0.5mm SBT DC data - Ironwood Electronics

Ironwood Electronics
SBT 0.5mm Socket
DC Measurement Results
prepared by
Gert Hohenwarter
6/21/2006
GateWave Northern, Inc.
1
Table of Contents
TABLE OF CONTENTS .......................................................................................................................................... 2
OBJECTIVE ......................................................................................................................................................... 3
METHODOLOGY.................................................................................................................................................. 3
Test procedures ................................................................................................................................................. 4
Setup ................................................................................................................................................................. 4
MEASUREMENTS ................................................................................................................................................. 6
Current carrying capability (socket) ................................................................................................................. 6
Current carrying capability (contact in air) .................................................................................................... 10
GateWave Northern, Inc.
2
Objective
The objective of these measurements is to determine the DC current carrying ability,
resistance, and temperature rise during operation.
Methodology
A four terminal (Kelvin) measurement setup is used that includes a computer
controlled voltage source as well as a current source capable of delivering 10 A. The
voltage developed across the contact is recorded in a Kelvin (four terminal)
measurement at separate terminals.
GateWave Northern, Inc.
3
Test procedures
During testing drive current is increased in steps of 50 mA to the maximum value.
The dwell time for each current step is 60 seconds.
Setup
For current handling tests, all contacts are isolated except for one.
The SBT 0.5mm socket test components are placed 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.
Fig. 1 SBT 0.5mm socket test arrangement
Once the data are available, they are processed to reveal the resistance and power
dissipation as a function of drive current.
A second digital meter records the temperature of a small thermocouple (0.028”)
located near the driven pin. The thermocouple’s access location is about in the center
of the pin.
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The SBT 0.5mm socket is modified to allow thermocouple access and held in a fixture similar
to the one shown in Fig. 2:
Fig. 2 SBT 0.5mm socket mounting and fixturing example
GateWave Northern, Inc.
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Measurements
Current carrying capability (socket)
The measured current – voltage relationship for the SBT 0.5mm socket is shown below:
V and R as a function of drive current I
600
V[mV] / R [mOhms]
500
400
V
R
300
200
100
0
0
1
2
3
4
I [A]
5
GW N 404
Fig. 3 Voltage and resistance as a function of drive current
Above 4.5A thermal runaway occurs.
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6
The accompanying power dissipation in the connection is computed from applied
current and observed voltage:
P as a function of drive current I
3000
2500
P [mW]
2000
1500
1000
500
0
0
1
2
3
4
I [A]
5
G W N 404
Fig. 4 Power dissipation as a function of drive current
Another important parameter is the temperature rise as a function of drive level. As
stated above the temperature rise is measured via thermocouple in proximity with the
pin. This implies that temperature readings at the thermocouple will be lower than
those at and inside the pin itself.
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7
Temperature rise as a function of drive current I
140
120
dT [deg C]
100
80
60
40
20
0
0
1
2
3
4
I [A]
5
GW N 404
Fig. 5 Temperature rise as a function of drive current
Dwell times during this test are set to 1 minute per data point to let the temperature
increase to level off before acquiring the data point. Nevertheless it should be kept in
mind that the metal contacts at either end afford excellent heat removal from the
contact area. In an environment with lower thermal conductivity the temperature rise
during testing and the subsequent resistance increase as well as the current handling
may therefore be less than indicated here.
Another set of data was acquired with the drive current held constant and while
recording temperature as a function of time. The result is shown in Fig. 6 below:
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Temperature rise as a function of time
40
35
30
dT [deg C]
25
1A
1.5A
20
2A
2.5A
3A
15
10
5
0
0
5
10
15
t [min]
20
G W N606
Because of the low thermal mass of the contact under load the initial temperature rise
is very rapid. The slow increase of temperature with time up to about 10 minutes is
likely due to gradual warm-up of the surroundings and the metal structures that feed
the current to the contact.
GateWave Northern, Inc.
9
Current carrying capability (contact in air)
The measured current – voltage relationship for the SBT 0.5mm socket contact suspended in
air between two metal plates is shown below:
V and R as a function of drive current I
250
V[mV] / R [mOhms]
200
V
R
150
100
50
0
0
2
4
6
I [A]
8
GW N 404
Fig. 6 Voltage and resistance as a function of drive current
Above 7A a nonlinearity developed in the resistance and the test was terminated.
GateWave Northern, Inc.
10
The accompanying power dissipation in the connection is computed from applied
current and observed voltage:
P as a function of drive current I
1800
1600
1400
P [mW]
1200
1000
800
600
400
200
0
0
2
4
6
I [A]
8
GW N 404
Fig. 7 Power dissipation as a function of drive current
Again, temperature rise is measured via thermocouple in proximity with the contact.
This implies that temperature readings at the thermocouple will be lower than those at
and inside the contact itself.
GateWave Northern, Inc.
11
Temperature rise as a function of drive current I
200.0
180.0
160.0
dT [deg C]
140.0
120.0
100.0
80.0
60.0
40.0
20.0
0.0
0
2
4
6
I [A]
8
GW N 404
Fig. 8 Temperature rise as a function of drive current
GateWave Northern, Inc.
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