IPC-TM-650 EN 2022 试验方法.pdf - 第294页

only this length is used in the calculation, otherwise the dis- tance between the grips is used as the initial gauge length. The result is expressed in percent and reported to two signifi- cant figures. percent elongatio…

4.7

Extension Indicators (optional)

Extension

indicators

(e.g., extensometers) must be designed as to minimize stress

on the specimen at the contact points of the specimen and

the indicator. Clip type extensometers are not recommended

for this reason. Laser extensometers can be used if the

method of marking the specimen does not induce any stress

or strain into the specimen (e.g., scratching the specimen) or

change the specimen in any fashion (e.g., heating the

specimen).

4.8

Calibration

The

thickness gauge should be calibrated

every six months using standard gauge blocks. The blades on

the film cutter should be resharpened or replaced at least

once a year. The load cell on the tensile tester should be cali-

brated at least once a week following the manufacturer s rec-

ommended procedure. Also, the stops which control the ini-

tial grip separation should be checked once a week.

5.0

Procedure

5.1 Operating Conditions

The

tests should be conducted

at 23 ± 2°C and 50 ± 5% relative humidity.

5.2

Preparation of Test Specimens

5.2.1

The

test specimens should be conditioned at 23 ±

2°C and 50 ± 5% relative humidity for not less than 24 hours

prior to testing. Refer to ASTM D 618.

5.2.2

The

free films are placed between two cover sheets of

clear film (MylarT* or equivalent) to facilitate handling of the

specimens.

5.2.3

Cut

at least 10 specimens 76.20 mm long and 12.70

mm wide. No specimen shall vary by more than 2% in width

along its entire length. The utmost care must be exercised in

cutting specimens to prevent nicks and tears along the edges

of the specimen that are likely to cause premature failure. If

the properties in the plane of the film are not isotropic (e.g.,

the films were not prepared by spin coating), then ten films

must be cut in both the machine direction (MD) and transverse

direction (TD).

5.4

Testing

5.4.1

Measure

and record the thickness of the test speci-

men to an accuracy of 0.1 µm at no fewer than five different

places within the gauge length area. Refer to ASTM D 1005

and AST D 2370.

5.4.2

Set

the initial gauge length (grip separation) at 25.4

mm and the rate of grip separation at 5.08 mm/min.

5.4.3

Place

the specimen in the grips of the testing

machine, taking care to align the long axis of the specimen

with an imaginary line joining the points of attachment of the

grips to the machine. The specimen should be aligned as per-

fectly as possible with the direction of pull so that no rotary

motion that may induce slippage will occur in the grips.

Tighten the grips evenly and firmly to the degree necessary to

minimize slipping of the specimen during testing. The use of

air activated grips facilitates the mounting of the specimen in

the grips.

5.4.4

Start

the test and record the load versus extension.

5.4.5

Repeat

steps 5.4.1 - 5.4.4 for each series of ten

specimens.

5.5

Calculations

5.5.1

For

each series of ten specimens, the arithmetic mean

and standard deviation of each property for the specimens

with the five highest tensile strengths shall be calculated to the

proper number of significant figures. This is done on the basis

that the expected errors (nicks or flaws in the specimen,

breaks within the grips, specimen slippage, etc.) would all

tend to produce lower results. The standard deviation is cal-

culated as follows and reported to two significant figures:

√

i = 1

−

(

i = 1

)

N(N−1)

where

Xi is the value of a single observation (i = 1 through N),

N is the number of observations, and s

the estimated stan-

dard deviation.

5.5.2

Tensile Strength

Tensile

strength is calculated by

dividing the load at break by the original minimum cross-

sectional area. The result is expressed in megapascals (MPa)

and reported to three significant figures.

tensile strength =

(load at break)

(original

width)(original thickness

5.5.3

Percent Elongation

Percent

elongation is calculated

by dividing the elongation at the moment of rupture by the ini-

tial gauge length and multiplying by 100. When gauge marks

or extensometers are used to define a specific test section,

IPC-TM-650

Number

2.4.18.3

Subject

Tensile

Strength, Elongation, and Modulus

Date

7/95

Revision

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only

this length is used in the calculation, otherwise the dis-

tance between the grips is used as the initial gauge length.

The result is expressed in percent and reported to two signifi-

cant figures.

percent elongation =

(elongation at rupture) x 100

(initial

gage length)

5.5.4

Young’s Modulus

Young’s

modulus is calculated by

drawing a tangent to the initial linear portion of the stress-

strain curve, selecting any point on this tangent, and dividing

the tensile stress by the corresponding strain. For purposes of

this calculation, the tensile stress shall be calculated by divid-

ing the load by the average original cross section of the test

specimen. The result is expressed in gigapascals (GPa) and

reported to three significant figures.

Young’s modululus =

(load at point on tangent)

(original

width)(original thickness)

(elongation at point on tangent)

(initial

gage length

5.5.5

Toe Compensation

(from

ASTM D 882) In a typical

stress-strain curve (see below), there is a toe region, AC,

which does not represent a property of the material. It is an

artifact caused by a take-up of slack, and alignment or seat-

ing of the specimen. In order to obtain correct values of such

parameters as modulus, strain, and yield point, this artifact

must be compensated for to give the corrected zero point on

the strain or extension axis. In the case of a material exhibiting

a region of Hookean (linear) behavior as shown below, a con-

tinuation of the linear (CD) region of the curve is constructed

through the zero-stress axis. The intersection (B) is the cor-

rected zero-strain point from which all extensions or strains

must be measured, including the yield point, if applicable. The

elastic modulus can be determined by dividing the stress at

any point along line CD (or its extension) by the strain at the

same point (measured from point B, defined as zero-strain).

6.0

Notes

The

tensile properties determined using this test

method will vary with method of specimen preparation, speci-

men thickness, specimen width, rate of grip separation, initial

gauge length, type of grips used, and method of measuring

extension. The tensile strength and elongation are sensitive to

the specimen dimensions and any flaws in the specimen.

Young’s modulus is an index of the stiffness of the specimen

and is sensitive to the rate of grip separation. Note that mate-

rials that fail by tearing give anomalous data that cannot be

compared with those from normal failure (rupture). A tear fail-

ure is a tensile failure characterized by fracture initiating at one

edge of the specimen and progressing across the specimen

at a rate slow enough to produce an anomalous stress-strain

curve. Results obtained using different specimen dimensions

or at different rates of grip separation are not comparable;

consequently, when trying to make quantitative comparisons

between specimens or between laboratories, these factors

must be carefully controlled.

2.4.18.3-01

Figure

Strain

Stress

IPC-TM-650

Number

2.4.18.3

Subject

Tensile

Strength, Elongation, and Modulus

Date

7/95

Revision

age3of3

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Scope

This

test is to determine the tensile strength and

elongation on specimens exposed to mechanical loads.

Applicable Documents

None

Test Specimen

The

test specimen shall consist of a strip

of flexible material 152.4 mm long x 12.7 mm wide. A mini-

mum of 10 specimens, five from the machine direction, and

five from the transverse direction, shall be prepared.

Apparatus

4.1 Equipment

Tinius-Olson

Super L Tester or equivalent

(with appropriate load cell). The machine used for tension test-

ing shall be in current calibration. The loads used in determin-

ing tensile strength shall be within the loading range of the

testing machine.

4.2

Gripping Devices

Various

types of gripping devices

may be used to transmit the measured load applied by the

testing machine to the test specimens. To ensure axial tensile

stress within the gauge length, the axis of the test specimen

should coincide with the centerline of the heads of the testing

machine.

4.3

Sample Cutter

Thwing

Albert Sample Cutter, Model

No. JDC-50, or equivalent.

4.4

Etcher

4.5

Sander

4.6

Micrometer

with 0.0025 mm resolution

4.7

Conditioning

chamber or work area 23°C ± 2°C, 50% ±

5% RH

Procedure

5.1 Preparation of Specimens

5.1.1

Condition

specimens for 24 hours at 23°C ± 2°C and

50% ± 5% relative humidity (RH). Stabilization time may be

reduced if statistically sound evidence has been generated on

the specific product line to support shorter conditioning times

to reach equilibrium.

5.1.2

Cut

at least 10 specimens, 152.4 mm long by 12.7

mm wide, using a precision sample cutter, which produces

smooth and undistorted edges. Specimens may be sanded

on the edges with 400-600 grit emery paper to further smooth

the edges and improve the repeatability of the test.

5.2

Test

5.2.1

Measure

and record the width and thickness of the

specimen at several points along its length. Calculate the mini-

mum cross-sectional area using the measured width. For

coated materials, ignore the thickness of the coating,

assumed to contribute nothing to the tensile properties of the

composite, and use the nominal substrate thickness for the

cross-sectional area calculation.

5.2.2

Set

the grip separation to 101.6 mm and the rate of

grip separation to 50.8 mm per minute.

5.2.3

Place

the test specimen in the grips of the testing

machine, taking care to align it with the centerline of the grips.

There should be no slack in the specimen.

5.2.4

Start

the machine and record load versus extension

(grip separation).

5.3

Evaluation

5.3.1

Tensile

strength shall be calculated by dividing the

load at break by the original cross-sectional area of the speci-

men. Average the five values obtained for the machine direc-

tion samples and report the average. Average the five values

obtained for the transverse direction samples and report the

average.

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.4.19

Subject

Tensile

Strength and Elongation, Flexible Printed

Wiring Materials

Date

5/98

Revision

Originating Task Group

Flex Peel Strength Test Methods Task

Group (D-13A)

Material

in this Test Methods Manual was voluntarily established by Technical Committees of the 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 the IPC.

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