the real cost of not testing v3.ppt - nordic test · pdf filethe real cost of not testing! ......

23/11/2010111 Nordic Test Forum

The Real Cost of Not Testing!The Real Cost of Not Testing!

Michael J [email protected]


AgendaAgenda

• 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


Market Pressures- Product ComplexityMarket Pressures- Product Complexity

• 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

30 mm

20 mm

15 mm

10 mm(.4 in.)

QFP

BGATAB

COB

CSPFC


Market Pressures- Design Anywhere Build AnywhereMarket Pressures- Design Anywhere Build Anywhere

• 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

Volume

Time to Profit

Time


Manufacturing Test and Inspection StrategyManufacturing Test and Inspection Strategy


Cost of Test ModelsCost 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?


Where are the costs in Test and Inspection?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



• 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.



• Controllable/Variable Costs– Dependent on board mix

• Programming and Fixturing Costs • Beat Rate• DPMO

– Quality– Repair– Scrap


Cost of Test Models- based on DPMO

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.


DPMO Model Requires - Production and process information: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


• 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

Production and process information:Production and process information:


ICT and Functional Model for Manufacturing TestICT and Functional Model for Manufacturing Test

In-circuit Functional SystemTest

DPMO in

Repair loop effectivenessDebug and

Repair costs

Test System CapabilityDefect Coverage

DPMO out

Scrap rate and costs

DPMO – Defects Per Million Opportunities


AOI and AXI have a Different ModelAOI and AXI have a Different Model

AXI/AOI

Scrap Rate and Costs(What gets repaired?)

Test System CapabilityDefect Coverage

Debug and Repair

Analysis

DPMO in

DPMO out

TestInspection

Defects and False fails


Field Returns are the hidden cost of low defect detectionField 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


System Capability ModelingSystem Capability Modeling


Medium Complexity, Low Volumes – Medium Cost AreaMedium Complexity, Low Volumes – Medium Cost Area


Medium Complexity, Low Volumes – Medium Cost Area - No AOIMedium Complexity, Low Volumes – Medium Cost Area - No AOI


Medium Complexity, Low Volumes –Medium Cost Area - No ICTMedium Complexity, Low Volumes –Medium Cost Area - No ICT


Medium Complexity, Low Volumes –Medium Cost Area - No AOI and ICTMedium Complexity, Low Volumes –Medium Cost Area - No AOI and ICT


High Volume Motherboard –Low Cost AreaHigh Volume Motherboard –Low Cost Area


High Volume Motherboard –Low Cost Area – No AOIHigh Volume Motherboard –Low Cost Area – No AOI


High Volume Motherboard –Low Cost Area – No ICTHigh Volume Motherboard –Low Cost Area – No ICT


High Volume Motherboard– Low Cost Area – 80% ICT coverageHigh Volume Motherboard– Low Cost Area – 80% ICT coverage


Coverage Vs. CostsCoverage 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.


ConclusionConclusion

• 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!


QuestionsQuestions

Ref:IPC-7912 Calculation of DPMO and Manufacturing Indices for Printed Board AssembliesIPC-9261 In Process DPMO and Estimated Yield for PWAsThe Economics of Automatic Testing - Brendan DavisThe Low-Cost Board Test Handbook - Craig T. Pynn

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