IPC-TM-650 EN 2022 试验方法.pdf - 第679页

geometric mean of the sample set and can be calculated from the following: IR avg = 10 [ 1 N Σ 1 N log 10 ( IR ) i ] Where: N = Number of Test Points (12 nominal for each set of three patterns). IR i = individual insulat…

When

used for qualification purposes, the base laminate will

be FR-4 epoxy-glass with 17 µm [0.5 oz equivalent] unpro-

tected copper metalization.

Apparatus

4.1

clean test chamber capable of producing and record-

ing an environment of 35°C ± 2°C [95°F ± 3.6°F] and 88%

-0+5% relative humidity, and that allows the insulation resis-

tance of the patterns to be measured under these conditions.

The chamber must be capable of maintaining these conditions

under load (i.e., with specimens in place).

4.2 Measuring

equipment such as that described in ASTM

D-257 with a range up to 10

ohm

and capable of yielding an

accuracy of ± 5% at 10

ohm

and an applied potential of 100

Vdc.

Test

5.1 Sample Sizes

•

Three test patterns are produced for test with no applied

solder mask and no applied flux (controls).

• Three test patterns are produced for test using the candi-

date material(s) and process(s).

• Sample preparation and enumeration shall also be in accor-

dance with IPC-J-STD-004 ‘‘SIR samples for Flux Qualifica-

tion.’’

5.2

Sample Identification

Use

a non-contamination

method for identifying the test sample (e.g., vibrating scribe).

During this process, handle the samples by the edges only or

using non-contaminating gloves.

5.3

Wire Attach

Cover

the test patterns with non-

contaminating film, such as aluminum foil or plastic film, to

prevent flux spattering during the wire attach process. Use

water white rosin (non-activated flux) or dry-solder (no flux at

all) to solder PTFE-insulated wires to the connection points of

the specimens. Do not attempt to remove the flux residues.

Alternatively, connections may be made by mechanical pres-

sure connections (e.g., alligator clips).

NOTE: Because of the very high resistance levels typically

used as pass-fail criteria for this method, a connector-based

or other fixtured setup is not recommended, due to leakage

currents, unless these systems can be shown to have no sig-

nal degradation compared to hardwiring.

It is an option to pre-condition test samples for 24 hours at 23

°C [73 °F] and 50% R.H. before testing.

5.4

Placing in Chamber

Place

the specimens in the envi-

ronmental chamber in a vertical position such that the airflow

is parallel to the direction of the board in the chamber. Allow

at least 1.25 cm [0.5 in] between each test sample. Dress all

wiring away from the test patterns. Route the wires to the

outside of the chamber. Set the chamber temperature to

35°C [95°F] and 85% minimum relative humidity, with a ramp

time of not less than one hour. There is no electrical potential

applied to any test pattern during the first 24 hours of test

exposure.

5.5

Resistance Measurements

After

24 hours of test

exposure with no applied electrical potential, measure the

insulation resistance of each pattern using an applied voltage

of 100 ± 2 volts DC and an electrification time of 60 seconds.

NOTE: It is recommended that the temperature and humidity

levels be verified to be within the recommended limits prior to

beginning the resistance measurements.

Each comb pattern requires four test measurements. Mea-

surements are made between (see Figure 1):

• Pad 1 to Pad 2

• Pad 3 to Pad 2

• Pad 3 to Pad 4

• Pad 5 to Pad 4

Pads 2 and 4 are at one potential and Pads 1, 3, and 5 are at

ground potential (see Note 6.3).

Determine the means of the dataset as outlined in 5.6.

After the 24 hour measurements, apply a bias of 48 volts DC

to all test patterns, using the same polarity as used for the

resistance measurements.

After an additional 72 hours (96 hours total), repeat the mea-

surement series using an applied voltage opposite in polarity

to that of the conditioning bias.

Remove all bias from the test specimens and return the cham-

ber to ambient conditions over a one hour period. Remove all

samples from the chamber for visual examination.

5.6

Data Analysis

The

average insulation resistance for

each sample group, taken at 24 hours and again at 96 hours,

shall be greater than the minimum set forth in IPC-J-STD-004.

The average insulation resistant (IR

avg

)

shall be defined as the

IPC-TM-650

Number

2.6.3.6

Subject

Surface

Insulation Resistance - Fluxes - Telecommunications

Date

01/04

Revision

age2of3

电子技术应用　　　　　　　ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ

geometric

mean of the sample set and can be calculated from

the following:

avg

= 10

[

log

(IR)

]

Where:

= Number of Test Points (12 nominal for each set of three

patterns).

individual insulation resistance measurements (see 6.6

for an example).

No individual insulation resistance value may be more than a

factor of 10 below the specified minimum value.

Where an assignable cause of low insulation resistance, which

is properly attributable to the laminate itself, or to the process

used to produce the PCB, can be found, then such a value

can be excluded from calculating the average value, provided

that at least 10 (of the original 12) test points are included in

the average.

Such assignable causes include the following:

• Contamination on the insulating surface of the board, such

as lint, solder splines or water droplets from the chamber.

• Incompletely etched patterns that decrease the insulating

space between the conductors by more than the amount

allowed in the appropriate design requirements drawing.

• Scratched, cracked, or obviously damaged insulation

between conductors.

5.7

Visual Analysis

Discoloration

of the patterns (green,

blue-green, blue, or blue-black coloration of the conductors)

shall be considered a failure.

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 oven. Water spot-

ting may also be observed in some ovens where the airflow in

the chamber is from back to front. In this case, water conden-

sation on the cooler oven window can be blown around the

oven as micro-droplets which deposit on test specimens and

cause dendritic growth if the spots bridge the distance

between two electrified conductors. Both of these conditions

must be eliminated for proper testing.

6.2 Tight

control of the test humidity is critical for this test

method. A difference of 5% relative humidity can result in a

0.5 - 1.0 decade difference in the measured resistance. . The

uniformity of the environment is also important. A fully loaded

chamber, where airflow is severely impeded, may have a

30-40% RH range within the chamber workspace.

6.3

The

polarity of the applied voltage is not important as

long as the application is consistent (e.g., Pads 1, 3, 5 are

positive and 2, 4 are at ground potential, vs. Pads 2 and 4

positive, and Pads 1, 3, 5 at ground potential).

6.4

The

0.318 mm [0.0125 in] lines/space pattern can also

be found on the obsolete IPC-B-25 standard test board. This

board was re-designed for improved SIR measurement accu-

racy (better routing of traces) and carries the designation IPC-

B-25A. Pattern D of the B-25A board is preferred over the B/E

pattern of the IPC-B-25.

6.5

ave

also referred to as the geometric mean of the

data set. Most spreadsheet packages contain functions for

calculating the geometric mean of a data set. If you are com-

puting the geometric mean of a large dataset, the spread-

sheet may come back with an error because the number is so

large. In such cases, use the antilog of the LogOhm average

to arrive at the geometric mean. See the following example.

6.6

Example of Numerical Calculations

Three

5-point test patterns (4 measurements each)

LogOhms = base-10 logarithm of measured resistance

Average of LogOhms = 11.84

Antilog of LogOhm Average = 6.94E+11 ohms =

Geometric Mean = IR

ave

No.

Resistance (Ohms) LogOhms

3.98E+11 11.60

2 1.58E+11 11.20

3 6.31E+11 11.80

4 7.94E+11 11.90

5 1.00E+12 12.00

6 1.00E+12 12.00

7 3.98E+11 11.60

8 1.58E+12 12.20

9 1.26E+12 12.10

10 1.26E+12 12.10

11 1.00E+12 12.00

12 3.98E+11 11.60

IPC-TM-650

Number

2.6.3.6

Subject

Surface

Insulation Resistance - Fluxes - Telecommunications

Date

01/04

Revision

age3of3

电子技术应用　　　　　　　ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ

1 Scope This test method is used to quantify the deleteri-

ous effects of fabrication, process or handling residues on

Surface Insulation Resistance (SIR) in the presence of mois-

ture. The electrodes are long parallel traces (printed inter-

digitated comb patterns) on a standardized printed board or

assembly. Samples shall be conditioned and measurements

taken at a high humidity. Electrodes are electrically biased

during conditioning to facilitate electrochemical reactions.

Specifically, this method is designed to:

• Simultaneously assess

a) leakage current caused by ionized water films and

b) electrochemical degradation of test vehicle, (corrosion,

dendritic growth).

• Provide metric(s) that can appropriately be used for binary

classification (e.g., go/no go, pass/fail).

• Compare, rank or characterize materials and processes.

2 Applicable Documents

2.1 IPC

IPC-A-24-G-KIT

Surface Insulation Resistance - Gerber Kit

J-STD-004 Requirements for Soldering Fluxes

IPC-A-600 Acceptability of Printed Boards

IPC-9201 Surface Insulation Resistance Handbook

2.2 American Society for Testing and Materials (ASTM)

ASTM D 257

Standard Test Methods for DC Resistance or

Conductance of Insulating Materials

2.3 American National Standards Institute (ANSI)/NCSL

International

ANSI/NCSL Z540-1

Calibration Laboratories and Measuring

and Test Equipment - General Requirements

ANSI/NCSL Z540-2 American National Standard for

Expressing Uncertainty - U.S. Guide to the Expression of

Uncertainty in Measurement

2.4 International Electrotechnical Commission

IEC-61189-5

Test methods for electrical materials, intercon-

nection structures and assemblies - Test methods for printed

board assemblies

3 Test Samples The type and number of test samples

(coupons) as well as method of preparation and test require-

ments should be described in the governing specification

(e.g., J-STD-004) or procurement documentation.

If this test method is being used as a stand-alone document,

decisions should be made regarding what samples might be

the most appropriate for test. This SIR method should not be

considered standard unless standard test vehicles are used.

Vehicles prepared for flux qualification shall be handled in a

way that minimizes the possibility of ionic contamination. Use

of ion-free gloves and wrap/bags is required. If testing a pro-

cess, standard shipping and handling procedures shall be

used.

For further information about sampling and sampling sizes see

7.1 and 7.1.2.

The IPC-A-24-G-KIT artwork package provides the necessary

Gerber files for the fabrication of the standard IPC-B-24 test

board used with this test method.

3.1 Test Controls Two cleaned bare IPC-B-24 test boards

(bare copper on FR-4) shall be used as chamber controls.

3.1.1 Visually inspect the boards for any obvious defects, as

described in IPC-A-600. If there is any doubt about the over-

all quality of any test sample, the board should be discarded.

3.1.2 Clean each control board by using deionized or dis-

tilled water and scrubbing with a soft bristle brush for a mini-

mum of 30 seconds. Spray rinse thoroughly with deionized or

distilled water. Rinse cleaned area thoroughly with virgin

2-propanol.

An alternative cleaning method is to place the test board in an

ionic contamination tester containing 75% 2-propanol, 25%

deionized water and process the solution until all ionics have

been removed.

1. www.ipc.org/onlinestore

3000 Lakeside Drive, Suite 309S

Bannockburn, IL 60015-1249

IPC-TM-650

TEST METHODS MANUAL

Number

2.6.3.7

Subject

Surface Insulation Resistance

Date

03/07

Revision

Originating Task Group

SIR Task Group (5-32b)

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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