Cohu, Inc. · NASDAQ:COHU
Cohu — Technical Presentation (May 2020)
20 slides from Cohu's technical presentation, May 2020
Slide 1: Production Wafer Probe of 77-81 GHz Automotive Radar Applications
Production Wafer Probe of 77-81 GHz Automotive Radar Applications Marty Cavegn (Cohu) Jory Twitchell (NXP) Jason Mroczkowski (Cohu) Virtual Event ● May 11-13, 2020
Slide 2: Outline
Outline • Introduction – Automotive Radar Devices and Testing • Benefits and Challenges in testing the new generation • Testing requirements and options – Pogo with PCB absorber – Membrane Solution – xWave with absorber • Advantages • Modification to the standard xWave • Test Results – Initial and c
Slide 3: Introduction
Introduction • Automotive Radar has been used since 2007 – First Generation (Approximately 2007 – 2013) • 28 Ghz • Short range • Limited functionality – Second Generation (Approximately 2014 – 2018) • 80 Ghz – improved resolution • Longer range • Increased functionality • Now entering a third genera
Slide 4: Introduction – Cont.
Introduction – Cont. • Second Generation – Devices packaged in traditional formats (i.e. BGA, QFN, etc.) – Multiple packages for receiver (RX), transmitter (TX) and voltage controller (VCO) – Packages combined into module – Testing required at multiple levels (wafer, film frame, package, transceiver
Slide 5: Benefits in testing the new generation
Benefits in testing the new generation • Third Generation – Die level integration of receiver (RX), transmitter (TX) and voltage controller (VCO) – Packages no longer required – Testing required at wafer and WLCSP • ambient, hot, cold, fewer total tests and less repetition (4 total) – Built-in Self
Slide 6: Challenges in testing the new generation
Challenges in testing the new generation • Built-in Self Test (BIST) – Requires the I/O for the high frequency signals to be properly terminated while still providing a path for sourcing a DC voltage to the DUT. – New functionality in the test hardware/probehead – Dual frequency ranges to optimize w
Slide 7: Challenges in testing the new generation (cont.)
Challenges in testing the new generation (cont.) • Multi Site Testing – Coplanarity challenges • Reduction of forces • Adding support for PCB (Bridge Beam) – Site to site alignment – Site to site variation – CTE • Contact Technology – Dual – Spring Probes for standard signals – Leadframe for RF freq
Slide 8: Test Solutions – Absorber on PCB
Test Solutions – Absorber on PCB • 90° transition at PCB creates significant signal reflection Production Wafer Probe of 77-81 GHz Automotive Radar Applications 8
Slide 9: Test Solutions – Prototype Build Leadframe with PCB Connection
Test Solutions – Prototype Build Leadframe with PCB Connection Lead Frame • 90° transition at PCB Spring creates significant signal reflection Probe Retainer Body Issues Solved New Issues • Straight leadframe with shallow • Tolerances of absorber create angle connection to PCB reduces mechanical bow
Slide 10: Test Solutions – Prototype Build Leadframe with PCB Connection - MultiSite
Test Solutions – Prototype Build Leadframe with PCB Connection - MultiSite • Multi-site required some new thinking with leadframes fanning out at 45° from three sides Production Wafer Probe of 77-81 GHz Automotive Radar Applications 10
Slide 11: Challenges in Prototype Build
Challenges in Prototype Build • Bowing of Probehead – Additional mounting locations required – Reduction of force applied by absorbers – more compliant second layer – Redesign of components to add rigidity • Coplanarity of PCB – Stiffener in original design – Added adjustable support beam to coplana
Slide 12: Field Results – Initial Production with Prototype Build
Field Results – Initial Production with Prototype Build Total overdrive of about 11 mils to achieve continuity Successful but window was limited and production team wanted improvements Production Wafer Probe of 77-81 GHz Automotive Radar Applications 12
Slide 13: Test Solutions – Production Build
Test Solutions – Production Build Spring Damper Lead Frame Spring Probe Top Plate Retainer Body PCB • Spring damper to better support leadframes • Absorber damper to add compliance/reduce bowing of top plate Production Wafer Probe of 77-81 GHz Automotive Radar Applications 13
Slide 14: Field Results – Improved Production
Field Results – Improved Production • Full continuity at all temps at 8 mils of overdrive • Max overdrive of 13 mils allowed • 5 mil working window • Production team approved for release Production Wafer Probe of 77-81 GHz Automotive Radar Applications 14
Slide 15: Field Results – Ongoing concerns
Field Results – Ongoing concerns • Over 250,000 insertions on the first probe head • In-Situ cleaning as angled leadframes are more difficult to clean than pogo pins or flat leadframes – reviewing new cleaning media • Absorber system may degrade over time and require repair/improvement Production Wa
Slide 16: Strengths
Strengths • Excellent RF performance over a broad range of frequencies • Long life • Multi-site capability • Large compliance window Production Wafer Probe of 77-81 GHz Automotive Radar Applications 16
Slide 17: Weakness
Weakness • Complex to balance multiple contact technologies on one DUT • Some limits on the number and location of RF signals • In-situ cleaning is difficult • May need maintenance on absorpbtion system over time Production Wafer Probe of 77-81 GHz Automotive Radar Applications 17
Slide 18: Next Steps
Next Steps • Project has moved to production and additional test cells are being deployed to meet end user demand! • Testing in-situ cleaning media and methods • Testing life performance of absorption system • Better control of force on leadframes with modifications to support system (future project
Slide 19: Summary/Conclusion
Summary/Conclusion • Advances in IC design architectures and contacting methods make high volume test of automotive radar RF devices production capable with test resources already available on production floors. • Thank you to NXP for the opportunity and collaboration to make it happen! Production W
Slide 20: COPYRIGHT NOTICE
COPYRIGHT NOTICE This multimedia file is copyright © 2020 by TestConX. All rights reserved. It may not be duplicated or distributed in any form without prior written approval. The content of this presentation is the work and opinion of the author(s) and is reproduced here as presented at the 2020 Te