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Packaging ICs to survive the automotive environment

By Prasad Dhond [Amkor ®]

lectronic systems in safety mandates and and represent some consumer demand for E of the harshest application more convenience and conditions for integrated circuits comfort features. (ICs). The packaging for these ICs In addition to the must withstand a variety of tests that increasing electronic go well beyond conditions prevalent content, the number of in consumer, commercial and sold is increasing industrial qualifications. globally, especially in To survive these tests and operate China and emerging reliably over their expected lifetime markets. In the last decade, in a variety of vehicles and systems, new sales in China assembly processes for automotive ICs have grown at a rate of have several unique aspects to ensure almost 12% per year. Figure 1: Market experts forecast consistent growth for automotive ICs. packaging reliability and durability. The Increasing vehicle sales SOURCE: IC Insights. extent of unique processing and tests and higher electronic depends upon the vehicle system where systems penetration are the IC is employed. the automotive IC market, which is Getting into approximately $24B production vehicles in 2015, with a 5-year Some electronics in vehicles are CAGR of about 9% to obvious, while others are somewhat 10% (Figure 1). Over 70% of the automotive hidden. The obvious systems include AEC-Q100 grades vary based on the operating environment total available market Table 1: infotainment systems, digital displays, temperature range. instrument cluster, voice/data (TAM) is in the area of communications, back-up warning, analog (including linear AEC-Q100 grades adaptive cruise control, advanced driver regulators, components, DC-DC The Council assistance systems (ADAS), cabin converters, LED drivers and interface (AEC) has established AEC-Q100, environmental controls, components, such as USB drivers) and “Failure Based Stress Test systems, lane departure warning, and (MCUs). Qualification for Integrated Circuits” others in the compartment. The automotive market is an attractive [1], to provide standardized test The hidden vehicle systems include segment for most methodologies for reliable, high-quality control, cylinder deactivation, companies as it provides a more stable electronic components. electric power , electronic application base compared to cyclical Many of the tests in AEC-Q100 throttle control, deployment, mobile or consumer applications, are performed by the IC suppliers control, anti- , longer product life cycles, and higher themselves, but packaging-related electronic stability systems, and more. returns on investment. However, there tests may be performed by an OSAT Many of these hidden systems are are barriers to entry with very high as part of the IC qualification. mounted under the hood of the vehicle expectations of quality, reliability, The test requirements vary from where the ambient temperature can be handling and processing, all of which “under-the-hood” applications, 150˚C or higher. must be achieved at reasonable costs. to passenger compartment, and There are also continuously evolving other vehicle locations. The part Vehicle electronics growth quality and reliability requirements operating temperature grades are Over 50 different electronic systems that drive significant capital purchases. shown in Table 1. can be found in today’s high-end Working with the right outsourced The grades reflect different vehicles that implement the most semiconductor assembly and test application profiles from under the advanced . In fact, the (OSAT) partner can help address many hood to inside the cabin mounting number of automotive electronic of these challenges effectively. locations and apply to IC products systems is increasing due to government including microelectromechanical

REPRINT from Chip Scale Review September • October • 2015 [ChipScaleReview.com] systems (MEMS) sensors, power equipped with higher end models of array (FCBGA), flip-chip chip-scale devices, signal conditioning, MCUs and that are maintained at a package (fcCSP), system-in-package more. While 1 is most commonly different standard and subject to tighter (SiP), etc., which are relatively new to used in automotive, Grade 0 is for Cpk process capability requirements. automotive applications. For example, the more stringent applications, while Certified operators are specially trained during the assembly process of Grades 2 and 3 are more equivalent to to handle automotive devices and have FCBGA packages, safe launch could commercial qualifications. to meet certain minimum requirements include examining cross sections at to achieve and maintain certification. several different locations after the Special considerations for Process control can help solder ball attach process to make sure ensure that automotive devices are that the of the solder joints automotive ICs is robust. Although this represents processed only on designated automotive Semiconductor suppliers are not extra and time during pre- equipment by certified operators. always aware that a particular IC will production runs, the benefit is better end up being used in an automotive quality and a more robust process. It application – especially if it’s a Additional process steps also gives more confidence to both catalog IC being used in Grade 2 or Depending on the application semiconductor suppliers and Tier 1 Grade 3 applications such as after- profile, automotive devices could have suppliers about going into production market infotainment. If an IC is additional process steps compared to a with new technologies. designed explicitly for an automotive standard commercial IC to ensure the application, however, steps must be highest quality and reliability. These AEC-Q100 qualification taken to ensure that it is handled and typically include more stringent visual AEC-Q100 consists of a suite of processed differently than a standard inspections during assembly and 100% tests but only a subset of these tests commercial or industrial IC. Even a open-short testing at the end of the is directly related to the package 1ppm component failure rate translates assembly process. Some of the other and assembly. Some of these are “in into a 1.5% or 15000ppm failure rate additional process steps could be direct process” tests such as wire bond shear at the level. To ensure the highest plasma cleaning before wire bonding (WBS), wire bond pull (WBP), and safety standards, we need to have a goal to ensure a higher quality bond and others that an OSAT can perform. As of zero defects. plasma cleaning before mold. shown in Figure 3, the reliability tests When a product is identified for in test group A are the most applicable automotive use, IC suppliers, especially Safe launch to an OSAT. those familiar with automotive Safe launch is a process during Traditional JEDEC and AEC-Q100 requirements, usually have specific the pre-production phase where Test group A have various tests expectations for processing and handling manufacturers or assemblers inspect including pre-conditioning, temperature during the assembly process. the process at each step and verify that cycling (TC), temperature the particular step is done correctly bias (THB), unbiased highly accelerated Supplier management before the product moves to the next stress test (HAST) and high- one. This ensures that any issues with temperature storage life (HTSL). Table Early in the development process production processes are identified 2 shows the differences between the of an automotive IC, one of the major and addressed during the pre- standard JEDEC conditions vs. Grade considerations is business continuity production phase itself, before high- planning with respect to raw materials. volume production starts. Safe launch 0 and Grade 1 automotive reliability For instance, there have been major is even more important for advanced test conditions. An OSAT must have disruptions in the lead frame supply packages such as flip-chip ball grid reliability labs with capability and chain with recent accidents and some equipment to perform these tests. lead frame suppliers exiting the business. Supplier selection, redundancy, and process audits per automotive standards such as VDA6.3, are very important to ensure continuity and quality of supply for automotive ICs.

Automotive controls In addition to ensuring that factories have automotive certifications such as TS16949, automotive products should be subject to tighter controls on the factory floor. Among other things, these controls might include designated automotive equipment (Figure 2), specially trained operators, error-proofing systems and hands-free processing systems. Designated automotive lines are usually Figure 2: Typical wire bond assembly process steps and special identification label for designated automotive equipment.

REPRINT from Chip Scale Review September • October • 2015 [ChipScaleReview.com] A critical component in being able to achieve aggressive year-on-year cost reductions is to use copper wire on wire bond products. Traditionally, gold has been the wire of choice, but due to cost and high-temperature performance where Kirkendall voiding is observed between the gold and aluminum interface, most new wire bonded automotive devices are using copper wire. Most major IC suppliers are either already qualified, or are in the process of qualifying copper wire for automotive applications. Lead frame, chip-scale package (CSP) and ball grid array (BGA) packages are in volume production for infotainment and engine control applications, and there is also increasing acceptance in Figure 3: AEC-Q100 qualification test flow [1]. other applications such as powertrain and chassis. Safety applications, however, have been slower to adopt the use of copper wire. The use of copper wire is not without its own set of challenges. Apart from the usual workability challenges of Cu wire, recent testing [2] has raised some concerns related to Pd coated copper (PCC) bond wire for very stringent automotive applications. In these studies, HTSL testing performed at above 150˚C showed degradation of bond pull test (BPT) results seen over time, as well as cracks at the stitch bond area. While PCC wire passes the AEC-Q100 Grade 0 min levels, there are some concerns regarding the margin in very stringent applications where the IC must operate at temperatures over 150˚C for extended periods of time. Table 2: AEC-Q100 qualification tests within an OSAT company’s scope. Further evaluations are necessary to validate the findings of the above- Figure 4 shows the tests that Amkor Special BOM considerations mentioned study and determine the typically performs for AEC-Q100 In addition to special processing, right material set to achieve robust qualifications. Based on equipment automotive applications frequently performance for AEC-Q100 Grade availability, or in some cases the require special material sets or BOM. 0 and beyond. Amkor has ongoing equipment’s capability, alternate tests For lead frame products, some of the evaluations to determine appropriate may be acceptable. For example, main material considerations are: wire BOMs for various products. The instead of unbiased HAST, autoclave type, epoxy mold compound (EMC), evaluation matrix for lead frame or temperature humidity (without die attach (DA) materials, and lead products consists of variations of wire bias) are acceptable tests. These tests frame features. type, EMC and lead frame design are used to characterize the bill of Lead frames with roughened surfaces features. The primary goal of these materials (BOM) for AEC-Q100 Grade are often used to enhance EMC evaluations is to develop a BOM 1 and Grade 0 applications. Different adhesion. Roughened lead frames can recommendation for AEC-Q100 Grade package families are evaluated to be used in combination with unique 0, with secondary goals of extended determine the most robust the most design features that are etched or testing beyond the Grade 0 limits, to robust bill of materials (BOM) to stamped onto the lead frame surface to achieve zero delamination and meet qualify for Grade 0 and other grades. improve delamination performance. other stringent automotive criteria.

REPRINT from Chip Scale Review September • October • 2015 [ChipScaleReview.com] automotive customers, as well as access to the Japanese automotive market. Evolving packaging technologies from leaded to surface mount to MEMS, 3D and die-level packaging will continue to place even more stringent demands on IC packages in automotive applications. Working with a seasoned expert OSAT can mean the difference between survival and failure in automotive applications.

References 1. AEC-Q100 Rev H, Failure Mechanism Based Stress Test Qualification for Integrated Circuits, http://www.aecouncil.com/ Documents/AEC_Q100_Rev_H_ Base_Document.pdf 2. Krinke JC et al. High temperature ® Figure 4: AEC-Q100 Group A tests performed by Amkor Technology . degradation of palladium coated copper bond wires. Microelectron Some of the Amkor package are running and the processor feeds Reliab (2014), http://dx.doi. families that are popular in automotive the results to . Since these org/10.1016/j.microrel.2014.07.097 electronic systems include: SOIC, systems require real time processing, TSSOP, MLF®/QFN, TQFP, BGA, it is critical that the response time be Stacked CSP, fcCSP, FCBGA and as fast as possible. As a result, systems Biography TMV ®. Dual lead frame products designers choose either SiP or fcCSP Prasad Dhond received his BSEE such as SOICs and TSSOPs represent type of packaging to keep the processor from The U. of Texas at Austin, and the highest volume. Quad lead and memory as close as possible to MBA from Southern Methodist U. and frame packages, as well as BGAs, each other. is Sr. Director Dual & Quad Leadframe ® are popular for automotive MCUs. Products at Amkor Technology ; The increasing use of non-wire bond Assembly solutions for automotive [email protected] products such as CSP and through- IC packages mold via (TMV ®) is occurring in ICs provide the for the infotainment and ADAS systems. technology inside the automotive electronic systems that deliver control Evolving automotive packaging features, convenience, connectivity requirements and keep safe and Increasing in ADAS and comfortable. To achieve the reliability infotainment is bringing advanced that automakers demand, IC suppliers technologies to the automotive space must approach IC packaging with at a much faster rate than ever before. considerably different packaging Growing familiarity with smartphone techniques. These include additional technology is increasing consumer controls on the floor, expectations in the car. Consumers additional process steps during now expect their car to seamlessly assembly, and using the right material talk to their phones, and they want to set that has been proven to survive be able to run the same apps that they automotive reliability tests. are used to running on their phones, As an OSAT supplier with many in their cars. New safety systems in years of automotive experience, the cars are slowly transitioning from Amkor Technology® has extensive driver assistance to highly automated, understanding of the requirements of on their way to becoming autonomous. automotive OEMs and Tier 1 suppliers Autonomous operation requires and can provide guidance and direction automotive systems to continuously in assembling automotive products, monitor the surroundings and take especially to customers with limited preventive actions in case an incident automotive experience. Our joint happens. In such a system, there are venture with J-Devices is expected several sensors that feed real time data to expand and provide even greater to a processor, where several algorithms assembly and test capabilities for

REPRINT from Chip Scale Review September • October • 2015 [ChipScaleReview.com]