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6/12/02 IBM RESEARCH Page [1]
Area Array Cobra Probe Card With 5 GHz. Bandwidth
Raphael RobertazziIBM Research
6/12/02
6/12/02 IBM RESEARCH Page [2]
Outline• Motivation: Test High Speed Area Array ICs In The
Development Stage, At Wafer Level.– Improve The Bandwidth Of Cobra Probe Cards
For At Speed (10Gb/s) Test.– Performance Equal To Or Better Than Membrane
Probes, Extension To Higher Frequencies.• New Hand Wired Space Transformer
Concept / Implementation.• Experimental Results.
– Rise Time / Bandwidth Measurements.– 10 Gb/s Serializer/Deserializer Wafer Level BERT
Test.• Conclusions.
6/12/02 IBM RESEARCH Page [3]
Motivation
• Wafer Level, Developmental Testing Of High Pin Count Communications ICs.– Connection To C4 Arrays (Cobra Probe).– Large Numbers (~100) Of Medium Speed (0.5-1
Gb/S) Data Lines.– Microwave (10 Gb/S) Data Rates On Selected
Lines.– Complex, Multiple Power Domains.– Path To 40 Gb/s Test.
6/12/02 IBM RESEARCH Page [4]
Conventional Cobra Probe Card
Substrate
Space XFMCobra Head
Pogo PinPad
Low SpeedLine
6/12/02 IBM RESEARCH Page [5]
High Performance Cobra Probe Card
Substrate
50 Ohm Micro Coax
ATE Data Cable
Signal/Ground Twisted Pair
Space XFMCobra Head
Pogo PinPad
Transition Near Space XFM
Medium Speed Line High Speed Line
Low SpeedLine
6/12/02 IBM RESEARCH Page [6]
Probe Card Photo
6/12/02 IBM RESEARCH Page [7]
Space Transformer
C4 Image
Micro-Coax100 µm
6/12/02 IBM RESEARCH Page [8]
Probe Card On HP83K Test System
High Speed Micro-Coax
Medium Speed Twisted Pair
6/12/02 IBM RESEARCH Page [9]
Probe Card Features
• Space Transformer Manufacturable In 4-6 Weeks.• Addition Of Medium Speed Differential Lines Capable
Of 3-4 X Bandwidth Of Standard Space Transformer Lines (92 Ports).
• Addition of High Speed Lines Capable Of 20 XBandwidth of Standard Space Transformer (4 Ports).
• Other Improvements Relevant to Microprocessor Test And Decreased Probe Card Manufacturing Time.
6/12/02 IBM RESEARCH Page [10]
TDT Characterization
HP54120B
Cobra Probe
500 Ohm Picoprobe
6/12/02 IBM RESEARCH Page [11]
TDT For Medium And Low Speed Lines
6/12/02 IBM RESEARCH Page [12]
Low and Med Speed Line Rise Time Comparison
2160980Low530355Med
τ10/90
(ps)
τ20/80
(ps)
6/12/02 IBM RESEARCH Page [13]
TDT For High Speed Lines
6/12/02 IBM RESEARCH Page [14]
High Speed Line Rise Time
6440
τ10/90
(ps)
τ20/80
(ps)
6/12/02 IBM RESEARCH Page [15]
SerDes Output Experiment
HP54120B
Cobra Probe
SerDes ICτr < 20ps
6/12/02 IBM RESEARCH Page [16]
SerDes Output Data
6/12/02 IBM RESEARCH Page [17]
SerDes BERT Experiment
6/12/02 IBM RESEARCH Page [18]
10 Gb/s Eye Diagram
6/12/02 IBM RESEARCH Page [19]
10 Gb/s BERT Results At Wafer Level
Error Rate* =1.3 x 10-8231 –1
Error Free Over 30 Min. Experiment
27 –1 -> 223 –1
CommentPattern
* Repairing Rx Ground Should Allow Long Pattern To Run Error Free
6/12/02 IBM RESEARCH Page [20]
Extending Bandwidth
• Bandwidth Of Current Design Limited By Cobra Head.– Rise Time Of High Speed Lines
Determined By L/R Time Of Head.
• Paths to Higher Frequencies:– Redesign Head For 50 Ohm Path From
Coax To Chip.– Reduce Distance Between Coax And Chip.
6/12/02 IBM RESEARCH Page [21]
TFI Contactor Reduces L/R Time
Substrate
Space XFMTFI Contactor
Detail
100 µm
Lp = 20 pH, Lp/R = 0.4 ps
6/12/02 IBM RESEARCH Page [22]
Conclusion
• Demonstration Of A New Cobra Probe Card With Increased Bandwidth:– 20X Bandwidth Improvement Over Conventional Cobra
Probe Card (Micro Coax).– 3-4X Bandwidth Improvement Over Conventional Cobra
Probe Card (Twisted Pair And Direct Cable To Card Connection).
• High Speed Line Bandwidth Limitation Gated By Cobra Head.Paths To Higher Frequencies:– Engineering 50 Ohm Cobra Head.– Using TFI Contactor.
• New Probe Card Can Be Constructed In 4-6 Weeks.
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