Part quality-presentation-how-to-test-when-what-it-all-means

© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com © 2004 – 2010

Part Quality: How to Test, When to Test, and What Does It All Mean?

DfR Open House

March 18, 2013

Presented by: Greg Caswell

Ed Wyrwas

© 2004 - 2007 © 2004 - 2010 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com

o Determining the appropriate testing methodology for

any evaluation requires a requisite understanding of

the component/part, the stresses it may see during its

use environment, and the potential failure modes that a

testing activity might uncover.

o DfR is skilled at numerous testing activities

o This talk will identify several and explain their respective

merits.

How To Test


o Wear-out is caused by electrolyte diffusion through the end seal

o Increased temperature increases rate of diffusion

o As electrolyte volume decreases, ESR increases

o DfR Solutions used temperature dependent rate of weight loss testing and

critical weight loss dependence on % ESR increase(failure identified as 200%)

to predict characteristic life of capacitors

Electrolytic Capacitor Wearout Behavior

y = 0.0239x R² = 0.9975

0

2

4

6

0 100 200 300

Weig

ht Lo

ss (

mg)

Time (hrs)

Average Weight Loss Over Time 2

105C=0.0258 mg of electrolyte/hour

y = 0.0062x R² = 0.9825 0

0.5

1

1.5

0 200

Weig

ht Lo

ss (

mg)

Time (hrs)



y = 0.004x R² = 0.9904

0

0.5

1

0 100 200 300

Weig

ht Lo

ss (

mg)

Time (hrs)




o Based on rates at 105°C, 85°C, and 76°C

o Expected rate at 45°C 0.0008 mg of electrolyte/hr

o Balance only reads to tenths of a mg

o Modeled using an exponential function

o Data fits well to model

Results: Rate of Weight Loss Temperature Dependence

y = 7E-05e0.053x R² = 0.9919

0

0.005

0.01

0.015

0.02

0 20 40 60 80 100

Ra

te o

f W

eig

ht Lo

ss (

mg

/hr)

Temperature (°C)

Rate of Weight Loss Temperature Dependence


o Exponential function fits relationship between mass loss and % increase in ESR

o Models a sharp increase in ESR after a given mass loss

o Sharp increase in ESR is seen around critical weight loss of 1500 mg

Results: % Increase in ESR with Weight Loss

y = 3.4859e0.0027x R² = 0.88

0

200

400

600

800

1000

0 500 1000 1500 2000 2500

% Inc

ESR

Weight Loss (mg)

% Increase in ESR with Weight Loss


o If failure is defined as a 200% increase in ESR, then

characteristic life for the aluminum electrolytic capacitors

tested is:

o 58,100 hours at 105°C

o 248,000 hours at 85°C

o 349,000 hours at 76°C

o 1,870,000 hours at 45°C, based on rate of weight loss

temperature dependence

Discussion: Characteristic Lifetime Estimates


o Analysis estimates

characteristic life is

~60,000 hrs

o Caps are rated to

10,000 hrs

o Characteristic life (η)

is 63.2% failure

o Assuming β = 4 o Conservative

estimate based upon previous life studies

o <0.1% unreliability

at 10,000 hours

Discussion: Characteristic Life vs. Time to First Failure


o Customer’s reliability goal was an annualized failure rate (AFR) of <0.5%

o AFR should be calculated using disk drive wearout parameters and not an arbitrary MTBF number

o Drive constituent and wearout mechanism

o Bearings, platter, axle – mechanical shock and high temperatures

o Bearing lubrication – high temperatures, low temperatures, and humidity

o Platter – electro-magnetic field

o Armature, head, slider – mechanical shock, wearout from use (load-unload process)

Hard Drive Testing


o Utilization inefficiency can be defined as the excess number of times the disk drive performs this 7-step load-unload routine:

1. Motor acceleration 2. Slider loading 3. Track following 4. Armature sweeping 5. Track following 6. Slider unloading 7. Motor deceleration

o Reducing the number of times the disk drive performs this routine extends the drive’s life. Most high reliability disk drives are spec’d for 500k-600k load-unload (LUL) cycles.

o Customer stated that the disk drive will contain their system’s operating system and act as a data logging storage device. This means that they can control, with software, how often the disk drive spins down by enabling a “capacity assessment” or “lookup” routine.

HDD Testing Approach


o AFR was calculated using two utilization criteria: Inefficiency and Data logging interval

o Inefficiency consists of the percentage of time the operating system starts and stops the hard drive during normal, non-data logging use

o Array analyzed: 100%, 50%, 25%, 10%, 5%, 2.5%, 1%, and 0.5%

o Data logging interval considers a LUL cycle to write data to the drive

o Array analyzed: 1hr, 30min, 15min, 10min, 5min, 1min, 30sec, and 10sec

o A combination of these two criteria, High-to-low inefficiency and long-to-short intervals, were weighted against a total LUL cycle count of 600k cycles for the drive

HDD Results

Total Load-Unload Cycles

6.00E+05 0.01% 0.01% 0.03% 0.04% 0.09% 0.44% 0.87% 2.59%

0.5% Inefficency 43.8 87.6 175.2 262.8 525.6 2628 5256 15768

Yearly: 8760 17520 35040 52560 105120 525600 1051200 3153600

Hourly: 1 2 4 6 12 60 120 360

Datalogging Cycle: 1 hr 30 min 15 min 10 min 5 min 1 min 30 sec 10 sec

Utilization Breakdown by Load-Unload Cycles

Annualized Failure Rate (AFR) by Load-Unload Routine Utilization


Ion Chromatography

DfR’s recommended limits are derived

from experience and experiments using

printed circuit boards

Contaminant

Upper Control

Limit**

(µg/in2)

Maximum

Level

(µg/in2)

Bromide 10 15

Chloride 2 4

Fluoride 1 2

Nitrate 4 6

Nitrite 4 6

Phosphate 4 6

Sulfate 4 6

Total Weak

Organic Acids 50 100


o A DfR customer wanted to know if the flux in the flux pens they were using

would induce low surface insulation resistance (SIR) and asked DfR for assistance

in performing an electomigration test following IPC-TM-650 2.6.14-1.

Electrochemical Migration Testing (ECM)

As the purpose of this test was to see the

potential for unactivated flux to contribute

to electromigration, the test vehicles were

not sent through reflow or wave solder

process. The samples were set up for

monitoring and stabilized in a 65C, 85%RH

environment in accordance with IPC-TR-

476A recommendations for 96 hours.

Following the 96 hour stabilization period,

the samples were energized and

resistance monitored to date for one week.


o There are two pathways that migration can take. The first is over an external surface, often referred

to as electrochemical migration (ECM) or dendritic growth. The second is through an internal path which

can be created by problems within the laminate such as delamination and is usually called a

conductive anodic filament (CAF).

o A liquid medium is required for several purposes. It must dissolve the metal ions and allow electrical

conduction via ion migration. Water from humidity is the most common medium (either adsorbed as

mono-layers or condensed).

o The bias applies a force on any positive ions present (such as those on the surface of some metals),

driving them to migrate through the medium from anode to cathode. Such ions will deposit on the

surface of the cathode, reducing the distance and resistance between those electrodes.

o There were no signs of migration or reduced surface resistance as shown in the graphs.

Electrochemical Migration Testing (ECM)

Control Boards – No Flux Fluxed Test Boards


o 22 nm technology, while displaying an impressive combination of

leading edge computation power and off-the-shelf pricing, has a

severe risk factor: its primary markets have design environments of

home / office and design lifetimes of between 18 months and five (5)

years. While the manufacturer tries to provide some guidance on

reliability, these reports are not available to all customers, they provide

no insight on how adjustments in electrical or environmental parameters

could improve or reduce reliability, and they provide no prediction of

performance beyond five (5) years.

o How do we test to a thirty year lifetime and induce semiconductor

wearout mechanisms on a COTS microprocessor?

Advanced Microprocessor Testing (IC Wearout)


o Baseline testing to stabilize the processors was conducted under the

following thermal-electrical loading. It is worth noting that the clock

speed is nearly 16% above the published maximum clock speed of 3.8

GHz.

o Why would we test at these conditions?

o Appropriate to drive Dielectric Breakdown and Hot Carrier Injection mechanisms

o DfR has extensive knowledge

on the mechanisms that lead to

failure of integrated circuits

Advanced Microprocessor Testing (IC Wearout)


Test Conditions – Design of Experiment

o Voltage, frequency, and operational stress are controlled through burn-in and benchmarking software. Initial characterization was performed to determine the combinatorial limits of voltage, frequency and operational states for the microprocessor.

o The ‘hot side’ of the test is controlled by COTS radiator setups (one per system). These temperatures are controlled by modifying the fan speed on the radiator block.

o The ‘cold side’ of the test is controlled by a closed loop water block with external chiller. The chiller is set to -25°C.

o Both sides of the test are using propylene glycol as the transfer solution in the heat exchanger.

From Chiller To Chiller

Chiller

Cold Side

Hot Side

To Chiller

From Chiller

Water block

Water block


o The product was subjected to a customer directed HALT process to uncover

design and/or process weaknesses. During the test process, the product was

subjected to progressively higher stress levels brought on by thermal dwells,

vibration, rapid temperature transitions and combined environments

HALT Testing (Avionics Case Study)


HALT Testing

Step Stress Temperature Testing

-100

-50

0

50

100

Time

Tem

pera

ture

(°C

)

T.setpoint

T.product

T.ambient

T1

T2

T3

T4

Vibration Stepping within Thermal Operating Limits

-60

-40

-20

0

20

40

60

80

100

120

Time

Tem

pera

ture

(°C

)

0

5

10

15

20

25

30

35

40

45

50

Grm

s

T.setpoint

T.products

T.ambient

T1

T2

T3

T4

V.setpoint

V.product

Vibration Combined Stress Plot Thermal Operating Limit Plot


o A DfR customer was interested in dielectric

withstanding voltage testing for polymeric conformal

coating per IPC-TM-650 2.5.7.1 which involves 0 to

1500VAC over 15 seconds at 100VAC per second

ramp followed by 1500 VAC for 1 minute.

Dielectric Withstanding Voltage Testing

All six PCBs arced and shorted

during the initial voltage ramp

Arcing and shorting occurred

consistently between 1.0 and

1.5kV


o A customer asked DfR for assistance in performing an

elevated temperature power cycle fan test.

o The fans of a particular lot were failing at an elevated

rate during burn in testing that subjected the product to

elevated temperatures and power cycling.

o Initial failure analysis reports from the manufacturer

suggested that the failures were due to foreign

material intrusion into the fan which caused wear

between the stator and impeller magnet. The initial

conclusion made by the manufacturer was that the

failures were caused by the customer.

Fan Testing


o This failure theory was deemed implausible by our customer and DfR for the following reasons: o The failure mode has been duplicated under test in a

relatively clean environment

o The amount of dust accumulated on the fan blades appears typical and does not indicate usage in a harsh environment

o Composition of the foreign material contains elements that are typically contained in metals and filled plastics:

o Silicon – source, filler material used in plastic

o Iron (Ferrite) – impeller magnets

o Zinc – corrosion inhibitor used on metal (galvanization) stators

o DfR set up a special thermal/power cycling test of the fans to verify operation and reliability

Fan Testing


Fan Testing

DfR created a custom circulating thermal chamber constructed to simultaneously test 32 fans. The chamber

is designed to regulate the air to a set temperature and provide even and consistent air resistance when the

fans are powered.

Thirty two fans were placed in the circulating thermal chamber in two banks of 16, as shown. The banks of

fans are facing opposite directions such that the air circulates in the chamber. Heater elements mounted

in the ends of the chamber provide additional heating to maintain the chamber temperature at 70°C.

The fans are wired to the power supplies with current sense resistors in series with the return line of each

fan. The voltage drop across the sense resistor is monitored by the data logger and recorded at 30

second intervals.


o A DfR customer requested that DfR perform development testing for a 12x12mm QFN to

include mechanical robustness (shock, vibration) for laptop applications

o Primarily two vibration tests are used in the technical specifications for desktop and

laptop applications: IEC 68-2 and MIL-STD-810F. The MIL-STD is primarily limited to

‘ruggedized’ versions of desktop and laptop products. When faced with multiple test

standards, most component manufacturers who have worked with DfR Solutions have

selected the most rigorous to ensure the widest acceptance among their potential

customers. Therefore, DfR recommended vibration testing be performed as per MIL-STD-

810F (Method 514, Proc I, Cat. 24). Board design was in accordance with JESD22B113

for an eight layer construction populated with 15 QFNs in very specific locations.

Vibration


o The maximum measured shock produced by the DfR

tower is 3000g. The shock load selected for the QFN

test activity was 1500g. This allowed for a 100%

engineering margin in the equipment capability and

ensured repeatability.

Shock


Ball Shear

“Slow” ball shear (<800 μm/s)

“Impact” ball shear (>800μm/s, 0.5m/s common)


Ball Shear Fractography

JEDEC diagram of brittle, interfacial fracture in shear. Solder pad

or intermetallic compound with no plastic deformation should be

partially or fully visible.

JEDEC diagram of ductile fracture in shear. Plastic deformation

of solder is observed.

Slow shear

Impact shear


Slow shear

Impact shear

Ball Shear Force Results

Impact shear is a more appropriate method of testing solder joints for variability in intermetallic

compound. In this case, no major anomalies were observed between the 5 reballers under investigation,

however statistical analysis revealed moderate differentiation.


o A 1000 hour combinatorial test was designed to meet JEDEC

JESD 219 industry specification for solid state drive endurance

testing

o 95% input/output (IO) utilization

o Power cycling and ‘environmental interrupt’

o Steady state or temperature cycling

o The target MTBF of this RDT was 2 million hours

o Due to the large number of failures in this reliability test, the failure

rate of this SSD population is 266,360 FIT

o The corresponding MTBF is 3,754 hours

o Root cause analysis identified a manufacturing defect and issues

with quality and workmanship in the failed population

Solid State Drive Reliability Demonstration Testing


o Test population: 396

o Total failures: 128

o Total Device Hours: 317226

o Confidence Level: 60%

o Failure Rate: 266k FIT

o MTBF: 3754 hours

o Norris-Landzberg Acceleration factor (Temperature cycling)

o No acceleration factor due to static temperature exposure

o Arrhenius Acceleration factor (Test Duration)

o Calculated as 1.56X

Failure Rate and MTBF


o Walk-in Chamber capability o Chambers 1 and 2 (6’x8’), Chamber 3 (6’x10’)

o Chamber 3 is currently set up with a testing capacity of 1000 solid state or hard disk drives

o 5 C/min ramp rates, thermocouples inside and outside of chamber, air flow control

o Customer-side remote access to test monitoring (web interface)

DfR’s BIG Chambers


Optocoupler Testing

2 chamber test set

up (left), DUT and

control board in

chamber (top and

right)

Control Board

DUT


o Current Transfer Ratio (CTR), is the gain of the optocoupler.

It is the ratio of the phototransistor collector current

compared to the infrared emitting diode (IRED) forward

current expressed as a percentage (%).

CTR=(IC/IF)*100

o The CTR depends upon the current gain (hfe) of the

transistor, the supply voltage to the phototransistor, the

forward current through the IRED and operating

temperature.

CTR Definition


Optocoupler Testing

T = 100°C T = 125°C

If1 = 50 mA 20

optocouplers

20

optocouplers

If2 = 60 mA 20

optocouplers

20

optocouplers

Little or no change in the Current Transfer

Ratio (CTR) was observed on two different

manufacturer’s Optocouplers after

exposure to 110C or 150C at 10/20 mA

current

Raising current levels provided

insight into degradation


o How robust is a power

supply’s design?

o Electrical and EMI analysis

o Impedance Loading

o Physical construction

overview

o Thermal review

o Electrical derating

o Quality control

Power Supply Testing


Counterfeit Device Testing

Suspect capacitor - group 2

0.0E+00

1.0E-04

2.0E-04

3.0E-04

4.0E-04

5.0E-04

6.0E-04

7.0E-04

8.0E-04

9.0E-04

1.0E-03

-60 -40 -20 0 20 40 60 80 100 120

Temperature (°C)

Dis

sip

ati

on

fa

cto

r

Cap 4 - Bag 10

Suspect capacitor - group 3

0.0E+00

2.0E-04

4.0E-04

6.0E-04

8.0E-04

1.0E-03

1.2E-03

-60 -40 -20 0 20 40 60 80 100 120

Temperature (°C)

Dis

sip

ati

on

fa

cto

r

C7 SN2854 - 0632


o Cyclic Bend

o Temperature/Humidity/Bias

o Flammability

o Sweat

o Salt fog

o Sulfur

o Connector mating

o Dielectric

o Fourier Transform Infra-Red

o Circuit Board SIR

o Digital Image Correlation

Other Testing


o Critical component strategy

o Design review

o Critical component identification

o Component qualification reliability testing

o Lifetime limiting components

o Lifetime results of test coupled with DfR’s Sherlock software

results in aggregate reliability assessment

o Alternate use environment than previously tested or

you have no experience (where does institutional

knowledge apply?)

o New designs

o New parts and materials technologies

When to Test?


o Can facilitate lowering of warranty costs

o Can determine life expectancies of devices in your

design

o Can help meet customer or industry requirements

o Can also determine manufacturing defects

o An determine design weak points, margins, functional

limitations

o Let DfR work with you to establish a viable and cost

effective test program.

What Does it All Mean?

Part quality-presentation-how-to-test-when-what-it-all-means

Engineering

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