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