Area Array Probe Card Interposer Raphael Robertazzi IBM Research 6/4/01 6/4/01 IBM RESEARCH Page [1]
Motivation: Outline Probe Cards for Testing Complex ICs in the Developmental Stage. Hand Wired Space Transformer Limitations. Bandwidth / Power Supply Bypassing for High Speed / High Current Parts. Interposer Concept / Implementation. Experimental Results. Conclusions. 6/4/01 IBM RESEARCH Page [2]
Motivation Developmental Testing of Complex ICs. Space XFM Required. Probe Cards Need to be Manufactured Quickly (<12 weeks). Ceramic Modules Not an Option. Membrane Probe Technology Still Too Immature for Complex Area Arrays of Ports. Needle Cards Unusable. Only Viable Option is Hand Wired Space Transformer / Cobra Probes 6/4/01 IBM RESEARCH Page [3]
Hand Wired Space Transformer Limitations Bandwidth < 600 MHz Rise time > 2nS Current < 30 Amps Prone to Net List Errors 6/4/01 IBM RESEARCH Page [4]
Requirements For Two ICs Under Development Microprocessor Part More Than 7000 Ports. Probe Card #1 Accessed 866 Ports. Current Draw 100 Amps At Full Speed Clock Line Bandwidth > 1GHz. Communications Part 10 Gb/s Input Port High Quality RF By Pass. Power Net Diagnostics (Noise). 6/4/01 IBM RESEARCH Page [5]
Desirable Performance Enhancements High Speed I/O Lines ( 1-10 GHz and Beyond). High (100 Amp) Current Drive, More Power Pins, and Low Inductance By Pass. Power Grid Diagnostics. Lithographic Implementation of the Power Net. Ability to Repair Nets. Decreased Probe Card Fabrication Time. 6/4/01 IBM RESEARCH Page [6]
Hand Wired Space Transformer Cobra Probecard Magnet Wire Pogo Pin Pad Substrate Head Space XFM Cobra Probes 6/4/01 IBM RESEARCH Page [7]
BUMP HIGH SPEED LINE Application of the Interposer NORMAL CONFIGURATION VESPAL SPACE TRANSFORMER SPACE TRANSFORMER LEAD COBRA WRIRE J971 COBRA HEAD HIGH SPEED CONNECTOR WITH KAPTON INTERPOSER VESPAL SPACE TRANSFORMER J971 COBRA HEAD BUMP DETAIL MICROSTRIP TRACE HIGH SPEED LINE 6/4/01 IBM RESEARCH Page [8]
Interposer Features Through Connection to Wire Bundle High Speed Line (4-1) GND Plane By Pass Capacitor Bump Cobra Probe Wire VDD Plane Low Inductance Ground Connection for High Speed Line and Supply By Pass Port to Port Connection 6/4/01 IBM RESEARCH Page [9]
Interposer Photo (Standard Flex Process) Through Connection High Speed Line VDD Plane Kapton Substrate 6/4/01 IBM RESEARCH Page [10]
Interposer Photo (Micro-Via Flex Process) Through Connection VDD Plane 25 µm Via Kapton Substrate 6/4/01 IBM RESEARCH Page [11]
Interposer Schematic Microstrip Trace SMB Jack Kapton Sheet Mounting Frame 6/4/01 IBM RESEARCH Page [12]
Interposer on Test System 6/4/01 IBM RESEARCH Page [13]
TDR Characterization HP54120B Cobra Probe 6/4/01 IBM RESEARCH Page [14]
TDR Results 2 ns/div 500 ps/div TDR of J971 Cobra Card, τ = 1.15 ns. TDR With Interposer Mounted, τ = 250 ps. 6/4/01 IBM RESEARCH Page [15]
TDT Characterization 500 Ohm Picoprobe HP54120B Cobra Probe 6/4/01 IBM RESEARCH Page [16]
TDT Results 500 ps/div 500 ps/div TDT of Interposer + Cobra Head, τ = 246 ps. TDT of Interposer Alone, τ = 214 ps. 6/4/01 IBM RESEARCH Page [17]
S - Parameter Characterization HP8753B Cobra Probe 50 Ohm Through Quartz Substrate 6/4/01 IBM RESEARCH Page [18]
S Parameter Results 1.0 0.8 0.6 50% @2.45 GHz CPCI Installed Hand Wired Cobra Alone Quartz Substrate Through S21 0.4 0.2 50%@0.65 GHz 0.0 0 1 2 3 4 5 6 f (GHz) 6/4/01 IBM RESEARCH Page [19]
Cobra Head Bandwidth Estimates Estimated S21 For Cobra Head Correcting For Connector and Microstrip Losses Extrapolated S21 1.0 0.8 0.6 0.4 (20/80) % Rise Time = 56 ps 4 GHz BW Cobra Head, Probe Separation 11 mils. 0.2 0 1 2 3 4 5 6 f (GHz) 6/4/01 IBM RESEARCH Page [20]
Interposer For Biasing Chip C4s Current Injection X-Section: About 225 #36 Wires at 1 Inch For 1 Oz. Copper. Current Collection Kapton Interposer 6/4/01 IBM RESEARCH Page [21]
Current Capacity #36 (5 mil) Magnet Wire = 19.6 Mils. 350 Wires 6900 Mils. 1Oz Cu = 1.4 Mils Thick @1 inch diameter 4400 Mils. Calculated Resistance = 0.19 mω, Injecting on a 10 Inch Circle and collecting On a 1 Inch Circle, for 1.8 µω cm, 1 Oz. Copper. 1 Oz Plane Can Provide at Least 64% of the Capacity of a Large (350 wire) Power Net 6/4/01 IBM RESEARCH Page [22]
Bias Experiment 8.5 4.8 2.5 Current Injection, 10 Amps 3.1 Potential, mv 2.7 2.3 Current Collection Copper Plane On Interposer 6/4/01 IBM RESEARCH Page [23]
Conclusion Demonstrated 4X Bandwidth Improvement Over Hand Wired Space XFM Alone. Bandwidth Limitation Gated by Connector, Not Cobra Head. Interposer Can Add Extra Current Supply Capacity and High Quality, Low Inductance By Pass Capacitance. Interposer Provides a Quick Repair / Reroute Capability for Probe Card. 6/4/01 IBM RESEARCH Page [24]