cost of mems testing: a strategic … - mems investor journal.pdfcost of mems testing: a strategic...

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

[email protected]

3rd Annual MTR Conference| October 2011

mailto:[email protected]

Outline

MEMS Investor Journal, Inc. | Consulting Services Group | [email protected]

Introduction

Test Challenges & Strategy

Case Study | LV Sensors

Lessons Learned

Summary

Outline


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


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


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)?


Analog Devices’ 10 DOF

Size: 23x23x23mm

Test Challenges & Strategy

Cost of MEMS Testing


Cost of Test Complexity


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


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


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


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


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


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


NI PXI ATE System

Case Study | LV Sensors



MEMS by Government Mandate


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



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.


Investor Relations


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


Final Test Requirements (Excerpt)


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)


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


2-Axis Accelerometer

Test Points: ±1g, 2-axis (X & Z)

Sensitivity, noise measurements…


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


Unit Final Test Cost Calculation


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


Multitest In-Strip Handler w/ MEMS Test Module

The Chosen Path


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


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


Incoming Inspection

DUT Carrier Loader

Pressure & Motion Test

System

RF Test System

Pack in T&R

Outgoing Inspection

Final Test | DUT Carrier Loader


Tube Input, 22” Plastic Tubes

Magazine Output, 16x16 DUTs

DUT carrier

Final Test | Pressure & Motion System


Pressure

Station

Hot

Pressure

Station

Ambient

Pressure

Station

Hot

Motion

Station

Ambient

16-Up DUT

Carrier

Final Test System Architecture


Test Site 1 Temperature 1

Pressure

Handler 2

Controller

Pressure and Rotation Test Server (LAN, Data Base, SPC, Internet)

ATE Controller

Pressure

Controller


Pressure

Handler 2

Controller

ATE Controller

Pressure

Controller


Pressure

Handler 2

Controller

ATE Controller

Pressure

Controller


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


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


Test Flow Diagram Extended


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


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


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



Lessons Learned | Supplier Selection


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


Custom, custom, custom

Lessons Learned | Custom Systems


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

http://www.ni.com/lwcvi/whats_new.htm

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


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


SPEA Modular MEMS Test System

Summary


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


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


Mårten Vrånes

Director, MEMS Testing and Reliability

Consulting Services Group

MEMS Investor Journal, Inc.

C: 707.583.3711

[email protected]

mailto:[email protected]

cost of mems testing: a strategic … - mems investor journal.pdfcost of mems testing: a strategic...

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