IPC-TM-650 EN 2022 试验方法.pdf - 第303页

IPC-2422-7 Figure 7 Corners Supports R1 R1 R2 Supporting Jacks or Blocks IPC-2422-8 Figure 8 Highest Point Measurement Measure at This Point Measure at This Point R2 R2 R1 IPC-TM-650 Number 2.4.22 Subject Bow and Twist (…

5.3.2

Support

the other two corners with leveling jacks or

some other appropriate devices, ensuring the two raised cor-

ners are of equal height from the datum surface. This may be

checked by using the dial indicator (see Figure 7).

5.3.3

Using

the dial indicator, measure the highest raised

portion on the board and record the reading as R1 (see Fig-

ure 8).

5.3.4

Without

disturbing the sample, take a reading with the

dial indicator on one of the corners contacting the surface (R2)

and record the reading (see Figure 8).

5.3.5

Take

the diagonal measurement of the sample and

record the reading.

5.3.6

Calculation

Deduct

the measured R2 from the mea-

surement R1. This difference is denoted as twist. Divide the

measured deviation by the recorded length and multiply by

100. The result of this calculation is the percentage of twist.

Percentage Twist =

R1 − R2

100

6 Notes

None

IPC-4442-5

Figure

5 Measurement of Twist

R = Highest

oint of Board

Shim under raised

corner of A.

B, C, and D touching

Datum Surface. Only

one corner may be

physically restrained.

IPC-2422-6

Figure

6 Sample Placement

▼

R2 Lowest

Corners

Raised Parallel

Surfaces

IPC-TM-650

Number

2.4.22

Subject

Bow

and Twist (Percentage)

Date

6/99

Revision

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IPC-2422-7

Figure

7 Corners Supports

Supporting Jacks or Blocks

IPC-2422-8

Figure

8 Highest Point Measurement

Measure at

This Point

Measure at

This Point

IPC-TM-650

Number

2.4.22

Subject

Bow

and Twist (Percentage)

Date

6/99

Revision

age5of5

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1.0

Scope

This

method covers the measurement of bow

and twist by maximum vertical displacement of an unre-

strained panel of either cut to size panels or finished rigid

printed boards including single- and double-sided, multilayer,

and the rigid segments of rigid flex printed circuits. This test

method is only applicable to laminates greater than or equal to

0.5 mm [0.020 in] in thickness. This test method can also be

used after etching or after thermal stress with requirements as

agreed between user and vendor.

2.0

Applicable Documents

None

3.0 Test Specimen

The

test specimen for incoming

inspection shall be 300 x 300 mm ± 2mm[12x12in±0.08

in] in size. For smaller panel sizes and finished printed wiring

boards, use actual size. A minimum of three specimens is

required per sample, when evaluating pressed laminate

sheets.

4.0

Apparatus

4.1

Sample

Shear

4.2

Granite

Surface Plate or Equivalent

4.3

Feeler

Gauges or Equivalent

4.4

Micrometer

5.0

Test Procedure

5.1 Preparation of the Test Specimen

5.1.1

For

laminate sheet, the test specimens are to be cut

in such a fashion as to minimize mechanical flexing.

5.1.2

For

cut to size panels or printed wiring boards, use

actual size.

5.1.3

Mark

the specimen for traceability. No mechanical or

chemical pre-cleaning is permitted on the specimens.

5.2

Measurement of Bow and Twist

5.2.1

Place

the test panels on the surface plate such that

the maximum vertical displacement is observed. The panel

should be turned over in establishing the maximum vertical

displacement. The maximum vertical displacement may be a

corner or a side of the test specimen as illustrated in Figures

1 and 2.

5.2.2

Measure

the maximum vertical displacement by

inserting the feeler gauges between the surface plate and the

bottom surface of the laminate.

5.2.3

Verify

the thickness measurement by measuring the

total thickness of the feeler gauges with the micrometer.

5.2.4

Record

the maximum vertical displacement in 0.25

mm [0.01 in]. One value is recorded per test specimen. This is

the bow and twist of the test specimen.

IPC-24221-1

Figure

IPC-24221-2

Figure

The

Institute for Interconnecting and Packaging Electronic Circuits

2215 Sanders Road • Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.4.22.1

Subject

Bow

and Twist—Laminate

Date

5/93

Revision

Originating Task Group

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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