Nick Arnal, Jason Entenmann, Chris ThompsonDr. Gokhan MucmuURL: www.interconnectcharacterization.weebly.com
Test Fixture to Characterize Elastomeric Interconnects
Critical Design Review (CDR)January 29, 2013
EEL 4914 Engineering Design II
CHRIS ADD PIC
Problem Statement
Our task is to a characterize elastomeric interconnects for Harris Corporation Measure S-parameters, continuity, and contact resistance Characterize two different styles of elastomeric interconnects All while undergoing 500 cycles of temperature cycling (-55°C to 125°C)
Sample Elastomeric ConnectorTemperature Cycle Profile
Design Approach
We are designing a test fixture with multiple circuit boards to be placed in a temperature chamber Elastomeric connectors conduct when compressed 10-15%. They will be
sandwiched between a pair of circuit boards with RF cables running to outside of the oven.
2-3 elastomeric connectors per circuit board
Example of Test Fixture in Oven
Measurement Equipment
S-parameters VNA
Continuity Custom designed circuit
Contact Resistance
4-probe multimeter
System Block Diagram
S-parameter Measurements
A 20GHz Agilent 8720ES VNA will be used The S-parameters will be measured for one connector at a time Cables pairs will be interchanged by hand The VNA will be calibrated up to the cable mount Characterized cables will be removed from the measurement by de-
embedding (next slide)
De-embedding Process via MATLAB
Cable Measurement
Continuity Measurements
Continuity for each connector is determined by a comparator circuit (see next slide) Digital HIGH sent to Arduino if RCONN>1000Ω (discontinuity) Digital LOW sent to Arduino otherwise (continuity)
Sample rate = 10kHZ per connector (10,000 samples/second)
Continuity Test Circuit Channel
Max current through connector (RCONN=0, VS=5V)
Discontinuity Trigger voltage (RCONN≥1kΩ)
R1/R2 Voltage divider sets VREF
Max current draw from Vs ≈ 2mA / channel LM339 response time - 1.3µs
Temperature Sensing Circuit
LM35 will be mounted on the board to verify the temperature -0.55V to 1.25V output shifted to 0.9V to 4.5V by the op-amp
summer
Arduino Timing Diagram
The Arduino will process both the continuity test and the temperature Continuity test results (# of discontinuities out of 10,000 per connector)
and temperature recorded from Arduino to computer every second• Communication process takes about 2ms
This cycles continuously repeats
RF Circuit Design
RF Circuit Design Requirements
Minimal design for truest results of connectors/interconnects Frequency Range: 0.5 to 18GHz Temperature Design: -55 to 125 C Compression requirements: 15% +/- 5% (For Interconnect #1 and
#2)
RF Circuit Design
Software / Calculations ANSYS HFSS v.15 Simulation Software
• Full circuit design and simulation in frequency ranges LineCalc
• Transmission line calculations ADS
• AutoCAD and Gerber circuit files for fabrication
Circuit Design
GPO Connector / Interconnect Specifications Three piece connection design Impedance: 50 Ohms Frequency: DC to 40GHz Temperature Design: -65 to 165 C
Circuit Design
Interconnect #1 and #2 SpecificationsCustom Interconnects per Harris’ requirements Compression Rating: 15% +/- 5% Designed for frequency and temperature ratings Correct alignment for true results
PCB
PCB
Heat Sink(Spacer)
Interconnect
Circuit Design
Design and Simulation: GPO Simple two layer, two board design Microstrip lines on the inner side of boards Stand-offs will be used to hold the system together
Circuit Design
Design and Simulation: GPO Transmission Results, S21
Circuit Design
Design and Simulation: GPO Reflection Results, S11
Circuit Design
Completed Design: GPO Two connector/interconnect setups
Circuit Design
Design and Simulation: Interconnect #1 and #2 Simple two layer, two board design Micro-strip lines on outer sides of boards Aluminum Spacers are used on inside to act as heat-sink and
alignment tool for interconnects
PCB
PCB
Heat Sink(Spacer)
Interconnect
Circuit Design
Design and Simulation: Interconnect #2 Transmission Results, S21
Circuit Design
Design and Simulation: Interconnect #2 Reflection Results, S11
Circuit Design
Design and Simulation: Interconnect #1 S11 and S21 Results
Circuit Design
Completed Design: Interconnect #1 Three interconnect setup
Contact Resistance
Using a typical Multimeter 4 probe test Only on one type of connector being tested
Boards are same size as other test boards Wires soldered directly to board DC test
25
Software and Equipment
Design Tools Board design
HFSS, Pspice Fixture design
SolidWorks Data processing and control
Programming in C# MATLAB for data processing
Measurement & Test Equipment Agilent 20GHz VNA Thermotron Temperature
Chamber 4-point Multimeter Arduino MEGA
Action Items
Test Fixture Assembly and Test Readiness Review (TRR) – February 26th
• Fabricate and build test fixture• Manufacture all test boards
• Run software for one full cycle to validate functionality• Test fit fixture and boards, test for contact resistance
Product Testing – February 26th – April 16th
Analyze Results / Final Report– April 16th – May 14th
Testing Plan
Summary/Accomplishments
MeasurementsTest cable has been characterized, more have been
orderedMATLAB de-embedding program written and
workingContinuity test written on ArduinoTemperature sensor circuit built
SoftwareFully automated program to run tests and alert team
of anomalies in the system during test has been created
Summary
Circuit DesignGPO, interconnect #1 and #2
• Boards and interconnects designed in HFSS• Boards and interconnects simulated from 0-20GHz• Quotes from multiple companies for board fabrication
Fixture HardwareFixture designed in SolidWorks and CTE and
vibrational testing has been simulated