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Meet the challenge microelectronics

How inspection advancements have changed the manufacturing process
Meet the challenge microelectronics

Each new generation of product must outperform its predecessors, in smaller package sizes and without significant increase in costs. As the size of devices continues to get smaller, the need for increasingly powerful measurement techniques increase to analyse ever more densely populated circuit boards. At smaller scales, the effect of every imperfection becomes magnified, while new design complications begin to have a measurable impact on performance.

Due to market drive electronic packages were designed so all the required information could be manufactured into a smaller footprint and 3D stack PCB and complex Ball Grid Array (BGA) were used providing a solution to the problem of producing a miniature package for an integrated circuit with many hundreds of pins. Most BGA packages have many solder balls, but to visually inspect through Automated Optical Inspection (AOI) is impossible as only the outer ball row can be seen. For rows of balls inside the package the only solution was X-ray inspection which can easily identify defects and failures through real-time imaging and defect analysis to the highest level of detail.

Traditional inspection methods
With more and more demand put on quality, flexibility and modularity, and the domination of miniaturisation and high volumes, inspection has become challenging. The process in which inspection is carried out on microelectronic packages has evolved with technology becoming more advanced and intricate in its workings. Originally inspection was carried out as visual, manual or destructive forms where PCB were physically cut to get to the point of interest. Inspection would then take place with an SEM (Scanning Electron Microscope) or through cross sectional analysis, these are expensive and time consuming methods requiring inspection to be done in specialist laboratories.
The use of AOI machines is a popular method in inspection. AOI is the automated visual inspection of PCB manufacture which uses a camera to scan the assembly for defects that would lead to board failure. It can be used at many stages through the manufacturing process including bare board inspection and solder paste inspection. It could not however, effectively inspect the PCBs used in microelectronics, and there was always the element of user error and objectiveness resulting in an un-true analysis of the PCB and ultimately leading to failure. This in-turn increases time spent on the manufacturing process, resulting in cost implications.
Regulations changed the face of microelectronics’ manufacture
Another factor that changed the electronics manufacturing process over the last ten years considerably was the implementation of strict lead-free regulations. The Restriction of Hazardous Substances Directive (RoHS), restricted the use of certain hazardous substances in electrical and electronic equipment, together with the Waste Electrical and Electronic Equipment Directive (WEEE) which sets collection, recycling and recovery targets for electrical goods. These restrictions caused uncertainty in the manufacturing process and an enhanced number of defects with faulty PCBs increasing. Lead-free materials are relatively more brittle and do not have the same flexibility required, leading to new materials being developed with solders made of alternative alloys.
AOI and X-ray systems were successfully used for the inspection of joints soldered using traditional lead alloys, however the move towards lead-free soldering technologies and the effect on joint integrity, made AOI systems less reliable. One reason for this doubt was whether existing AOI systems would understand the new algorithms required and if final results would be ‘true’. This loss of trust pathed the way for the increased introduction of modern X-ray inspection onto the shop floor including Computed Tomography (CT) inspection systems as it stood up to the requirements needed to inspect lead-free and increasingly smaller electronic packages easily without the need for destructive testing.
Demand for quality
Microelectronics demand quality, flexibility and modularity and with miniaturised packages increasing in cost it was even more important to detect faults early. One of the most recent additions to the Nikon inspection portfolio is the upgraded XT V 160, a high-precision, flat-panel based X-ray inspection system that facilitates real-time imaging and defect analysis to the highest level of detail. The XT V 160 includes on-screen or precision joystick control; system users can easily operate the fast and accurate 5-axis sample manipulator. Real-time X-ray allows them to intuitively navigate complex printed circuit boards and electronic components and quickly trace defects. In automated inspection mode, samples can be inspected at the highest throughput. Users benefit from low maintenance costs and high reliability which has been designed into the system. It also uses open-tube design, so the electron beam producing filament can be replaced by the operator at a fraction of the cost of closed-tube designs and can be carried out in-house, thus reducing downtime and replacement costs. This advancement in X-ray inspection ensures precise assessment of intricate microelectronics.
The importance of automation
The use of high performance X-ray inspection is becoming more and more important, with vital inspection required at early stages of the manufacturing process without the detrimental ‘slice and inspect’ methods which cause further problems and money loss. With increasing system integration, new 3D packages like package-on-package (PoP) incorporate multiple dies stacked on the top of each other and multi-level wire bonding which achieves the small footprint required by microelectronics. These increasingly complex ‘next generation’ packages require the use of specialised X-ray and 3D Computed Tomography (CT) techniques for inspection of high-tech devices where inspection can be isolated to the area of interest and carefully examined to avoid future failure through virtual micro-sectioning.
Microelectronics are consistently getting more and more complex and in demand in a number of industries from consumer electronics through to automotive and defence so getting the right inspection technique is imperative. This increased requirement has also lead to the demand in automation as global competition increases, especially from Asian countries which are starting to produce more high performance products. The requirement to maintain low costs is vital and the most feasible way to achieve this, is to increase throughput in order to accomplish economies of scale, but high throughput brings inherent risks and costs, from an inspection point of view. In order to minimise these costs, it is important to have systems which can provide a level of inspection with automating some of the more routine tasks. This automation must take place with confidence and provide a low level of false call rates.
The implementation of an effective automation platform during inspection is a must in modern microelectronics. Packages like Nikon’s user-friendly graphical interface Inspect-X enables automation programs to be created without the need to code or program. Combining C.Clear, it provides next generation real time image enhancements, meaning that live inspection images are of the highest quality in terms of detail and clarity. C.Clear, is a key function for manufacturers looking for highest performance real-time inspection, enabling easier viewing of any defects present, as well as requiring less operator training, which would normally entail some post-process image enhancement and analysis. Defects are detected correctly first time, especially hard to detect faults within multi-tier BGA or complex bond wires. C.Clear enables manufacturers to increase inspection throughput with confidence and to reduce false call rates, leading to improved quality and efficiency – a must in high-demand and highly technical microelectronic packages.
The future of inspection in microelectronics
With complex microelectronic package demands increasing and the need for smaller and efficient packages, the complexities of these smaller footprints will only cause more failures during manufacturing making inspection even more of a priority, but it has to be an inspection method that can examine clearly and easily without any destruction due to the expense caused by traditional methods. The electronics industry continues to increase component densities requiring very high-resolution image acquisition with fast processing and analysis becoming compulsory. The only reliable method lies with 3D X-ray inspection that can inspect stacked packages in a non-destructive manner. The development of these automated inspection systems is continually being developed and is being designed to keep up with the drive towards modular systems that can form all the inspection tasks necessary for complete inspection including X-ray, CT and semi-automatic techniques. Continued development in inspection is the key to success of microelectronics in the future and Nikon is continuously working on systems that are ahead of the high-tech microelectronic manufacturing process and the important inspection process.
Software like Inspect-X will be integral to the future of microelectronics with the ability to be flexible and to handle many different applications inspecting quickly, precisely and easily with defects indicated specifically to stop faults reaching the end stage during manufacture. Software that allows data to be shared with a universally shared platform is also evolving so a synergy can be created between all systems allowing information that can be shared to be a must have addition during automation and a driver for the future of inspection.
Current Issue
Titelbild EPP EUROPE Electronics Production and Test 11
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11.2023
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