Freescale, the Freescale logo, AltiVec, C-5, CodeTEST, CodeWarrior, ColdFire, C-Ware, t he Energy Efficient Solutions logo, mobilegt, PowerQUICC,

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1 TM February 2012 Freescale, the Freescale logo, AltiVec, C-5, CodeTEST, CodeWarrior, ColdFire, C-Ware, t he Energy Efficient Solutions logo, mobilegt, PowerQUICC, QorIQ, StarCore and Symphony are trademarks of Freescale Semiconductor, Inc., Reg. U.S. Pat. & Tm. Off. BeeKit, BeeStack, ColdFire+, CoreNet, Flexis, Kinetis, MXC, Platform in a Package, Processor Expert, QorIQ Qonverge, Qorivva, QUICC Engine, SMARTMOS, TurboLink, VortiQa and Xtrinsic are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners Freescale Semiconductor, Inc.

2 Hybrid/EV Powertrain Stop/Start Regenerative Braking Driver Information Infotainment Telematics Theater Quality Multimedia Powertrain Control Engine Control Gasoline Management Fuel Injection Chassis Braking Systems Electronic Power Steering Active Suspension Safety Airbags with Faster Impact Detection Electronic Stability Program Collision Avoidance and Adaptive Cruise Control Body Electronics Body Control Module Seat, Door, and Window Control Remote Control HVAC Control Lighting Control/Bending/Leveling Automotive Networking/ Communication Bus communication network Local area network Multimedia and infotainment networking Increasing processor content in electronics systems Emerging or increasing integration: Hybrid/EV powertrain, advanced safety, infotainment Traditional: Powertrain and chassis 2

3 Powertrain control one of the early adopters of electronics systems Qualified on legacy or stable packages such as PBGAs Customer base strives for consistency of BOM across product life In 2008 Freescale has had to react to a major change in PBGA substrate supply. Factor Customer Expectation Supply Chain Reality Package BOM Substrate BOM* Die attach epoxy Wire Mold compound Solder ball* Supplier stability Substrate supplier* Substrate materials *Areas of interest in this study No change to BOM once qualified. No change to suppliers or materials once qualified. BOM driven by consumer market market packaging trends: halogen free, Pb-free, etc. Freescale s 1 st - and 2 nd level suppliers vulnerable to macroeconomic conditions or unexpected disruptions: business realignment, geopolitical events, natural disasters, etc. 3

4 Freescale Automotive MCUs are commonly in the 388 and 272 PBGA packages. Qualified and shipping for 10+ years Package Body Size BGA Pitch Die Size Ball Diameter 272 PBGA 27 x 27 mm 388 PBGA 27 x 27 mm 1.27 mm 10.8 x 10.1 mm 1.00 mm 10.0 x 10.0 mm Substrate Layers Package Thickness 0.76 mm (max) 0.60 mm (max) PBGA Cross-section 388 PBGA BGA side 272 PBGA BGA side 4

5 Freescale BOM A Legacy material set B Hybrid Interim migration path C Preferred 388 and 272 PBGA BOM matrix Supplier Old New_1 New_2 New_1 New_2 Substrate Supply Chain Substrate Core Freescale Supply Chain Soldermask Mold Compound Halogencontaining Halogencontaining Halogencontaining Halogenfree Halogenfree Halogenfree Halogenfree Halogenfree Halogenfree Solder Ball Alloy Notes SnPb Baseline - BOM majority in use today for Automotive SnPb Pb-free Maintains compatibility with customer SnPb board attach process New products are launched with this BOM The study was designed to collect solder joint reliability data on the current package, BOM, and supplier as a baseline and collect the same SJR data on the proposed replacement suppliers or BOM for comparison 5

6 Package Test setup Daisy chain versions of the 388 and 272 PBGA Mounted to complimentary PCBs. SMT, PCB and Substrate Parameters SMT Parameter SnPb Ball Pb-free Ball Paste alloy SnPb SnAgCu Peak reflow C C Daisy chain connection scheme Single test board with 15 PBGAs PCB Parameter 388 PBGA 272 PBGA Thickness 1.58 mm 1.00 mm Cu Layers 4 4 Pad NSMD NSMD Pad Diameter 0.58 mm 0.40 mm Pad Finish Sn OSP Substrate Parameter 388 PBGA 272 PBGA Thickness 0.55mm 0.55 mm Cu Layers 2 2 Pad SMD SMD Pad Diameter 0.50 mm mm Pad Finish NiAu NiAu 6

7 Monitor PCB s monitored continuously in-situ Use event detectors to monitor daisy chain continuity 300 Ohms or higher is considered a failure - IPC-785-SM Typically start resistance is about 1 Ohm Record cycle at which a net/part fails Chambers Air Temperature Cycling (ATC) Single chamber - air temperature changed inside chamber Long ramp times, about 10C/minute For automotive Freescale uses -40/125 C condition Air-to-Air Thermal Shock (AATS) Dual chamber - move boards/parts between chambers Short ramp times, less than 5 minutes For automotive Freescale use -40/125 C condition Daisy chain resistance net Data logging system Single Chamber ATC System Dual Chamber AATS System 7

8 1A. 388 PBGA substrate BOM and supplier, SnPb ball Old New_2 New_1 New Vendors/BOM at least as reliable as Old Vendors/BOM for SnPb Vendor differences noted on otherwise identical (New) BOMs 8

9 1B. 272 PBGA substrate BOM and supplier, SnPb ball Old New_1 New_2 Net reliability improvement in moving from Old vendor/bom to New vendors/bom Vendor differences noted on otherwise identical (New) BOMs 9

10 2A. 388 PBGA - different Pb-free ball alloy Old SnPb New SAC387 New SnAg Pb-free BOM has longer life, higher reliability than Old Further improvement seen on SnAg alloy compared to SAC Substrate supplier difference can still be observed 10

11 2B. 272 PBGA - different Pb-free ball alloy Old SnPb New SAC387 New SnAg Pb-free BOM has longer life, higher reliability than Old Further improvement seen on SnAg alloy compared to SAC Substrate supplier difference can still be observed 11

12 3. Other analysis and 272 PBGA Package Warpage Old Old New New Old halogen-containing substrate has higher warpage in heating and cooling zones. Halogen-free substrate does not warp as much in heating and cooling zones. Same warpage profile observed between halogen-free suppliers. 12

13 4. Other analysis substrate construction Baseline: Halogen-containing Old supplier Similar mechanical (thickness) spec between old and new. New_1 and New_2 substrates have different glass cloth stack up due to supplier preference. The core material used is the same halogen-free core from the same core material supplier. Freescale studies are underway to collect materials properties on finished (bare) substrates. Halogen-free New_1 supplier 0.045mm 0.025mm Soldermask 0.550mm 0.410mm Copper Layer Core Laminate Halogen-free New_2 supplier 13

14 5. Post-cycling dye penetrant failure analysis PBGA Baseline: Halogen-containing Old supplier SnPb ball Halogen-free New_1 SnPb ball Halogen-free New_2 SnPb ball Halogen-free New_1 SnAg ball Halogen-free New_2 SnAg ball Cracked solder joints are consistently in the center thermal ball group and interior perimeter balls - regardless of material set, substrate supplier, or ball alloy vendor 388 PBGA results similar, not shown No new failure modes or patterns seen. 14

15 There is a clear trend showing a board level reliability gain when: changing from the Old halogen-containing to the New halogen-free substrate BOM. Pb-free ball alloys are employed. SnAg shows a further gain compared to SAC. The halogen-free BOM with the SnAg solder ball has the highest solder joint reliability among the configurations tested. Substrate supplier differences may be observed, but are not a major influence in the board level gains seen. Failure locations and patterns remain similar regardless of BOM, supplier, or ball alloy. These changes do not influence the solder joint fatigue mechanisms at play. 15

16 A change from legacy PBGA BOMs with halogen-containing substrates and SnPb solder balls to an environmentally preferred BOM with halogen-free substrates and Pb-free solder ball alloys provides a clear improvement in board level reliability in the packages studied. A clear win for the customer application and the environment! 16

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