IPC-TM-650 EN 2022 试验方法--.pdf - 第86页

Figure 2A C ircuit for R esistance Measurements Figure 2B Id eal Probe Plac ement on Pad IPC-TM-650 Number Subject Date Revision Page 2 of 4 2.2.13.1 Thickness, Plating in Holes Microhm Method 1/83 A 3.3 Operating Condit…

100%1 / 824
IPC-TC-500
NOTE:
Figure 1 Resistance Calculation of Plated-Through
Connection
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Page 1 of 4
IPC-TM-650
TEST
METHODS
MANUAL
1
.0
Scope
1.1
A
nondestructive
inspection
method
for
determining
the
quality
of
plated-through
connections
in
printed
wiring
boards.
1
.2
Theory.
Copper
will
display
a
resistivity
of
known
value
depending
upon
the
geometry
of
the
shell
and
the
conductiv¬
ity
of
the
copper.
If
the
shell
is
not
uniform,
defects
such
as
cracks,
voids,
or
thin
spots
in
the
copper
will
cause
the
mea¬
sured
resistance
to
be
higher
than
the
theoretical
value.
This
value
is
computed
by
using
the
equation
given
in
Fig.
1
.
2
.0
Applicable
Documents
Specification
for
copper
plated
through
hole,
two-sided
boards,
rigid.
3
.0
Test
Specimen
3.1
Description
of
Specimens.
The
following
types
of
specimens
can
be
tested
using
the
equipment
specified
herein:
(1)
Printed
wiring
boards,
either
two-sided
or
multilayer,
which
can
fit
properly
within
the
neck
of
the
test
meter.
In
testing
of
plated-through
holes
in
two-sided
。广
multilayer
printed
wiring
boards,
the
measurement
is
the
resis¬
tance
of
the
plating
in
the
hole
only
and
/s
not
related
to
any
interconnected
circuit
terminating
in
that
hole,
unless
there
is
electrically
parallel
circuit,
ie,
two
or
more
holes
located
within
0.25"
of
each
other.
(2)
Printed
wiring
boards
up
to
3/8"
in
thickness.
(3)
Plated-through
connections
of
any
diameter
which
can
be
spanned
conveniently
by
the
probes.
3.2
Specimen
Preparation.
Insulating
materials
such
as
flux,
conformal
coatings,
encapsulating
compounds,
adhe¬
sives,
mold
release
compounds,
etc.,
shall
be
removed
from
the
terminal
areas
to
allow
a
positive
metal-to-metal
contact
to
be
made
between
the
probes
and
the
plated-through
hole
terminal
area.
Closely
spaced
conductors
shall
be
masked
to
prevent
the
probes
from
bridging
between
the
terminal
areas
and
adjacent
conductors.
Whatever
material
is
used
to
mask
the
conductors
shall
be
located
in
such
a
manner
that
the
probes
are
not
separated
from
the
hole
to
be
measured.
Number
2.2.13.1
Subject
Thickness,
Plating
in
Holes
Microhm
Method
Date
1/83
Revision
A
Originating
Task
Group
Printed
Board
Test
Methods
Task
Group
(7-1
Id)
where:
R
=
resistance
(ohms)
T
=
thickness
of
PWB
(inches)
D
=
diameter
of
drilled
hole
(inches)
t
=
copper
plating
thickness
in
hole
'(inches)
NOTES:
1.
It
is
assumed
that
the
conductivity
of
the
copper
is
100
percent
I
ACS.
2.
To
compute
the
value
of
t
with
known
values
of
D,
T,
and
R,
use
the
following
equation:
t
=
0.5D-[0.25D-^I]
-
where
R
=
resistance
(microhms)
and
D,
T,
and
t
are
in
inches.
Figure 2A Circuit for Resistance Measurements
Figure 2B Ideal Probe Placement on Pad
IPC-TM-650
Number
Subject Date
Revision
Page 2 of 4
2.2.13.1
Thickness,
Plating
in
Holes
Microhm
Method
1/83
A
3.3
Operating
Conditions.
The
evaluation
of
the
plated-
through
holes
shall
be
performed
at
room
temperature
(68°
to
75°
F)
and
the
printed
wiring
boards
to
be
evaluated
shall
be
stabilized
at
that
temperature
for
approximately
one
hour
prior
to
evaluation.
4.0
Apparatus
4.1
Description
of
Equipment.
The
microhm
resistance
meter
used
in
the
nondestructive
testing
employs
the
stan¬
dard
four*probe
technique.
The
equipment
is
portable
and
suitable
for
bench
operation.
The
equipment
consists
of
two
essential
parts:
(1)
the
mechanical
portion
for
providing
physical
attachment
with
the
test
specimen
and
(2)
the
electrical-electronic
portion
for
providing
the
microhm
readout
of
the
through
connection
being
measured
The
probes
are
tension-suspended
to
ensure
positive
interfa¬
cial
contact
with
the
termination
areas
over
a
range
of
mate¬
rial
thicknesses.
4.2
The
meter
impresses
a
constant
ac
current
into
the
through
connection,
and
the
voltage
that
develops
across
the,
hole
is
sensed.
This
voltage
is
amplified
and
observed
visually
on
a
suitable
meter
or
a
digitized
readout.
See
circuit
diagram
in
Fig.
2A.
5.0
Procedure
5.1
Calibration
of
Equipment.
In
order
to
provide
valid
resistance
measurements,
the
equipment
must
be
calibrated
as
specified
in
the
manufacturers'
instruction
manual
5.2
Test
Steps.
The
steps
to
be
performed
in
evaluating
the
quality
of
plated-through
holes
in
printed
wiring
board-
are
as
follows:
5.2.1
Calibrate
the
equipment.
5.2.2
Prepare
and
condition
the
specimen(s)
to
be
inspected
per
3.2.
5.2.3
Position
the
printed
wiring
board
between
the
probes
as
shown
in
Fig.
2B.
Plated
Hole
5.2.4
Depress
the
upper
probes
until
they
Awes,
come
locked
over
the
plated-through
hole.
IPC-TM-650
Number
Subject Date
Revision
Page 2 of 2
2.2.18
Determination
of
Thickness
of
Laminates
by
Mechanical
Measurement
12/94
5.3.2.2.2.1
Calculate
the
overall
nominal
thickness
by
add¬
ing
to
the
base
nominal
thickness
the
total
thickness
of
the
metallic
cladding.
Thickness
of
metallic
cladding
shall
be
based
on
.035
mm
[0.0014
in]
per
45.7
g
[1.0
oz],
or
as
sup¬
plied
by
the
foil
supplier.
5.3.2.2.2.2
Calculate
the
minimum
and
maximum
limits
by
subtracting
and
adding
the
required
tolerance
from
the
over¬
all
nominal
thickness.
5.3.2.2.2.3
Measurements
taken
after
specimen
prepara¬
tion
per
5.1
.2
shall
be
compared
with
the
minimum
and
maxi¬
mum
limits
as
determined
in
5.
3.2.2.
2.
5.4
Report
Unless
otherwise
specified,
report
the
average,
minimum
and
maximum
readings,
and
compliance
with
requirements,
if
applicable.
6.0
Notes
6.1
Use
of
hand
or
manual
micrometers
should
be
carefully
administered.
Pressure,
anvil
shape,
and
other
features
of
the
micrometer
and
its
use
must
follow
accepted
industry
practices,
if
not
defined
in
the
applicable
specification.