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1 
Test Plan Development using Physics of Failure: The DfR Solutions Approach 
Cheryl Tulkoff, ASQ CRE 
ctulkoff@dfrsolutions.com
2 
Introduction 
oAgenda 
oIntroduction to Test Plan Development 
oIntroduction to Physics of Failure Methodology for Test Plan Development 
oVirtual Qualification Option 
oAfter Release 
oCase Study 
Power Cycling 
Vibration 
Temperature/ 
Humidity 
Mechanical Shock 
Temperature Cycling
3 
oHow can you be sure that you have the best test plans for your specific need? 
oDfR Solutions has worked closely with over 500 OEMs in multiple industries developing hundreds (thousands??) of test plans. 
oDfR Solutions experts have written product specs for these organizations. 
oThrough close collaboration with industry leading electronics manufacturers and deep industry knowledge, DfR Solutions delivers the right test for the right product every time! 
Test Plan Development
4 
Test Plan Development 
oProduct test plans are critical to the success of a new product or technology 
oStressful enough to identify defects 
oShow correlation to a realistic environment 
oDfR Solutions approach 
oIndustry Standards + Physics of Failure 
oResults in an optimized test plan that is acceptable to management and customers 
•MIL-STD-810, 
•MIL-HDBK-310, 
•SAE J1211, 
•IPC-SM-785, 
•Telcordia GR3108, 
•IEC 60721-3, etc. 
•PoF!
5 
oPoF Definition: The use of science (physics, chemistry, etc.) to capture an understanding of failure mechanisms and evaluate useful life under actual operating conditions 
oUsing PoF, design, perform, and interpret the results of accelerated life tests 
oStarting at design stage 
oContinuing throughout the lifecycle of the product 
oStart with standard industry specifications 
oModify or exceed them 
oTailor test strategies specifically for the individual product design and materials, the use environment, and reliability needs 
Physics of Failure (PoF)
6 
Industry Testing Falls Short 
oLimited degree of mechanism-appropriate testing 
oOnly at transition to new technology nodes 
oMechanism-specific coupons (not real devices) 
oTest data is hidden from end-users 
oQuestionable JEDEC tests are promoted to OEMs 
oLimited duration (1000 hrs) hides wearout behavior 
oUse of simple activation energy, with incorrect assumption that all mechanisms are thermally activated, can result in overestimation of FIT by 100X or more
7 
oFailure of a physical device or structure (i.e. hardware) can be attributed to the gradual or rapid degradation of the material(s) in the device in response to the stress or combination of stresses the device is exposed to, such as: 
oThermal, Electrical, Chemical, Moisture, Vibration, Shock, Mechanical Loads . . . 
oFailures May Occur: 
oPrematurely 
oGradually 
oErratically 
Physics of Failure Definitions
8 
Critical Elements for Developing Robust Test Plans 
oTest Objectives! 
oComparison 
oQualification 
oValidation 
oResearch 
oCompliance 
oRegulatory 
oFailure analysis 
oElements 
oReliability Goals 
oDesign 
oMaterials 
oUse Environment 
oBudget 
oSchedule 
oSample availability 
oPracticality 
oRisk
9 
Define Reliability Goals 
oIdentify and document two key metrics 
oDesired lifetime 
oDefined as time the customer is satisfied with 
oShould be actively used in development of part and product qualification 
oProduct performance 
oReturns during the warranty period 
oSurvivability over lifetime at a set confidence level 
oMTBF or MTTF (try to avoid unless required by customer) 
9
10 
Test Plan Development – Define Use Environment 
oThe critical first step is a good understanding of the shipping and use environment for the product. 
oDo you really understand the customer and how they use your product (even the corner cases)? 
oHow well is the product protected during shipping (truck, ship, plane, parachute, storage, etc.)? 
oDo you have data or are you guessing? 
oTemp/humidity, thermal cycling, ambient temp/operating temp. 
oSalt, sulfur, dust, fluids, etc. 
oMechanical cycles (lid cycling, connector cycling, torsion, etc.) 
10
11 
Identify Use Environment 
o Old School Approach: Use of industry/military specifications 
oMilitary, IPC, Telcordia, ASTM….. 
oAdvantages 
oNo additional cost! 
oSometimes very comprehensive 
oAgreement throughout the industry 
oMissing information? Consider standards from other industries 
oDisadvantages 
oMost more than 20 years old 
oAlways less or greater than actual (by how much, unknown) 
IPC SM785 
MIL HDBK310
12 
Use Environment (cont.) 
oBetter Approach: Based on actual measurements of similar products in similar environments 
oDetermine average and realistic worst-case 
oIdentify all failure-inducing loads 
oInclude all environments 
oManufacturing 
oTransportation 
oStorage 
oField
13 
Examples of Failure Inducing Loads 
•Temperature Cycling 
–Tmax, Tmin, dwell, ramp times 
•Sustained Temperature 
–T and exposure time 
•Humidity 
–Controlled, condensation 
•Corrosion 
–Salt, corrosive gases (Cl2, etc.) 
•Power cycling 
–Duty cycles, power dissipation 
•Electrical Loads 
–Voltage, current, current density 
–Static and transient 
•Electrical Noise 
•Mechanical Bending (Static and Cyclic) 
–Board-level strain 
•Random Vibration 
–PSD, exposure time, kurtosis 
•Harmonic Vibration 
–G and frequency 
•Mechanical shock 
–G, wave form, # of events 
Reliability Improvement with Design of Experiment, Second Edition, By Lloyd Condra
14 
Use Environment: Best Practice 
oUse standards when… 
oCertain aspects of your environment are common 
oNo access to real use environment 
oMeasure when… 
oCertain aspects of your environment are unique 
oStrong relationship with customer 
oDo not mistake test specifications for the actual use environment 
oCommon mistake
15 
Failure-Inducing Load Example: Electrical Environments 
oOften very well-defined in developed countries 
oIntroduction into developing countries can sometimes cause surprises 
oRules of thumb 
oChina: Can have issues with grounding (connected to rebar?) 
oIndia: Numerous brownouts (several a day) 
oMexico: Voltage surges
16 
Failure Inducing Temperature: Transport & Storage 
Container and Ambient Temperature 
15.0 
25.0 
35.0 
45.0 
55.0 
65.0 
75.0 
0 50 100 150 200 250 300 350 400 450 
Hours 
Temperature (°C) 
Container Temp (°C) 
Outdoor Temp (°C) Temp. 
Variation 
In a 
Trucking 
Container
17 
Temperature: Long-Term Exposure 
o For electronics used outside with minimal power dissipation, the diurnal 
(daily) temperature cycle provides the primary degradation-inducing 
load 
Month Cycles/Year Ramp Dwell Max. Temp (oC) Min. Temp. (oC) 
Jan.+Feb.+Dec. 90 6 hrs 6 hrs 20 5 
March+November 60 6 hrs 6 hrs 25 10 
April+October 60 6 hrs 6 hrs 30 15 
May+September 60 6 hrs 6 hrs 35 20 
June+July+August 90 6 hrs 6 hrs 40 25 
Phoenix, AZ
18 
Humidity / Moisture (Rules of Thumb) 
oNon-condensing 
oStandard during operation, even in outdoor applications 
oDue to power dissipation 
oCondensing 
oCan occur in sleep mode or non-powered 
oDriven by mounting configuration (attached to something at lower temperature?) 
oDriven by rapid change in environment 
oCan lead to standing water if condensation on housing 
oStanding water 
oIndirect spray, dripping water, submersion, etc. 
oOften driven by packaging
19 
General Test Plan Development Outline – PCBA Example 
oComponent qualification (with end product in mind) 
oThermal cycling, high temp, T&H, etc. 
oPCBA qualification 
oThermal cycling 
oHALT/HAST 
oDrop/shock 
oHeat age 
oSystem level qualification 
oShock and Vibration 
oDust testing 
oTorsion 
oEtc. 
19
20 
Test Plan Development – for PCBAs continued… 
oDevelop a comprehensive test plan 
oAssemble boards at optimum conditions 
oRework specified components on some boards 
oVisually inspect and electrically test 
oC-SAM & X-ray inspect critical components on 5 or more boards (+3 reworked for BGAs) 
oUse these boards for further reliability testing (TC, HALT, S&V) 
oPerform failure analysis 
oCompile results and review
21 
21 
Assemble at Optimum Conditions 66 pcs 
Visual Inspection 66 pcs 
Electrical Continuity Test (DC devices) 66 pcs 
Send to Intel 10 pcs 
X-Section Analysis (Devices ?) 2 pcs 
Thermal Cycle Test (0/100C) 12 pcs 
X-Section Analysis 
(Devices ?) 
1 pcs 
Non-Op + Cont (S & V) 
4 pcs 
X-Section Analysis (Devices ?) 1 pcs 
Square Wave (S & V) 4 pcs 
X-Section Analysis (Devices ?) 1 pcs 
2 
4 
4 
1 
1 
4 
HALT (Duration ?) 4 pcs 
X-Section Analysis (Devices ?) 1 pcs 
4 
1 
1 
Dye / Pry Analysis 
(Devices ?) 
1 pcs 
1 
1 
4 
1 
Dye / Pry Analysis (Devices ?) 1 pcs 
Dye / Pry Analysis (Devices ?) 4 pcs 
Dye / Pry Analysis (Devices ?) 1 pcs 
Thermal + Non-Op +Cont (S & V) 
4 pcs 
X-Section Analysis 
(Devices ?) 
1 pcs 
1 
Dye / Pry Analysis (Devices ?) 1 pcs 
1 
12 
10 
Example of a Test Plan (Notebooks) 
Use for Rework Section* 
25 pcs 
25 
1 
2 
2 
7 
2 
2 
NOTES: 
* - Rework should follow the supplier’s standard 
process for removing and replacing components 
Number in lower right corner of box represents 
Remaining quantity from that test element.
22 
oEffective failure analysis is critical to reliability! 
oWithout identifying the root causes of failure, true corrective action cannot be implemented 
oRisk of repeat occurrence increases 
oUse a systematic approach to failure analysis 
oProceed from non-destructive to destructive methods until all root causes are identified. 
oTechniques based upon the failure information specific to the problem. 
oFailure history, failure mode, failure site, failure mechanism 
Don’t Overlook Failure Analysis!
23 
Virtual Qualification (VQ, Modeling) 
oThis assessment uses physics-of-failure-based degradation models to predict time-to-failure 
oModels include 
oInterconnect fatigue (solder joint and plated-through hole) 
oCapacitor failure (electrolytic and ceramic) 
oIntegrated circuit wearout 
oCustomers develop a degree of assurance that their product will survive for the desired lifetime in the expected use environment
24 
Sherlock ADA – A Reliability Assurance CAE Tool Suite - the Physics of Failure App. 
It is not at the Iphone or Droid App store. 
But yes there is now a Physics of Failure Durability Simulation App 
24
25 
The 4 Parts of a Sherlock PoF Analysis 
1)Design Capture - provide industry standard inputs to the modeling software and calculation tools 
2)Life-Cycle Characterization - define the reliability/durability objectives and expected environmental & usage conditions (Field or Test) under which the device is required to operate 
3)Load Transformation – automated calculations that translates and distributes the environmental and operational loads across a circuit board to the individual parts 
4)PoF Durability Simulation/Reliability Analysis & Risk Assessment – Performs a design and application specific durability simulation to calculates life expectations, reliability distributions & prioritizes risks by applying PoF algorithms to the PCBA model 
25
26 
oLighting products customer was attempting to develop a product qualification plan 
oSherlock identified appropriate test time and test condition based on field environment and likely failure mechanism 
PoF Modeling & Test Plan Development
27 
When to Repeat Testing: Change Control 
oInadequate change control is responsible for many (some would say most) field failures. 
oExamples would include 
oBurning Li notebook batteries 
oElectrolytic capacitor leakage 
oRecent flip chip underfill problems 
oCoin cell battery contact failure 
oHeat sink clogging failure 
oDDR2 Memory modules 
oImAg corrosion 
oAll changes need to be evaluated carefully (testing to failure recommended). 
27
28 
On-Going Reliability Testing 
oQualification shows that a limited number of early manufactured products (maybe even from a pilot line) are reliable. 
oIt’s often not possible to create every permutation of component suppliers in the qual builds. 
oHow do you know the product will remain reliable as you go to high volume and new component suppliers are introduced? 
oThere is no perfect answer but an ORT program can help. 
28
29 
Case Study: Solar Micro-Inverter Reliability 
oThe electronic components used in a micro-inverter are commercial off-the-shelf (COTS) 
oParts designed for consumer electronics but need to survive 25 years in solar installations 
oOutdoor/Partially Protected & Temp Not Controlled 
oLack of industry standards for testing
30 
What can be done? 
oHow can a micro-inverter supplier design the product to meet the requirements AND convince the customer of this? 
oOne new method: model the reliability of an electronic assembly in a variety of conditions based on the design (before building anything). 
oDesign for Reliability (DfR) concepts and Physics of Failure (PoF) are used.
31 
Are there Methods to Model these Failure Mechanisms? 
oYes! 
oAlgorithms exist to estimate the failure rate from solder joint fatigue for different types of components. 
oIPC TR-579 models PTH reliability 
oRisk for CAF can be determined 
oFinite Element Analysis can be used for Shock & Vibration risk. 
oMTBF calculations can be performed to estimate component failure rates.
32 
Micro-Inverter Environment 
oExtreme hot and cold locations (AZ to AK) 
oPossible exposure to moisture/humidity 
oLarge diurnal thermal cycle events (daily) 
oLargest temp swings occur in desert locations where it can reach 64C in the direct sun down to 23C at night (Δ41C)
33 
Potential Inverter Failure Mechanisms 
oSolder joint fatigue failure 
oPlated through hole fatigue failure 
oConductive anodic filament formation (CAF) 
oShock or Vibration (during shipping) 
oComponent wear out
34 
PTH Fatigue Results - Example
35 
Combined (SJ & PTH) Lifetime Prediction 
oCombines analysis results into overall failure prediction curve 
PTH 
Solder Joint 
Combined
36 
Combined Failure Rate is Provided
37 
Additional Uses for Modeling 
oUse Sherlock to determine thermal cycle test requirements. 
oUse to modify mount point locations 
oUse to determine ESS conditions 
oComponent Replacement 
oDetermine impact of changing to Pb-free solder 
oDetermine expected warranty costs
38 
38 
Summary 
oProduct test plans are critical to the success of a new product or technology 
oStressful enough to identify defects 
oShow correlation to a realistic environment 
oPoF Knowledge can be used to develop test plans and profiles that can be correlated to the field. 
oChange control processes and testing should not be overlooked (reliability engineer needs to stay involved in sustaining). 
oOn-going reliability testing can be a useful (but admittedly imperfect) tool. 
oPoF Modeling is an excellent tool to help tailor & optimize physical testing plans

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Test Plan Development using Physics of Failure: The DfR Solutions Approach

  • 1. 1 Test Plan Development using Physics of Failure: The DfR Solutions Approach Cheryl Tulkoff, ASQ CRE ctulkoff@dfrsolutions.com
  • 2. 2 Introduction oAgenda oIntroduction to Test Plan Development oIntroduction to Physics of Failure Methodology for Test Plan Development oVirtual Qualification Option oAfter Release oCase Study Power Cycling Vibration Temperature/ Humidity Mechanical Shock Temperature Cycling
  • 3. 3 oHow can you be sure that you have the best test plans for your specific need? oDfR Solutions has worked closely with over 500 OEMs in multiple industries developing hundreds (thousands??) of test plans. oDfR Solutions experts have written product specs for these organizations. oThrough close collaboration with industry leading electronics manufacturers and deep industry knowledge, DfR Solutions delivers the right test for the right product every time! Test Plan Development
  • 4. 4 Test Plan Development oProduct test plans are critical to the success of a new product or technology oStressful enough to identify defects oShow correlation to a realistic environment oDfR Solutions approach oIndustry Standards + Physics of Failure oResults in an optimized test plan that is acceptable to management and customers •MIL-STD-810, •MIL-HDBK-310, •SAE J1211, •IPC-SM-785, •Telcordia GR3108, •IEC 60721-3, etc. •PoF!
  • 5. 5 oPoF Definition: The use of science (physics, chemistry, etc.) to capture an understanding of failure mechanisms and evaluate useful life under actual operating conditions oUsing PoF, design, perform, and interpret the results of accelerated life tests oStarting at design stage oContinuing throughout the lifecycle of the product oStart with standard industry specifications oModify or exceed them oTailor test strategies specifically for the individual product design and materials, the use environment, and reliability needs Physics of Failure (PoF)
  • 6. 6 Industry Testing Falls Short oLimited degree of mechanism-appropriate testing oOnly at transition to new technology nodes oMechanism-specific coupons (not real devices) oTest data is hidden from end-users oQuestionable JEDEC tests are promoted to OEMs oLimited duration (1000 hrs) hides wearout behavior oUse of simple activation energy, with incorrect assumption that all mechanisms are thermally activated, can result in overestimation of FIT by 100X or more
  • 7. 7 oFailure of a physical device or structure (i.e. hardware) can be attributed to the gradual or rapid degradation of the material(s) in the device in response to the stress or combination of stresses the device is exposed to, such as: oThermal, Electrical, Chemical, Moisture, Vibration, Shock, Mechanical Loads . . . oFailures May Occur: oPrematurely oGradually oErratically Physics of Failure Definitions
  • 8. 8 Critical Elements for Developing Robust Test Plans oTest Objectives! oComparison oQualification oValidation oResearch oCompliance oRegulatory oFailure analysis oElements oReliability Goals oDesign oMaterials oUse Environment oBudget oSchedule oSample availability oPracticality oRisk
  • 9. 9 Define Reliability Goals oIdentify and document two key metrics oDesired lifetime oDefined as time the customer is satisfied with oShould be actively used in development of part and product qualification oProduct performance oReturns during the warranty period oSurvivability over lifetime at a set confidence level oMTBF or MTTF (try to avoid unless required by customer) 9
  • 10. 10 Test Plan Development – Define Use Environment oThe critical first step is a good understanding of the shipping and use environment for the product. oDo you really understand the customer and how they use your product (even the corner cases)? oHow well is the product protected during shipping (truck, ship, plane, parachute, storage, etc.)? oDo you have data or are you guessing? oTemp/humidity, thermal cycling, ambient temp/operating temp. oSalt, sulfur, dust, fluids, etc. oMechanical cycles (lid cycling, connector cycling, torsion, etc.) 10
  • 11. 11 Identify Use Environment o Old School Approach: Use of industry/military specifications oMilitary, IPC, Telcordia, ASTM….. oAdvantages oNo additional cost! oSometimes very comprehensive oAgreement throughout the industry oMissing information? Consider standards from other industries oDisadvantages oMost more than 20 years old oAlways less or greater than actual (by how much, unknown) IPC SM785 MIL HDBK310
  • 12. 12 Use Environment (cont.) oBetter Approach: Based on actual measurements of similar products in similar environments oDetermine average and realistic worst-case oIdentify all failure-inducing loads oInclude all environments oManufacturing oTransportation oStorage oField
  • 13. 13 Examples of Failure Inducing Loads •Temperature Cycling –Tmax, Tmin, dwell, ramp times •Sustained Temperature –T and exposure time •Humidity –Controlled, condensation •Corrosion –Salt, corrosive gases (Cl2, etc.) •Power cycling –Duty cycles, power dissipation •Electrical Loads –Voltage, current, current density –Static and transient •Electrical Noise •Mechanical Bending (Static and Cyclic) –Board-level strain •Random Vibration –PSD, exposure time, kurtosis •Harmonic Vibration –G and frequency •Mechanical shock –G, wave form, # of events Reliability Improvement with Design of Experiment, Second Edition, By Lloyd Condra
  • 14. 14 Use Environment: Best Practice oUse standards when… oCertain aspects of your environment are common oNo access to real use environment oMeasure when… oCertain aspects of your environment are unique oStrong relationship with customer oDo not mistake test specifications for the actual use environment oCommon mistake
  • 15. 15 Failure-Inducing Load Example: Electrical Environments oOften very well-defined in developed countries oIntroduction into developing countries can sometimes cause surprises oRules of thumb oChina: Can have issues with grounding (connected to rebar?) oIndia: Numerous brownouts (several a day) oMexico: Voltage surges
  • 16. 16 Failure Inducing Temperature: Transport & Storage Container and Ambient Temperature 15.0 25.0 35.0 45.0 55.0 65.0 75.0 0 50 100 150 200 250 300 350 400 450 Hours Temperature (°C) Container Temp (°C) Outdoor Temp (°C) Temp. Variation In a Trucking Container
  • 17. 17 Temperature: Long-Term Exposure o For electronics used outside with minimal power dissipation, the diurnal (daily) temperature cycle provides the primary degradation-inducing load Month Cycles/Year Ramp Dwell Max. Temp (oC) Min. Temp. (oC) Jan.+Feb.+Dec. 90 6 hrs 6 hrs 20 5 March+November 60 6 hrs 6 hrs 25 10 April+October 60 6 hrs 6 hrs 30 15 May+September 60 6 hrs 6 hrs 35 20 June+July+August 90 6 hrs 6 hrs 40 25 Phoenix, AZ
  • 18. 18 Humidity / Moisture (Rules of Thumb) oNon-condensing oStandard during operation, even in outdoor applications oDue to power dissipation oCondensing oCan occur in sleep mode or non-powered oDriven by mounting configuration (attached to something at lower temperature?) oDriven by rapid change in environment oCan lead to standing water if condensation on housing oStanding water oIndirect spray, dripping water, submersion, etc. oOften driven by packaging
  • 19. 19 General Test Plan Development Outline – PCBA Example oComponent qualification (with end product in mind) oThermal cycling, high temp, T&H, etc. oPCBA qualification oThermal cycling oHALT/HAST oDrop/shock oHeat age oSystem level qualification oShock and Vibration oDust testing oTorsion oEtc. 19
  • 20. 20 Test Plan Development – for PCBAs continued… oDevelop a comprehensive test plan oAssemble boards at optimum conditions oRework specified components on some boards oVisually inspect and electrically test oC-SAM & X-ray inspect critical components on 5 or more boards (+3 reworked for BGAs) oUse these boards for further reliability testing (TC, HALT, S&V) oPerform failure analysis oCompile results and review
  • 21. 21 21 Assemble at Optimum Conditions 66 pcs Visual Inspection 66 pcs Electrical Continuity Test (DC devices) 66 pcs Send to Intel 10 pcs X-Section Analysis (Devices ?) 2 pcs Thermal Cycle Test (0/100C) 12 pcs X-Section Analysis (Devices ?) 1 pcs Non-Op + Cont (S & V) 4 pcs X-Section Analysis (Devices ?) 1 pcs Square Wave (S & V) 4 pcs X-Section Analysis (Devices ?) 1 pcs 2 4 4 1 1 4 HALT (Duration ?) 4 pcs X-Section Analysis (Devices ?) 1 pcs 4 1 1 Dye / Pry Analysis (Devices ?) 1 pcs 1 1 4 1 Dye / Pry Analysis (Devices ?) 1 pcs Dye / Pry Analysis (Devices ?) 4 pcs Dye / Pry Analysis (Devices ?) 1 pcs Thermal + Non-Op +Cont (S & V) 4 pcs X-Section Analysis (Devices ?) 1 pcs 1 Dye / Pry Analysis (Devices ?) 1 pcs 1 12 10 Example of a Test Plan (Notebooks) Use for Rework Section* 25 pcs 25 1 2 2 7 2 2 NOTES: * - Rework should follow the supplier’s standard process for removing and replacing components Number in lower right corner of box represents Remaining quantity from that test element.
  • 22. 22 oEffective failure analysis is critical to reliability! oWithout identifying the root causes of failure, true corrective action cannot be implemented oRisk of repeat occurrence increases oUse a systematic approach to failure analysis oProceed from non-destructive to destructive methods until all root causes are identified. oTechniques based upon the failure information specific to the problem. oFailure history, failure mode, failure site, failure mechanism Don’t Overlook Failure Analysis!
  • 23. 23 Virtual Qualification (VQ, Modeling) oThis assessment uses physics-of-failure-based degradation models to predict time-to-failure oModels include oInterconnect fatigue (solder joint and plated-through hole) oCapacitor failure (electrolytic and ceramic) oIntegrated circuit wearout oCustomers develop a degree of assurance that their product will survive for the desired lifetime in the expected use environment
  • 24. 24 Sherlock ADA – A Reliability Assurance CAE Tool Suite - the Physics of Failure App. It is not at the Iphone or Droid App store. But yes there is now a Physics of Failure Durability Simulation App 24
  • 25. 25 The 4 Parts of a Sherlock PoF Analysis 1)Design Capture - provide industry standard inputs to the modeling software and calculation tools 2)Life-Cycle Characterization - define the reliability/durability objectives and expected environmental & usage conditions (Field or Test) under which the device is required to operate 3)Load Transformation – automated calculations that translates and distributes the environmental and operational loads across a circuit board to the individual parts 4)PoF Durability Simulation/Reliability Analysis & Risk Assessment – Performs a design and application specific durability simulation to calculates life expectations, reliability distributions & prioritizes risks by applying PoF algorithms to the PCBA model 25
  • 26. 26 oLighting products customer was attempting to develop a product qualification plan oSherlock identified appropriate test time and test condition based on field environment and likely failure mechanism PoF Modeling & Test Plan Development
  • 27. 27 When to Repeat Testing: Change Control oInadequate change control is responsible for many (some would say most) field failures. oExamples would include oBurning Li notebook batteries oElectrolytic capacitor leakage oRecent flip chip underfill problems oCoin cell battery contact failure oHeat sink clogging failure oDDR2 Memory modules oImAg corrosion oAll changes need to be evaluated carefully (testing to failure recommended). 27
  • 28. 28 On-Going Reliability Testing oQualification shows that a limited number of early manufactured products (maybe even from a pilot line) are reliable. oIt’s often not possible to create every permutation of component suppliers in the qual builds. oHow do you know the product will remain reliable as you go to high volume and new component suppliers are introduced? oThere is no perfect answer but an ORT program can help. 28
  • 29. 29 Case Study: Solar Micro-Inverter Reliability oThe electronic components used in a micro-inverter are commercial off-the-shelf (COTS) oParts designed for consumer electronics but need to survive 25 years in solar installations oOutdoor/Partially Protected & Temp Not Controlled oLack of industry standards for testing
  • 30. 30 What can be done? oHow can a micro-inverter supplier design the product to meet the requirements AND convince the customer of this? oOne new method: model the reliability of an electronic assembly in a variety of conditions based on the design (before building anything). oDesign for Reliability (DfR) concepts and Physics of Failure (PoF) are used.
  • 31. 31 Are there Methods to Model these Failure Mechanisms? oYes! oAlgorithms exist to estimate the failure rate from solder joint fatigue for different types of components. oIPC TR-579 models PTH reliability oRisk for CAF can be determined oFinite Element Analysis can be used for Shock & Vibration risk. oMTBF calculations can be performed to estimate component failure rates.
  • 32. 32 Micro-Inverter Environment oExtreme hot and cold locations (AZ to AK) oPossible exposure to moisture/humidity oLarge diurnal thermal cycle events (daily) oLargest temp swings occur in desert locations where it can reach 64C in the direct sun down to 23C at night (Δ41C)
  • 33. 33 Potential Inverter Failure Mechanisms oSolder joint fatigue failure oPlated through hole fatigue failure oConductive anodic filament formation (CAF) oShock or Vibration (during shipping) oComponent wear out
  • 34. 34 PTH Fatigue Results - Example
  • 35. 35 Combined (SJ & PTH) Lifetime Prediction oCombines analysis results into overall failure prediction curve PTH Solder Joint Combined
  • 36. 36 Combined Failure Rate is Provided
  • 37. 37 Additional Uses for Modeling oUse Sherlock to determine thermal cycle test requirements. oUse to modify mount point locations oUse to determine ESS conditions oComponent Replacement oDetermine impact of changing to Pb-free solder oDetermine expected warranty costs
  • 38. 38 38 Summary oProduct test plans are critical to the success of a new product or technology oStressful enough to identify defects oShow correlation to a realistic environment oPoF Knowledge can be used to develop test plans and profiles that can be correlated to the field. oChange control processes and testing should not be overlooked (reliability engineer needs to stay involved in sustaining). oOn-going reliability testing can be a useful (but admittedly imperfect) tool. oPoF Modeling is an excellent tool to help tailor & optimize physical testing plans