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Editor's Note: This column originally appeared in the December 2012 issue of SMT Magazine.I was recently driving through Germany and was surprised by the huge number of solar panels on house roofs--even in the smallest villages. Approximately 5.3% of all energy in Germany is solar, with a total installed capacity of 29.1 GW (20 conventional power plants). Other sources of sustainable energy in the country include wind, biomass, geothermal, hydropower, and biogenic fuels.
In 2012, more than 20% of all power in Germany is renewable. In May 2011, government officials announced a plan to shut down all nuclear reactors by 2022. Physicist Amory Lovins remarked, “Chancellor Merkel was so shocked by the Fukushima disaster that she turned Germany’s focus from nuclear to energy efficiency and renewables. That’s supported by three-quarters of Germans and opposed by no political party.”
Impact on Power Grid Design
This sustainable energy revolution will have great impact on how the power grid is designed and operated. In a classic power distribution grid, all power is generated in a limited number of large-scale power plants and consumed by industry, transportation, offices, public institutions (including street lights), and households. Power generation is large scale and separate from power consumption locations. Transportation, conversion, and consumption are designed for one-way energy flow. Energy meters also register one-way energy consumption.
Renewable energy instead combines multiple, decentralized power generation points with multiple, decentralized power consumption points. To make this even more complex, power generation and consumption points should switch instantaneously, depending on weather conditions and energy consumption needs.
I visited the Econexis house, a demo house for smart grids, in Zwolle, the Netherlands. Built on a beautiful green-lined plot behind the main office of grid administrator Enexis, the house demonstrates what is possible for energy conservation and generation in a private home. The house is covered by nearly 100 square meters of solar panels, and uses geothermal heating and cooling. Moreover, the “waste” heat from, for example water used for showers and washing machines, is not flushed away with the sewage, but passed through a heat exchanger for house heating.
Much of the time the house can be heated and cooled in an energy-neutral way and often generates considerably more electricity than it consumes. That surplus electricity can be stored in the batteries of the electric car, in a separate battery energy storage system (BESS), or fed back into the (smart) grid so no overcapacity is lost. An energy computer recommends the best time of the day for the owner to switch on large, energy-consuming appliances like the washing machine and dishwasher. When there is not enough wind or solar energy, the house switches automatically to conventional power as generated by a large-scale power plant.
Corresponding Demands on Power Electronics
All this presents a tremendous challenge for the design of intelligent power distribution grids (smart grids), smart meters, distributed energy storage systems, power conversion (PV inverters), and power management systems (PMS). For a smooth transition, specific requirements must be met by the power electronics systems involved: Ultimate reliability (in the Netherlands the average grid downtime per year is approximately 20 minutes, which represents an availability of > 99.996 %); long lifetime (>20 years); remote access; and control (automated meter reading, software uploading).
The market growth of related power electronics is expected to be considerable. Compounded average annual growth rate (CAAGR) for 2012-2020 is expected to be around 8%. This market growth will also be fuelled by the increasing importance of e-cars and related infrastructure (charging stations). Electric cars have considerable (power) electronics content. For instance, the Opel Ampera/Chevy Volt has 18 electronic modules (DC-AC and AC-DC inverters/converters, power management systems, communication modules, battery control modules). As with smart grids the electronics content of an e-car is mission-critical: Lifetime of greater than 15 years, operating temperature range -40°C to +155°C, shock resistance up to 40g , reliability on module level < 10 DPM, and voltage and current level up to 400 V/300 A.
Ultra-High-Quality Power Electronics
Smart grids and e-mobility will be the main drivers toward ultra-high-quality power electronics.
Take a closer look at the characteristics of power electronics boards. Depending on the functionality, an average component count of 600 can be expected (typically 150 to 1,300 components per board). The smallest component type is typically 0603 (sometimes 0402). The largest components are IGBTs, transformers, electrolytic capacitors, and cooling bodies. Here component dimensions can be up to 45 x 45 mm (175 x 40 mm), with a maximum height of up to 50 mm. Component masses can be up to 750 grams!
Handling such a wide component range on a single SMD pick-and-place system can cause a serious headache. Most machines use multiple nozzle placement heads and these heads have a (very) limited component range per head type and are awkward for power electronics manufacturing, as many different heads are needed to cover the entire component range. The heads also have restricted component heights which cause problems when component heights vary considerably.
Since voltage and current levels in power components can be considerable, these components must be connected to the substrate by firm solder joints. Through-hole power components are, therefore, often combined with SMD-type power components, and pin-through-hole (PTH or pin-in-paste) technology frequently merges these different manufacturing technologies. Here, components with multiple thick leads are pressed into paste-filled plated holes in the PCB. Placement force can be up to 40N and heavy IGBTs can require up to 100N.
SMD Assembly Must be Versatile
Aside from technological requirements, manufacturing requirements will also dictate pick-and-place requirements for power electronics assembly. The most important manufacturing requirements are placement process control (< 5 DPM), just-in-time (JIT) production, connected production lines, blocked-parts management, production flexibility (rush orders, NPI, stock control), and traceability.
These challenging requirements demand modular and flexible SMD assembly systems. The systems should have integrated programmable placement force control (up to 40N), tall component capability (35 mm, sometimes up to 50 mm), integrated placement process control (parallel placement process < 5 DPM), mechanical grippers for heavy components, traceability, and fast product changeover.
Maintaining prosperity and breaking dependence on fossil fuels, which are becoming scarce and contributing to carbon emissions, requires a change from conventional to renewable energy. This transition will happen in the next 15 to 30 years and demands high-performance SMD production. Making our own energy brings power to the people! In addition to playing the clarinet in two bands, Assembléon’s Sjef van Gastel has another passion: SMT. He has been with the company since its start-up as a Philips division in 1979. As the current Manager for Advanced Development, he combines his experience as systems architect and machine designer to explore technical and business opportunities from emerging technologies. van Gastel holds many patents and is a frequent speaker at international conferences related to SMT. He is also the author of “Fundamentals of SMD Assembly,” which has become a standard piece of literature in the industry.