IPC-TM-650 EN 2022 试验方法.pdf - 第18页

In interpreting test results, it is essential that all values are known to be valid. Usually the values are placed in one of the three following categories and evaluated to ultimately arrive at a sound decision: a. Resul…

The

following guidelines should be used for numerical report-

ing:

1. Follow the IPC policy for the use of metric and English

units.

In an effort to prepare the industry for a full change to

complete metric measurements in IPC standards and

specifications, the Technical Activities Executive Commit-

tee (TAEC) voted on a new way for both to be included.

Through this new metric conversion policy, IPC docu-

ments will have hard metric numbers and parenthetical

soft imperial numbers with appropriate units.

The hard metric numbers will represent accuracy of the

numerical values as decided by the working committee/

task group according to their respective contexts.

For

example:

The

working committee/task group will decide whether a

hard metric number should be represented as:

1.3 mm (any value within the range of 1.25 mm to 1.34

mm is acceptable), or

1.30 mm (any value within the range of 1.295 mm to

1.304 mm is acceptable).

The soft imperial numbers will have one significant digit

more than the metric numbers to capture the accuracy

represented by the metric numbers.

For

example:

3m(one

significant digit) converts to 118.1102 in, which

will be documented as 3 m [120 in] (two significant dig-

its because the zero is a placeholder).

3.0 m (two significant digits) converts to 118.1102 in,

which will be documented as 3.0 m [118 in] (three sig-

nificant digits).

9.17 m (three significant digits) converts to 30.0853 ft,

which will be documented as 9.17 m [30.09 ft] (four sig-

nificant digits because all zeros embedded between non-

zero digits are significant).

2mm(one significant digit) converts to 0.07874016 in,

which will be documented as 2 mm [0.079 in] (two sig-

nificant digits because the zeros are placeholders used to

locate the decimal point).

66 µm (two significant digits) converts to 0.002598425 in,

which will be documented as 66 µm [2.60 mil] (three

significant digits because the non-truncated zero is not a

placeholder).

725 µm (three significant digits) converts to 0.02854331

in, which will be documented as 725 µm [28.54 mil] or

[0.02854 in] (appropriate units are determined by the

context of numerical values and both have four significant

digits).

3.8X10

-6

converts to 1.496063 X 10

-4

in,

which will

be documented as 3.8X10

-6

m [1.50 X 10

-4

in] (if sci-

entific numerical format is appropriate).

2. Spell out numbers one through ten, except in use with

measurement and time.

3. Spell out any numbers at the beginning of a sentence.

4. When reporting numbers less than a whole number,

place a zero to the left of the decimal point.

5. Report average results to the same amount of significant

figures as the numbers being averaged.

6. When readings reach maximum of test equipment or

maximum of practical values, precede the number with

‘‘greater than’’ or ‘‘>’’ and explain the reason for not

going to the limit.

7. Always report results in the same unit of measurement as

that of the requirement.

8. In reporting ranges use the preposition ‘‘to,’’ not a

hyphen as: 3 cm to 9 cm.

9. Report portions of a unit of measure in the singular.

10. Mark a failed result in such a way as it will stand out to

the reader. Later state what this marking signifies.

11. When tabulating, use clearly defined headings.

12. Clarify when more than one set of numbers is in a tabu-

lation of statement.

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST METHODS MANUAL

Number

1.6

Subject

Numerical

Reporting

Date

01/03

Revision

Originating Task Group

N/A

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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interpreting test results, it is essential that all values are

known to be valid. Usually the values are placed in one of the

three following categories and evaluated to ultimately arrive at

a sound decision:

a. Results are declared valid. A decision can be made imme-

diately

b. Results obviously must be discarded. Specimens that

break or otherwise fail because of some obvious flaw, or

that do not behave in the same general manner as the

other specimens, should be discarded. Retests should be

performed on new specimens.

c. Results deviate from the mean value. All test data obtained

from properly performed tests must be included in deter-

mining mean and standard deviation unless there is an

assignable cause not to do so.

The above information is to be used if not found in an indi-

vidual test method.

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST METHODS MANUAL

Number

1.7

Subject

Reporting,

Invalid Test Results

Date

01/03

Revision

Originating Task Group

N/A

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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Scope

Tests

performed on presumably identical samples

under seemingly identical conditions do not always yield iden-

tical results. This is due to errors inherent in every measure-

ment or evaluation. During the development of a new test

procedure or use of an existing test procedure, this variability

must be understood and precautions taken to ensure that it is

controlled to within necessary limits. Performance of this test

method will help to estimate measurement error and trouble-

shoot causes of measurement variability. Use of this test

method will provide some evidence that a new test procedure

is suitable for use when submitted for review, or an existing

test procedure is capable of measuring the applicable param-

eter.

This method provides a standard procedure for determining

the precision of a test method involving binary data or tests

that result in two outcomes. These include evaluations where

the results are recorded as pass/fail or go/no-go. Examples

include solderability tests and visual inspections. This method

helps to estimate how often the disposition is performed cor-

rectly.

This method is not useful for measurements which result in

variables data, or where more than three repeated measure-

ments or more than ten testers are used. These situations are

covered under other methods (see 6.1).

1.1 Definitions

Accuracy

–

The

difference between an observed measure-

ment and the true (but perhaps unknown) value being mea-

sured.

Precision

–

The

closeness to each other of repeated mea-

surements of the same quantity.

Binary

Data –

Inspections

or tests in which parts are placed

in one of two classes. This includes pass/fail, go/no-go tests

and inspections.

Applicable Documents

The

test procedure under evalu-

ation.

Test Specimens

The

test specimens used will be as

specified in the test procedure under investigation.

The number and types of test materials to be used will

depend on the range of levels in the class of materials to be

tested. If it is known that precision is worse at one end of the

range, evaluation could be limited to that end of the range. In

general, evaluations are generally advisable for all combina-

tions of materials, levels, set-ups, and conditions. If resources

are limited, begin the study with those combinations deemed

to be the most critical, or where measurement error is likely to

be greatest.

The number of samples will also depend on the difficulty

involved in obtaining, processing, and distributing the test

specimens, the difficulty, length of time required for, and

expense of performing the test, and other prior known infor-

mation.

This test method will assume that evaluations can be repeated

on the same samples. For situations where this is not possible

or the sample is consumed during the test, other methods

may be better suited (see 6.1).

Apparatus

The

apparatus used will be as specified by

the test procedure under investigation.

Procedure

5.1 Planning Evaluation

Keep the evaluation as simple as

possible to obtain data that is free of unintended secondary

effects.

Prepare a procedure that is complete and describes the test

parameters as well as recommended techniques for assess-

ing the outcome. Include known best practices and draw

extensively on the experience of test users.

The method used in this procedure allows for up to 10 test

conditions. Solicit participants from among the community of

facilities with the proper equipment, competent operators and

familiarity with the test. In order to obtain representative pre-

cision estimates, do not select only from a small group of

users who are considered exceptionally qualified. Be sure to

specify any special calibration procedures or material prepara-

tion requirements.

The analysis method used in this procedure allows for up to

10 repeated evaluations per sample. Carefully evaluate the

materials to determine the appropriate classification or dispo-

sition before the study. Choose material representing a likely

range of conditions normally encountered during routine tests

or inspections. Randomize the samples prior to dividing into

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST METHODS MANUAL

Number

1.8

Subject

Measurement

Precision Estimation for Binary Data

Date

01/03

Revision

Originating Task Group

Measurement Precision Task Group (7-11a)

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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