Obsolescence management & the impact on reliability


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The secondary market is often the supply chain of last recourse when a component product goes obsolete or is under production constraints. While it is possible to get high quality, genuine parts, it is also possible to get nonconforming, reworked, or counterfeit components. What is most frustrating is that it is increasingly difficult to differentiate genuine parts from their counterfeit equivalents.
Historically, the secondary market provided a mechanism for finding parts in short supply or at reduced cost. Today, high-reliability system manufacturers are less willing to risk contamination of their supply chain with potentially substandard parts in order to save a few dollars on the cost of a part. The proliferation of counterfeit components has led to a contraction of the secondary market and an increase in the cost of parts in the marketplace.

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Obsolescence management & the impact on reliability

  1. 1. Obsolescence  Obsolescence Management & The  Management & The p y Impact on Reliability Cheryl Tulkoff ©2012 ASQ & Presentation Cheryl Presented live on Jull 12th, 2012http://reliabilitycalendar.org/The_Reliability_Calendar/Webinars_liability Calendar/Webinars ‐_English/Webinars_‐_English.html
  2. 2. ASQ Reliability Division  ASQ Reliability Division English Webinar Series English Webinar Series One of the monthly webinars  One of the monthly webinars on topics of interest to  reliability engineers. To view recorded webinar (available to ASQ Reliability  Division members only) visit asq.org/reliability ) / To sign up for the free and available to anyone live  webinars visit reliabilitycalendar.org and select English  Webinars to find links to register for upcoming eventshttp://reliabilitycalendar.org/The_Reliability_Calendar/Webinars_liability Calendar/Webinars ‐_English/Webinars_‐_English.html
  3. 3. Obsolescence Management 
 & The Impact on Reliability ASQ Reliability Division Webinar Cheryl Tulkoff, ctulkoff@dfrsolutions.com July 12, 2012 – 2010© 2004 - 2007 2010
  4. 4. Abstract Component obsolescence management is a strategic practice that also mitigates the risk of counterfeit parts. Left unchecked, obsolescence issues increase support costs and development and production costs. So, planning ahead is key. For companies that proactively manage component availability and obsolescence, the effect of long-term storage on manufacturability and reliability is an area of major concern. When component obsolescence isn’t planned for, the secondary market is often the supply chain of last recourse. While it is possible to get high quality, genuine parts, it is also possible to get nonconforming, reworked, or counterfeit components. And, it is increasingly difficult to differentiate genuine parts from their counterfeit equivalents. Historically, the secondary market provided a mechanism for finding parts in short supply or at reduced cost. Today, high-reliability system manufacturers are less willing to risk contamination of their supply chain with potentially substandard parts in order to save a few dollars on the cost of a part. The proliferation of counterfeit components has led to a contraction of the secondary market and an increase in the cost of parts in the marketplace. This webinar will cover strategies that can be used to protect your company and products against obsolescence risk. Topics include relevant industry standards, use of Managed Supply Programs (MSP) and Contract Pooled Options, plus long term storage recommendations and practices.© 2004 - 2007 2010
  5. 5. Obsolescence Management o A strategic practice that also mitigates the risk of counterfeit parts o Anticipate & plan for: o Supplier disruption o End of life parts o Aging technologies o Long life programs o Planning ahead is key! o For companies that proactively manage component availability and obsolescence, the effect of long-term storage is the area of major concern.© 2004 - 2007 2010
  6. 6. The Reliability Issues…. o The effect of long-term storage on manufacturability and reliability is the area of major concern o Many issues can arise depending on the technology and storage environment. o Mechanisms of concern include: o Solderability o Stress driven diffusive voiding o Moisture o Kirkendall voiding o Tin whiskering o Of all of these, solderability / wettability remains the number one challenge in long-term storage.© 2004 - 2007 2010
  7. 7. So, What do You Need to Know? o Industry Standards for Storage Reliability o Use of Managed Supply Programs (MSP) and Contract Pooled Options o Long Term Storage Recommendations and Practices o Awareness of Long Term Storage Reliability Issues© 2004 - 2007 2010
  8. 8. Industry Standards: ANSI-GEIA-STD-0003 o PROCEDURES FOR LONG TERM STORAGE OF ELECTRONICS o This document is generated to provide an industry standard for Long Term Storage (LTS) of electronic devices by drawing from the best long term storage practices currently known. o For the purposes of this document, LTS is defined as any device storage for more than 12 months but typically much longer. o While intended to address the storage of unpackaged semiconductors and packaged electronic devices, nothing in this standard precludes the storage of other items under the storage levels defined herein.© 2004 - 2007 2010
  9. 9. ANSI-GEIA-STD-0003 Standard o Packaged Electronic Devices o Electronic Devices are defined as any packaged electrical, electronic, electro-mechanical (EEE) item, or assemblies using such items. o This standard is intended to ensure that adequate reliability is achieved for devices in user applications after long term storage. o Users are encouraged to request data from suppliers to this specification that demonstrates a successful storage life requested by the user. o This standard is not intended to address built-in failure mechanisms that would take place regardless of storage conditions. o Unpackaged semiconductors o Unpackaged semiconductors are semiconductor wafer or dice.© 2004 - 2007 2010
  10. 10. ANSI-GEIA-STD-0003 Standard o Table of Contents: o ACKNOWLEDGMENTS o FOREWORD o 1 PURPOSE o 1.1 Scope o 2 REFERENCE DOCUMENTS o 3 REQUIREMENTS o 3.1 Storage Conditions o 3.2 Storage containers o 3.3 Levels o 3.4 Storage Elements o 3.5 Long Term Storage Control© 2004 - 2007 2010
  11. 11. MIL-HDBK-338B Viewpoint o ELECTRONIC RELIABILITY DESIGN HANDBOOK o It has often been assumed in the making of reliability predictions that the failure rate of an electronic equipment and/or it constituent parts is insignificantly small or even zero during the times when the equipment is switched off, deenergized or otherwise nonoperational. o Evidence in the field shows otherwise and experimental data indicates that the failure rates of many components are still very significant even when no electrical stresses are applied. This results from the fact that when the electrical stresses are removed, many other stresses such as temperature, acceleration, shock, corrosive influences, humidity, etc., are still present.© 2004 - 2007 2010
  12. 12. MIL-HDBK-338B Viewpoint o For example, with semiconductors, temperature has a very marked influence; even at room temperatures, the temperature dependent failure mechanisms within the items are continually active. o For some components, the storage failure rate is even greater than the operating failure rate at the lower stress levels. o This is the case for some types of resistors (eg. carbon composition) where, under storage conditions, there is no internal heat generation to eliminate humidity effects. o It is also well known that certain types of electrolytic capacitor need a reforming process after a long period of storage.© 2004 - 2007 2010
  13. 13. Critical Elements of a Long Term Storage Program o Asset Security o Protect against loss, theft o Component Inspection o Authenticity & quality o Product genealogy (origins) & condition o Data records for manufacture, transportation, and short term storage o Environmental data, Lot codes, Date codes o Storage Environment o GEIA Standards o Active desiccant storage at less than 5% relative humidity o Dry nitrogen storage per MIL-PRF-27401. o Data Management o Maintain and manage individual date and lot codes. o Assured Supply© 2004 - 2007 2010
  14. 14. Product Genealogy – Example of Supply Chain Complexity Courtesy of Lloyd Condra, Boeing© 2004 - 2007 2010
  15. 15. Managed Supply Programs (MSPs) o Several companies offer MSPs as an industry service. Some of their offerings include: o Purchasing and holding of obsolete components o Long term storage services o Component contract financing o Stock pooling and optional stock holdings o Product quality inspection and management o Contract terms up to 20 years© 2004 - 2007 2010
  16. 16. Contract / Stock Pooling Options o Pay a percentage of part cost over some defined time interval from mfg or MSP provider o Less Purchase Investment o Purchasing parts means an upfront cost for the value of the parts. o The percentage will ensure that the part or parts that you need are stocked and available when needed o Less Inventory Cost o Insurance o Risk of losing or damaging stocked parts o Storage space o Warranty o The warranty starts when a part is purchased from the pool o With purchased parts, the 1st year warranty granted already starts on the date of purchase.© 2004 - 2007 2010
  17. 17. Proper IC Storage Die / Wafer Hermetic Packages Plastic Packages – 2010© 2004 - 2007 2010
  18. 18. Proper IC Storage o For long-term programs, some form of storage should be considered. But, it does present problems: o Practical/physical space, mechanical, financial, and counterfeit products. o With appropriate care, ICs can be stored at the die/wafer level, or as “finished goods” (packaged). o What do we mean by long-term storage? o Commercial: 2 years is very long-term. o Military: 20 years and beyond is common. Courtesy John O’Boyle – QP Semiconductor© 2004 - 2007 2010
  19. 19. Die/Wafer Storage - a.k.a “Die Banking” o Successful storage methodologies include special bagging, environmental controls and periodic monitoring. o Requires care, cleanliness (particulates and gases), and benign temperatures. o IDMs (integrated device mfgs) do this but few distributors do. o Controlled atmosphere “dry boxes” (dry nitrogen purged storage). o Dry bagged/vacuum storage. o Oxygen barrier bags designed specifically for long-term storage. Courtesy John O’Boyle – QP Semiconductor© 2004 - 2007 2010
  20. 20. Die/Wafer Storage Advantages o Compact – container on the right holds 9 wafers with gross die count of 64,000. (Note Data CD in photo) o Flexible form factor – can build parts in any desired package. Courtesy John O’Boyle – QP Semiconductor© 2004 - 2007 2010
  21. 21. Hermetic Packages o Minimize moisture intrusion o 20 year storage is routine o Metal TO-3 “can” o Ceramic and side-brazed packages o DIP, LCC, flat pack, and PGA o Keep them dry and in environments low in sulfur, chlorine, and hydrocarbons to preserve solder finish on lead frame.© 2004 - 2007 2010
  22. 22. Hermetic Disadvantages/Advantages o Cannot change package type. o Slightly more expensive to store than die bank. o Large storage space required. o Easy storage infrastructure. o Long life time storage.© 2004 - 2007 2010
  23. 23. Common Misconceptions about Plastic o Come from the manufacturer in sealed packaging and thus don’t need special handling/storage. o Not rated as moisture sensitive and thus okay. o Safe to store in a “normal room” environment.© 2004 - 2007 2010
  24. 24. Plastic Packageso Plastic is hygroscopic o Attracts water molecules from the environment. o Achieve equilibrium in 4 to 28 days depending on molding compound. o Normal room considered “wet” for plastic ICs (LAX annual average RH: +70%*) o Store in “dry bags” or in a Source: Plastic Package Moisture-Induced Cracking, April 2006, National Semiconductor Application Note <10% RH environment * LAX weather station - indoor data over 31 years.© 2004 - 2007 2010
  25. 25. Wait a Minute! o “4 days?” o That’s the time for the moisture to reach equilibrium o Takes a longer time for damage to occur o “Normal room is WET?” o Well, when the device is turned on, the die heats and the moisture is driven out. o But you don’t normally store them powered up, do you? Courtesy John O’Boyle – QP Semiconductor© 2004 - 2007 2010
  26. 26. But, Water doesn’t hurt Plastic! o It’s not the plastic we’re worried about! o Water leaches/reacts with: o Materials out of the mold compound o Elements in the gases in the environment o Other materials deposited on the outside of the package. o Water corrodes and degrades the metal pads and wires and results in device failure. o Isn’t plastic “rated” as non-moisture sensitive? o Yes. But this rating is for IC/board assembly for reflow solder heat induced delamination and popcorning. o Contrary to popular belief, it is not a rating for long- term storage! Courtesy John O’Boyle – QP Semiconductor© 2004 - 2007 2010
  27. 27. IC Storage: Good and Bad News o Good: You can store wafers, die, or packages o Wafers or hermetic parts: store in a dry environment. o Plastic finished goods require a dry environment with periodic monitoring. o Having spares essentially eradicates the problem of locating EOL/obsolete parts in the future. o Bad: May be prohibited by regulation (FAR). o Federal Acquisition Regulations (FAR) often limits procurement to one or two years. o Systems manufacturers have rarely funded this long-term procurement on their “own dollar.”© 2004 - 2007 2010
  28. 28. Storage Options: Summary© 2004 - 2007 2010
  29. 29. Long Term Storage Case Study o In this case study, solderability was assessed for: o Components from three different reels o Stored for up to five years to determine how much additional storage life was available. o Either an ASIC in a SOIC package or a MOSFET in a TO-252 package. o In both package styles, the lead frame plating was tin-based.© 2004 - 2007 2010
  30. 30. Case Study (continued) o Type of plating material drives the appropriate solderability test o In this case, tin can either oxidize and/or form intermetallics with the base metal underneath. o Both reactions can detrimentally reduce the solderability of the component. o To assess these reactions, the components were subjected to steam aging to accelerate storage related effects on solderability. o Elevated temperature accelerates tin-copper intermetallic growth o Steam accelerates tin oxide formation. o Components were then tested for solder wettability using a wetting balance test.© 2004 - 2007 2010
  31. 31. Steam Aging Apparatus and Approach • The steaming apparatus was constructed as per IPC-TR-464. • Components are placed in the “dead bug” position on an inert and heat resistant polypropylene stage. • With this method, components are held at approximately 93°C, between 80% and 90% relative humidity (RH), and no more than 1 1/2" from the surface of the boiling water. • Each day exposed to this accelerated steam aging method is considered equivalent to one year in storage. Three components from each reel were aged for 0, 12, 24, 48 and 72 hours, corresponding to 0, 0.5, 1, 2 and 3 years of additional storage. Apparatus for Steam Aging© 2004 - 2007 2010
  32. 32. Solderability Measurements o Measurements of the wettability of the leads performed using a solder meniscus measuring device (Wetting Balance) for each component. o All parts were tested with a standard RMA flux. o Recommended procedure detailed in IPC/EIA J-STD-002C. o 3 components from each reel were tested.© 2004 - 2007 2010
  33. 33. Solderability Measurements o The acceptance criterion from J-STD-002C is provided in Chart 1 below o Set A more stringent than Set B.© 2004 - 2007 2010
  34. 34. Case Study Results o TO252 (production year 2003). Solderability is already impaired. o Dashed line indicates a part which was tested with a more active water soluble flux. Notice the significant improvement in wettability. o Suggests the mechanism for poor wetting is thick oxide (as opposed to intermetallic formation). Wetting Force DCC03994DC 400 350 300 Hours Aged 250 0 0 Force (uN/mm) 200 0 12 12 150 12 24 100 24 24 48 50 48 48 0 72 72 -0.5 0.5 1.5 2.5 3.5 4.5 5.5 72 -50 -100 time (seconds)© 2004 - 2007 2010
  35. 35. Case Study Results o TO252 (production year 2000). Even though this part is older, initial solderability is superior to the 2003 part. o After 12 hours of steam aging (equivalent to six months), solderability has deteriorated. Wetting Force DK0060112G 400 350 300 Hours 250 Aged Force (uN/mm) 0 200 0 0 12 150 12 12 100 24 24 24 50 48 48 48 0 72 -0.5 0.5 1.5 2.5 3.5 4.5 5.5 72 72 -50 -100 time (seconds)© 2004 - 2007 2010
  36. 36. Case Study Results o SOIC (production year N/A). Solderability degrades slowly. o The part does not become completely unwettable, like the TO252 parts, but fails IPC criteria after 24 hours of steam aging (equivalent to 1 year of storage). Wetting Force SOIC 400 350 300 Hours Aged 250 0 Force (uN/mm) 0 200 0 12 150 12 12 24 100 24 24 48 50 48 48 0 72 -0.5 0.5 1.5 2.5 3.5 4.5 5.5 72 72 -50 -100 time (seconds)© 2004 - 2007 2010
  37. 37. Discussion and Conclusions o The same components produced by the same manufacturer can display very different behaviors in regards to long-term solderability. o This was seen with the TO252 parts, where the parts fabricated in 2000 had better wettability than the parts fabricated in 2003. o Therefore, any component or obsolescence storage strategy should involve an initial solderability assessment of each part and date code combination.© 2004 - 2007 2010
  38. 38. Discussion and Conclusions o Any concern with poor solderability, if driven by oxidation formation, can be potentially mitigated through the use of more aggressive flux formulations. o This may require contingency planning for assembly of components after long-term storage, including movement from L to M to possibly H flux chemistries and introducing modified cleaning processes to ensure these chemistries are effectively removed after soldering. o It also clearly demonstrates that the most critical parameter to control during long-term storage is temperature, as oxide formation can be potentially remedied while intermetallic formation cannot.© 2004 - 2007 2010
  39. 39. Long Term Storage Reliability Issues Intermetallics Stress driven diffusive voiding Tin whiskering Moisture Kirkendall voiding – 2010© 2004 - 2007 2010
  40. 40. Intermetallics / Oxidation o Intermetallic compounds form when two unlike metals diffuse into one another creating species materials which are combinations of the two materials. o Intermetallic growth is the result of the diffusion of one material into another via crystal vacancies made available by defects, contamination, impurities, grain boundaries and mechanical stress o There are a number of locations within the electronic package where these dissimilar metals are joined. o These include: o Die level interconnects, wire bonds o Plating finishes on lead frames o Solder joints, flip chip interconnects, etc...© 2004 - 2007 2010
  41. 41. Intermetallics / Oxidation Growth of intermetallics during the storage period may occur and may reduce the strength or increase the resistance of the interconnect due to the properties of the intermetallic or from Kirkendall voiding. Intermetallic layer thickness can be estimated by following equation: X= Kt 1/2 Where X is the intermetallic layer thickness, t is the time and K is the rate constant which is calculated by following: K=Ce -E/KT Where C is the rate constant (there are nine different ones listed by Philofsky), e is the activation energy (typically 0.4 to 0.9 eV), K is the Boltzmann constant, and T is the temperature in absolute scale.© 2004 - 2007 2010
  42. 42. Stress Driven Diffusive Voiding o Stress Driven Diffusive Voiding in on-die interconnects results from the mismatch in coefficient of thermal expansion between the dielectric layers and the metallization itself. o Aluminum has a very high coefficient of thermal expansion (~27 ppm/ºC) while SiO2 has a fairly low coefficient of thermal expansion (~4 ppm/ºC). o Since metal deposition operations during semiconductor manufacturing are performed at elevated temperatures, the metallization contracts as it cools, causing it to be in tensile state. o These tensile stresses relax over a period of time resulting in small movements (diffusion) of metal atoms. o This movement can result in a void or an open interconnect.© 2004 - 2007 2010
  43. 43. Stress Driven Diffusive Voiding o Compressive stresses from the molding process can also cause movement of metallization atoms. This can cause thinning of the interconnect resulting in greater current densities during operation. o These current densities may be sufficiently high to cause electromigration which can also lead to an interconnect open. Image courtesy of Micron© 2004 - 2007 2010
  44. 44. Tin Whiskers o A tin whisker is a single crystal growth that can occur on tin plated lead frames. o Mechanism for the growth is not clearly understood but it does appear to be related to compressive stresses in the plating, moisture, and contamination. o May be an issue for alloy 42 lead frames with pure tin platings since large compressive stresses are present due to the CTE mismatch between the alloy 42 and the tin. o Tin whiskers can lead to shorting, intermittent errors, and high frequency issues.© 2004 - 2007 2010
  45. 45. Moisture o Depending on storage time & conditions, parts may be subjected to moisture. o May be from o Overloading of the desiccant with moisture o Failure of the storage bags o Improper storage. o Presence of moisture can lead to corrosion issues and other failures such as popcorning.© 2004 - 2007 2010
  46. 46. Failure Modes Encountered With Stored Electronic Components Component Failure Modes Batteries Dry batteries have limited shelf life. They become unusable at low temperatures and deteriorate rapidly at temperatures above 35C. The output of storage batteries drops as low as 10 percent at very low temperatures. Capacitors Moisture permeates solid dielectrics and increases losses which may lead to breakdown. Moisture on plates of an air capacitor changes the capacitance. Coils Moisture causes changes in inductance and loss in Q. Moisture swells phenolic forms. Wax coverings soften at high temperatures. Connectors Corrosion causes poor electrical contact and seizure of mating members. Moisture causes shorting at the ends. Relays & Solenoids Corrosion of metal parts causes malfunctioning. Dust and sand damage the contacts. Fungi grows on coils. Resistors The values of composition-type fixed resistors drift and these resistors are not suitable above 85C. Enameled and cement-coated resistors have small pinholes which bleed moisture, accounting for eventual breakdown. Precision wire-wound fixed resistors fail rapidly when exposed to high humidities and to temperatures at about 125c. Diodes, transistors, and microcircuits Plastic encapsulated devices offer poor hermetic seal resulting in shorts or opens caused by chemical corrosion or moisture. Motors, Blowers, and Dynamotors Swelling and rupture of plastic parts and corrosion of metal parts. Moisture absorption and fungus growth on coils. Sealed bearings are subject to failure. Plugs, jacks, Dial-Lamp sockets Corrosion and dirt produce high resistance contacts. Plastic insulation absorbs moisture. Switches Metal parts corrode, and plastic and wafers warp due to moisture absorption. Transformers Windings corrode causing shorts or open circuits.© 2004 - 2007 2010
  47. 47. Printed Circuit Board Storage o Common Pb-free board platings: o Electroless nickel/immersion gold (ENIG) o Immersion tin (ImSn) o Immersion silver (ImAg) o Organic solderability preservative (OSP) o Pb-free HASL o Failure mechanisms or quality issues are pretty well known at this point. o Black Pad with ENIG o Creep Corrosion with ImAg© 2004 - 2007 2010
  48. 48. Printed Circuit Board Storage o If you have always used SnPb HASL plated boards, the biggest change will be storage times. o Except for ENIG, which many companies avoid because of cost, all alternative Pb-free platings should be limited to 12 months of storage. o Over time ImSn will form intermetallics (temperature), OSP-coated copper will oxidize (humidity), and ImAg will tarnish (gaseous sulfides).© 2004 - 2007 2010
  49. 49. KIRKENDALL VOIDING o Another issue with board plating that also involves solder is Kirkendall voiding o Occurs when voids form at the interface between two dissimilar materials due to differential diffusion. If these voids coalesce, solder joint failure is more likely, especially under mechanical shock/drop conditions.© 2004 - 2007 2010
  50. 50. General Storage Reliability Checklist© 2004 - 2007 2010
  51. 51. Summary o Managing obsolescence issues is critical! o Anticipate and plan o Implement a robust long term storage program which considers: o Asset Security o Component Inspection o Product genealogy (origins) & condition o Storage Environment o Data Management o Assured Supply o Be aware of the potential reliability issues.© 2004 - 2007 2010
  52. 52. Instructor Biography o Cheryl Tulkoff has over 22 years of experience in electronics manufacturing with an emphasis on failure analysis and reliability. She has worked throughout the electronics manufacturing life cycle beginning with semiconductor fabrication processes, into printed circuit board fabrication and assembly, through functional and reliability testing, and culminating in the analysis and evaluation of field returns. She has also managed no clean and RoHS-compliant conversion programs and has developed and managed comprehensive reliability programs. o Cheryl earned her Bachelor of Mechanical Engineering degree from Georgia Tech. She is a published author, experienced public speaker and trainer and a Senior member of both ASQ and IEEE. She holds leadership positions in the IEEE Central Texas Chapter, IEEE WIE (Women In Engineering), and IEEE ASTR (Accelerated Stress Testing and Reliability) sections. She chaired the annual IEEE ASTR workshop for four years and is also an ASQ Certified Reliability Engineer. o She has a strong passion for pre-college STEM (Science, Technology, Engineering, and Math) outreach and volunteers with several organizations that specialize in encouraging pre-college students to pursue careers in these fields.© 2004 - 2007 2010
  53. 53. Contact Information Any Questions? Contact Cheryl Tulkoff, ctulkoff@dfrsolutions.com, 512-913-8624 Connect with me on Linked In! www.dfrsolutions.com© 2004 - 2007 2010