The Real Cost of Not Testing!

Transcription

1 The Real Cost of Not Testing! Michael J Smith Smithmj@btinternet.com 1 Nordic Test Forum

2 Agenda Market Trends Manufacturing Test and Inspection Strategies Cost of Test Models Where are the costs in Test and Inspection? Examples Medium Volumes, High Complexity, Medium cost region High Volumes, Medium Complexity, Low cost region Conclusion 2 Nordic Test Forum

3 Market Pressures - Product Complexity 30 mm 20 mm 15 mm 10 mm (.4 in.) QFP BGA TAB COB CSP FC Test and Inspection Challenges Loss of ICT physical access and visible access New packaging technologies: BGA, CCGA, FCA Requirement for ultra lower voltage test ISP and Flash Programming Phase Change Memory Reduced diagnostic resolution at Functional and System Test Increased manufacturing process complexity, greater challenges for first pass yield E.g. Lead Free 3 Nordic Test Forum

4 Market Pressures - Design Anywhere Build Anywhere Volume Time to Profit Test and Inspection Challenges Designed in US/Europe without a designated manufacturer Manufacturer in Mexico, China, Ukraine.. Changing business models OEM,EMS and ODM Shortage of skilled development and debug labor for test development Need for shorter test development time and fixture lead times Shortage of skilled development and debug labor for test development Changing customers quality expectations? Start NPI 4 Nordic Test Forum Time

5 Manufacturing Test and Inspection Strategy 5 Nordic Test Forum

6 Manufacturing Test and Inspection Strategy 6 Nordic Test Forum

7 Manufacturing Test and Inspection Strategy 7 Nordic Test Forum

8 Cost of Test Models Times 10 Rule After each stage in the process it costs10 times the amount to detect and repair a defect. Economics of Automatic Testing Definitive book on the economics of testing Looks at cost of test, defect distribution and even cost of money Others? 8 Nordic Test Forum

9 Where are the costs in Test and Inspection? Fixed Cost/Known Costs Capital outlay Test and Inspection Systems amortized over 3-10 years AOI AXI ICT Functional Support Costs These tend to be 4-10% of capital outlay can be dwarfed by downtime! MTBF and MTTR can be more important 9 Nordic Test Forum

10 Where are the costs in Test and Inspection? Fixed Cost/Known Costs - Continue Overheads Floor space Can be at a premium Power/services Operators Tends to be fixed cost to cover shift Some systems need more operators? Only becomes variable if cycle time exceeds beat rate» Including repair loop Handler Removes operators and does improve quality. 10 Nordic Test Forum

11 Where are the costs in Test and Inspection? Controllable/Variable Costs Dependent on board mix Programming and Fixturing Costs Beat Rate DPMO Quality Repair Scrap 11 Nordic Test Forum

12 Cost of Test Models - based on DPMO DPMO Defects Per Million Opportunities: The number of defects in every million opportunities. By taking into account opportunities for defects, and not just defects, we can compare processes of differing complexity. Many organizations have documented expected DPMO s (inemi) and can be used to develop/measure best in class manufacturing environments. DPMO can be measure at many different levels in a manufacturing environment - Process Capability. 12 Nordic Test Forum

13 DPMO Model Requires - Production and process information: Board Assumptions Number of Solder Joints Number of Components Annual Production Volume Value of Board If/When Scrapped Beat Rate Vs. Cycle Time Repair Assumptions Repair Yield Number of Repair Cycles Permitted 13 Nordic Test Forum

14 Production and process information: Defect Rate Assumptions (Process Capability) - can be overall or sum of the individual parts Electrical DPMO Structural DPMO Debug/Diagnosis and Repair Costs Hourly Labor Cost of Verification/Diagnosis Hourly Labor Cost of Repair Time to Verification /Diagnose One Defect Time to Repair One Defect Re-Test Cost Cost of Field Failures/Returns 14 Nordic Test Forum

15 ICT and Functional Model for Manufacturing Test DPMO in In-circuit Test System Capability Defect Coverage Functional System Test DPMO out Repair loop effectiveness Debug and Repair costs Scrap rate and costs 15 Nordic Test Forum DPMO Defects Per Million Opportunities

16 AOI and AXI have a Different Model Test System Capability Defect Coverage AXI/AOI Analysis Test Inspection DPMO out DPMO in Defects and False fails Debug and Repair Scrap Rate and Costs (What gets repaired?) 16 Nordic Test Forum

17 Field Returns are the hidden cost of low defect detection Real Vs. Calculated field failures Not all defects cause faults Redundant Power Connections. Decoupling capacitors, Unused parts etc. but these can effect reliability and therefore in a simple world DPMO that escape have a probability of causing a field failure. Electrical tests such as Incircuit, functional and system use the board in the same way as it is intended and therefore reduce that risk but it can be assumed that 50% of escaped DPMO s cause field failures 17 Nordic Test Forum

18 System Capability Modeling 18 Nordic Test Forum

19 Medium Complexity, Low Volumes Medium Cost Area 19 Nordic Test Forum

20 Medium Complexity, Low Volumes Medium Cost Area 20 Nordic Test Forum

21 Medium Complexity, Low Volumes Medium Cost Area - No AOI 21 Nordic Test Forum

22 Medium Complexity, Low Volumes Medium Cost Area - No ICT 22 Nordic Test Forum

23 Medium Complexity, Low Volumes Medium Cost Area - No AOI and ICT 23 Nordic Test Forum

24 Medium Complexity, Low Volumes Medium Cost Area - No AOI and ICT 24 Nordic Test Forum

25 High Volume Motherboard Low Cost Area 25 Nordic Test Forum

26 High Volume Motherboard Low Cost Area 26 Nordic Test Forum

27 High Volume Motherboard Low Cost Area No AOI 27 Nordic Test Forum

28 High Volume Motherboard Low Cost Area No ICT 28 Nordic Test Forum

29 High Volume Motherboard Low Cost Area 80% ICT coverage 29 Nordic Test Forum

30 Coverage Vs. Costs Even a small decrease in defect coverage can have a major impact on cost. AOI and ICT No AOI No ICT Removing a test stage will Increase overall operational costs! Increase field return costs. 30 Nordic Test Forum

31 Conclusion DPMO (Defects Per Million Opportunities ) is a valid way to measure Process Capability. DPMO can measure the effectiveness of a manufacturing process DPMO can help measure the cost of defects in the process and determine the most cost effective inspection solution. DPMO can indicate THE REAL COST OF NOT TESTING! 31 Nordic Test Forum

32 Questions Ref: IPC-7912 Calculation of DPMO and Manufacturing Indices for Printed Board Assemblies IPC-9261 In Process DPMO and Estimated Yield for PWAs The Economics of Automatic Testing - Brendan Davis The Low-Cost Board Test Handbook - Craig T. Pynn 32 Nordic Test Forum