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 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. 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. 4 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 GateWave Northern, Inc. 5 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. GateWave Northern, Inc. 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. GateWave Northern, Inc. 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: GateWave Northern, Inc. 8 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. 12