Packaging Ics to Survive the Automotive Environment
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Packaging ICs to survive the automotive environment By Prasad Dhond [Amkor Technology®] lectronic systems in cars safety mandates and and trucks 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 vehicles 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 vehicle 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. driving the automotive IC market, which is Getting electronics 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, power components, DC-DC The Automotive Electronics Council assistance systems (ADAS), cabin converters, LED drivers and interface (AEC) has established AEC-Q100, environmental controls, navigation components, such as USB drivers) and “Failure Mechanism Based Stress Test systems, lane departure warning, and microcontrollers (MCUs). Qualification for Integrated Circuits” others in the passenger compartment. The automotive market is an attractive [1], to provide standardized test The hidden vehicle systems include segment for most semiconductor methodologies for reliable, high-quality engine control, cylinder deactivation, companies as it provides a more stable electronic components. electric power steering, electronic application base compared to cyclical Many of the tests in AEC-Q100 throttle control, airbag deployment, mobile or consumer applications, are performed by the IC suppliers transmission control, anti-lock brakes, 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 technologies. 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 machines that are maintained at a package (fcCSP), system-in-package more. While Grade 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 automation can help solder ball attach process to make sure ensure that automotive devices are that the metallurgy of the solder joints automotive ICs is robust. Although this represents processed only on designated automotive Semiconductor suppliers are not extra work 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 car 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 humidity 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