IPC-TM-650 EN 2022 试验方法--.pdf - 第371页

Figure 1 T est Fixture Configuration Sample Strap 2PL Base Plate IPC-TM-650 Page 3 of 4 Number 2.4.41.2 Revision A Subject Coefficient of Thermal Expansion — Strain Gage Method Date 05/04 5.3.5 Place the gage/terminal ass…

100%1 / 824
IPC-TM-650
Number Subject Date
Revision
Page 6 of 7
2.4.54
TestMethodforThermalTransmissionPropertiesof
09/2022
MetalBasedPrintedBoards(MBPB)
N/A
Equation 14). With the thickness from the microsection it is possible
to calculate the apparent thermal conductivity of the dielectric
layer (Table 1 Equation 16). This calculated value must be shown
in the measurement report including the dimensions (mm²K/W)
(Table 1 Equation 15) as well as the apparent thermal conductivity
in W/(mK) (Table 1 Equation 16) and the thicknesses in µm.
5.10
Measure three identical samples across the board and list
all results in the measurement report. In addition, the mean value
and the standard deviation must be listed as well in the report.
5.11
To measure the DIE thickness a cross section according to
IPC-TM-650 Test Method 2.1.1 should to be made.
5.12
To embed the sample, the specimen is first cut in half using
a e.g., metal saw. Afterwards the specimen gets embedded,
grinded and polished.
5.13
The thicknesses of the top and dielectric layer are measured
in the microsection on five different points using a microscope.
Calculate the middle value of the five measured values for each
layer. From the total thickness of the sample, the thickness of
the base layer can be determined by subtraction (see Table 1
Equation 17).
1
2
3
Figure5LayerStructureofaMetal-BasedBoard
Note1: Top layer: d
top,
see 1.3.1
Note2: Dielectric layer: d
die
Note3: Base layer: d
base
Figure 1 Test Fixture Configuration
Sample
Strap 2PL
Base Plate
IPC-TM-650
Page 3 of 4
Number
2.4.41.2
Revision
A
Subject
Coefficient
of
Thermal
Expansion
—
Strain
Gage
Method
Date
05/04
5.3.5
Place
the
gage/terminal
assemblies
in
their
original
position
over
the
reference
lines,
using
only
enough
pressure
to
allow
the
assemblies
to
be
tacked
down.
Overlay
the
gage/
terminal
area
with
thin
pieces
of
PTFE
tape,
and
anchor
them
in
position
with
pieces
of
Mylar
tape
across
the
ends.
5.3.6
Cut
the
silicone
gum
pads
to
size
slightly
larger
than
the
gage/terminal
areas,
carefully
centering
them
in
position.
Larger
pads
may
restrict
proper
spreading
of
the
adhesive
and
entrap
residual
solvents
during
the
curing
process.
5.3.7
Use
spring
clamps
or
dead
weights
to
apply
pressure
(275
to
350
kN/m2
[40
to
50
psi])
and
place
in
the
curing
oven
which
is
to
be
at
room
temperature.
5.3.8
Raise
the
temperature
to
100
±
3
[212
°F
土
6
°F]
(use
79
[174
°F]
if
using
M-Bond
600)
at
a
rate
of
3
to
11
℃
/min
[5
°F
to
20
°F/min],
and
cure
for
4
1/2
to
5
hours.
Air
bubble
entrapped
in
the
adhesive,
uneven
glue
lines,
and
high
adhesive
stresses
often
result
from
starting
with
a
hot
oven.
5.3.9
Remove
the
specimens
after
allowing
the
oven
to
cool
below
55
[131
°F],
remove
clamps
and
Mylar
tape,
and
clean
the
entire
surface
with
isopropyl
alcohol
to
remove
residual
tape
adhesive.
Wipe
dry
with
a
gauze
sponge.
5.3.10
Post
cure
for
2
to
2
1/2
hours
at
40
[104
°F]
(30
[86
°F]
per
M-Bond
instructions)
above
the
test
upper
limit
temperature.
Care
must
be
taken,
if
base
materials
hav¬
ing
low
Tg
values
(FR-4)
are
to
be
tested.
5.3.1
1
Bond
the
solder
tabs
6.4
mm
[0.25
in]
from
the
strain
gages.
The
gage
leads
are
to
looped
slightly
prior
to
soldering
to
prevent
inducement
of
strain
resistance
changes.
Solder
tabs
may
be
attached
in
the
same
step
as
the
strain
gages.
5.4
Specimen
Fixture
Preparation
(If
required,
Figure
1)
5.4.1
The
PCB
and
titanium
silicate
standards,
once
assembled
with
the
strain
gages,
are
fixtured
to
prevent
bend¬
ing
or
warping
by
the
straps
labeled
PL
in
Figure
1
during
the
temperature
cycle
test.
The
fixture
used
for
the
specimens
will
not
interfere
with
the
thermal
expansion
of
the
specimens
being
tested.
The
fixture
is
constructed
of
1
.25
mm
[0.050
in]
thick
Alloy
42
plated
with
0.025
mm
[0.001
in]
of
copper.
This
material
was
chosen
because
of
its
thermal
expansion
properties
that
are
close
to
that
of
the
test
specimens.
Plated
Alloy
42
straps
are
used
to
gently
hold
the
specimen
flat
to
the
fixture.
Other
materials
that
may
closely
match
the
GTE
of
the
test
speci¬
men
may
be
used.
5.5
Test
Configuration
Connect
two
strain
gages,
one
to
the
test
specimen
and
one
to
the
to
the
titanium
silicate
stan¬
dard,
in
adjacent
arms
forming
a
half
bridge;
the
remaining
half
of
the
Wheatstone
bridge
being
completed
with
the
Wheatstone
bridge
instrument
(see
Figure
2).
Repeat
for
the
remaining
two
strain
gages,
one
on
the
test
specimen
and
one
on
the
titanium
silicate
standard
with
a
second
Wheat¬
stone
bridge
instrument
in
the
circuit.
Attach
(tape)
thermocouple
to
the
sample
within
a
6.0
mm
[0.25
in]
of
the
measurement
area.
5.6
Specimen
Conditioning/Thermal
Cycling
Clean
the
specimens
by
immersing
in
M-Line
solvent
with
agitation
for
15-20
seconds.
Allow
to
dry
for
1
to
1
1/2
hours
at
40
±
5
℃
[105
°F
±
9
°F]-
5.6.1
Place
the
specimens
and
the
reference
standards
in
the
thermal
cycling
chamber
(with
programmable
temperature
control)
set
at
20
[68
°F]
and
allow
to
stabilize
for
30
to
40
minutes
or
as
required
to
relieve
strain
gage
attachment
stresses.
5.6.2
Increase
temperature
at
a
rate
of
2
℃
/min
[3
°F/min]
up
to
130
[266
°F]
or
other
test
temperature
designated,
allowing
the
specimens
to
stabilize
for
1
0
minutes
or
longer,
if
Example:
Note:
Figure 2 Wheatstone Bridge Instrumentation Hookup
R Gage on Unknown
R Gage on Standard
R Standard Resistors on Instrument
M Direct Reading Strain Meter
External or Measurement
Half Bridge
Internal or Instrument
Half Bridge
U
S
K
R
U
R
S
R
K
R
K
M
IPC-TM-650
Page 4 of 4
Number
2.4.41.2
Revision
A
Subject
Coefficient
of
Thermal
Expansion
—
Strain
Gage
Method
Date
05/04
required.
Decrease
the
temperature
to
-55
±
2
[-67
°F
±
3
°F]
or
other
temperature
designated
and
allow
to
stabilize
for
10
minutes
or
until
no
further
changes
are
noted
on
the
meter.
Increase
the
temperatures
to
25
[77
°F]
at
the
same
rate
and
allow
the
specimens
to
stabilize.
5.6.3
Throughout
the
thermal
cycle,
the
temperature
and
change
in
resistance
as
noted
on
the
meter(strain)
should
be
recorded
at
the
desired
time
and
temperature
(two
minute
intervals).
5.7
Calculation
of
CTE
Plot
the
gage
resistance
versus
the
temperature.
Measure
the
slope
of
the
line
between
the
temperatures
of
interest
and
record.
The
equation
for
calculating
the
Coefficient
of
Thermal
Expan¬
sion,
8,
are:
8
二
AR/R(GF)AT
Where
8
二
the
coefficient
of
thermal
expansion
R
=
gage
resistance
reading
AR
二
the
change
in
resistance
reading
AT
二
the
change
in
temperature
GF
=
the
Gage
Factor
of
a
particular
gage
and
gage
con¬
figuration
and
is
furnished
by
the
strain
gagemanufacturer.
The
GF
for
the
WK
gage
is
near
2.1
Resistance
reading
at
20
[68
°F]
=
352.39
Resistance
reading
at
1
70
[338
°F]
=
353.40
GF
as
furnished
by
manufacturer
=
2.11
(353.40-352.39)
(353.40
X
2.11
X
150)
二
9.03
ppm/℃
The
graph
plot
of
AR/AT
will
allow
selection
of
any
tem¬
perature
point.
All
strain
and
temperature
data
should
be
recorded
on
a
disk.
Software
packages
are
available
that
the
raw
data
(resistance
changes
and
temperature)
to
strain
and
temperature.
The
software
compensates
for
gage
factor
with
temperature,
apparent
strain
of
the
gage,
and
the
bridge
configuration
in
reducing
the
data.
The
software
also
uses
the
data
from
the
titanium
silicate
standard
to
adjust
the
reduced
data
of
the
test
specimen.
6
Notes
6.1
Suggested
Sources
of
Materials
6.1.1
Source
of
Adhesive
System
M
icro-
Measurements
Division
Measurements
Group
Inc.
P.
O.
Box
27777
Raleigh,
NG
27611
Phone:
(919)
365-3800
6.1.2
Information
Bulletin
Micro-Measurements
Division
Measurement
Group
Inc.
P.O.
Box
27777
Raleigh,
NO
27611
Phone
(919)
365-3800
Bulletin
#
B1
30-10
6.1.3
Titanium
Silicate
Standard
Corning
Glass
works
Corning,
NY
14831
Micro-
Measurements
Division
Measurement
Group
Inc.
P.O.
Box
27777
Raleigh,
NG
27611
Phone
(919)
365-3800