensated

conductivity cell and monitor, means for solution agitation and

a means for removing, deionizing and re-introducing the sol-

vent mixture into the test tank before a new test is started.

The equipment may also have the capability of heating the

2-propanol/DI water mixture to accelerate and improve the

efficiency of extraction of ionic material from poorly accessible

regions, such as under surface-mounted components.

6.3 Procedure

6.3.1 Solvent Systems

See 5.3.1.

Number

2.3.25

Subject

Detection and Measurement of Ionizable Surface Contaminants by

Resistivity of Solvent Extract (ROSE)

Date

11/12

Revision

IPC-TM-650

—

Note:

Important

Parameters

Page