ASQ RD Webinar: Improved QFN Reliability Process
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The presentation by Dr. John Ganjei discusses the reliability process improvements for Quad Flat No-lead (QFN) packages, highlighting challenges in solderability and the lack of industry standards. With QFNs expected to represent 15% of all integrated circuits, methods for enhancing solderability and reliability, such as chemical plating, are proposed. The ongoing need for consensus on preconditioning requirements for these components is emphasized to improve reliability and performance in assembly.
ASQ RD Webinar: Improved QFN Reliability Process
- 1. Improved QFN Reliability Process Dr. John Ganjei ©2014 ASQ & Presentation Ganjei http://reliabilitycalendar.org/webina rs/
- 2. ASQ Reliability Division English Webinar Series One of the monthly webinars on topics of interest to reliability engineers. To view recorded webinar (available to ASQ Reliability Division members only) visit asq.org/reliability To sign up for the free and available to anyone live webinars visit reliabilitycalendar.org and select English Webinars to find links to register for upcoming events http://reliabilitycalendar.org/webina rs/
- 3. ASQ RD Webinar Series Improved QFN Reliability Process Thursday January 9, 2014 9-10am PST Presented by: Dr. John Ganjei 3
- 4. Outline/Agenda • Introduction –Design and criteria • Discussion Topics –Industry requirements • Performance Assessment –Various solderability tests • Summary • Acknowledgements –MacDermid Southeast Asia Team
- 5. Introduction • Move to HDI implied BGAs would replace QFNs – difficulties could be avoided but still achieve desired performance with QFN • It is expected in 2013, the use of QFNs will represent 15% of all integrated circuits • Prismark Partners has stated that the QFN is the fastest growing package excluding flip-chip chip scale
- 6. Design • A copper foil lead frame is pattern etched or punched for the package assembly process. • Singulation can be either punched or sawn. – copper edges become exposed leaving terminations susceptible to oxidation – can degrade solderability during component assembly to the mating circuit board.
- 7. Design • The designer must consider: – some devices may have oxidized and termination ends will not ‘wet’ during assembly processing. JH JT JH G Solder fillet on bare Cu terminal end with oxidation build-up JT G Solder fillet on coated or plated terminal end Reference: IPC Webinar June 23, 2011
- 8. Industry Requirements • Currently there are no industry (IPC or JEDEC) requirements for toe fillet wetting • OEMs are working toward stronger industry wide specifications to ensure the performance and reliability of this component style. • An industry group should decide on the appropriate preconditioning and fillet height requirements
- 9. Toe Fillet Solderability BOARD LEVEL ASSEMBLY AND RELIABILITY CONSIDERATIONS FOR QFN TYPE PACKAGES Ahmer Syed and WonJoon Kang Amkor Technology, Inc. Finite element simulations and actual test data generated by customer have shown that the fillets - if formed - can improve the board level reliability by as much as 2X for a package with large die to package size ratio. The fillet extends the length of solder joint and provides a longer path for the crack to go through the entire joint, thus improving the reliability. Soldered fillet would deliver higher joint reliability More soldered interface Enable inspectability
- 10. Process Introduction • Proposed chemical plating for producing a solderable sidewall – Can be applied vertically, horizontally or in barrel machines • Will clean the edges and make a more uniform surface for plating. • Flank plating can be performed on parts after singulation – either mounted on tape or in singulated form. • No appearance or morphology change is observed to the original electroplated tin
- 11. Performance Assessment • Effect on part integrity and electrolytic tin plating • Laboratory solderability testing – Dip and look • Assembly simulation at HKUST
- 12. Performance Assessment Cu oxides Sawing burr Before the process After the process
- 13. Performance Assessment Before the process 1000x After the process 1000x • After proposed process, no appearance or morphology change is observed from the original tin plating of the DAP and lead terminals by scope or visual
- 14. Solderability: “Dip and Look” Test Method Tweezers JESD22-B102E • • • • Solder: Sn96.5 Ag3.0 Cu0.5 Solder temp: 245 C Flux type:ROL0 Immersion time in flux: 5 -10sec. – Flux drip time ~ 10 sec. before dipping into the solder • Immersion time at solder: 5 sec. • Use tweezers to grasp two corner of testing unit and dip the whole unit at 90 into the solder Solder pot
- 15. Solderability: “Dip and Look” Test Method Pre-condition QFN 64L “Dip & Look” Solderability Testing Unit Fillet qty < 75% wetting % Solderability As received After 8 hrs steam age After 16 hours bake 4 4 4 256 256 256 For all conditions, Cu does not wet As received After 8hr steam age After 16hr bake @ 155C 0 1 1 100 99.61 99.61
- 16. Solderability: Assembly Simulation QFN 64L PCB Mounting Solderability Testing Pre-condition Unit Fillet qty < 75% wetting % Solderability As received 4 256 0 100 After 8 hrs steam age 4 256 10 96.09 After 16 hrs bake 4 256 5 98.05 For all conditions, Cu does not wet As received After 8 hr steam age After 16 hr bake 155oC Non wetting Less wetting • QFN 64L can achieve 100% solder coverage as received • Some less wetting observed after the steam aging and high temperature exposures
- 17. Solderability after Bake Performance Punched Process cut edge after plating Sawn Edge Process cut edge after plating
- 18. Solderability after Steam Aging Punched Process cut edge after plating Sawn Edge Process cut edge after plating
- 19. Summary: Challenge No existing or proposed JEDEC standard for the following requirements • Aging environment – – • Solder toe fillet – – – • • Steam or bake Dwell time area coverage and yield of successful lead coverage testing protocol PCB footprint Long term reliability testing 19
- 20. Summary: Challenge • A process that can provide a solderable flank after component molding and singulation has been described – should provide significant advantages in inspectability and solder joint reliability. • Testing and further evaluations are ongoing with key OEMs and assembly houses – we hope to report these results as they progress. • An industry consensus of required preconditioning to determine shelf life prior to assembly is needed for further qualification of this and other potential solutions.
- 21. Acknowledgements • I’d like to thank my coauthors – Mr. Rich Retallick – Ms Lenora Toscano – Especially Dr. Gu Hong for his research and development efforts which made this paper possible – Also the team at HKUST Thank You!