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SEMI G23-0996 © SE MI 1980, 1996 2 principles, conduct the actual measurement to get the best result. 7.2 To get an accurate measureme n t , maintain equal probe angle an d distance. 8 Apparatu s 8.1 LCR Meter 8.1.1 F o …

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SEMI G23-0996 © SEMI 1980, 19961
SEMI G23-0996
TEST METHOD FOR INDUCTANCE OF INTERNAL TRACES OF
SEMICONDUCTOR PACKAGES
NOTE: This entire document was revised in 1996.
1 Purpose
This test method describes the measurement method for
the inductance of internal traces of semiconductor
packages.
2 Scope
2.1 This test method is applicable for the measurement
of package inductance that is greater than 0.5 nH.
2.2 This document describes the measurement of a pin
grid array, one of the package types, as a sample.
2.3 This test method is also applic able to other types
of packages.
2.4 The inductance in this docume nt is limited to that
of internal traces only and does not contain the portions
contributed by the exposed areas such as pins and
wires.
2.5 This document uses SI units.
3 Limitation
It is not practical to apply this test method for fine-pitch
packages where traces or pads (point A of Figure 1)
cannot be connected to with two probes.
4 Referenced Documents
None.
5 Terminology
5.1 internal inductance (of packages) — Inductance of
the circuit that comprises the signal path starts from the
shoulder or in the center of the outside lead (point A of
Figure 1) and ends at the end of the lead on the cavity
side of the lead (point B of Figure 1). The return path is
made by tying all other traces (except for the target
trace in the same electric potential) together. The target
trace is tied to the return path at the bonding finger (see
Figure 2).
Figure 1
Internal Inductance Measurement
Figure 2
Concept of Internal Inductance
5.2 four-point probe — The probe consists of four
coaxial measuring terminals, H
c
(current high), H
p
(potential high), L
c
(current low) and L
p
(potential low),
to measure impedance. Independent coaxial cables are
used between the package being measured and the
measurement instrument to minimize the effect caused
by mutual inductance (between terminals) and/or
interferences from the measured signals (see Figures 3
and 6).
6 Summary of Method
Fabricate the package to be measured. Then measure
the inductance of internal traces using the four terminal
probe method.
7 Interference
7.1 It is desirable that an operator who is familiar with
the measuring system, measuring method, and
SEMI G23-0996 © SEMI 1980, 1996 2
principles, conduct the actual measurement to get the
best result.
7.2 To get an accurate measurement, maintain equal
probe angle and distance.
8 Apparatus
8.1 LCR Meter
8.1.1 Four terminal probe attachmen t capability
8.1.2 Capable of measuring at the frequency of 10
MHz or higher
8.1.3 Measurement error of less than 0.1 nH for the
measurement range more than 1 nH at the measurement
frequency
8.2 Four Terminal Probe — See F igure 3.
Figure 3
Configuration of Four Terminal Probe
8.2.1 Residual Inductance — less than 1 nH
9 Material
9.1 Copper Plate
9.1.1 Plating — gold
9.1.2 Thickness — 2 mm or thicker
9.2 Insulator — such as Teflon
9.3 Silver Foil
9.3.1 Thickness — around 50 µm
9.4 Solder or Conductive Paste
9.4.1 Resistivity — 10
-4
Ω · m or less
10 Test Specimens
10.1 Preparation of Sample — Conduct the circuit by
measuring the trace as a signal path and the rest, which
has a different potential from this signal path, will be
the return path, as follows:
10.1.1 All the bonding fingers shall b e soldered or
pasted together at the bond finger area to form a short
circuit.
NOTE 1: The short circuit area shall be 0.5 mm from the tip
of the bond fingers. The entire bond fingers shall not be short
circuited (see Figure 4).
Figure 4
Sample Preparation (Part of Bonding Finger)
10.1.2 Short all pins or leads except f or the ones with
the same potential as the trace being measured.
NOTE 2: The location for the short circuit shall be as close as
possible to the bottom of the pins or the braze pad of the leads
to minimize the inductance caused by the pins or leads.
NOTE 3: In case of Pin Grid Array packages, it is
recommended to press 50 µm thickness silver foil, which is
the same size of package, through the pins. In case of Flat
Packages, it is recommended to solder silver foil (or a copper
foil) at the braze pads of the leads.
11 Preparation of Apparatus
Before starting the measurement, warm up the
instruments as specified in the manual.
12 Calibration
Before starting the measurement, calibrate the
instruments as specified in the manual.
13 Procedures
13.1 Measurement of Residual Inductance
13.1.1 Set the LCR meter to the induc tance
measurement mode.
13.1.2 Measure the inductance by conducting the four
terminal probe on the gold plated copper plate as shown
in Figure 5.
Figure 5
Measurement of Residual Inductance
SEMI G23-0996 © SEMI 1980, 19963
NOTE 4: The angle between the potential terminal probe and
the current terminal probe has to be maintained at a right
angle (90°). This is to nullify the mutual interference caused
by the magnetic flux.
13.2 Measurement of the Resultant Inductance
13.2.1 Place the sample on the insulator such as
Teflon.
13.2.2 Set the probe at the bottom of the pin of the
trace being measured and at the closest traces belonging
to the short circuit as shown in Figure 6.
Figure 6
Probing Method
NOTE 5: The probes H
p
and H
c
are attached/placed onto the
pins to be measured and the probes L
p
and L
c
are
attached/placed onto the short circuit.
14 Calculation
14.1 The inductance of the internal trace is calculated
as follows:
Internal Inductance (nH) = Measured Inductance —
Residual Inductance
14.2 Round the second digit after th e decimal point to
the unit of 0.1 nH.
15 Report
The following information shall be reported:
• Brief description of the package
• Measurement instrument or system
• Measurement frequency
• Measurement pin numbers
• Inductance — Raw data as well as the average in
case of multiple measurements.
16 Accuracy
Using the same samples, four different packaging
manufactures were tested. The following results were
obtained:
Repeatability — ± 0.2 nH
Reproductibility — ± 0.5 nH
17 Related Documents
SEMI G24 — Test Method for Measuring the Lead-to-
Lead and Loading Capacitance of Package Leads
SEMI G25 — Test Method for Measuring the
Resistance of Package Leads