IPC-TM-650 EN 2022 试验方法.pdf - 第234页

5.1.2 Use the micrometer to determine the specimen thick- ness, t, at the test region of the specimens to the nearest 0.0025 mm [0.0001 inch]. In the case of single-sided or cover-coated specimens, core thickness, t M , …

1.0

Scope

With

this test method the flexural fatigue life for

any given bend radius, the flexural fatigue behavior and the

ductility of the conductor metal in percent deformation after

tensile failure can be determined.

Note: The indirect determination of conductor ductility by

using a fatigue test is made necessary by the geometry and

dimensions of foil samples which make tensile elongation and

rupture tests inadequate for ductility determination.

2.0

Applicable Documents

IPC-TM-650

Method

2.1.1, Microsectioning

IPC-TM-650

Method

2.4.18, Tensil Strength and Elongation,

Copper Foil

IPC-D-330

IPC

Design Guide

3.0

Test Specimen

3.1

The

test coupon shown in Figure 1 is the recommended

standard test specimen pattern for either single- or double-

sided flexible printed wiring.

3.2

The

conductor width of the standard test pattern (Figure

1) can be changed to determine line width effects.

Note: Narrow conductor width will result in reduced flex lives

due to an increased flaw size/conductor width ratio. Wide

conductors result in increased flex lives due to longer crack

propagation times and the possibility of strain relief due to

cracks propagating in close proximity from opposite conduc-

tor edges.

3.3 Actual

flexible printed wiring product, whole or sections

thereof, can be used if the circuit geometry is such that the

long dimension is at least 63.2 mm [2.5 inches], the wide

dimension no more than 38.1 mm [1.5 inches], and the con-

ductors in the long direction can be electrically connected in

series to give a pattern similar to the standard test pattern (see

Figure 1).

4.0

Apparatus

4.1

Ductility

Flex Tester, Universal Mfg., Model FDF or 2FDF

or equivalent (see 6.4 and Figure 2).

4.2 Sample

cutter, punch or tensile cut router. Note 6.3.2.

4.3

Micrometer

tool capable of measuring 0.0025 mm

[0.0001 inch].

4.4

Hewlett-Packard,

HP-67, Programmable Calculator or

equivalent.

4.5

Sample

holders, 203.2 x 12.7 mm [8 x 1/2 inch] of very

flexible material, e.g., epoxy-impregnated glass cloth, paper,

etc.

4.6 Microscope

5.0

Procedure

5.1 Preparation of Samples

5.1.1

Use

the sample cutter to cut the 3.2 mm [1/8 inch]

wide test specimen. Examine each specimen for nicks, cuts,

or curled edges. Discard any specimen with defects.

IPC-2431-1

Figure

1 Test coupon conﬁguration (recommended)

▼

45327

104mm

[4.10]

76.2mm

[3.00"]

NOTE 3

3.81mm [.150] (NOTE 1)

NOTES:

1. 0.76mm [.030"] Conductor width,

0.76mm [.030"] spacing

2. Pattern on opposite circuit

sides are identical

3. 5-digit lot number of

production lot.

▼

2.54mm

[.100"] 12.7mm

[.050"] 12.7mm

[.050"]

88.9mm

[3.50"]

The

Institute for Interconnecting and Packaging Electronic Circuits

2215 Sanders Road • Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.4.3.1

Subject

Flexural

Fatigue and Ductility, Flexible Printed

Wiring

Date

3/91

Revision

Originating Task Group

N/A

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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5.1.2

Use

the micrometer to determine the specimen thick-

ness, t, at the test region of the specimens to the nearest

0.0025 mm [0.0001 inch]. In the case of single-sided or

cover-coated specimens, core thickness, t

has to be deter-

mined also (see Figure 2).

Note: Thickness is a critical parameter in the determination of

fatigue ductility. A 10% error in t

results

in a 14% error in D

Note: For

asymmetric configuration (2nd configuration in Fig-

ure 2) the core thickness, t

is preferably determined as a

fraction of the specimen thickness, t, from a microsection pre-

pared per IPC-TM-650, Method 2.1.1, and measured with a

metallurgical microscope at 200X minimum with a suitable filar

eyepiece or reticle. The measurement is to be made from the

valley of the rough surface to the smooth surface or valley to

valley where both surfaces are rough. The t

to be made

once on a batch or lot basis, and this fractional value of t

then multiplied by all other micrometer, t, values to achieve

core values for all samples. This applies only to the second

and third configuration in Figure 2, where t

cannot

be deter-

mined by a micrometer.

5.1.3

For

standard test coupons, connect the meander pat-

terns on opposite circuit sides in series and attach thin relay

leads to the free ends of the meander patterns. For nonstand-

ard test specimens, connect all conductors to be tested and

monitored in series and attach thin relay leads to the two free

ends.

5.1.4

Attach

test specimen to the ends of 2 sample holders

with adhesive tape and clamp 224 grams [8 ounces] circuit

weight to free ends of sample holders to form a loop (see Fig-

ure 3).

Note: For flexural fatigue tests lasting in excess of 1000

cycles, the adhesive tape attachment needs to be substantial

enough to prevent relative sliding of specimen and sample

holder as a result of the cyclic flexure movements.

5.2

Test Procedure

5.2.1

Mount

mandrels to flex tester, adjust the support roller

positions for a clearance of 1.27 mm [0.05 inches] (shim pro-

vided) between rollers and mandrels.

Note: For the ductility test, it is important that the specimens

fail between 30 and 500 cycles. Suggested mandrel diam-

eters are 19.05 mm [0.750 inch] for double-sided circuitry and

6.35 mm [0.250 inch] for single-sided circuitry, but for some

samples, mandrel diameters different from these diameters

may be necessary. Larger mandrel diameters result in longer

cyclic life and smaller diameters in shorter life.

IPC-2431-2

Figure

2 Minimum core thickness

COVERCOAT

▼

t = t

SUBSTRATE

CONDUCTOR

SUBSTRATE

CONDUCTOR

SUBSTRATE

IPC-2421-2

Figure

3 Fatigue ductility ﬂex tester

IPC-TM-650

Number

2.4.3.1

Subject

Flexural

Fatigue and Ductility, Flexible Printed Wiring

Date

3/91

Revision

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5.2.2

Mount

test specimen between mandrels, plug relay

leads into relay jacks, set counter to zero, and start flex tester.

5.2.3

Electrical

discontinuity constitutes failure and the flex

tester stops automatically.

5.2.4

Record

cycles-to-failure indicated on counter.

5.3

Evaluation

5.3.1 Ductility Test

5.3.1.1

Calculate

the ductility for each specimen by itera-

tively solving the formula below:

−0.6

0.75

+ 0.9

[

exp(D

)

0.36

]

(0.1785

log

)

−

= 0

where:

fatigue ductility, inch/inch (x100,%)

cycles-to-failure

ultimate tensile strength, psi

E = modulus of elasticity, psi

core thickness, inch

t = specimen micrometer thickness, inch

ρ = mandrel radius of curvature, within 0.005 mm [0.0002

inch]

Note: This formula is exact only for symmetric cross sections.

In the case of nonsymmetrical single-sided laminate, the

uncertainty of the location of the neutral axis introduces some

error. The error in D, is kept below 20% if

[

−1

]

substrate

≤ 0.1

IPC

Design Guide, IPC-D-330, Section 6, ‘‘Flexibility Consid-

erations in Design of Flexible Printed Wiring,’’ gives more

detailed information for the accurate determination of the loca-

tion of the neutral axis and the cyclic strains.

Note: Determine S

per IPC-TM-650, Method 2.4.18.

Determine E during the test for S

unloading and reloading

after about 2% elongation and measuring the slope of the

reloading curve.

Note: The calculator program described in paragraph 6.2

solves the ductility formula and conveniently prompts for all

necessary input parameters.

5.3.1.2

Report

the average product ductility from at least

three specimens.

5.3.2

Fatigue Test

The

number of cycles-to-failure, is the

flexural fatigue life in fully reversed bending for the bend radius

corresponding to the radius (1/2 diameter) of the test mandrel

used. An average flexural life from at least three specimens

should be reported.

5.3.3

Fatigue Behavior

The

fatigue behavior of a sample

can be obtained by determining the flexural fatigue life with a

number of different diameter mandrels. Plotting the results in

a strain range versus fatigue life Manson-Coffin plot log ∆ε =

[2t

/(2tρ +

t)] versus log N

)

allows intra- and extrapolation to

other bend radii or fatigue lives.

5.3.4

The

flexural fatigue life at bend radii other than the

mandrel radius can also be obtained by evaluating the ductil-

ity formula for the flex life in cycles-to-failure using the product

ductility determined in 5.3.1.2 and the desired bend radius.

6.0 Notes

For

further technical details, reference the mate-

rial shown below.

6.1

Document

in paragraph 2.0.

6.2

Engelmaier,

W., ‘‘Fatigue Ductility for Foils and Flexible

Printed Wiring.’’ Program No. 1883D HP-67/97 User’s

Library, Hewlett Packard Co., Corvallis, Oregon, 1978.

6.3

Engelmaier,

W., ‘‘Fatigue Ductility Flex Tester,’’ Drawing

L520163, Bell Telephone Laboratories, Inc., Whippany, New

Jersey, 1978.

6.4

Test Equipment Sources

The

equipment sources

described below represent those currently known to the

industry. Users of this test method are urged to submit addi-

tional source names as they become available, so that this list

can be kept as current as possible.

6.4.1

Fatigue

Ductility Flex Tester, Universal Mfg. Co., Inc.,

1168 Grove St., Irvington, NJ 07111; 201-374-9800.

6.4.2

JDC

Precision Sample Cutter Model JDC 125-N or

equal.

IPC-TM-650

Number

2.4.3.1

Subject

Flexural

Fatigue and Ductility, Flexible Printed Wiring

Date

3/91

Revision

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