Design For Reliability at the Board Level - DfR Solutions · o MIL-STD-810, o MIL-HDBK-310, o SAE J1211, o IPC-SM-785, o Telcordia GR3108, o IEC 60721-3, etc. o Advantages o No additional

© 2004 - 2007© 2004 - 20109000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com© 2004 – 2010

Design For Reliability at the Board Level

Raytheon Women in Engineering Lunch and Learn

March 11, 2014

© 2004 - 2007© 2004 - 20109000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com

o What are you doing today?

o Specs?

o Handbooks?

How is this working for you?

Today


Insanity

Einstein’s Definition of Insanity:

Doing the same thing over and over and over and over again

And expecting different results

It is time to stop the insanity!


What is Design for Reliability (DFR)?

o Reliability is the measure of a product’s ability to

o …perform the specified function

o …at the customer (with their use environment)

o …over the desired lifetime

o Design for Reliability is a process for ensuring the

reliability of a product or system during the design

stage before physical prototype

o Often part of an overall Design for Excellence (DfX)

strategy (DFM, DFT, DFR, DFS)


Why DFR Now?

o Product Differentiation

o As electronic technology reaches maturity, there is less separation in traditional metrics of price and performance

o Ensuring reliability is becoming increasingly difficulto Increasing complexity of

electronic circuits

o Increasing power requirements

o Introduction of new component and material technologies

o Introduction of less robust components (COTS)


Why DFR? Leverage in Design Cost Control

70% of a Product’s Total Cost is Committed by Design

http://www.ami.ac.uk/courses/topics/0248_dfx/index.html


Reduce Costs by Improving

Reliability Upfront

Why DFR? Earlier is Cheaper


Faster time to market

Why DFR? Faster Time to Market

P. Smith and D. Reinertsen. Developing Products In Half The Time (New York Van Nostrand Reinhold. 1991). 4.


How DFR? Implementation

o Many organizations have developed DfR Teams to

speed implementation

o Success is dependent upon team composition and gating

functions

o Challenges: Classic design teams consist of

electrical and mechanical engineers trained in the

‘science of success’

o DFR requires the right elements of personnel and tools


o Component engineer

o Physics of failure expert (mechanical / materials)

o Manufacturing engineer

o Box level (harness, wiring, board-to-board connections)

o Board / Assembly

o Engineer cognizant of environmental legislation

o Thermal engineer (depending upon power requirements)

o Reliability engineer?

o Depends. Many classic reliability engineers provide NO

value in the design process due to over-emphasis on

statistical techniques and environmental testing

How DFR? Team Members


How DFR? Timeline

Goal: Simultaneously

optimizing the design

Reality: Need for specific gating

activities (design reviews)

Ramp Up

Launch

&

Production

Start-Up

Production

Gate 1

Idea

Submission

Project

Charter

Gate 2

Business

Plan

Gate 3

Update Plan

& AR

Gate 4

Final Check

Gate 5

Process

Audit

Gate 6

Market

Research

Design

&

Development

Concept

Development

& Project

Planning

Concept

Feasibility

Idea

Generation

FunctionalPerformance

Design forReliability

Design forManufacture

Design forSourcing


DFR Outline

o DfR at Concept / Block-Diagram Stage

o Specifications

o Part selection

o Derating and uprating

o Design for Manufacturability

o Reliability is only as good as what you make

o Wearout mechanisms and physics of failure

o Predicting degradation in today’s electronics


Design For Reliability

At Concept: Specifications


Concept / Block Diagram

o Can DFR mistakes occur at this stage?

o No………..and Yes

o Failure to capture and understand product

specifications at this stage lays the groundwork for

mistakes at schematic and layout

o Important specifications to capture at concept stage

o Reliability expectations

o Use environment

o Dimensional constraints


o Typical reliability metrics

o Desired Lifetime / Product Performance

o Desired lifetime

o Defined as when the customer will be satisfied

o Should be actively used in development of part and product qualification

o Product performance

o Returns during the warranty period

o Survivability over lifetime at a set confidence level

o Try to avoid MTBF or MTTF

Reliability Goals


Why is Desired Lifetime Important?F

ailu

re R

ate

Time

Electronics: 1960s, 1970s, 1980s

No wearout!

Electronics: Today and the Future

Wearout!


o Low-End Consumer Products (Toys, etc.)

o Do they ever work?

o Cell Phones: 18 to 36 months

o Laptop Computers: 24 to 36 months

o Desktop Computers: 24 to 60 months

o Medical (External): 5 to 10 years

o Medical (Internal): 7 years

o High-End Servers: 7 to 10 years

o Industrial Controls: 7 to 15 years

o Appliances: 7 to 15 years

o Automotive: 10 to 15 years (warranty)

o Avionics (Civil): 10 to 20 years

o Avionics (Military): 10 to 30 years

o Telecommunications: 10 to 30 years

Desired Lifetime: Examples


Product Performance: Warranty Returns

o Consumer Electronics

o Table on right

o Low Volume, Non Hi-Rel

o 1 to 2%

o Industrial Controls

o 500 to 2000 ppm (1st Year)

o Depends on complexity, production volumes, and risk sensitivity

o Automotive

o 1 to 5% (Electrical, 1st Year)

o Can also be reported as problems per 100 vehicles

ProductRepair rate (%)

[First 3 Yrs]

Desktop PC 37

Laptop PC 33

Refrigerator: side-by-side (with icemaker and

dispenser) 28

Washing machine 22

Refrigerator: top- and bottom-freezer (with icemaker) 17

Projection TV 16

Vacuum cleaner (excluding belt replacement) 13

Dishwasher 13

Clothes dryer 13

Microwave oven (over-the-range) 12

Electric range 11

Camcorder 8

Digital camera 8

Refrigerator: top- and bottom-freezer (without

icemaker) 8

TV: 30- to 36-inch 7

TV: 25- to 27-inch 5

Consumer Reports 2006


Product Performance: Survivability

o Some companies set reliability goals based on survivabilityo Often bounded by confidence levels

o Example: 95% reliability with 90% confidence over 15 years

o Advantageso Helps set bounds on test time and sample size

o Does not assume a failure rate behavior (decreasing, increasing, steady-state)

o Disadvantageso Can be re-interpreted through mean time to failure (MTTF) or

mean time between failures (MTBF)


Limitations of MTTF/MTBF

o MTBF/MTTF calculations tend to assume that failures are random in nature

o Provides no motivation for failure avoidance

o Easy to manipulate numbers

o Tweaks are made to reach desired MTBF

o E.g., quality factors for each component are modified

o Often misinterpreted

o 50K hour MTBF does not mean no failures in 50K hours

o Better fit towards logistics and procurement, not failure avoidance


Identify Field Environment

o Approach 1: Use of standards

o MIL-STD-810,

o MIL-HDBK-310,

o SAE J1211,

o IPC-SM-785,

o Telcordia GR3108,

o IEC 60721-3, etc.

o Advantages

o No additional cost!

o Sometimes very comprehensive

o Agreement throughout the industry

o Missing information? Consider standards from other industries

o Disadvantages

o Most more than 20 years old

o Always less or greater than actual (by how much, unknown) IPC SM785

MIL HDBK310


Field Environment (cont.)

o Approach 2: Based on actual measurements of similar products in similar environments

o Determine average and realistic worst-case

o Identify all failure-inducing loads

o Include all environments

o Manufacturing

o Transportation

o Storage

o Field


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


Field Environment (Best Practice)

o Use standards when…

o Certain aspects of your environment are common

o No access to use environment

o Measure when…

o Certain aspects of your environment are unique

o Strong relationship with customer

o Do not mistake test specifications for the actual use

environment

o Common mistake with vibration loads


Temperature: USA Worst-Case (Ambient)

TemperatureAvg. U.S.

CLIM Data

Avg. U.S.

Weighted by Registration

(Source: Confidential)

Phoenix

(hrs/yr)

U.S.

Worst Case

(hrs/yr)

95F (35C) 0.375% 0.650% 11% (948) 13% (1,140)

105F (40.46C) 0.087% 0.050% 2.3% (198) 3.8% (331)

115F (46.11C) 0.008% 0.001% 0.02% (1.4) 0.1% (9)


Temperature: Closed Containers

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

Tem

pe

ratu

re (

°C)

Container Temp (°C)

Outdoor Temp (°C)

Temp.

Variation

Trucking

Container


Dimensions

o Keep dimensions loose at this stageo Large number of hardware mistakes driven by arbitrary size

constraintso Examples include poor interconnect strategies and poor

choices in component selection

o Case study: Use of 0201 chip componentso Tight dimensional requirements push designer towards

wholesale placement of 0201 componentso 0201 is not yet an appropriate technology for systems

requiring reliabilityo Result: Major issues at customers

o Use the Toyota approacho Except with sudden acceleration


Toyota Approach

o Western engineers o Define several product concepts

o Select the one that has the most promise

o Draw up specifications and divide them into subsystems;

o Subsystems are designed, built and rolled up for system testing.

o Failures? Rework the specs and the designs accordingly (non-optimized and confusing endeavor)

o Toyota engineerso Efforts concentrated at lowest

possible design level

o Thorough understanding of the technology of a subsystem so it can be used appropriately in future designs

Toyota's development engineers have been4X as productive as U.S. counterparts.

Why?

Focus on learning as much as possible

Use of that knowledge to develop a stream of excellent products


Toyota Example: Radiators

o Traditional approach: Design radiator for a specific vehicle based on mechanical specifications written for that vehicle

o Toyota approach: considers a range of radiator solutions based on cooling capacities and the cooling demands of various engines that might be used.

o How the radiator actually fits into a vehicle would be kept loose so that Toyota's knowledge of radiator technology could be used to create the optimum design

o Toyota's system is "test & design" rather than the traditional "design & test."

o Toyota engineers test at the fundamental knowledge level so they don't have to test at the later, more expensive stages of design and prototyping


Traditional NPI Cycle


NPI Cycle Using PoF Modeling


o DfR Solutions: Leverages the knowledge and understanding of the processes and mechanisms that induce failure to predict reliability and improve product performance

o Army: An engineering-based approach to reliability that uses modeling and simulation to eliminate failures early in the design process by addressing root-cause failure mechanisms in a Computer-Aided- Engineering environment

o NASA-JPL: Modeling of failure mechanisms, based on science/engineering first principles, that support deterministic or probabilistic predictions of reliability and provide a scientific basis for determining the effectiveness of screens or inspections

What is Physics of Failure (PoF)?


Physics of Failure (PoF) Modeling Dates back to 1960’s

211

2

2

1 11exp

TTK

E

V

V

t

t

B

a

n

)%063.0exp(~51.0~

exp RHkT

eVT f

aGGA

h

GA

h

AE

L

AE

LFLT

bcc

c

ss

s

9

2

221112


Physics of Failure (cont.)

o Reliability is the measure of a product’s ability to

o …perform the specified function

o …at the customer (with their use environment)

o …over the desired lifetime

o Physics of failure therefore requires an understanding of

the design, desired lifetime and use environment

o Design: Architecture + Materials

o Desired lifetime: When the customer will be satisfied

o Use environment: Must include assembly, transportation,

storage, operation

o Translation: PoF takes more effort


o What is susceptible to long-term degradation in electronic designs?

o Ceramic Capacitors (oxygen vacancy migration)

o Integrated Circuits (EM, TDDB, HCI, NBTI)

o Memory Devices (limited write cycles, read times)

o Electrolytic Capacitors (electrolyte evaporation)

o Resistors (if improperly derated)

o Silver-Based Platings (if exposed to corrosive environments)

o Relays and other Electromechanical Components

o Light Emitting Diodes (LEDs) and Laser Diodes

o Connectors (stress relaxation)

o Tin Whiskers

o Interconnects (Creep, Fatigue)

o Plated through holes

o Solder joints

PoF and Wearout


Wearout Example – Integrated Circuits (ICs)

1995 2005 2015

0.1

1.0

10

100

1000

Year produced

Known trends for TDDB, EM and HCI degradation

(ref: extrapolated from ITRS roadmap)

Mean

Service

life, yrs.Computers

laptop/palm

cell phones

Airplanes

0.5 mm 0.25 mm 130 nm 65 nm 35 nm

Process Variability

confidence bounds

Technology


o The majority of electronic failures are thermo-

mechanically related*

o By thermally induced stresses and strains

o Root caused to excessive differences in coefficient of

thermal expansion

Desired Lifetime (Solder Wearout)

*Wunderle, B. and B. Michel, “Progress

in Reliability Research in Micro and

Nano Region”, Microelectronics and

Reliability, V46, Issue 9-11, 2006.

A. MacDiarmid, “Thermal Cycling Failures”, RIAC Journal,

Jan., 2011.


o JEDEC JESD47 Guidelines for Component Qualification

o Requires 2300 cycles of 0 to 100C

o Testing often done on thin (down to 20 mil / 0.5 mm) coupons

o Testing on a thin coupons can extend lifetimes by

2X to 4X

o Current components may only survive

500 cycles of 0 to 100C

o This is less than 10% of the 6000

cycles recommended by IPC-9701

Industry Response to Solder Wearout?


PoF Example: Solder Joint (SJ) Wearout

o Elimination of leaded devices

o Provides lower RC and higher package densities

o Reduced compliance

Cycles to failure

-40 to 125C QFP: >10,000 BGA: 3,000 to 8,000

QFN: 1,000 to 3,000CSP / Flip Chip: <1,000


PoF Example: SnAgCu Life Model

o Modified Engelmaier

o Semi-empirical analytical approach

o Energy based fatigue

o Determine the strain range (g)

o C is a correction factor that is a function of dwell time

and temperature, LD is diagonal distance, is CTE, T

is temperature cycle, h is solder joint height

Th

LC

s

D g


PoF Example – SAC Model (cont.)

o Determine the shear force applied to the solder joint

o F is shear force, L is length, E is elastic modulus, A is the area,

h is thickness, G is shear modulus, and a is edge length of

bond pad

o Subscripts: 1 is component, 2 is board, s is solder joint, c is

bond pad, and b is board

o Takes into consideration foundation stiffness and both

shear and axial loads

aGGA

h

GA

h

AE

L

AE

LFLT

bcc

c

ss

s

9

2

221112


PoF Example – SAC Model (cont.)

o Determine the strain energy dissipated by the

solder joint

o Calculate cycles-to-failure (N50), using energy

based fatigue models for SAC developed by

Syed – Amkor

10019.0

WN f

sA

FW g5.0


Validation – Chip Resistors

100

1000

10000

100 1000 10000

Cycles to Failure (Experimental)

Cy

cle

s t

o F

ailu

re (

Pre

dic

ted

)


PoF Example – SAC Reliability (cont.)

o How to ensure 10 year life in a realistic

worst-case field environment for

industrial controls?

o American Southwest (Phoenix)

o Dominated by diurnal cycling

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

+10C at max temperature due to solar loading


PoF Example – SAC Reliability (cont.)

o Total damage in desert environment

over 10 years

o Total damage in one cycle of -40C to

85C test environment

o Total cycles at -40C to 85C to

replicate 10 yrs in desert

0.02604

0.00012

222 cycles

At 1 cycle/hour, approximately 1 day of test equals 1 year in the field


PoF-Based Analysis a Reality?


Results

47

Constant Failure Rate

Generic Actuarial MTBF Database

PTH Thermal

Cycling Fatigue

Wear Out

Thermal

Cycling

Solder

Fatigue

Wear Out

Vibration

Fatigue

Wear Out

Over All

Module

Combined

Risk


Summary DFR at the Board Level

o To avoid design mistakes, be aware that functionality

is just the beginning

o Be aware of industry best practices

o Maximize knowledge of your design as early in the

product development process as possible

o Practice design for excellence (DfX)

o Design for Manufacturability

o Design for Test

o Design for Reliability

o Design for Sustainability

© 2004 - 2007© 2004 - 20109000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com© 2004 – 2010

Questions??Discussion

Tom O’Connor, DfR Solutions

301-640-5812

[email protected]

Documents

Design For Reliability at the Board Level - DfR Solutions · o MIL-STD-810, o MIL-HDBK-310, o SAE J1211, o IPC-SM-785, o Telcordia GR3108, o IEC 60721-3, etc. o Advantages o No additional