Kapton CSP Socket DC Measurement

Aries
Kapton CSP socket
DC Measurement Results
prepared by
Gert Hohenwarter
8/6/2004
GateWave Northern, Inc.
1
Table of Contents
TABLE OF CONTENTS .......................................................................................................................................... 2
OBJECTIVE ......................................................................................................................................................... 3
METHODOLOGY.................................................................................................................................................. 3
Test procedures ................................................................................................................................................. 4
Setup ................................................................................................................................................................. 4
MEASUREMENTS ................................................................................................................................................. 6
Resistance ......................................................................................................................................................... 6
Current carrying capability............................................................................................................................... 7
Leakage current ................................................................................................................................................ 9
GateWave Northern, Inc.
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Objective
The objective of these measurements is to determine the DC performance of an Aries
Kapton CSP socket. Measurements are to determine parameters relevant to test
applications. Among those are current carrying ability, contact resistance and leakage
as a function of voltage.
Methodology
A four terminal (Kelvin) measurement setup is used that includes a computer
controlled voltage source capable of delivering 10 A. The voltage developed across
the contact is measured with a HP 3456A DMM and yields a V-I record.
Contact resistance testing as a function of displacement is performed in a test fixture
with a calibrated LDT linked to the data acquisition system and the same 4 terminal
measurement setup as used for the V-I-curve determination.
Leakage testing relies on acquisition of a large number of data points with
subsequent averaging to reduce noise as much as possible. In this manner, pA
leakage currents can be detected.
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Test procedures
During testing drive current is increased in binary steps up to a maximum of 0.3 A.
The dwell time for each current step is 0.5 s for V/I curves.
Setup
For current handling tests, all contacts are grounded except for one.
The Kapton CSP socket is placed into the test setup between two metal plates. Au
over Ni plating was applied to the surfaces of the brass plates. A four terminal (Kelvin)
measurement setup is used that included a computer controlled current source capable
of delivering 10 A. The voltage developed across the contact is recorded at separate
terminals with an HP3456A digital voltmeter.
Figure 1 Kapton CSP socket test arrangement; the marked pin is driven
Once the data are available, they are processed to reveal the resistance and power
dissipation as a function of drive current.
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For leakage measurements the shorting plate on the DUT side is removed and an
excitation applied to the connection under test.
The Kapton CSP socket is held in a fixture consisting of insulating material similar to
the one shown in Fig. 2:
Figure 2 Kapton CSP socket mounting plate example
Leakage testing is performed via computer controlled voltage source and DMM.
Voltage is increased in small steps and the associated current is recorded. From these
values, resistance is computed.
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Measurements
Resistance
The resistance as a function of deflection is an important quantity since it testifies to
the minimum compression required to achieve a valid and stable electrical connection.
The observed curve for the Aries Kapton CSP socket is shown below:
Cres (z)
250
R [mOhms]
200
150
100
50
0
0
10
20
z [um]
30
GW N 504
Figure 3 Contact resistance as a function of displacement
This measurement includes the contact resistance at the pads (Cres) and the dc
resistance of the contact itself. For this graph, the value z=0 represents the maximum
compression in operation, i.e. with the DUT fully inserted.
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6
Current carrying capability
The measured current – voltage relationship for the Kapton CSP socket shows a
linear slope:
V and R as a function of drive current I
250
V[mV] / R [mOhms]
200
150
V
R
100
50
0
0
0.5
1
1.5
I [A]
2
GW N 404
Figure 4 Voltage and resistance as a function of drive current
There are no anomalies in this response. The slight resistance rise at the low end is
due to inaccuracies in the 10A current source at extremely low current settings.
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The accompanying power dissipation in the connection exceeds 100mW at currents
above about 1.7A:
P as a function of drive current I
140
120
P [mW]
100
80
60
40
20
0
0
0.5
1
1.5
I [A]
2
GW N 404
Figure 5 Power dissipation as a function of drive current
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Leakage current
Any conductive path between contacts can and will cause difficulties for accurate
testing of devices with high input impedances. Thus, leakage current was measured as
a function of excitation voltage between two adjacent connections:
I [pA]
Leakage current as a function of voltage
50
45
40
35
30
25
20
15
10
5
0
0
2
4
6
V
8
10
GW N 404
Figure 6 Leakage current as a function of drive voltage
Leakage is very low and is at the system limits.
When computing the corresponding resistance, very large values result:
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Resistance as a function of voltage
10000
R [GOhm]
1000
100
10
1
0
2
4
6
V
8
10
GW N 404
Figure 7 Leakage resistance as a function of drive voltage
The resistance values are well above 1000 GigaOhms for all excitation voltages.
GateWave Northern, Inc.
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