1.0mm SBT DC data - Ironwood Electronics

Ironwood Electronics SBT 1.00mm contact
DC Measurement Results
prepared by
Gert Hohenwarter
2/28/2008
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
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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.
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Test procedures
During testing drive current is increased in steps of 50 mA to the maximum value.
Because of the low thermal mass a fast response of the contact itself occurs. The dwell
time for each current step is thus set to 10 seconds.
Setup
For current handling tests, all contacts are isolated except for one.
The SBT 1.00mm contact 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 1.00mm contact test arrangement
GateWave Northern, Inc.
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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 (0.010”)
located near the driven pin. The thermocouple’s access location is about in the center
of the pin.
The SBT 1.00m contact is modified to allow thermocouple access and held in a fixture similar
to the one shown in Fig. 2:
Fig. 2 SBT 1.00mm contact mounting and fixturing example
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Measurements
Current carrying capability (socket)
The measured current – voltage relationship for the SBT 1.00mm contact is shown below:
V and R as a function of drive current I
180
V[mV] / R [mOhms]
160
140
V
120
R
100
80
60
40
20
0
0
2
4
6
I [A]
8
GWN 404
Fig. 3 Voltage and resistance as a function of drive current
No thermal runaway occurs up to the maximum tested current of 8A.
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6
The accompanyi ng power dissipation in the connection is computed from applied
current and observed voltage:
P as a function of drive current I
1400
1200
P [mW]
1000
800
600
400
200
0
0
2
4
6
I [A]
8
GWN 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
dT [deg C]
120
100
80
60
40
20
0
0
2
4
6
I [A]
8
GWN 404
Fig. 5 Temperature rise as a function of drive current
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 different than indicated here. This holds especially
true for thick circuit boards where ground and power planes are far from the contact
point.
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
16
14
12
dT [deg C]
10
1A
1.5A
8
2A
2.5A
3A
6
4
2
0
0
2
4
6
8
10
t [min]
12
GWN606
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
current to the contact.
GateWave Northern, Inc.
9
Current carrying capability (contact in air)
The measured current – voltage relationship for the SBT 1.00mm contact contact suspended in
air between two metal plates is shown below:
V and R as a function of drive current I
120
V[mV] / R [mOhms]
100
V
80
R
60
40
20
0
0
2
4
6
I [A]
8
GWN 404
Fig. 6 Voltage and resistance as a function of drive current
No irregularities occur. Values recorded for this contact are slightly below those for the
enclosed one in part because of the lower contact resistance which leads to less
dissipation
GateWave Northern, Inc.
10
The accompanyi ng power dissipation in the connection is computed from applied
current and observed voltage:
P as a function of drive current I
1000
900
800
P [mW]
700
600
500
400
300
200
100
0
0
2
4
6
I [A]
8
GWN 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
90
80
70
dT [deg C]
60
50
40
30
20
10
0
0
2
4
6
I [A]
8
GWN 404
Fig. 8 Temperature rise as a function of drive current
GateWave Northern, Inc.
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