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COST OF MEMS TESTING:
A STRATEGIC PERSPECTIVE
MÅRTEN VRÅNES
DIRECTOR, MEMS TESTING AND RELIABILITY
CONSULTING SERVICES GROUP
MEMS INVESTOR JOURNAL, INC.
C: 707.583.3711
3rd Annual MTR Conference| October 2011
Outline
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Introduction
Test Challenges & Strategy
Case Study | LV Sensors
Lessons Learned
Summary
Outline
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Total MEMS Market
2011: $10.5B
Consumer Electronics Growth
2011: >140%, totaling $428M
Major MEMS Market Trends
Exponential growth
Commoditization
Increased complexity & sophistication
Higher level of integration
Smaller form factor
Lower ASP
More complex test requirements…
Motorola Xoom2
Integration
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Integration is Highly Desirable
Lower unit cost
Smaller form factor
Common manufacturing platform
Common process flow
Customer value-added
Fewer external components
Minimize assembly costs
Minimize inventory costs
Minimize test costs
…
InvenSense 6 DOF, 9-Axis fusion
Integration
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But, there are some complicating factors
Value-added yield loss
Assembly/packaging
Electrical probe
Final test
Form factor compromises
Complicated redesign
Longer tapeout cycles
Process mismatches
Loss of product flexibility
Test complexity
SMI/ELMOS Co-Integrated Pressure Sensor
Integration
Integration of Multiple Functions
10 Degrees-Of-Freedom (DOF)
3-Axis Accelerometer
3-Axis Gyroscope
3-Axis Magnetometer
1 Barometric Pressure Sensor
~3x3x1mm QFN package
How do you test this (efficiently)?
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Analog Devices’ 10 DOF
Size: 23x23x23mm
Test Challenges & Strategy
Cost of MEMS Testing
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Cost of Test Complexity
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Overhead
- Administration
- Management
- Facilities & Rent
- Utilities: Power, Air, Vacuum
Investment
- Capital Equipment
- Handler: Kit & MEMS Stimuli
- Auto. Test Equipment (ATE)
- Test SW & Database
- Depreciation Rate
- Equipment Lifetime
Labor & Material
- Direct Labor: Operators
- Indirect Labor: Technicians,
Engineers, Managers
- Test boards: DUT & Load
- Contactors & Cabling
- Consumables & Spare Parts
Yield
- Contactor Repeatability
- Assembly Failures (eg. WB)
- Unit Functional Test Yield
- Re-Testing
Utilization
- Setup & Product Conversion
- Temperature Ramp & Settling
- Uptime & Utilization
- MTBA, MTBF & MTTR
- Operator Training
- Equipment Maintenance Level
Throughput
- Handler Index Time
- Soak Time (eg. temperature)
- Physical Stimuli Settling Time
- DUT Test Time
- Parallelism (i.e. Contact Sites)
- Effective Throughput
Cost Assignment
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Direct Costs Indirect Costs
Variable Costs
Direct Labor
Consumables
Wear Parts
• Contactors
• Load Boards
• DUT Boards
Spare Parts
Throughput
Yield
Utilization
Indirect Labor
Maintenance
Service
Calibration Services
Utilities
Facilities & Rent
Fixed Cost
Capital Cost
• Depreciation Period
• Useful Lifetime
• Reusability
Management
Administration
Facilities
Assignment of Costs to Cost Object
Cost-
behavior
Pattern
Test Strategy Definition
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A MEMS Test Strategy is:
Helping the overall company gain “sustainable”
competitive advantage
Proactive actions to achieve the best possible test
solution in terms of cost, timeliness, and overall risk
Reactive actions to unanticipated developments and
unforeseen conditions
Work in progress, to be modified over time in reaction
to changing external and internal forces
Actively supported by upper level management
Test Strategy Definition
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A MEMS Test Strategy is Not:
Fixed, one-time exercise
Empowering employees to make strategic decisions
Simply stating use company XYZ for all material
handling, company XYZ for all physical test stimuli and
company XYZ for all test instrumentation
Deciding that all systems and platforms should be “off-
the-shelf”
Choosing the perceived lowest cost solution
Crafting a Strategy
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Strategy should be based on:
Previous experiences
Existing knowledge base and know-how
Supplemented by sound engineering principles and well-informed business decisions
Periodic reviews to ensure alignment with:
Corporate goals
Market forces
Updated competitor analysis
Changes in the product portfolio and product roadmap
Changes in customer expectation, needs and requirements.
Test System Approaches
Traditional Approach
Dedicated, custom or semi-custom test systems
Expensive, one-off solutions
Low reusability & salvage value
Lack of off-the-shelf alternatives
Emerging Approach
Automation companies catching up
Developing off-the-shelf solutions
Lead customers cover partial NRE
Combine proven automation with MEMS test concepts
Focus on modular systems
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Multitest 99xx Gravity Handler
Competitive Advantage | Test
If there are viable off-the-shelf automation options, these are available to everyone else...
How then, can you get ahead?
Fewer physical test points
Ambient temperature test only
Lower-cost test instrumentation
Transfer final tests to wafer probe
Lower test coverage supported by statistical sampling
Smaller footprint, lower power consumption
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NI PXI ATE System
Case Study | LV Sensors
Cost of MEMS Testing
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MEMS by Government Mandate
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TREAD Act – US Market
In 2005, Firestone recalled 6.5 million tires due to tread separation on Ford vehicles
President Clinton signed the TREAD Act requiring Tire Pressure Warning Systems (TPMS)
NHTSA stipulated “direct” sensor solutions to be implemented in 2008
Phase-in schedule
20% Compliance for Model Year 2006
70% Compliance for Model Year 2007
100% Compliance for Model Year 2008
Europe mandated TPMS on all new vehicles by 2012
Specific Performance Requirements
TPMS must be equipped in all four tires. Spare tire is not required
TPMS must operate when the ignition is on
TPMS must warn when tires are under-inflated by 25% or more
TPMS must alert the driver when there is a system malfunction
TPMS warning light must stay on until the tire is inflated to proper pressure
TPMS warning light must stay on until the system malfunction is corrected
Business Idea
To develop the next generation integrated TPMS device, addressing the emerging markets to be mandated in the US (safety driven), Europe (environmentally driven), and later, Asia.
To raise sufficient capital to develop a device exceeding the performance of existing products in the market at lower cost and with value-added features.
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Investor Relations
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Typical Investor Expectations
10x return, targeting IPO
Billion dollar market opportunity
Series A sufficient to last until revenue
Revenue in 1 year
Break even in 2-3years
Typical Industry Expectations
4 years to develop a new MEMS product from inception to production
$45M investment needed
3-4 CEOs
LV Sensors raised $15M for their Series A
Integrated TPMS Solution
Sensing
Pressure
Temperature
Voltage
Motion/Acceleration
Auto-Location
Identification
Serial Number in NVM
Control
Microcontroller
Firmware: State Machine
Sensor Interface (ADC) and Processing
Oscillators
Timers
RAM, ROM & NVM
Inputs
Physical Stimuli
LF Pick-Up Coil
Automatic Gain Control
Command Decoder
Outputs
RF Transmitter
315MHz / 434MHz
ASK / FSK Modulation
Power (External)
Lithium Ion Battery
Battery-Less
Energy Harvester
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Final Test Requirements (Excerpt)
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General Requirements
Continuity & communication
Analog Requirements
LF Input
AGC sensitivity, phase noise, wake threshold, dmod threshold…
RF Output
Frequency bands, harmonics, PLL startup time, PA output power…
Current Consumption
Run current, sleep current, RF current…
Timing
System timer accuracy
Functional Requirements
EEPROM r/w, voltage levels…
Embedded code download & execution
Final Test Requirements (Excerpt)
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Functional Requirements
Pressure Sensor
Test Points Range 1: 0 to 637.5kPa (Small/Medium Car)
Test Points Range 2: 0 to 900kPa (SUV/Small Truck)
Test Points Range 3: 0 to 1,400kPa (Truck/Bus)
Accuracy calibration: gain & offset
Temperature
Test Points: 25 & 60°C
Accuracy calibration: gain & offset
2-Axis Accelerometer
Test Points: ±1g, 2-axis (X & Z)
Sensitivity, noise measurements…
Accuracy calibration: gain & offset
BERU TPMS modules
Test Capacity Calculation Example
Throughput Targets
Test System #1(PT)
4 test stations
16 units parallel testing
0.25s per DUT per station
UPH: 3,600
Test System #2 (RF)
1 test station
4 units per cycle
1s per DUT per station
UPH: 3,600
Parameter Value
Gross UPH 3,600
Work Hours/Shift 8
Shift/Day 3
Work Hours/Day 24
Work Days/Week 7
Uptime % (inc. setup) 90%
Utilization Factor 75%
Net Capacity/Hour - Units 2.4K
Net Capacity/Week - Units 408K
Net Capacity/Year - Units 20M
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Unit Final Test Cost Calculation
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Item Value
Annual Volume 20M
System Cost (excluding one-time NRE) $1,000,000
Depreciation Cost Per Unit (5 year lifetime)* $0.01
Staffing Required 2
Direct Labor Cost Per Unit @ $20 Per Hour $0.02
Final Test Yield 95%
Total Unit Cost (excluding overhead; consumables, facility etc.) $0.03
Given a $2 ASP and 50% gross margin, the test cost per unit is ~3% of the unit cost .
Total Annual Revenue: : 20M x 0.95% yield x $2 = $38M
*Salvage value set to $0.
Final Test System Options
Standard Systems
No one off-the-shelf system could encompass all the test requirements
Incompatible non-standard 24-pin SSOP package
Semi-Custom Systems
Use standard systems / sub-systems where available
Supplement with custom modules to cover all test requirements
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Multitest In-Strip Handler w/ MEMS Test Module
The Chosen Path
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Test System Platform Solution
Custom Handlers
Custom & Standard Test HW
Custom Test SW
Custom Load Board
Custom DUT Board
Custom Pogo Pin Contactors
Custom DUT Carriers
Custom Data Logging
Internalized System Integration LV Sensor’s ASIC
Custom Test Systems
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Design to Spec
Build to Spec
Flexibility
Hand-Pick Sub-Systems
Tailor to Exact Specification
Turnkey Solution
Assume Greater Responsibility
Leverage Existing Technology
Risk: Cost, Time & Performance
NRE
Reusability
Residual Value
Timeliness
At Supplier’s Mercy
Limited Legacy & Unproven in the Field
Low Throughput
High Maintenance
Expensive Duplication
Access to Viable Suppliers
“Re-Inventing the Wheel”
Limited Field Support
Final Test Flow Diagram
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Incoming Inspection
DUT Carrier Loader
Pressure & Motion Test
System
RF Test System
Pack in T&R
Outgoing Inspection
Final Test | DUT Carrier Loader
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Tube Input, 22” Plastic Tubes
Magazine Output, 16x16 DUTs
DUT carrier
Final Test | Pressure & Motion System
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Pressure
Station
Hot
Pressure
Station
Ambient
Pressure
Station
Hot
Motion
Station
Ambient
16-Up DUT
Carrier
Final Test System Architecture
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Test Site 1 Temperature 1
Pressure
Handler 2
Controller
Pressure and Rotation Test Server (LAN, Data Base, SPC, Internet)
ATE Controller
Pressure
Controller
Test Site 2 Temperature 2
Pressure
Handler 2
Controller
ATE Controller
Pressure
Controller
Test Site 3 Temperature 1
Pressure
Handler 2
Controller
ATE Controller
Pressure
Controller
Test Site 4 Temperature 1
Rotation
Handler 2
Controller
ATE Controller
Test Site 5 Room temperature
RF
Handler 3
Controller
ATE Controller
RF Test Server (LAN, Master Data Base
for all DUT Data logs,
SPC, Internet)
Rotation Controller
RS
-232
, IE
EE
-488
or
US
B
PXI Based PXI Based PXI Based PXI Based PXI Based
Final Test | Extended
Additional Requirements
Functional testing at extreme temperatures
Screening of defects at extreme temperatures
Mechanical shock conditioning of accelerometer
Stiction testing of accelerometer
Extended test coverage
Re-spec’ing of test criteria requiring additional test hardware
Aggressive production schedule
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Mechanical Shock Conditioner
(R&D Version)
Mechanical Shock Conditioner
(Production Version)
-40C COLD CHAMBER
125C HOT CHAMBER
AMBIENT CHAMBER
COOLING SYSTEM CONTROLLER
TOUCH SCREEN GUI INTERFACE
PXI BASED ATE SYSTEM
Final Test | Final Func. Test System
Overview
3 Test Sites
Hot, cold & ambient
4 Tracks, gravity-feed
4 DUTs per site
1 Lasermarker
Tube In / tube out
DUT binning
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Test Flow Diagram Extended
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Incoming Inspection
Shock Conditioning
DUT Carrier Loader
Pressure & Motion Test
System
Stiction Testing
RF Test System
Final Functional Test
Pack in T&R
Outgoing Inspection
Test Capacity Comparison
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Parameter Planned Actual
Gross UPH 3,600 2,000
Work Hours/Shift 8 8
Shift/Day 3 3
Work Hours/Day 24 24
Work Days/Week 7 7
Uptime % (inc. setup) 90% 90%
Utilization Factor 75% 75%
Net Capacity/Hour - Units 2.3K 1.4K
Net Capacity/Week - Units 390K 233K
Net Capacity/Year - Units 19M 10M
Unit Test Cost Comparison
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Item Planned Actual
Annual Volume 10M (20M) 10M
System Cost* (excluding one-time NRE) $1M $2M
Depreciation Cost Per Unit (5 year lifetime) $0.02 $0.04
Staffing required 2 4
Direct Labor Cost Per Unit @ $20 Per Hour $0.034 $0.067
Final Test Yield 95% 85%
Total Unit Cost (ex. overhead; consumables, facility etc.) $0.06 $0.13
Given a $2 ASP and 50% margin, the actual test cost per unit is ~13% of the unit cost .
Total Annual Revenue: 10M x 0.85% x $2 = $17M
*Salvage value set to $0.
Lessons Learned
Cost of MEMS Testing
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Lessons Learned | Supplier Selection
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Due Diligence
Financial & technical
Resources & key personnel
Proven Technology
Delivery track record
System generation/revision
How many proven systems in the field?
Project Costing and Timeline
What is realistic?
Benchmark with other, similar projects
Business Risk
How much risk are you willing to take?
How much is at stake… prosperity, survival?
Lessons Learned | Custom Systems
Internalization
Internal support during development
Internal support on an ongoing basis
Supplier Support
Warranty
Maintenance contracts
Future system upgrades & add-ons
Price guarantee
Market Availability
Alternative sources for spare parts
Alternative sources for support
Alternative sources for maintenance
Alternative sources for upgrades
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Custom, custom, custom
Lessons Learned | Custom Systems
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IP & Rights
No exclusivity, limited exclusivity or full exclusivity
Source code
Software
Embedded code
Data logging
Database schema
Mechanical drawings
Electrical drawings
Concepts and know-how
Supplier spin-off products
National Instruments’ LabWindows/CVI
Lessons Learned | Test Creep
Customer Requirements
Customer mandated tests
Product Specification
Spec changing during product development
Added/removed functionality with new revisions
Insufficient Test Coverage
Guaranteed by design not guaranteed by design
Sampling not guaranteeing performance
Error modes discovered during characterization
Verification of trimmed/calibrated parameters
Extended operating ranges testing needed
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Lessons Learned | Cost Minimization
Higher Parallelism
Physical limitations
Diseconomies of scale
Move Final Tests Upstream
Wafer probe limitations
Package effects
Common Test Platform
R&D, engineering and production
Appropriate System for Application
Consider lower cost ATE alternatives
Footprint, power consumption
Fewer Physical Test Points
Guarantee by design
Sample testing
Predict calibration coefficient
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SPEA Modular MEMS Test System
Summary
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A clear strategy is imperative to the success of
MEMS testing
Custom and standard test systems must be carefully
chosen for the application
Test specifications and requirements will change
throughout a product development process
Final Note
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Oftentimes, the hardest battle in MEMS testing is to
convince upper management and investors that
MEMS testing is not an incremental extension of
semiconductor testing, but more an order of
magnitude more complex.
Third-party consultants can provide unbiased
evaluation of existing test methodologies and help
improve MEMS test strategies and operations.
Contact Information
MEMS Investor Journal, Inc. | Consulting Services Group | [email protected]
Mårten Vrånes
Director, MEMS Testing and Reliability
Consulting Services Group
MEMS Investor Journal, Inc.
C: 707.583.3711