Application Report
May 2008

Component Reliability After Long Term Storage
R. R. Madsen

ABSTRACT
Each year the semiconductor industry routes a significant volume of devices to recycling sites forno reliability or quality rationale beyond the fact that those devices were stored on a warehouse
shelf for two years. This study identifies the key risks attributed to extended storage of devices
in uncontrolled indoor environments and the risk mitigation required to permit safe shelf-life
extension. Component reliability was evaluated after extended storage to assure component
solderability, MSL stability and die surface integrity. Packing materials were evaluated forcustomer use parameters as well as structural integrity and ESD properties. Results show thatcurrent packaging material (mold compound and leadframe) is sufficiently robust to protect theactive integrated circuits for many decades and permit standard reflow solder assembly beyond
15 years. Standard packing materials (bags, desiccant, and humidity cards) are robust for a 32
month storage period that can be extended by repacking with fresh materials. Packing materials
designed for long term storage are effective for more than five years.

Trademarks are the property of their respective owners

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CONTENTSABSTRACT ------------------------------------------------------------------------------------------------- 1
LIST OF FIGURES ---------------------------------------------------------------------------------------- 3
INTRODUCTION------------------------------------------------------------------------------------------- 4
BACKGROUND-------------------------------------------------------------------------------------------- 4
PROCEDURE----------------------------------------------------------------------------------------------- 4
EXCLUSIONS ---------------------------------------------------------------------------------------------- 5
RISK ASSESSMENT ------------------------------------------------------------------------------------- 5
DEVICE SPECIFIC RISKS ------------------------------------------------------------------------------ 5
PACKING MATERIALS SPECIFIC RISKS --------------------------------------------------------- 6
DEVICE SAMPLES INCLUDED IN THE EVALUATION ---------------------------------------- 7
PACKAGE SPECIFIC TESTING ---------------------------------------------------------------------- 8
LEAD SURFACE EXAMINATION AND INTERNAL VISUAL---------------------------------- 8
SOLDERABILITY TEST --------------------------------------------------------------------------------- 9
MSL VERIFICATION TEST ----------------------------------------------------------------------------- 9
EXAMINATION AND PHOTOGRAPHS OF PACKING MATERIALS --------------------- 10
TRIBOCHARGE EVALUATION TOOL ------------------------------------------------------------ 11
PBFT – PEEL BACK FORCE TOOL --------------------------------------------------------------- 12
SUMMARY OF RESULTS ---------------------------------------------------------------------------- 13
CONCLUSION-------------------------------------------------------------------------------------------- 13
ACKNOWLEDGMENTS ------------------------------------------------------------------------------- 14
GLOSSARY OF TERMS------------------------------------------------------------------------------- 15

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LIST OF FIGURES
Figure 1 - Optical Micrograph of 74AC11175DWR device showing representative leadappearance....................................................................................................................................... 8
Figure 2 - Optical Micrograph of 74AC11175DWR representative device lead ........................... 8
Figure 3 - FESEM Micrograph of 74AC11175DWR representative device leads - Bottom side ofpackage ........................................................................................................................................... 8
Figure 4 - FESEM Micrograph of 74AC11175DWR representative of device lead - Bottom of
package ........................................................................................................................................... 8
Figure 5 - Representative EDS spectrum of 74AC1175DWR lead surface showing typicalelements present.............................................................................................................................. 8
Figure 6 - Optical Micrograph of 74AC11175DWR representative die overview showing noabnormities...................................................................................................................................... 9
Figure 7 CSAM image of TPS2201 prior to moisture/reflow simulation. No significant
delamination observed. ................................................................................................................... 9
Figure 8 CSAM image of TPS2201 post Moisture/reflow simulation. Minor leadframedelamination observed. ................................................................................................................... 9
Figure 9 DAC7612U devices in a moisture barrier bag. ............................................................. 10
Figure 10 74ACT11374DWR devices in original sealed pizza box............................................ 10
Figure 11 TSC2101IRGZR devices in original sealed pizza box................................................ 10
Figure 12 GD75232DWR devices in original sealed moisture barrier bag. ................................ 11
Figure 13 TSC2101IRGZR devices in original sealed moisture barrier bag............................... 11
Figure 14 TSC2101IRGZR devices in original tape and reel with 1 desiccant and moisture
indicator labels. ............................................................................................................................. 11
Figure 15 ESD Analyzer with Faraday cup and voltage field meter. ........................................... 11
Figure 16 Peel-Back Force Test (PBFT) System......................................................................... 12
Figure 17 PBFT screen shot......................................................................................................... 12
Figure 18 Less than 20 volts detected during measurement of the static charge generated during
peel back testing............................................................................................................................ 12

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INTRODUCTION
This paper defines the risk factors associated with extended storage of plastic encapsulated
integrated circuits in a warehouse (uncontrolled indoor environment) and the materials andpractices required to assure the quality and reliability of the devices to the end user.

BACKGROUND
It is not uncommon in the electronics industry to specify a maximum time interval from device
manufacture to shipment and receipt by the customer. The origins of date code age restrictions
are not well documented, but it is probable that limitations of the packing materials for moisturesensitive components and post storage solderability of SnPb or Sn finishes contributed to theconcerns of customers that led to the shelf life restrictions.
Prior to 1995, the U. S. Military specified electrical retest of devices if a 3 year date code
window was exceeded. In 1995, the military specification that mandated electrical retest after 3
years was revised and that requirement was removed entirely. The military now prohibits datecode restrictions on component orders.4
A comprehensive evaluation of Long Term Storage devices was started in 2004 by engineers in
Dallas and Freising, utilizing both current devices and devices stored for >2 years in a warehouseenvironment. That study which included ATE re-verification of electrical performance,
concluded that no reliability or quality issues would result from storage of devices well beyond a
5 year period.2

PROCEDURE
This study evaluated twenty devices packed in tubes or tape and reel that had been stored in awarehouse environment (<40°C and <90% RH) for periods of time ranging from two toseventeen years. The acronym LTS (Long Term Storage) is used to identify this aged material.
Packing materials were examined for signs of deterioration – this included tribocharging tests on
clear tubes, black conductive tubes, and the cover tapes on T&R to evaluate the effectiveness of
topical antistats. The “as opened” status of humidity indicator cards was noted and the cards
were placed in a humidity monitored environment to test for functionality. Paper labels were
examined for legibility and adhesion. Peel force testing was conducted on T&R. All packing
materials were representative of the vendors and materials used at the time of manufacture.
The devices contained in the packing materials were carefully examined for signs ofdeterioration. Leads and pads of ten devices were examined microscopically and with SEM forany signs of corrosion or contamination. The surface areas of the leads were evaluated with EDS
for any foreign material. Moisture/reflow testing verified MSL performance.

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EXCLUSIONS
Devices with a NiPdAu lead finish were the primary focus in this evaluation. Other lead finishes
exhibited satisfactory solderability after simulated LTS; however, this study did not include
materials such as matte tin or solder bumps.

RISK ASSESSMENT
DEVICE SPECIFIC RISKS
Risk

Risk Mitigation
No failure mechanisms have been identified that would
compromise the electrical performance or circuit
reliability of LTS devices. HTOL and HTSL qualification
data provides the best estimate of parametric performanceover time. Devices are biased during HTOL testing – thisis worst case compared to unbiased storage.

Device functionality and parametricperformance after extended periods of shelfstorage.
Exposure to the ambient atmosphere forextended periods of time may oxidize the leadsurface impacting solder wetting duringassembly.

Moisture absorbed in the epoxy matrix ofdevices categorized as MSL 2 to 6 could
vaporize during reflow solder assembly andcrack the package.

Devices stored for extended periods may
exhibit corrosion of bond pads or interconnect
metallization.

Devices that incorporate non-volatile memory
may suffer data retention issues after long

5 Component Reliability After Long Term Storage

FIT rates for Analog products have been in single digits
for the past decade. This assures us that biased andunbiased devices would remain within data sheet limits
far beyond the design life of the device.
Aging studies have shown that NiPdAu lead finish
devices pass solderability requirements beyond 8 years1.
Actual testing of LTS devices indicates that storage for 15
years does not compromise solderability2.
Devices targeted for LTS are packed in special metallizedbags that are sealed with desiccant and a HIC. Moisturediffusivity of the MBB has been measured3 and devices
are transferred to new bags with fresh desiccant on aperiodic basis.

Package qualifications include autoclave tests to evaluate
the effect of moisture on die metallization (Galvanic
corrosion). Devices routinely pass high temperature andhumidity testing, which consists of 240 hours of autoclave
at 121° and 100% RH which would translate to >7 years
at 55°C and 60% RH and over 10 years at lower
temperatures.
Routine device qualifications include data retention tests
performed at elevated temperatures. Existing data assures

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Risk

Risk Mitigation

storage intervals.

us that biased and unbiased devices would maintain data
integrity far beyond the design life of the device.

PACKING MATERIALS SPECIFIC RISKS
Risk

The static dissipative properties of tubes ortape and reel may degrade over time
resulting in potential ESD damage to LTS
devices.

Risk Mitigation
Tubes:
Tribocharge testing was conducted on LTS
conductive and static dissipative tubes.
Comparisons with fresh tubes from stock
indicate device charge generation in aged
tubes was comparable to new tubes.
Tape and Reel:
Static field meter data taken during detape
operations indicate that no significant
tribocharging occurs on LTS sample reels.
Carrier tape pull testing indicated that the
LTS reels require no special handling or
adjustments to detape tooling duringassembly.

Storage bags may leak, allow moisture toenter, and cause problems for MSL.

Label adhesives may fail or the ink
marking could fade making lot history or
device identification difficult.

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MBB:
A breach of the MBB seal would be
detected with a color change of the HIC
and appropriate disposition of containedmaterial.
Extended storage bag manufacturer’s data
supports 5 year storage capability.
Independent validation of Water Vapor
Transmission Ratio (WVTR) for extended
storage bags (5 years) was conducted at acontract lab5.
Evaluation of material samples indicate no
degradation in legibility or label adhesion
after >17 years.

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DEVICE SAMPLES INCLUDED IN THE EVALUATIONTAPE & REELDEVICE Name

Test Group

Year
PackedLMV331IDBVR

1

2006

SN103770LPR

2

1991

PTSC2101IRGZR-1

3

2004

GD75232DWR

4

2004

74AC11175DWR

5

1999

TSC2101IRGZR

6

2005

74ACT11374DWR

7

2000

TPS2201IDFR

8

2001

CDC341DW

92000

PCM1803DB

10

1999

SN101013N

11

1998

Reel incardboard box SOT23 DBV
Reel in black
conductive bag
TO92
LP
Reel incardboard box
VQFN RGZ
Reel in moisturebarrier bag
SOIC DW
Reel incardboard box
SOIC DW
Reel in moisturebarrier bag
SOIC RGZ
Reel incardboard box
SOIC DW
Reel incardboard box
SSOP DF
Reel incardboard box
SOIC DW
Reel incardboard box
SSOP DB
Reel incardboard box
PDIP
N

SN74AVC1G14DBVR

12

2002

Reel in Sealed
Static shield bag SOT23 DBV

5SN74AHC1GU04DBVR

13

2003

Reel in Sealed
Static shield bag SOT23 DBV

5

Test
Group

Year
PackedStorage

Pkg
Pkg
Group

Pin
5
3
48
20
20
48
24
30
20
20
16

TUBES
DEVICE Name

Storage

Pkg
Pkg
Group

DRV135UAA

2001

ADS7846N

B

2002

PGA205BP

C

2004

INA118U

D2001

INA155UE

2001

DAC7612U

F

2002

Black Tube in
Sealed Moisture
Barrier Bag
SOIC
DBlack Tube in
Sealed Moisture
Barrier Bag
TSSOP PW
Black Tube in
Sealed Moisture
Barrier Bag
PDIP
NBlack Tube in
Sealed Moisture
Barrier Bag
SOIC
DBlack Tube in
Sealed Moisture
Barrier Bag
SOIC
DBlack Tube in
Sealed Moisture
Barrier Bag
SOIC
D

2001

Antistatic Tube inopened moisturebarrier bag
SOT223 DCY

REG117AG

7 Component Reliability After Long Term Storage

Pin

8

16

16

8

8

8

4

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PACKAGE SPECIFIC TESTING
LEAD SURFACE EXAMINATION AND INTERNAL VISUAL

Figure 1 - Optical Micrograph of 74AC11175DWR
device showing representative lead appearance

Figure 3 - FESEM Micrograph of 74AC11175DWR
representative device leads - Bottom side of package

Figure 2 - Optical Micrograph of 74AC11175DWR
representative device lead

Figure 4 - FESEM Micrograph of 74AC11175DWR
representative of device lead - Bottom of package

Figure 5 - Representative EDS spectrum of 74AC1175DWR lead surface showing typical elements present.

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Figure 6 - Optical Micrograph of 74AC11175DWR representative die overview showing no abnormities.

SOLDERABILITY TEST
No indication of solderability degradation was observed in LTS or laboratory aged samples.
Shelf-Life Evaluation of Lead-Free Component Finishes 1
TID – Old Datecode Study – 2007 (Evaluation Work DW Package) 2

MSL VERIFICATION TESTLTS devices were evaluated with standard JEDEC MSL verification tests. Obviously, time zerodata was not available for the retained samples; however, comparisons with MSL CSAM data for
current devices in similar packages revealed comparable performance. No evidence of package
cracks or other anomalies were observed in the test samples.

Figure 7 CSAM image of TPS2201 prior tomoisture/reflow simulation. No significant
delamination observed.

9 Component Reliability After Long Term Storage

Figure 8 CSAM image of TPS2201 post
Moisture/reflow simulation. Minor leadframedelamination observed.

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EXAMINATION AND PHOTOGRAPHS OF PACKING
MATERIALS
Devices were shipped directly to the evaluation lab with the existing packing materials and labels
intact. The metallized heat sealed bags were opened and the contents photographed. Humidity
Indicator Cards (HIC) were examined.

Figure 9 DAC7612U devices in a moisture barrier bag.

Figure 10 74ACT11374DWR devices in original
sealed pizza box.

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Figure 11 TSC2101IRGZR devices in original sealed
pizza box.

May 2008

Figure 12 GD75232DWR devices in original sealed
moisture barrier bag.

Figure 13 TSC2101IRGZR devices in original sealed
moisture barrier bag.

Figure 14 TSC2101IRGZR devices in original tape and reel with 1 desiccant and moisture indicator labels.

TRIBOCHARGE EVALUATION TOOL

Figure 15 ESD Analyzer with Faraday cup andvoltage field meter.

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PBFT – PEEL BACK FORCE TOOL

Figure 16 Peel-Back Force Test (PBFT) System.

Figure 17 PBFT screen shot.

Figure 18 Less than 20 volts detected during measurement of the static charge generated during peel back testing.

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SUMMARY OF RESULTS
•
•
•
•
•
•
•

No failure mechanisms have been identified that would compromise the reliability ofplastic encapsulated ICs with NiPdAu lead finish stored for extended periods of time in awarehouse environment.
Tribocharge voltages on LTS tape and reel samples during cover tape removal werecomparable to current tape and reel samples.
Tribocharge data from clear antistat tubes and black conductive tubes were compared to
fresh tubes from stock. Charges measured on devices removed from the aged tubes werecomparable to new tubes.
Surface analysis of LTS leads revealed expected elements. SEM and optical microscopy
revealed nothing abnormal. No degradation of the lead finish was observed.
HIC color change with humidity was observed with all cards from the current qualified
vendor.
Solderability of LTS leads met all expectations and was indistinguishable from current
devices.
No degradation of MSL performance was observed.

CONCLUSION
The shelf life of LTS devices as determined by solderability, SEM visual, SEM spectral analysis,
optical microscopy, MSL performance, solderability, and decapsulation/visual is >15 years.
IC packing material shelf life is limited by moisture diffusion through the MBB. A standard
MBB maintains satisfactory moisture levels for 32 months. LTS bags control moisture levels
beyond 5 years.

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ACKNOWLEDGMENTS
The author wishes to recognize the following individuals for their professional assistance:
Alison Brown of TI Dallas for Technical AssistanceBill Brumley of TI Tucson for Technical Assistance
Lucas Copeland of TI Tucson for Optical and SEM Analysis
Albert Escusa of TI Dallas for Technical AssistanceRin Key of TI Dallas for Technical Assistance
Sreenivasan Koduri of TI Dallas for Technical Assistance
Bernhard Lange of TI Germany, Lead Engineer for Solderability Testing, Wetting Balance, andSurface Resistivity Analysis in the 2004 Long Term Storage Study
Dave McKeehan of TI Oslo, Project Manager for the 2004 Long Term Storage StudyFred Miranda of TI Tucson for Tribocharge Evaluations, PBFT Testing, and MSL
Characterization in the current study.
Julie Terlisner of TI Tucson for Report Formatting and Editing
Todd Wyant of TI Dallas for Long Term Storage Bag Evaluation
Mark Yampolsky of TI Tucson for Technical Assistance

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GLOSSARY OF TERMS
Desiccant: A hygroscopic substance used to remove moisture from moisture barrier bags.
Humidity Indicator Card: (HIC) – A card printed with a moisture sensitive chemical (cobalt
chloride) that changes from blue to pink in the presence of water vapor.
Long Term Storage: (LTS) – Storage of devices in an uncontrolled indoor environment for
more than two years.
Moisture Barrier Bag: (MBB) – Storage bag manufactured with a flexible laminated vapor
barrier film that restricts transmission of water vapor.
Nickel, Palladium, Gold: (NiPdAu) – Metal layers that are pre-plated on leadframes to enable
solderability.
Shelf Life: The time that moisture sensitive devices may be stored in MBB with desiccant andHIC or MSL 1 devices stored at room ambient.
Water Vapor Transmission Rate: (WVTR) – A measure of permeability of MBBs to water
vapor.

1

Douglas W. Romm, Donald C. Abbott, Bernhard Lange “Shelf-Life Evaluation of Lead-Free Component Finishes”(June 2004)2

Andreas Huber, Bernhard Lange “TID Old Datecode Study 2007” (October 12, 2004)

3

Lee Lewis, Eddie Moltz “Semiconductor Packing Evaluation for Extended Shelf Life” (March 18, 2003)

4

NEDA Publication, “Managing Date Code Restrictions on Orders for Electronic Components” (2002)

5

Howard Immel, Dan Hammack “Mocon Testing Service Job Number: 32678T” (April 30, 2008)15 Component Reliability After Long Term Storage

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