0.4mm SBT DC data - Ironwood Electronics

Table of Contents
TABLE OF CONTENTS ................................................................................................................................................ 2
OBJECTIVE ................................................................................................................................................................ 3
METHODOLOGY......................................................................................................................................................... 3
Test procedures ........................................................................................................................................................ 4
Setup......................................................................................................................................................................... 5
Current carrying capability ..................................................................................................................................... 8
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Objective
The objective of these measurements is to determine the DC performance of a Ironwood
Electronics SBT contact. Measurements are to determine current carrying ability.
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. A 4 terminal setup
(Kelvin measurement) setup is used and the DMM is operated in compensated mode to
remove the effects of thermo-electric voltages due to dissimilar metals.
For the current handling tests the temperature rise in the center of the pin is
measured with a thermocouple as drive current levels are gradually increased.
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Test procedures
Figure 1 Test setup
During I-V testing, the z value is adjusted to nominal operating position and drive
current is increased in steps of 0.05 A up to the maximum tolerable level. The dwell
time for each current step is 1 s for V/I curves. Once the data are available, they are
processed to reveal the resistance, power dissipation and temperature as a function of
drive current.
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Setup
The SBT contact is installed in a small test socket which is attached to an Au
covered brass base plate (see Fig.2). Testing is performed in a setup similar to the one
shown in Fig. 3:
Figure 2 SBT contact mounting plate example
Au over Ni plating was applied to the surfaces of the brass plate. Material type and
thickness specifications were identical to those used for PCBs.
The current/voltage probe consists of a copper post with suitably shaped surface.
This surface is Ni and Au plated. The post has two connections, thus allowing for a
four terminal measurement with very low residual resistance (about 1 milliOhm).
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Figure 3 Test setup for 4 terminal (Kelvin) measurements
It should be kept in mind that in this setup the spring probe presses against two
surfaces that are very well heat sunk.
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The DUT with its plate is mounted in a test stand with XYZ adjustment capability:
Figure 4 Test stand
This setup has a micrometer screw that allows repeatable adjustments in the Z
direction. Also included is a transducer that converts Z position to an electrical signal
for the data acquisition.
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Measurements
Current carrying capability
The measured current – voltage relationship for two Ironwood Electronics SBT contacts is
recorded for a gradually increasing drive current:
V and R as a function of drive current I
V[mV] / R [mOhms]
100
90
V
R
80
70
60
50
40
30
20
10
0
0
0.5
1
I [A]
1.5
2
GWN 404
Figure 5 Voltage and resistance as a function of drive current
There are no anomalies in the response. Also of interest is power dissipation in the
contact and a derivative plot (see below).
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P as a function of drive current I
0.2
0.18
0.16
0.14
P [W]
0.12
0.1
0.08
0.06
0.04
0.02
0
0
0.5
1
1.5
I [A]
2
GWN 404
Figure 6 Power dissipation as a function of drive current
dP/dI as a function of drive current I
0.25
dP/dΙ [W/A]
0.20
0.15
0.10
0.05
0.00
0
0.5
1
I [A]
1.5
2
GWN 405
Figure 7 Derivative power dissipation as a function of drive current
Power dissipation follows a square law up to a current value of 1.4 A.
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∆T as a function of drive current I
40
35
∆T [deg C]
30
25
20
15
10
5
0
0
0.5
1
1.5
I [A]
2
GWN 405
Figure 8 Temperature rise as a function of drive current
The temperature rise above ambient increases as drive currents increase. It reaches
20 C at a current level of 1.45 A. A derivative plot is shown in Figure 9 :
d(∆T)/dI as a function of drive current I
45.0
40.0
d(∆Τ)/dΙ [deg C/A]
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
0
0.5
1
1.5
I [A]
2
GWN 405
Figure 9 Derivative temperature rise as a function of drive current
GateWave Northern, Inc.
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