IPC-TM-650 EN 2022 试验方法.pdf - 第542页
IPC-25512-5-17 Figure 5-17 SET2DIL Waveforms G + G q1 q2 G + G G + G TDR TDT NEXT FEXT TDT FEXT FEXT FEXT TDT TDT NEXT TDR NEXT + TDT TDR + FEXT Note: = Near End Cross Talk = Far End Cross Talk Figure 5-18 SET2DIL TDT , …
The same technique can be used for extracting the resistive
and dielectric losses in the presence of metal roughness and
dielectric inhomogeneities and for differential wiring.
5.4 SET2DIL Procedure This specification outlines the
fundamental principles behind SET2DIL; the exact method will
be instrument-dependent. Vendors providing SET2DIL capa-
bility are responsible for ensuring correlation between stan-
dard SDD21 measurements (VNA) and their implementation of
SET2DIL.
5.4.1 SET2DIL Structure The SET2DIL structure is a
101.6 mm [4.0 in] representative piece of the differential pair
(or single-ended signal) being characterized (see Figure 5-15).
It has an effective length of 203.2 mm [8.0 in]. A ‘‘thru’’ struc-
ture is used as a reference (see Figure 5-16).
5.4.2 SET2DIL Measurement A TDR pulse is injected into
‘‘q1’’ while the waveforms at q1 and q2 are monitored. The
q1 waveform will represent single-ended impedance with the
far end cross talk (FEXT) pulse superimposed on that. Like-
wise, the q2 waveform will represent the near end cross talk
(NEXT) pulse with the TDT pulse superimposed on that (see
Figure 5-17).
5.4.3 SET2DIL TDD21 Extraction The TDT pulse is
extracted from the q2 waveform, and the FEXT pulse is
extracted from the q1 waveform. FEXT is subtracted from TDT
to form TDD21. A detailed description of the waveform
manipulation is available as the 2010 DesignCon paper
‘‘SET2DIL: Method to Derive Differential Insertion Loss from
Single-Ended TDR/TDT Measurements.’’ Figure 5-18 shows
the extracted waveforms and the resultant TDD21.
5.4.4 SET2DIL SDD21 Calculation The FFT of the deriva-
tive of TDD21 is divided by the FFT of the derivative of the
‘‘thru’’ waveforms to calculate SDD21 of the SET2DIL struc-
ture. Figure 5-19 shows the time and frequency domain wave-
forms (SET2DIL frequency domain results compared to VNA
measurements on the right). SDD21 as a function of fre-
quency can then be compared to expected values to deter-
mine if the printed board construction is adequate to meet the
insertion loss requirements of the design.
IPC-25512-5-15
Figure 5-15 SET2DIL Test Structure
G
+
G
q1 excitation/
measurement
DUT/2 (4")
q2 measurement
DUT looped back
at end
Lead-
de-embedded;
must be minimized
IPC-25512-5-16
Figure 5-16 SET2DIL ‘‘thru’’ Structure
Ref Structure
(thru)
G
-
+
G
q1: excitation
q2: measurement
IPC-TM-650
Number
2.5.5.12
Subject
Test Methods to Determine the Amount of Signal Loss on
Printed Boards
Date
07/12
Revision
A
Page 21 of 24
IPC-25512-5-17
Figure 5-17 SET2DIL Waveforms
G
+
G
q1
q2
G
+
G
G
+
G
TDR
TDT
NEXT
FEXT
TDT
FEXT
FEXT
FEXT
TDT
TDT
NEXT
TDR
NEXT + TDT
TDR + FEXT
Note:
= Near End Cross Talk
= Far End Cross Talk
Figure 5-18 SET2DIL TDT, FEXT, and TDD21 Waveforms
q1 final
q2 final
SET2DIL
TDD21
Td Td
t0 t1 t2
IPC-TM-650
Number
2.5.5.12
Subject
Test Methods to Determine the Amount of Signal Loss on
Printed Boards
Date
07/12
Revision
A
Page 22 of 24
5.5 FD Procedure This specification currently outlines
measuring Frequency Domain characteristics using a VNA
(Vector Network Analyzer). Optionally, a TDT (Time Domain
Transmission) system may instead be used to create the
frequency domain loss data. The TDT essentially compares
the FFT (Fast Fourier Transform) of a calibration ‘‘through’’ to
the FTT of the test sample. The output is the S21 scattering
parameter matrix.
5.5.1 VNA Settings Recommended settings for the VNA
include an IF bandwidth of 1 kHz and a step size of 10 MHz.
5.5.2 VNA Calibration A short, open, load, and through
(SOLT) calibration must be preformed to obtain accurate VNA
measurement. This calibration shall be done at the tip of the
probing solution; therefore, the calibration structure will
depend on the probing solution used.
5.5.3 FD Measurement Adherence The metric used to
determine material ‘‘goodness’’ is insertion loss. Insertion loss
(IL) is defined as the negative of S21 expressed in decibels.
The through scattering parameter, S21, is a direct output from
the VNA or a TDT instrument. The insertion loss fit is used to
determine passing and failing lines. The slope the Insertion
loss fit, ma, can be used as another metric. Figure 5-20 illus-
trates the insertion loss of a line, the respective fit, and limit
regions.
The slope, m
a
, is representative of the average IL obtained
from the test sample. This slope should be less than the
slope, m
spec
, of the pass/fail line that is material dependent.
Figure 5-19 SET2DIL SDD21 Calculation
thru
SET2DIL
TDD21
0 2 4 6 8 10 12
x 10
9
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
VNA vs. SET2DIL (raw and fitted), L1, 100 ohms
Frequency (Hz)
SDD21 Magnitude (dB)
VNA 370HR
SET2DILraw 370HR
SET2DILfit 370HR
IPC-25512-5-20
Figure 5-20 Illustration of Insertion Loss Fit and Passing
and Failing Regions
Failing region high
Insertion
Loss
Fit Line
Failing region low
Frequencyf1
dB
f2
IPC-TM-650
Number
2.5.5.12
Subject
Test Methods to Determine the Amount of Signal Loss on
Printed Boards
Date
07/12
Revision
A
Page 23 of 24