IPC-TM-650 EN 2022 试验方法--.pdf - 第303页

Figure 7 Corners Su pports R1 R1 R2 Supporting Jacks or Blocks Figure 8 Highest Point Measurement Measure at This Point Measure at This Point R2 R2 R1 IPC-TM-650 Page 5 of 5 Number 2.4.22 Subject Bow and Twist (Percentag…

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Figure 5 Measurement of Twist
R
A
C
D
B
R = Highest
Point of Board
Shim under raised
corner of A.
B, C, and D touching
Datum Surface. Only
one corner may be
physically restrained.
Figure 6 Sample Placement
R2 Lowest
Corners
R2 R2
R1
Raised Parallel
Surfaces
IPC-TM-650
Page 4 of 5
Number
2.4.22
Subject
Bow
and
Twist
(Percentage)
Date
6/99
Revision
C
I
PC-4442-5
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.
_
DO
Percentage
Twist
=
—
X
1
00
6
Notes
None
I
PC-2422-6
Figure 7 Corners Supports
R1 R1
R2
Supporting Jacks or Blocks
Figure 8 Highest Point Measurement
Measure at
This Point
Measure at
This Point
R2
R2
R1
IPC-TM-650
Page 5 of 5
Number
2.4.22
Subject
Bow
and
Twist
(Percentage)
Date
6/99
Revision
C
///////////
//////
/
/////////
I
PC-2422-7
I
PC-2422-8
None
Figure 1
Figure 2
The Institute for Interconnecting and Packaging Electronic Circuits
2215 Sanders Road • Northbrook, IL 60062-6135
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
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Page 1 of 2
IPC-TM-650
TEST
METHODS
MANUAL
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
3
.0
Test
Specimen
The
test
specimen
for
incoming
inspection
shall
be
300
x
300
mm
±
2
mm
[12
x
12
in
±
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
Number
2.4.22.1
Subject
Bow
and
Twist
—
Laminate
Date
Revision
5/93
C
Originating
Task
Group
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.