Plastic Package Reliability - Computer Action Team

1 C. Glenn ShirleyPlastic Package ReliabilityC. Glenn ShirleyIntegrated Circuits Design and Test LaboratoryElectrical and Computer EngineeringPortland State UniversityPortland, ~cgshirl/ C. Glenn ShirleyOutline Plastic packages Stress and Test Flows Thermal Mechanisms Moisture Mechanisms Thermo-mechanical Mechanisms Moisture-mechanical Mechanisms Technology Update8/2-4/2011 Plastic Package Reliability2 C. Glenn ShirleyPlastic-Encapsulated Microcircuits The course covers Plastic -encapsulated microcircuits. Molding compound (MC) in PEMs comes in direct contact with the die and chip Package Reliability3 Epoxy Based Molding CompoundSolder Grid ArrayBT Resin Multilayer PCBM etal Heat Sink PlateAg -Epoxy AdhesiveSolder BallsExpoxy Based Molding CompoundAg -Epoxy AdhesiveTape/AdhesiveDielectricCopper Heat SlugSingle LayerLead Frame C.

2 Glenn ShirleyPlastic-Encapsulated Microcircuits Die is mounted on a lead frame (A42 or Cu). Bonds are made by. Wirebond: Au or Al; mostly Au. TAB: Tape-Automated Bonding. C4: Controlled Collapse Chip Connect. Assembly is encapsulated in molding compound. Molding compound is in direct contact with die, wire bonds, etc. External leads are trimmed and solder Package Reliability4 Alloy 42 Fe 58% Ni 42% alloy with CTE matching Si. C. Glenn ShirleyMolding Compounds MC is thermoset (curing) epoxy, typically novolac. Cures at ~ 170-180 C. Silica filler controls CTE and increases thermal conductivity. MCs are (now) free of ionic contaminants. Glass Transition ~ 140 C. Moisture properties of MC: Permeable to moisture.

3 Absorbs moisture. Hygroscopic. 8/2-4/2011 Plastic Package Reliability5 Note distinction between thermosetand thermoplastic. C. Glenn ShirleyMolding Compound Properties At the glass transition (> 140 C)..8/2-4/2011 Plastic Package Reliability6MC strength decreasesCTE increasesL. T. Manzione Plastic Packaging of Microelectronic Devices, Van NostrandReinhold 1990. C. Glenn ShirleyMolding Compound Properties, ct d Molding compound strongly absorbs water. Saturationuptake is proportional to RH, and independent of temperature. Rateof uptake depends strongly on Package Reliability7L. T. Manzione Plastic Packaging of Microelectronic Devices, Van Nostrand Reinhold 1990. C. Glenn ShirleyOutline Plastic packages Stress and Test Flows Thermal Mechanisms Moisture Mechanisms Thermo-mechanical Mechanisms Moisture-mechanical Mechanisms Technology Update8/2-4/2011 Plastic Package Reliability8 C.

4 Glenn ShirleyLife of an Integrated Circuit8/2-4/2011 Plastic Package Reliability9 End-user EnvironmentAssemblyShippingStorageOEM/OD M AssemblySource: Eric Monroe, 2003 Mobile PCDTUser Drop & VibeShipping ShockTemp, RHPower CycleBendReflowHandling TempBAM!Bent Pins, SingulationTemperature CycleDesktopDTShipping ShockTemp, RHBendPower CycleReflowHandling TempBent Pins, SingulationTemperature CycleUser Drop & VibeKeypad pressDTShipping ShockTemp, RHBendReflowHandlingTemperature CycleBAM!HandheldSlide by Scott C. Johnson. C. Glenn ShirleyStress/Test Flow8/2-4/2011 Plastic Package Reliability10 Simulate shipping, storing, and OEM board mounting in-service end use pass/fail. Diagnose : JEP150 Stress-Test-Driven Qualification of and Failure Mechanisms Associated with Assembled Solid State Surface-Mount Components (JEDEC)PreconditioningEnvironmental StressElectrical Test, Failure Analysis C.

5 Glenn ShirleyIndustry Reliability Standards International ISO International Standard Organization IEC International Electrotechnical Commission Europe CEN, CENELECC omite Europ en de Normalisation lectrotechnique Japan JIS Japanese Industrial Standard, EIAJ US MIL (US Department of Defense), EIA/JEDEC8/2-4/2011 Plastic Package Reliability11 For US commercial products JEDEC standards have mostly superseded MIL standards. C. Glenn ShirleyPreconditioning Preconditioning simulates board assembly. Specified by JESD22-A113 FPreconditioning of Nonhermetic Surface Mount Devices Prior to Reliability Testing. IPC/JEDEC Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices8/2-4/2011 Plastic Package Reliability12 Free downloads, registration StressElectrical Test, Failure Analysis C.

6 Glenn ShirleyPreconditioning Flow8/2-4/2011 Plastic Package Reliability13 JESD22-A113 FIPC/JEDEC PreconditioningEnvironmental StressElectrical Test, Failure AnalysisSlide 50 C. Glenn ShirleyEnvironmental Test Stress-based testing (traditional). Standards: JESD47, MIL-STD-883. Pro: Well-established standards. Lots of historical data. Good for comparisons. Little information about mechanism or use is required. Con: Overstress: May foreclose a technology. Understress: Misses a mechanism. May not accurately reflect a use environment. Knowledge-based testing. Risk assessment of Use and Mechanism guides Package Reliability14 PreconditioningEnvironmental StressElectrical Test, Failure AnalysisTo keep things simple, we ll follow this approach.

7 C. Glenn ShirleyKnowledge-Based Test Knowledge-Based Testing Stress depends on knowledge ofuse conditions andmechanisms. Risk assessment, using methods JEDEC: JESD94, JEP143, JEP148 Sematech: Understanding and Developing Knowledge-based Qualifications of Silicon Devices #04024492A-TR Pro: Stresses fit the product and its use. May make a product feasible. Con: Easy to miss mechanisms in new technologies and overlook use conditions in new applications. Tempting to misapply to uprate devices, relax Package Reliability15 MechanismUse ConditionRisk AssessmentStressesPreconditioningEnviron mental StressElectrical Test, Failure Analysis C. Glenn ShirleyJESD47 Example8/2-4/2011 Plastic Package Reliability16 PreconditioningEnvironmental StressElectrical Test, Failure AnalysisNote: TS (JESD22-A106) and AC (Steam) (JESD22-A102)are not recommended.

8 Verydifferent from use. C. Glenn ShirleyFocus of this Stress Flow8/2-4/2011 Plastic Package Reliability17 ELFRHTOLTHB or HASTHTSL (Bake)TCPC1000 hrsJESD22-A1031000 hrs (85/85)JESD22-A10196 hrs (130/85)JESD22-A110700 cycles3 cycles/hr233 hrsJESD22-A104 Condition B or G(C is too severe)Early life failure hrsJESD22-A108 High temperatureoperating -1000 x 773 x 253 x 253 x 25 Assumptions168 h is equivalent to early life requirementSS computed from goal. eg. 3x611 = 1833(Lots x Units)PreconditioningEnvironmental StressElectrical Test, Failure Analysis C. Glenn ShirleySampling JESD47sample requirements are minimal. Single snapshot is a crude validation of the Reliability of the product. Small SS does not generate failures to give clues to process weaknesses.

9 Risks. Qualification hinges on single failures. Moral hazard to invalidate a failure is high. Lot-to-lot variation, excursions. Incoming materials, fablots, assembly lots, test Package Reliability18 C. Glenn ShirleySampling, ct d Number of lots covers risks of machine-to machine, day-to-day, etc. variation. Often minimum SS to validate a goal is chosen. Pro: Saves $, and there are no failures to explain. Con: Pass/fail of the qual is at the mercy of a single failure. Verrry tempting to invalidate a failure. Con: No mechanism learning. eg. To validate 500 DPM at ELFR using minimum SS at 60% confidence, 1833 units are required. 500 DPM is a typical goal (see ITRS)8/2-4/2011 Plastic Package Reliability196ln(1)ln(1 )1833500 10clSSD Useful mental furniture (Accept/Reject 0/1)PreconditioningEnvironmental StressElectrical Test, Failure Analysis C.

10 Glenn ShirleySampling, ct d For environmental stress, 77 is a typical SS, why? So, 0/1 accept/reject validates, to 90% confidence, a failure rate less than 3% at the accelerated condition. If the stress corresponds to the lifetime (eg. 7 years) then the average wearoutfailure rate is This falls into the range of Package Reliability202ln(1)ln(1 )ln(.1) ; 1033clSSD 293 10104897 365 24FR Fits PreconditioningEnvironmental StressElectrical Test, Failure Analysis C. Glenn ShirleyReliability Goals from ITRS 20098/2-4/2011 Plastic Package Reliability21 PreconditioningEnvironmental StressElectrical Test, Failure AnalysisInfant MortalityWear-outConstant fail C. Glenn ShirleyExample Data Additional attributes enhance value of data.