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