IPC-TM-650 EN 2022 试验方法.pdf - 第680页

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 t…

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.

Page1of4

ASSOCIATION CONNECTING

ELECTRONICS INDUSTRIES

During the remainder of the preparation, handle boards by the

edges only and use noncontaminating gloves.

3.1.3 Dry the cleaned boards for two hours at 50 °C.

3.1.4 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. (Kapak™ bags are avail-

able from Fischer, VWR and other distributors.)

3.1.5 When measured as described in Sections 4 and 5, if

the control board readings are less than 1000 MΩ at any point

after the initial 24 hours of SIR exposure, a new set of test

coupons shall be obtained and the entire test repeated.

3.2 Blank Process Controls If performing process valida-

tion testing, two samples from an unprocessed blank should

be run with the samples taken from the processed boards.

Values obtained from unprocessed board samples are useful

when failure is observed within the processed board sample.

Failure of the unprocessed samples may indicate a problem

with the incoming bare board rather than an assembly pro-

cess.

4 Equipment/Apparatus It is the responsibility of the user

of this method to verify equipment suitability. This method

intends for all tolerances to be interpreted as uncertainties

with a confidence interval of 95% as referenced in ANSI/NCSL

Z540-1 and ANSI/NCSL Z540-2. Quantitative, qualitative and

default information follow in the paragraphs below.

4.1 Electrometer Electrometer, High Resistance Meter,

Picoammeter or equivalent as described by ASTM D 257.

a) System must be capable of taking measurements and

controlling the switching automatically (unattended).

b) Minimum resistance measurement accuracy (not only

meter, but as implemented)

5% of full scale up to 10

Ω @5V

10% of full scale up to 10

Ω @5V

20% of full scale above 10

Ω @5V

c) Accuracy with respect to the ‘‘true’’ value requires assess-

ment of stability of the measurement system (after switch-

ing from bias voltage to the measurement voltage). There-

fore, if the system does not automatically assess stability

before logging, use an arbitrary time of one minute.

d) The system described in this section must be able to make

all measurements required within a 20 minute period and

meet the requirements of 5.3.

It is preferred that the resistance reading be stable before

acquiring the readings or data. If after one minute the signal

remains unstable, a measurement should still be recorded.

4.2 Switching System

a) Must have a channel-to-channel isolation resistance ten

times greater than the resistance of typical SIR require-

ments, or a default channel-to-channel isolation resistance

of 10

Ω.

b) <20-minute cycle while obtaining measurements as

described above.

c) Unique 10

Ω current limiting capability per channel.

4.3 Wire Attachments

a) Single solid copper wire with PTFE insulation.

b) Preferred solid wire solders (no flux), or nominally 1% by

weight rosin nonactivated. See wire attach section of this

document for more information.

c) Electrical (EMI) shielding to guard cabling from stray cur-

rents.

4.3.2 Alternative Wire attachments such as stranded wire,

non-PTFE insulation, edge connectors rather than hard wiring,

and guarding techniques may be used provided the system

accuracy is not compromised.

4.4 Controlled Temperature and Humidity Chamber

a) Produce 40±1°Cat90±3%R.H.

b) Continuous or semicontinuous recording of this environ-

ment.±2°Cand±3%R.H.

c) Samples should not significantly impede airflow.

d) Adequate mixing of water vapor and air is imperative to

ensure condensation does not occur anywhere in the

chamber except on/around cooling or dehumidification

coils. If any part of interior of the chamber is below the dew

point (possibly due to insulation or control issues), conden-

sation will occur. This is not necessarily a problem as long

as the samples are kept above the dew point and are

shielded from dripping or flying condensate.

4.5 Camera Camera capable of recording color image.

5 Test Procedure

5.1 Interconnect Samples

IPC-TM-650

Number

2.6.3.7

Subject

Surface Insulation Resistance

Date

03/07

Revision

Page2of4