IPC-TM-650 EN 2022 试验方法.pdf - 第299页

1 Scope This test method covers three procedures used to determine the bow and twist percentage of individual rigid printed boards, rigid portions of rigid-flex printed boards, and/or multiple printed panels. Measurement…

Where:

D1 = Hole diameter

D2 = Land diameter

L = Load (force)

Note: The formula given utilizes the diameter of both the land

and the hole in the determination of the area of the land,

rather than the radius of each. Thus, a factor of four is applied

to the numerator as the area of a circle as defined by using

the diameter is (π * (diameter)

)/4.

5.4 Evaluation Examine test specimen for loosening of

bond and for loosening of the land from the base material. It

shall be considered a failure when a land around an unsup-

ported hole is loosened.

6 Notes

6.1

Breaking of a wire, or wire pull-out, shall not be consid-

ered a failure, but the wire shall be resoldered and pulled

again.

6.2 The following details are to be specified in the applicable

performance specification:

a. Test specimen, if other than specified in 3.

b. Force, if other than specified in 5.3.3.

IPC-TM-650

Number

2.4.21

Subject

Land Bond Strength, Unsupported Component Hole

Date

01/07

Revision

Page2of2

Scope

This

test method covers three procedures used to

determine the bow and twist percentage of individual rigid

printed boards, rigid portions of rigid-flex printed boards,

and/or multiple printed panels. Measurements on non-

rectangular samples pose a unique testing problem and may

necessitate careful evaluation of the requirements imposed by

the users of this test method. This test method does not

describe the special considerations necessary when testing

the bow and twist of printed board assemblies (i.e., compo-

nent placement & weight, edge supports & connectors, etc.).

The first two procedures describe production (Go/No-Go)

methods that generally characterize the bow and twist as

being no more than a specific value. The other procedure is a

referee method used to precisely determine the twist.

1.1

Definitions

Bow

and twist are defined in IPC-T-50.

The definitions are repeated in this test method for conve-

nience.

1.1.1

Bow (Sheet, Panel, or Printed Board)

The

devia-

tion from flatness of a board characterized by a roughly cylin-

drical or spherical curvature such that, if the product is rect-

angular, its four corners are in the same plane (see Figure 1).

1.1.2

Twist

The

deformation of a rectangular sheet, panel,

or printed board that occurs parallel to a diagonal across its

surface, such that one of the corners of the sheet is not in the

plane that contains the other three corners (see Figure 2).

2 Applicable Documents

IPC-T-50

Terms

and Definitions for Interconnecting and

Packaging Electronic Circuits

IPC-TM-650

Test

Methods

Test Specimens

The

test specimens shall be in the form

of either printed boards or multiple printed panels (single-

sided, double-sided, multilayer, or rigid-flex boards).

3.1 For

non-rectangular test specimens, the most conve-

nient way to measure bow and twist is approximating a rect-

angle over the test specimen. To accomplish this, an imagi-

nary rectangle that totally encloses the sample must be

superimposed over the test specimen. The dimensions of this

superimposed rectangle should be the smallest that will fully

enclose the specimen. Although this technique will give an

approximation of bow and twist, the actual noted values will

be less than the actual bow and twist of the sample.

IPC-2422-1

Figure

1 Box

BOW

With constraining f

orce applied

to both corners of the same edge.

1 & 2 deflection from surface plane.

IPC-2422-2

Figure

2 Twist

oints A, B, C

Touching Base

With constraining force

applied to one corner only.

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.4.22

Subject

Bow

and Twist (Percentage)

Date

6/99

Revision

Originating Task Group

Rigid Printed Board Test Methods Task Group

(7-11d)

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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Equipment/Apparatus

4.1

Precision

surface plate

4.2

Thickness

measurement shims (feeler or pin gauges)

4.3

Leveling

jacks

4.4

Standard

metrology height dial indicator gauge

4.5

Gauge

blocks

4.6

Linear

measuring devices of suitable accuracy

4.7

Micrometer

of suitable accuracy for thickness measure-

ment

Procedure

Unless

otherwise specified, testing shall be

performed at standard laboratory conditions (see IPC-TM-

650, Section 1.3).

5.1

Production Testing (Bow)

5.1.1

Place

the sample on the surface plate. While applying

sufficient pressure to flatten the test sample, measure the

length and width of the sample and record it as length (L) &

width (W) (see Figure 3).

5.1.2

Calculate

the size of the feeler/pin gauge (Go/No-Go)

to be used for maximum bow percentage using the following

formula:

L (B)

100

Rw =

W (B)

100

Where:

Go/No-Go feeler/pin gauge size for sample length

Go/No-Go feeler/pin gauge size for sample width

L = Length measurement as determined above

W = Width measurement as determined above

B = Maximum allowable bow percentage

5.1.3

Place

the sample to be measured on the surface plate

with the convex of the sample facing upwards. For each edge,

apply sufficient pressure on both corners of the same sample

edge to ensure contact with the surface (see Figure 4).

5.1.4

Attempt

to slide the feeler/pin gauge of thickness R

under

the length side(s) of the sample and R

under

the width

side(s) of the sample. If the Go/No-Go feeler/pin gauge will

slide between the sample and the surface plate, the bow in

that direction exceeds the allowable percentage used in the

calculation above. Repeat this procedure until all sides of the

sample have been measured.

5.1.5

a determination of actual percentage of bow is

desired, repeat 5.1.1 through 5.1.4 using a feeler/pin gauge

that will easily fit between the side of the sample and the sur-

face plate. Continue to increase the feeler/pin gauge size until

the largest feeler/pin gauge that will fit between the sample

and the surface plate for both the length (x2) and width (x2) is

obtained. Measure this feeler/pin gauge with the micrometer

and record as R

Calculate

the percentage for bow as follows:

100 B

100

Where:

Percentage bow in the length direction

Percentage bow in the width direction

Measured maximum feeler/pin gauge size across

sample length

Measured maximum feeler/pin gauge size across

sample width

L = Length measurement as determined above

W = Width measurement as determined above

IPC-2422-3

Figure

3 External Measurements

IPC-TM-650

Number

2.4.22

Subject

Bow

and Twist (Percentage)

Date

6/99

Revision

age2of5

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