Pb-free Challenges for High Complexity Products. inemi Jan 16 th 2008

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Peregrine Damian Hunter
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2 Agenda RoHS 101 Typical complex of telecom products (different from consumable) Pb-free Concerns for High Complexity Products Components Challenges PCB laminate Tin Whisker Temperature Rating Process Challenges Reflow Rework Product Reliability Internal works External works with inemi, HDPUG Summary 2 Alcatel-Lucent 2007

4 RoHS Brief History Lots of discussion in the 90 s Draft released at the end of 90 s Legislation finalized in January 2003 RoHS: EU directive on a Restriction on the use of Hazardous Substances Bans some heavy metals and some brominated flame retardants (Directive Application Date: July 2006) 4 Alcatel-Lucent 2007

5 What is RoHS Means Products put on the market after July 1 st, 2006 required to ban : Lead (Pb) (0.1% limit) Found in PCBs, coating for component leads, terminations, etc. Mercury (0.1% limit) Found in batteries, electrical switches, paints Cadmium (0.01% limit) Found in batteries (accounts for 2/3 of cadmium use), thin film transistors, diodes and rectifiers, cables Hexavalent chromium (0.1% limit) Used in Zinc Chromate plating of steel (e.g. shelves, screws, etc.) PBB and PBDE (Brominated Flame Retardants) (0.1% limit) Found in some plastics (connectors, device packaging) * Limit by weight per homogeneous material 5 Alcatel-Lucent 2007

6 Key Exemptions (& Confusions) Lead in high melting temperature type solders (i.e. lead based alloys containing 85 % by weight or more lead) Lead used in compliant pin connector systems (add in Dec04 TAC) Lead in solders to complete a viable electrical connection between semiconductor die and carrier within integrated circuit Flip Chip packages (add in Dec04 TAC) Lead in solders for servers, storage and storage array systems, network infrastructure equipment for switching, signalling, transmission as well as network management for telecommunications (wording changed in Dec04 TAC) Commission exemption review start in Alcatel-Lucent 2007

7 What is Exemptions Means to High Rel Products Telecom OEM with High Reliability Products Can continue to build and sale equipments using the SnPb process and SnPb or Pb-free finish parts However we still need to make sure we removed other 5 materials Customer Products (E.g. Cell phone, VCR/DVD, etc.) Must be full RoHS compliant including Pb ban Spare parts, repairs, capacity expansions equipments are grandfather in the directive and do not have to be RoHS compliant 7 Alcatel-Lucent 2007

Typical High Complexity Telecom Products Typical Card Attributes: Card size: ~16 x 16 is very common. Close to ~22 in many cases. Card thickness: Typical > 0.093. Close to 0.120 is not uncommon.

9 Typical High Complexity Telecom Products Typical Card Attributes: Card size: ~16 x 16 is very common. Close to ~22 in many cases. Card thickness: Typical > Close to is not uncommon. Layer count: 16 up to sometime 28 layers Solder joint connection: Typical > Component count : Typical > 2000 Area Array (BGA, LGA) Device: from 3x3mm to 45x45mm. Typically I/O BGAs. Large CBGA and CCGA sometimes. 0.5mm pitch sometimes. Small discrete: 0402, AL CAP (expect to be very problematic in Pb-free), etc. Surface Finish: ENIG, HASL, IAg 9 Alcatel-Lucent 2007

10 Current State Alcatel-Lucent network infrastructure equipment is currently exempt for Pb-in-Solders from the EU RoHS Pb-free requirements Long life expectance in Telecom equipment; up to 20 (or 25) years Exemption was granted for reliability reasons Tremendous Pressure to Move to Pb-Free Assembly But the Reliability Questions (Problems) Remain! 10 Alcatel-Lucent 2007

11 Concerns Component Supply Chain is rapidly moving to Pb-free compatible components Consumer electronics industry is primarily Pb-free solder already BGA s with Pb-free solder balls are NOT backward compatible with SnPb soldering Serious reliability concerns and significant assembly challenges even for mixed assemblies without regard to reliability issues Availability of SnPb BGA s beyond the near term very questionable Limited availability in memories, and already some end of life notices for some Processors What IF the Lead exemption remove after 2010? 11 Alcatel-Lucent 2007

13 Bare Board Reliability Top SnPb rated Laminate Bottom Pb-Free rated laminate Run through Lead-Free reflow Profile at Same Time! Major Degradation of SnPb rated laminate 13 Alcatel-Lucent 2007 Weibull Analysis shows reduced PTH Reliability when run through Pb-Free Reflow * Works in the HDPUG consortium Laminate changes in high complexity product from typical high Tg FR4 to non-dicy cure FR4 is expected and this changes require $$$

14 Tin (Sn) Whisker *Raytheon *Cypress 14 Alcatel-Lucent 2007

Tin (Sn) Whisker inemi matrix co-developed with OEMs inemi Whisker Test requirements include Ambient storage High Temp/Humidity Temp Cycling Requirements are now documented in the JEDEC spec,

15 Tin (Sn) Whisker inemi matrix co-developed with OEMs inemi Whisker Test requirements include Ambient storage High Temp/Humidity Temp Cycling Requirements are now documented in the JEDEC spec, JESD-201 Ensure all suppliers follow the proper Tin Whisker mitigation practices, test & requirements. Alcatel-Lucent has been providing leadership in this area. Working with large number of OEM leveraging the wide networks in inemi. 15 Alcatel-Lucent 2007

16 Issue with Pb-free Devices Temperature Rating Melting point for SnPb solder is 183 o C Melting point for SnAgCu (SAC305, SAC405) solder is ~217 o C Key issues are Need to make sure the solder joints assembly will meet minimum 232 o C across the board Need to make sure the assembly will not exceed 260 o C (or 245 o C for large device) across the board Large delta Temp in product with very narrow process window Again, worst for large products to make sure small device don t go beyond 260 o C Still many suppliers not follow the IPC/JEDEC J-STD-020D spec which demand to meet the high temperature requirement 16 Alcatel-Lucent 2007

Also many other small discrete, prime example is AL CAP do not follow the spec as supplier explain this is for

17 Temperature Rating: Common Issues & Concerns Example of a small IC which should be rated at 260 o C per the JEDEC spec. Also many other small discrete, prime example is AL CAP do not follow the spec as supplier explain this is for IC package only. However the temperature requirements in process is no difference whether the device is an IC or not. The 260 o C for BGA rework requirement are being ignore by most suppliers 17 Alcatel-Lucent 2007

19 Reflow Challenges Very well put in the profile study done by Jabil On a high complexity card, we may still have component exiting the limit defined in the Jedec spec after 32 profile attempts Key questions/concerns: How many profiles we do today in a SnPb products? What if you have one of those AL CAP that rate at 230 o C? 19 Alcatel-Lucent 2007

Pb-free Rework Challenges Rework (BGA) optimization/repeatability project in inemi Hugh gaps in the industry If you want to be part of this, contact Jasbir (Jasbir.Bath@Flextronics.

20 Pb-free Rework Challenges Rework (BGA) optimization/repeatability project in inemi Hugh gaps in the industry If you want to be part of this, contact Jasbir Key issues: Suppliers for large BGA not committing to the 260 o C for 1 time rework as define in the Jedec spec Check the datasheet and follow up with your suppliers. Suppliers will tell you 260 o C is not needed. ALU DISAGREE. Studies done by ALU and CLS shown clearly the needs of 260 o C, or the compromise of the solder not reflow properly 20 Alcatel-Lucent 2007

22 Mildly Accelerated Thermal Cycling Test Must take out the unknown factors as much as possible Acceleration factors unknown Greatly reduces acceleration errors Eliminates/reduces high stress/strain effects that may result in failures in more highly accelerated conditions that don t really exist in field conditions Run side-by-side with SnPb versions Currently there is a lot of data tested in Highly Accelerated Temperature without a model to support these data Also many of these data sets are being questioned due to the test performed may not include parameters that may be key for Pb-free 32 boards each (SAC and SnPb) No Thermal Preconditioning Vibration Testing Age 1000 hours at 125 C Vibration Testing Functional Test over full product Temperature range before beginning and then every 300 thermal cycles Mildly Accelerated Thermal Cycle Test (Δ50 C) Dwell/Ramp (30mins) 22 Alcatel-Lucent 2007

23 Mildly Accelerated Thermal Cycling Test Internal Works: Real products with good sample size in SAC and SnPb built, tested Consortium Works: Large scale test vehicle with many different components to help understand different technologies that are not covered in the product testing More than a dozen model published in the last few years. But still a major issue in the industry with the lack of a recognized and validated model The above tests are to help us to understand the Pb-free products in the closer to field test condition Continue to work on an industry agreed model as the long term goal Important question is not whether SAC is better or worse than SnPb under Accelerated Thermal Cycling conditions, but whether field reliability requirements are met for SAC assemblies. JP Clech 23 Alcatel-Lucent 2007

Mixed Technology Internal Test Test vehicle, components, finishings and test conditions 265 x 212 mm, Single side reflow PBA 661 Components : Cristallo ASIC from ST (with SAC balls) and SnBi Al-Caps

24 Mixed Technology Internal Test Test vehicle, components, finishings and test conditions 265 x 212 mm, Single side reflow PBA 661 Components : Cristallo ASIC from ST (with SAC balls) and SnBi Al-Caps PB finishings : Immersion Ag, Immersion Sn and ENIG (SnPb HASL as baseline/reference) Thermo-mechanical stresses -25/+100 C 1500 thermal cycling -20/+85 C 300 thermal shocks Bending tests (2%) 24 Alcatel-Lucent 2007

25 Mixed Technology Internal Test If all the components (on PBA) are Pb-free compatible, process window opens (margins exist) In real case this is hard to control. Technological analyses show a good mixing of Pb. Still no Guarantee of Reliability! Thermo-mechanical test results are positive. But unclear on Complex PBAs, and the model to predict the relaibility. Current, ALU recommend don t assemble SAC BGA s with SnPb solder! - Reliability will be compromised - Process variables are essentially beyond control of the assembler 25 Alcatel-Lucent 2007

Key inemi Projects (for ALU) Mix Solder Technology - Continue working with other members in the inemi group to understand the impact and acceptance of

26 Key inemi Projects (for ALU) Mix Solder Technology - Continue working with other members in the inemi group to understand the impact and acceptance of mix solder technology (Pb-free BGA assemble in SnPb process) We need options in transition and also possibly for legacy products 26 Alcatel-Lucent 2007

Key inemi Projects in 08 (for ALU) Pb-free Alloy Alternatives Provide guidance to the industry that will help make Pb-free alloy proliferation easier to manage We need to determine existing knowledge

27 Key inemi Projects in 08 (for ALU) Pb-free Alloy Alternatives Provide guidance to the industry that will help make Pb-free alloy proliferation easier to manage We need to determine existing knowledge and critical gaps related to new Pb-free alloys, including data requirements and a table of issues to track Pb-free Early Failures We need to understand this better. Is it just outlier or it does happen more often in Pb-free compared to what we saw in SnPb 27 Alcatel-Lucent 2007

29 Summary There are still lots of issues & challenges High Reliability Products needs to overcome in the Pb-free transition Next 2-3 years are very critical, as some of the exemptions for the industry to use Pb may change We need to continue to work together in the industry through the consortium Encourage more suppliers to be actively participate in consortium like inemi Also suggesting different consortiums working closer together to avoid overlaps Too many issues and the issues are too broad for any one company or even consortium to take on! THANK YOU 29 Alcatel-Lucent 2007

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Pulse White Paper Regarding RoHS Compliance

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