IPC-TM-650 EN 2022 试验方法--.pdf - 第634页
computer controls the o ven temperature through a range of temperatures from 23 °C to 260 °C [73 to 500 °F]. The com- puter monitor s and records the equilibrium resistance for each temperature. The equation used to calc…
5.2.8.5
When an individual coupon delta reaches the rejec-
tion resistance, Method A stress cycle testing is stopped for
the coupon. The rejection criteria provides for early interven-
tion so failure analysis activities can try to find the root cause
for the failure with minimal collateral damage from the stress
cycle.
5.2.8.6
The heating and cooling resistance data is compiled
for each coupon’s performance throughout the stress testing.
The system software provides a download file to graph the
coupon’s performance. Data is compiled to create graphs of
each coupon’s performance throughout stress testing.
5.2.8.7
The data is tabulated into a test report for analysis.
5.2.8.7.1 Tabulation of Results for Single Sense
Testing
The test data should be organized to provide the
following:
• Test Coupon Description
• Test Parameters
• Sample ID
• Power Circuit (P) Cycles to Failure or End of Test
• Power Circuit Percent Change
• Sense Circuit (S) Cycles to Failure or End of Test
• Sense Circuit Percent Change
• Disposition of Test Results
5.2.8.7.2 Tabulation of Results for Dual Sense Testing
The test data should be organized to provide the same data
as described in 5.2.8.7.1 with the addition of the following:
• Sense Circuit (S1,S2) Cycles to Failure or End of Test
• Sense Circuit (S1,S2) Percent Change
5.2.8.8
The resistance data for the coupons are plotted on
resistance graphs to indicate how damage is accumulated
over the test cycles.
5.2.8.9 Microsection (Optional)
An appropriate number
of coupons are selected for microsection review. A small cur-
rent is placed on the failing circuit and observed under a ther-
mal camera (see 6.2 and Figure 6-1). The most damaged
interconnection is selected for microscopic review.
5.2.8.10
Review all the tabulated data for a determination of
the disposition of the coupons.
5.3 Method B Procedure
5.3.1
Unless otherwise specified by the user, the default test
condition be Tin/Lead Reflow in accordance with Table
5-2.
5.3.2 Assembly Precondition (Optional)
See Table 5-2
Note 1. See also 6.1.
5.3.3 Temperature Coefficient of Resistance Test
Sequence
The TCR is calculated once for each unique cou-
pon type or cell. Once determined, that TCR is used for
Method B testing of all coupons of that type or cell. Examples
of elements that can affect the TCR and therefore define a
coupon type/cell are: via structure (thru holes vs. buried vias
vs. microvias, etc.), via diameter, via length, total board thick-
ness, laminate/resin material, plating chemistry, type of via fill,
and surface finish.
5.3.3.1 Temperature Coefficient of Resistance
Deter-
mine the TCR of each unique coupon type or cell using the
average value from 2 to 4 coupon samples. Attach coupons
to each quick connect test fixture and close the oven door. A
Tin/Lead
Reflow
(Default)
8
23 to 220 °C
[73 to 428 °F]
5% per cycle or
10% from first
cycle
10
1 second
intervals
3°C / second 40 seconds
Lead-Free
Reflow
8
23 to 245 °C
[73 to 473 °F]
5% per cycle or
10% from first
cycle
10
1 second
intervals
3°C / second 40 seconds
These default test conditions represents assembly conditions, and therefore assembly preconditioning is not required. The available temperature test range
is from 23 to 300 °C [73 to 572 °F] to any number of cycles.
See 5.3.5.
Number
2.6.26
Subject
DC Current Induced Thermal Cycling Test
Date
5/14
Revision
A
IPC-TM-650
shall
Table
5-2
Method
B
Typical
Test
Conditions
Note
1.
Test
Condition
Number
of
Samples
Test
Temperature1
Failure
Threshold
(Resistance
Change)2
Number
of
Cycles
Data
Collection
Frequency
Temperature
Ramp
Rate
Dwell
at
Test
Temperature
Note
2.
Page
6
of
10
computer controls the oven temperature through a range of
temperatures from 23 °C to 260 °C [73 to 500 °F]. The com-
puter monitors and records the equilibrium resistance for each
temperature. The equation used to calculate the TCR for each
tested coupon is as follows:
TCR(T) =
(Rh − Rrm)
(Th − Trm) x Rrm
where:
TCR(T) = Calculated TCR for the coupon as a function of
intended Method B Test Temperature T
Th = Temperature of coupon at oven temperature
Rh = Resistance of coupon at oven temperature
Rrm = Resistance of coupon at ambient temperature
Trm = Ambient Temperature (approximately 23 °C [73 °F])
5.3.4 Stress Cycle Definition
The system calculates and
displays the coupon test temperature with the following equa-
tion:
T = Trm +
(R − Rrm)
(Rrm x TCR(T))
where:
TCR(T) = Measured thermal coefficient of resistance for this
type/cell of coupons (see 5.3.3.1)
Rrm = Resistance of coupon at ambient temperature
measured at start of each cycle
T = Coupon test temperature calculated at 1 second
intervals
R = Coupon resistance measured at 1 second intervals
Trm = Ambient temperature measured at each cycle
(approximately 23 °C [73 °F])
Alternately, this equation may be expressed in terms of the
target resistance that is equivalent to the targeted high tem-
perature for that coupon and cycle, as follows:
Target Resistance = Rrm x (1 + TCR(Th)[Th - Trm])
where:
Th = Target high test temperature
5.3.5 Failure Threshold
Three different failure criteria or a
combination of these three may be used for a Method B cycle
as shown below. Refer to definitions for the variable names
and the equation for Target Resistance in 5.3.3.
1) R-high. During any single cycle, R exceeds target value by
more than R1% (default R1 = 5%) anytime during cycle,
that is,
R-high failure threshold: R > Target Resistance x (1 + R1).
2) R-low. During any single cycle, the final Rrm(n) after cool-
ing is greater than Rrm(n-1) of the previous cycle by more
than R2% (default R2 = 5%), that is
R-low failure threshold: Rrm(n) Rrm(n-1) x (1 + R2).
3) R-delta. Coupon is failed at cycle n if the final Rrm(n) after
cooling is equal to or greater than R3% (default R3=10%)
change from Rrm(0) at the start of test prior to cycle 1.
R-delta Failure Threshold: Rrm(n) > Rrm(0) x (1 + R3).
5.3.6 Stress Cycle Test Sequence
The following para-
graphs detail the sequence for a single coupon; however this
sequence is done at all test heads simultaneously.
5.3.6.1
Stress test coupons are placed in the table top test
fixture. The test fixture includes a cooling fan and quick con-
nect housings for the test coupons.
5.3.6.2
The Method B test system uses the TCR and asso-
ciated equation (see 5.3.3) to heat the coupon with DC cur-
rent (variable level determined in 1 second intervals) to the
prescribed ramp rate and high test temperature. The com-
puter also monitors and records the relative changes in resis-
tance of the plated barrel throughout the heating cycle.
5.3.6.3
The dwell time at test temperature is followed by
forced air cooling. Cooling time is a function of overall thick-
ness and construction of the coupon. The computer monitors
and records the coupon’s performance throughout the cool-
ing cycle.
5.3.6.4
The individual coupons are continually thermal
cycled using their customized heating and cooling conditions
until one of the rejection criteria is achieved or the maximum
number of cycles is completed.
5.3.6.5
The heating and cooling resistance data is compiled
for each coupon’s performance throughout the stress testing.
The system software provides a download file to graph the
coupon’s performance. Data is compiled to create graphs of
each coupon’s performance throughout stress testing.
5.3.7 Graphing and Data Analysis
5.3.7.1 Tabulation of Results
Test results are typically
reported with the following information:
• Test Coupon Description
• Test Parameters: Temperature(s), ramp rate, dwell
Number
2.6.26
Subject
DC Current Induced Thermal Cycling Test
Date
5/14
Revision
A
IPC-TM-650
Page
7
of
10
• Sample ID
• Temperature Coefficient of Resistance for each test tem-
perature and ‘‘cell’’
• Cycles to fail
• Applicable failure criteria
• Failure point (temperature at fail, hot or cold side of cycle)
• Failure isolation and analysis, if applicable
• Disposition of Test Results
6 Notes
6.1 Assembly Preconditioning – Optional
The elevated
temperatures of the lead free assembly process impacts the
performance of the plated barrels and internal connections.
Assembly preconditioning is recommended before the DC
current induced thermal cycling. When an individual coupon
delta reaches the rejection resistance, stress cycle testing is
stopped for the coupon.
6.1.1 Method A
The available equipment ranges and typi-
cal assembly preconditions are provided in Table 6-1. Attach
the power cable at the same location as the Method A stress
test.
6.1.2 Method B
The Method stress test temperatures are
based on the assembly process temperatures (see Table 5-2).
6.1.3 Convection Reflow Assembly Simulation (Method
C)
The assembly temperatures are based on IPC-TM-650,
Method 2.6.27.
6.2 Microsection Evaluation – Optional
If detailed failure
analysis is desired to determine the exact location of separa-
tions and/or cracks, select an appropriate number of coupons
for failure analysis. Locate the failure location and microsec-
tion to determine the most likely cause of the failure. Micro-
section of failed coupons be performed in accordance
with IPC-TM-650, Method 2.1.1.
6.2.1 Locate Failure by Thermal Camera
Locate the fail-
ure by applying a small current to the failing circuit and
observe the thermal camera output (see Figure 6-1). The loca-
tion with the ’hottest’ thermal signature is selected for failure
analysis.
6.2.2 Locate Failure by Hot Plate
Locate the failure using
a hot plate set at 220 - 250 °C. The hot plate should be cov-
ered with Kapton tape or a similar electrical insulator to insu-
late the coupon from the hot plate surface. Place the coupon
on the hot plate and monitor the resistance change using a
4-wire multimeter. The location with the highest resistance or
open is selected for failure analysis.
6.2.3 Locate Failure by Resistance
Locate the failure
using a 4-wire multimeter. Electrical isolate the circuits, PTHs,
or conductors by cutting conductors. The location with a high
resistance or open is selected for failure analysis.
6.3 Methods Overview
Table 6-2 provides an overview of
the two methods described in this test method to measure
the change of resistance of plated barrels and/or internal con-
nections as they are subjected to thermal cycling.
Tin/Lead
Reflow
6
230°C
[446°F]
240°C
[464°F]
10% 6 5 seconds None
Lead Free
Reflow A
6
245°C
[473°F]
255°C
[491°F]
10% 6 5 seconds None
Lead Free
Reflow B
6
260°C
[500°F]
270°C
[518°F]
10% 6 5 seconds None
Number
2.6.26
Subject
DC Current Induced Thermal Cycling Test
Date
5/14
Revision
A
IPC-TM-650
shall
Figure
6-1
Microvia
Failure
Location
Table
6-1
Method
A
Assembly
Preconditioning
Test
Conditions
Condition
Number
of
Samples
Test
Temperature
Maximum
Test
Temperature
Resistance
Change
Number
of
Cycles
Precycle
Time
Window
Compensation
Page
8
of
10