Surface Mount Technology Trends in India
By Ankan Mitra
Surface mount technology (SMT) is one of the key factors for the shrinking electronics system-level packaging. The key drivers for SMT in India are the use of surface-mount devices (SMDs) in products developed indigenously by the Indian companies in the private as well as government sector, and the sourcing strategies of global electronics leaders and original equipment manufacturers (OEMs) to have their own manufacturing set-ups in India or outsourcing manufacturing to Indian or global contract electronic manufacturers (CEMs). With the electronics packaging being an ever-evolving field, and the focus on shrinking the size and having more packaging capability within the same or lesser real estate, component packaging has shrunk as well. Due to the condensed component structure, the component fan-out has increased multifold. To cater to this increased fan-out, printed circuit boards (PCBs) have moved from the conventional two-sided boards to multi-layer boards, with many manufacturers choosing high-density interconnect (HDI) methods for their designs.
PCBs, components and systems
Though SMD component manufacturing in India is not in line with global trends, some manufacturing is taking place. The majority of the components used for board manufacturing are still sourced from abroad. However, interconnect structure and PCB fabrication are moving quite closely with the global trends. A few PCB fabrication houses are capable of fabricating advance-level boards using HDI techniques. Most of the globally accepted low-loss laminate materials are available in India for PCBs. Various metallic and organic surface finishes are also available. The cumulative result is advanced PCBs that cater to both leaded and lead-free processes in India. Areas of growth for PCB manufacturing include flexible PCBs, metal-clad PCBs and PCBs with embedded discretes. Flexible PCB manufacturing that has 2D flexural capability can be seen widely in India, though 3D flexural capability is yet to catch up. Metal-clad PCBs manufactured in India are being used widely in LED applications, helping to meet mechanical design constraints.
PCBs by Indian OEMs with various embedded components are under prototype qualification stages. Especially for consumer electronics, these are set to see wide usage in the next few quarters. Though there has been commendable progress within PCB manufacturing, this segment is still at a nascent stage in India. The upward trend still stays within very few Indian and global PCB fabrication houses who have their manufacturing in India.
Solder and associated material
SMT is driving the advances in solder materials as the requirements for fine-pitch printing and reliable solder joint with minimal solder volume become a challenge. Smelting houses in India have been the main source of raw solder materials within the country for a long time. With leading global solder consumable manufacturers sourcing raw materials from India, the manufacturing processes for smelting houses now meet world-class levels. Also, a few global solder consumable manufacturers have set up offices in India offering high-quality support, which, in turn, has raised the support requirements from Indian solder consumable manufacturers. This finally benefits the customers, specifically the CEMs who normally interact with more than one supplier. The halogen-free requirement is another upcoming area of work. With this as a regulation, the challenges faced by the CEMs in India are very similar to the ones faced globally. This information is being used constructively by solder material manufacturers. Flux is now available in various forms—liquid, paste or solid—and various corrosion levels. This has significantly helped in soldering components of various types, which have various flux requirements within the same board, or which require more than one type of solder. One good example is customized components with castellation and thermal pad on the bottom. In this case, flux in paste is used as part of the solder paste and additional solid flux is used in castellation. PCB surface finishes and the chemicals used also have a heavy influence on the direction in which SMT moves. OEMs and subsequently PCB fabricators are moving away from the metallic (hot-air solder leveling) and electroplated finishes (electro less nickel immersion gold and electro less nickel electro less palladium immersion gold) towards organic finishes (organic solderability preservatives (OSPs)). Major challenges with the organic surface finish are the fidelity of contact during the test of the PCB assembly and traces of OSP left behind. Advances in this area with conductive solder finishes (which is under qualification with a few Indian PCB fabricators) will help mitigate this challenge and streamline the use of organic surface finishes. Various research projects for SMT are undertaken by Indian academic institutions in partnership with the industry. The primary focus is on alternative lead-free solder alloys with soldering profiles similar to legacy Sn63/Pb37 (tin-lead) alloy and also an alternative to the widely used SAC (An-Ag-Cu) alloys. PCB surface-finish defect elimination in the wet process is another primary research area.
Customized tooling has always been a requirement for electronics manufacturing. As miniaturized component usage increases manifold, new challenges are being faced by tool vendors. The first customized tool used in electronics manufacturing is the stencil. IPC-7095 and different stencil design patterns and requirements are already known to the stencil manufacturers in India. In addition to these, various types of step-etched (level-etched) stencils are now in practice. As more and more OEMs choose OSP as their preferred surface finish and move away from dual surface finish designs, additional solder deposition challenges are faced by the stencil manufacturers — for example, requirements of less than 0.1016 mm (4 mil) of overall solder deposition to allow for both EMI suppression effect as well as meet the stringent mechanical constraints. As SMD component usage far surpasses the use of through-hole components, specialized stencil designs and meeting stringent goals is being done in India help use intrusive solder techniques as the preferred method for soldering through-hole components, thereby reducing manufacturing steps significantly.
PCB assemblies that use adhesives for SMD component assembly require specialized wave-soldering pallets for soldering of component termination post-SMD assembly. Wave-soldering pallets meeting world-class standards are now available from Indian tool manufacturers. With SMD density increasing, the number of test-points needs to be reduced to meet the real-estate requirement. In-circuit test (ICT) still remains the preferred test and programming stage for PCB assemblies.
Facilities in conformance with ANSI/ESD S20.20 certification are one of the primary requirements for electronics manufacturing. With every CEM and OEM seeking to establish electrostatic discharge (ESD) protection in its facilities, higher-level segregation based on the ESD sensitivity of the components being handled is used. Also, within the same ESD-protected area, smaller areas with specialized facility requirements are established to handle higher-sensitivity components (like <100V sensitive components). Lead-free manufacturing is another driver for resource requirements. Special requirements such as nitrogen for high-temperature lead-free assembly introduce new requirements for facilities.
The growing demand for SMT in the electronics manufacturing segment in India has brought in the commitment from standardization organizations like IPC, Electrostatic Discharge Association (ESDA) and JEDEC. With its office in India, IPC has contributed significantly to awareness in the SMT domain through several international IPC training programs. The most widely used assembly standard that covers IPC-A-610 E has been translated into Hindi. As SMD packaging shrinks and stringent requirements must be revised, ESDA and JEDEC are coming up with joint standards, which are being reviewed by committees from ESDA India. These activities help contribute to the international platform from the Indian perspective, and incorporation of feedback encourages further progress and brainstorming in the developing areas.
SMT training is available in India at different levels. Training in equipment installation, handling and operation, and facility set-up is provided by the respective equipment vendor. However, operator-level training for hands-on repair or rework and inspection can be had within India. Engineer- and operator-level trainings in India are now on par with the internationally acceptable requirements, with IPC certifications available in India. Training covers design, SMT process set-up, process validation, assembly, repair, rework and inspection. Innovative ESD training programs, design for manufacturing, design for assembly and design for testability are some forthcoming areas. Program management for CEMs is also an area of development that is expected to come up in India. However, most of the training sessions are customer-driven, specifically for contrast electronics manufacturing where the customer requirement pushes the training type. This is unlike OEMs, which have their manufacturing set-up in India and impart internal training as new process requirements come up.
Product Data Management
An electronic product involves multiple manufacturers in the supply chain at system or sub-system level — PCB fabrication, ASIC development and fabrication, PCB assembly, mechanical assembly, and system integration and software installation. Many times these manufacturers refer to product information that is specific to their deliverables. For example, the mechanical parts manufacturer who never gets to see PCB fabrication data like Geber (file format used by PCB industry software) may lack valuable information that could be critical to the end-product’s quality.
Many services are now available from Indian companies that are increasingly participating in product data management. These services help to establish communication between participating partners as well as efficiently change the management. The IPC-2581 standard developed by IPC and International Electronics Manufacturing Initiative (iNEMI) is an XML-based scheme representing an intelligent data file format, which is increasingly being looked into by OEMs based out of India. These OEMs also participate in the IPC-2581 Consortium, which helps improve the standard from Indian manufacturing’s point of view. Specialized services with increasing PCB assembly complexity, specialized services are being provided by companies to OEMs and CEMs. These include design for excellence (design for reliability, design for testability and design for Six Sigma) and product data management services.
Use of SMT in electronics manufacturing is evolving. New services that support SMT are helping to set new benchmarks and improve manufacturing practices. The lacunae identified within this segment will be filled over the years, driven by other sub-segments.
Brief Bio of Author: Mr. Ankan Mitra is a Supply Chain Professional with a leading multinational company. He is experienced in Electronics Manufacturing, Design Verification and Design primarily in Telecommunication Design. He is closely associated with IPC activities in India and promotes ESDA India and SMTA India activities. Ankan is an electronics engineer and has completed his PGDBM from IIM Calcutta.