Trends demand placement performance
07 May 2006
This article outlines the technology drivers in the electronics industry and shows how one equipment manufacturer is responding to them
The trend in electronics products is for the size of products to decrease, together with their cost, and for performance expectations to increase, a trend which is continuing unabated. In order to achieve these expectations, leading manufacturers are developing solutions with technical approaches ranging from reducing component size and developing multilayer circuit boards with integrated components, all the way to the development of (sub)modules with the latest circuitry and connection technologies. As these developments become more complex, so does the requirement for highly advanced placement systems to support them.
01005 placement In order to increase the performance of electronics in the smallest possible space, reducing component sizes plays an important role. The 0201 technology (0.6 mm x 0.3 mm), for example, whose development began approximately eight years ago, has become the standard for low-cost high-tech applications. But the trend towards more miniaturisation continues, what was considered virtually impossible only a few years ago is now becoming reality: 01005 components with dimensions of only 0.4 mm x 0.2 mm, for example. Reliably processing such miniscule components requires a quantum leap in almost all aspects of surface mount technology. Here is what matters most with respect to 01005 components:
• Feeding them reliably and picking them up carefully (contact-less)
• Placing them gently into the solder paste deposit with forces of less than 2 N
• Adjusting the placement dynamics in such a way that prevents an extreme compression of the solder paste deposit.
Siemens paid attention to this when placement heads and digital vision systems were designed for their placement machines, so that 01005 components are accurately centred optically, and placed precisely, at speeds of up to 20,000 components per hour and with a precision of 55 æm at 4 sigma. The position of the vision system, located directly across the placement position, as well as the 20 nozzles which can rotate individually on the new Collect&Place head, saves time by adjusting the components to their correct position while the head is moving to the placement position.
'Advanced package' technologies
Chip-stacking or chip-size package (CSP) is another trend that has been popular for years and is almost standard with RAM packages. This stacking of components is an ideal approach to increasing packing density and electrical performance. Since no solder can be printed on the bottom CSP after it has been placed, the top CSP must be dipped into flux in line with the standard flip-chip process. This so-called flip-chip capability is the main requirement for the placement system with respect to CSP stacking. In addition, placing the top CSPs requires a specific placement sequence and in some cases even a position correction of the bottom CSP after it has been optically measured.
The use of bare-chip technologies like flip-chip and Chip-on-Board (COB) also continues to grow. Flip-chips will become even more popular in the future, thanks to the increasing popularity of RFID (radio frequency identification) labels for tracking people and objects. Since each smart label requires a flip-chip, the demand for flip-chips will increase immensely. According to conservative estimates, the demand for smart labels will reach four billion by 2008. Managing such huge volumes requires a high-performance system with bare-chip capabilities and guaranteed high throughput.
Trends in board technology
HDI (High Density Interconnection) boards are getting progressively thinner. For SMT placement machines, this means they must offer fixed vacuum supports or flexible board supports. The SIPLACE platform offers vacuum tools that either keep the boards in place via specially designed carrier boards, or feature freely programmable support that uses suction to support the boards wherever necessary.
Passive components like resistors, capacitors and inductors are also increasingly being integrated into the substrate, a technique that is referred to as embedded passives and is most frequently used with computer boards and high-frequency mobile communication modules. On the cost side, integrated resistors make the most sense in applications where the typical tolerances of about ñ20% are acceptable, i.e. in purely digital circuits.
Integrating not just passive but also active components (i.e., chips) is referred to as Chip-in-Polymer (ChiP) or Chip-in-Board (CIB). Because of its extreme packing density, this approach promises maximum electrical performance. Such applications require extreme placement accuracy, since no self-centering or placement deviation compensation through final wire bonding is possible. Handling very thin chips in the 50 æm range represents an additional placement equipment challenge since it requires wafer handlers for feeding dies or flip-chips, maximum placement precision and clean-room compatibility.
Optoelectric circuit boards
Developers are still working on addressing the high frequency problems in large multilayer modules with optical "internal layers". Logical applications for this technology are telephone switches and Internet routers. From a placement technology viewpoint, the precise alignment of optoelectronic components with the optical circuit board position is technically and economically problematic. Since it takes deviations of only a few micrometers to create impermissible signal attenuations, this type of circuit board is very unlikely to be in widespread use before 2010.
Submodules
The use of submodules is another trend in high-tech and low-cost electronics. Their outer dimensions are currently in the 10 mm x 10 mm range, but are getting smaller. These modules typically contain 10 to 20 passive components and one or two bare chips. Manufacturing such sophisticated submodules requires highly advanced placement systems since it frequently involves placing the smallest passive components (currently 0201s) as well as bare chips with COB or flip-chip technology. More than 1,000 components, especially small chip components like 0201s, can be placed on a single cluster during submodule production.
Conclusion
Developments in printed circuit board capability and complexity will continue in order to support product innovations. With component placement equipment at the heart of this process, today's customers require comprehensive solutions to enable them to meet these requirements. Some manufacturers need to perform multiple product changeovers every day, and so their placement machines must adjust easily to changing requirements. Also, machine performance alone is no longer the sole criterion, keeping non productive time to a minimum is equally important today, which is why features like offline programming, offline setup and offline optimisation are becoming more and more important and why software can often be the differentiator. The answer is a modular machine platform that can be easily adjusted to meet any requirement, and with software, service and support to ultimately provide a complete line and production solution that focuses on the overall concept. Only with this kind of approach will placement equipment providers help electronics manufacturers to be highly productive and successful in the future.
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