Board assembly trends and priorities: the latest drivers are conversion cost reduction, NPI time reduction, greater I/O density and environmental compliance.

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Board assembly accounts for most of the direct material cost, and is closely associated with component packaging, interconnection, inspection, thermal management, final assembly and environmental technologies. This article highlights a few trends identified by the board assembly chapter of the 2007 iNEMI Roadmap. To recap, the Roadmap uses product emulators to identify technology requirements, primarily from the OEM perspective, for five product sectors: automotive, defense and aerospace, office/large business/communication systems, medical, and portable/consumer. Though diverse in form and function, the product sectors reflect certain common priorities for board assembly.

Reduction in conversion costs. Conversion cost is the cost to take a group of parts and convert them to a functioning electronics assembly. Conversion cost is the price of a completed assembly (including test, material procurement cost, etc.) less material cost. In this way, all cost associated with manufacturing and testing the assembly is considered. All product sectors predict significant decreased conversion costs by 2017. Portable electronics appears to seek the most aggressive reductions, overtaking office systems products after 2011 (Figure 1). Defense products lags behind other sectors because of its focus on reliability over cost. Note that these conversion cost reduction numbers reflect OEMs' forecasted or expected cost reductions. The industry recognizes the challenges in being able to deliver such cost reductions, given the investment levels required and the increased variable costs accompanying technology transitions, such as the Pb-free conversion.

Lower escape and defect rates. The escape rate metric for board assembly is tied closely to conversion cost. All product sectors project an exponential decrease in DPMO levels. This trend is led by the automotive sector, while significant pressure is on the portable, medical and office equipment industries to improve escape rates. For the defense industry, escape rate reduction is not driven by cost so much as a need for increased quality and reliability. In light of tighter process windows because of the RoHS transition, obtaining such steep escape rate reductions presents yet another challenge. Renewed focus on DfX guidelines and design/manufacturing collaboration is required to reduce escape rates and improve quality levels.

Compounding the issue is the simultaneous need to reduce defect levels while products become smaller. With reduced pitch and increased I/O density trends, board suppliers' ability to reduce defects will be limited without significant disruptive advancements in interconnect technology. Nanotechnology may provide the advancements needed, enabling (for example) such interconnect concepts as carbon nanotubes or nanowires.

Manufacturing migration. Another significant contributor to conversion cost is the migration of electronics manufacturing to lower-cost geographies. The migration to China appears to be leveling, especially in the high-volume portable/consumer sector. China already produces about half the world's cellphones and almost two-thirds of the DVD players. EMS companies are now beginning to seek other nearby locations, such as India, both to act as a hedge to China and reach local markets.

NPI time reduction. The new product introduction time is the lapse between a design being released for alpha prototyping and its release to production (assuming prototype parts are available at release). Automotive shows the longest NPI times, followed by communications and defense, with portables, office equipment, and medical (externals only) showing similar behavior (Figure 2). In medical implantables, where regulatory approvals are required, cycle times are much longer.

With projected NPI cycle time reductions of more than 60% by 2017 will come new constraints on manufacturing processes and operations. In general, the projected rapid cycle time reduction will need to be met with business system changes within EMS and OEM organizations. An emerging area that can help with cycle time reduction is the use of DfX by EMS companies. EMS companies are being engaged early in the product development process and are providing upfront input to traditional DfX, such as design for manufacturing, assembly or test, as well as nontraditional DfX, such as design for supply chain, environment and recycling. DfX in the global outsourcing environment requires closer interactions and collaboration across the supply chain, including OEMs, EMS providers and the supply base. Industry standards need to be developed to facilitate and streamline the information flow.

Environmental compliance transition. The most pressing environmental legislation is the European Union's WEEE and RoHS Directives, which have already taken effect, along with environmental legislation in China and other nations. With defense, automotive and several other sectors forecasting a slower adoption timeline for RoHS compliance and Pb-free board assembly than most (Table 1), component traceability, availability, compatibility, and other issues associated with the coexistence of "dual alloys" (i.e., SnPb and Pb-free materials) have become areas of concern. "Backward compatibility" is one such technical issue under intense study. Over time, Pb-free board assembly adoption is expected to force conversion even in exempt industries, such as aerospace and defense, because of supply base dynamics. This de facto compliance with Pb-free materials for all product sectors may impact assembly reliability and create hidden costs for these industries. Furthermore, with product emulators forecasting increasing design-for-take-back requirements, materials and processes opportunities will result. However, future environmental restrictions may result in even further changes in materials and processes.

This article is continued online.

Dr. Dongkai Shangguan is vice president, assembly technology & platform realization at Flextronics (flextronics.com), and chair of the 2007 iNEMI Roadmap Board Assembly chapter; [e-mail]. For information about ordering the iNEMI Roadmap, visit inemi.org/cms/roadmapping/roadmaporder.html.

Dr. Dongkai Shangguan

Table 1. Forecasted Pb-Free Conversion by Product Sector

Sector          2005  2007     2009     2015     2017

Portable        SnPb  Pb-free  Pb-free  Pb-free  Pb-free
Medical         SnPb  SnPb     Mixed    Mixed    Pb-free
Defense         SnPb  SnPb     SnPb     SnPb     SnPb
Automotive      SnPb  SnPb     Pb-free  Pb-free  Pb-free
Office          SnPb  Pb-free  Pb-free  Pb-free  Pb-free
Communications  SnPb  SnPb     Pb-free  Pb-free  Pb-free