How to Develop Qualification Programs for Lead Free Products

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Moris Hoover
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1 How to Develop Qualification Programs for Lead Free Products by Mike Silverman Managing Partner Ops A La Carte mikes@opsalacarte.com (408)

2 Abstract There are significant reliability uncertainties around Lead-Free Solder. Even if your product does not need to be compliant, the materials and processes that make up your product are changing. As one major consumer product team concluded, doing nothing would double the field failure rate of the electronics. This implies that we must do more than just change solder and components when transitioning in order to achieve good reliability. We must also review the design.

3 Abstract During this time of rapid transition, there is a significant new body of knowledge to understand in order to determine the areas of greatest risk to the reliability of your product. Once we understand the risks, we must then incorporate this new knowledge into the redesign of the product.

4 Abstract In this presentation, we will highlight a few of these significant risk areas and show how techniques such as HALT and ALT can assure that the transition has been accomplished successfully from the perspective of Reliability.

Risks from Temperature Effects of Temperature Cycling on Long- Term Reliability of Pb-Free Solder Joints -55 to 125C, 70 minute cycle Can we predict time to failure for Pbfree

Components highly susceptible to solder joint fatigue Large chip resistors, Ceramic BGAs, 10 Leadless ceramic chip carriers, Non-underfilled CSPs, 8 Etc.

5 Risks from Temperature Effects of Temperature Cycling on Long- Term Reliability of Pb-Free Solder Joints -55 to 125C, 70 minute cycle Can we predict time to failure for Pbfree solder joints? YES So, when should you be concerned? Components highly susceptible to solder joint fatigue Large chip resistors, Ceramic BGAs, 10 Leadless ceramic chip carriers, Non-underfilled CSPs, 8 Etc. Max solder joint temperature greater 6 than 80ºC with dwell times greater 4 than 4 hours At least one thermal cycle per day and 2 a desired lifetime of more than 10 years 0 This slide provided courtesy of DfR Solutions SAC life / SnPb life 2512 Resistor on FR4 (25-80C) Ceramic BGA on FR4 (0-100C) Dwell Time (min)

6 Risks from Mechanical Loading (Effects of Board Flexing, Shock, and Vibration) Post-reflow handling Increased risk of failure? Conflicting results Sensitive to time after reflow Some companies moving to restrict boardlevel strain From 1000 to 750 to 500 microstrain Shock and Drop Some degradation in performance Board plating seems to play a large role (SnNi weaker than SnCu) Vibration SAC worse under low-cycle fatigue, where most failures occur PWB surface strain 3.0E E E E E E-04 SnPb SnAgCu This slide provided courtesy of DfR Solutions 0.0E+00 1, ,000 10,000,000 Cycles to Failure

7 HALT for RoHS at HALT and HASS Labs Pb-Free Results at

8 Results 10 Products went through A-B Comparison of Lead vs. Pb-Free at HALT & HASS Labs In all cases, both solder and components were changed to Pb Free. Boards went through design review and changes to deal with RoHS issues. Comparison was between products using Pb Solder and Pb Components vs. products using Pb Free Solder and Pb Free Components. We did not include mixed assemblies in this study (if we had, conclusions would be different - mixed assemblies have proven to produce weaker solder joints, especially with certain package types)

9 Results SUMMARY OF FINDINGS: No Significant Differences in Limits achieved!! Two Notes of Caution with this statement 1) In all cases, customers had gone through some level of Design Review and Design Changes before the HALT you cannot expect same results by just changing components 2) A change of limits from HALT does not always mean a change of reliability because acceleration factor is different between Lead & Pb-Free. HALT is a means of giving you a good approximation as to the change in reliability, but to know the exact change (in terms of MTBF), you must conduct a lower acceleration ALT.

10 Results Once we have redesigned the product and re-qualified it using HALT, we can then use this knowledge to write guidelines for future products. There are some generic lead-free design guidelines that exist, but because this is new and because of the many variables involved, most companies are developing their own and very little public info is available.

11 HALT for RoHS at National Instruments Pb-Free HALT Results at

12 RoHS Prototype Builds All real test and measurement products (not test vehicles) Prototypes to evaluate RoHS impact on design and process All assemblies HALT tested to failure, inspected, and cross-sectioned Split builds with RoHS and non-rohs Assemblies for comparison Design and process changes made to increase robustness No new RoHS failure modes but earlier onset of failures seen

13 RoHS Process Highlights Lead-Free Solder used: SAC305 alloy, no clean Immersion Silver, RoHS-designed PCBs Max Temperatures Reached: ~ 255C Incoming XRF validation on all parts

14 RoHS HALT Failure Analysis Cracked Solder Joint: BGA ball to BGA substrate PCB Laminate Cracks BGA, also called pad cratering

15 RoHS HALT Failure Analysis Cracked traces to BGA pads outer rows BGA pads separated from PCB

16 RoHS HALT Failure Analysis Cracks in BGA Laminate Laminate Cracks - Repair

17 RoHS Prototypes: HALT Failure Analysis Changes made as a result of FA: Enhanced ICT (In Circuit Test) Strain Test Process Reduced allowable strain from 1000 to 500 ue Restricted choice of PCB laminates Widened BGA traces, tear-dropped pads where feasible Restricted # and types of repair allowed Modified receiving processes: Added checks, XRF Modified manufacturing processes

18 HALT for RoHS at Xantrex Pb-Free HALT Results at

Objectives HALT products in the following order: Consumer product specifications: 0

Portable/Towable product specifications: -10 C to +60 C.

Vehicle/Distributed product specifications: -25 C to +65 C.

19 Objectives HALT products in the following order: Consumer product specifications: 0 C to +40 C (<$100). Residential product specifications: 0 C to +40 C. Portable/Towable product specifications: -10 C to +60 C. Programmable product specifications: 0 C to +50 C. Vehicle/Distributed product specifications: -25 C to +65 C. Determine robustness of RoHS products. Comparisons done on identical designs. Design issues will be resolved later. Note: All HALTs done on a QualMark OVS2.5xLF and OVS3 Typhoon chambers.

20 HALT Results for 175Watt Inverter Four each Pb-based and RoHS units were compared. The Pb units died at 5, 15, and 25Grms. Cold Hot Rapid Vibration Must Meet # Units Lead -40 C 100 C -50 C/80 C 18Grms -30 C/80 C 4 RoHS -30 C 90 C -50 C/80 C 22Grms -30 C/80 C 4

HALT Results for 100-200Watt Inverters Cold Hot Rapid Vibration Must Meet #

C -50 C/80 C -20 C/70 C -10 C/75 C 6Grms Not done 5Grms Not done -30 C/80 C -30

21 HALT Results for Watt Inverters Cold Hot Rapid Vibration Must Meet # Units Lead Lead Lead Lead -50 C -50 C -20 C -20 C 90 C 90 C 70 C 79 C -50 C/80 C -50 C/80 C -20 C/70 C -10 C/75 C 6Grms Not done 5Grms Not done -30 C/80 C -30 C/80 C -30 C/80 C -30 C/80 C RoHS -20 C 65 C -20 C/60 C 23Grms -30 C/100 C 4

22 HALT Results for 1KW Residential Inverter/Charger Lead RoHS Cold -20 C -30 C Hot 70 C 70 C Rapid -20 C/60 C -20 C/60 C Vibration 28Grms 25Grms Must Meet -30 C/80 C -30 C/80 C # Units 4 4

23 HALT Results for 1KW Residential Inverter/Charger Lead RoHS Cold -35 C -50 C Hot 110 C 100 C Rapid -40 C/95 C -40 C/90 C Vibration >22Grms >24Grms Must Meet -30 C/80 C -30 C/80 C # Units 22 2

24 Some Questions Any cost increase of RoHS vs Pb parts? Less than 5%. Should HALT dwell times change with RoHS? No. The air exchange rates are very high. With RoHS, can I use the Pb HASS profile? This is dependant on the OL and DL encountered. If the same, then yes. If not, then investigate root cause and make determination. Recommend rerunning life portion of POS.

25 Next Steps 1) Determine if you are going to transition to RoHS 2) Review your environment and assess the risks 3) Develop a customized test plan to mitigate the risks 4) Carry out the testing and feed the results back into the design process and of course, we can help you with all of these.

26 ANNUAL RELIABILITY SYMPOSIUM May 7-11, 2007 Santa Clara, CA 1) Design for Reliability (DfR) - Learn the building block tools for reliability during the concept and design phase. May 7-8 2) Design for Manufacturability (DfM) - Learn what tools are needed to produce great products with high quality. May 9 3) Design for Warranty Cost Reduction (DfW) - Introduces a proven warranty event cost model that helps identify warranty cost red. Solutions. May 10 4) Design of Experiments (DoE) - Includes basic statistics behind a DOE as well as a workshop in which we perform a DOE on a specific product. May ) Best Accelerated Reliability Test Methods: HALT, ALT, and RDT This course will review each of the best Accelerated Test Methods and show when to use each. Great for those already familiar with the concepts of HALT as well as those that are newcomers to the field. May 7-8 6) Fundamentals of Climatic Testing - Review the different types of climatic tests temperature, humidity, altitude, rain, solar, salt/fog, & more. May ) Software Reliability - Highlights best practices in S/W Reliability and explains their application & positive impact to each of the development life cycle phases: Concept, Design, Implementation, & Testing. May 11

27 NEW TEST LAB Ops A La Carte LLC is proud to announce that we now own and operate HIGHLIGHTS ABOUT Tested over 500 products in over 50 different industries Second oldest HALT facility in the world, established in 1995 (originally owned by QualMark) Most experienced staff with over 50 years of combined experience in HALT and HASS We only use degreed engineers to run all our HALT. HALT equipment has all latest technology only lab in region Our HALT/HASS services are fully integrated with our other consulting services. We provide HALT/HASS services on a world-wide basis, using partner labs for tests outside California. 990 Richard Ave., Suite 101 Santa Clara, CA (408) HALT and HASS Labs Ph: (408) Fx: (408) Richard Ave., Suite 101, Santa Clara, CA 95050

28 TEST LAB CAPABILITIES HALT & HASS Labs adds two more pieces of Reliability Test equipment. In addition to our two HALT chambers, we now have an electro-dynamic shaker capable of doing two axis sine and random, and we also have a Combined Temperature/Humidity chamber. Both chambers add versatility to the types of reliability tests we can perform. HERE IS A LIST OF SOME OF THE SPECS WE CAN TEST TO: DO160 IEC IEEE ISTA/ASTM JEDEC MIL-STD-810 SAE SEMI Telcordia and more HALT and HASS Labs Ph: (408) Fx: (408) Richard Ave., Suite 101, Santa Clara, CA 95050

Simple, Fast High Reliability Rework of Leadless Devices Bob Wettermann

Simple, Fast High Reliability Rework of Leadless Devices Bob Wettermann Recently, the impact of leadless device reliability after rework was investigated as part of a NASA/DoD project for different leadless