Category Archives: LEDs

GaN on GaN LEDs by SoraaSoraa announced yesterday the next generation of its high external quantum efficiency GaN on GaN LEDs. As described in Appl. Phys. Lett. 101, 223509, Soraa’s new LED outperforms the best-documented LED laboratory result by Nichia Chemical Co. at current densities of 100 A/cm2 and beyond.

“The record breaking performance from our next generation of GaN on GaN LEDs is a credit to the extremely talented research and development team at Soraa, and a testament to the vision of our founder and GaN on GaN pioneer, Dr. Shuji Nakamura,” said Mike Krames, CTO of Soraa. “But what’s amazing is that we have just scratched the surface in terms of performance gains from our GaN on GaN LED technology.”

Soraa’s GaN on GaN LEDs handle significantly more current and emit ten times more light per unit area of LED wafer material than conventional LEDs made by depositing GaN layers on cheaper foreign substrates like sapphire, silicon carbide or silicon. The company’s GaN on GaN technology leverages the advantages of the native substrate, including over a thousand times lower crystal defect densities that allow reliable operation at very high current densities (the same principle that enabled Blu-ray laser diodes). In addition to superior crystal quality, the native substrate’s optical transparency and high electrical and thermal conductivity enable a very robust, simple LED design that delivers maximum performance. Another advantage of the GaN on GaN approach is that it enables considerable flexibility in the choice of crystal growth plane.

 “We firmly believe that GaN on GaN is the future for LEDs and we’ve developed a comprehensive intellectual property program and patent portfolio covering the technology to maintain our leadership position.” added Krames.

Soraa leveraged the advantages of its first generation GaN on GaN LEDs by introducing in 2012 the true full-visible-spectrum LED MR16 lamps—a superior alternative to 50-Watt halogen MR16 lamps. Soraa’s LED MR16 lamps have a CRI of 95 and R9 of 95 (higher than most halogen lamps) and compared to halogen lamps, produce no UV or IR; last up to 10 times as long; use 75 percent less energy; run cooler; produce a much more consistent and efficient beam; and are compatible with existing lamp fixtures and lighting infrastructure.

CoorsTek, one of the largest technical ceramics manufacturers, today announced introduction of aluminum nitride substrates. Ideal for the rapidly growing LED market and other markets where high heat dissipation is useful, these ceramic substrates boast a thermal conductivity of 170 W/m K.

CoorsTek AlN (aluminum nitride) ceramic substrates feature a very high dielectric strength, are a non-toxic alternative to BeO (beryllium oxide), and exhibit a thermal expansion coefficient similar to Si, GaN, and GaAs semiconductors.

“While we already offer an extensive line of ceramic substrates, our new high performance aluminum oxide substrates cover high heat dissipation applications,” says Andrew Golike, electronics general manager for CoorsTek, Inc.

Established in 1910, CoorsTek is one of the largest technical ceramics manufacturer in the world with over 40 facilities in the Americas, Europe, and Asia.

Today, Research and Markets released the Gallium Nitride (GaN) Semiconductor Devices (Discretes & ICs) Market, Global Forecast & Analysis: 2012 – 2022. This research study on the GaN semiconductors market gives a detailed overview of the global GaN semiconductors market in the present scenario, and discusses the history, evolution, market by technology, market by products and devices, market by application segments, and by geography. Each classification done for the global GaN semiconductors market has an extensive segmentation with market estimates and forecasts till 2022 for each sub-market in terms of both – revenue and volume. The major GaN semiconductor products, namely the power semiconductors and opto-semiconductors, are analyzed in great detail throughout the research study in every type of classification.

GaN has turned out to be the choice for most of the power semiconductor applications and is quickly replacing the existing silicon technology, according to the report. The various properties of GaN,  such as wider bandgap, high break-down voltage, larger critical electric field, and higher thermal conductivity, let the GaN devices operate at higher voltages, high switching frequencies, handle higher power density, and offer enhanced power efficiency than the pure Si devices. These properties allow the GaN discretes like Schottky diodes, MOSFETs, and the other advanced transistors to operate at much higher voltage levels, which are difficult for the counterpart Si devices. GaN power semiconductors also help in reducing the conduction and switching losses, thereby offering higher efficiency in electronic systems. The major application segments of GaN power semiconductors currently are the inverters (& converters), RF devices, power supply modules, and motor drives being used across all the end user verticals.

In the aspect of opto-semiconductors, GaN has been increasingly used in LEDs, laser diodes, and optocouplers due to the primary characteristic of GaN showing much brighter emission characteristics than the other materials, such as Si, SiC, GaAs, and GaP. AlGaN, mixed with GaN, is used in opto-semiconductors designed for high-brightness and ultra-high brightness applications that operate at wavelengths <400 nm. This market is expected to have healthy demand due to the markets growing for green, blue, violet, purple, ultra-violet, and white LEDs. The growing market for solid state lighting applications in several areas of the consumer electronics, computers, automotive, industrial and military, aerospace and defense sectors is expected to boost the GaN opto-semiconductors market revenue over the years to come.

This report, based on the extensive research on the GaN semiconductors market and industry, is aimed at identifying the entire market for the GaN semiconductor devices, and all its sub-segments through extensively detailed classifications, in terms of both revenue and shipments. It focuses on giving a bird’s eye-view of the upcoming industry with regards to GaN semiconductor market with detailed market segmentations, combined with qualitative analysis at each and every aspect of the classifications done.

InfiniLED’s latest MicroLEDs, or µLEDs, have produced record optical beam intensity. This new device is capable of producing up to 1mW of light from a single 20µm pixel at 405nm. This is equivalent to a light output density of more than 300 W/cm2 – the highest recorded for a commercially available LED type device.

“These results highlight the capabilities of the MicroLED,” said Dr. Bill Henry, chief commercial officer of InfiniLED, “This device can be seen as a cross-over between the power and collimation of a laser and the simplicity of an LED. The unique devices enable a range of applications. This was achieved without the need for external optics indicating the potential for further improvement of the performance.”

The MicroLED combines the benefits of a laser and a LED to produce ultra-high light output. The MicroLED provides the wavelength flexibility, drive characteristics and simplicity of a LED as well as the power and collimated beam of a laser. The ability to produce such light intensity and control directly from the chip enables the light to be efficiently used in a range of applications.

InfiniLED has achieved this record performance using the patented MicroLED structure. A parabolic reflector is etched into the semiconductor material during the fabrication process. This places an optical component directly at the site of light generation and at the most effective position for control of the light produced. Not only has the light been shown to be extracted in ultra-high intensity but also at high efficiencies. By directing all the generated light through a single surface of the semiconductor, it can be efficiently collected and used in the wider system.

The MicroLED is currently being used in a range of applications included life sciences, consumer electronics and OEM equipment. The MicroLED (µLED) can be fabricated as a single pixel, large clusters of pixels or as addressable arrays where each pixel is individually switchable. The single pixels can be used to produce high intensity, collimated light over a small area or to produce useable light at ultra-low currents. The single pixels produce light with a few nanoamps of current. To produce larger amounts of light, clusters of tightly packed MicroLEDs are available. This results in high light density and collimated emission over a wider area. MicroLEDs (µLEDs) are also available as addressable arrays of pixels. The collimation from each pixel results in high packing densities and minimal crosstalk between the devices.

Additionally, the high current densities achievable and low capacitance allows the MicroLEDs to be switched at very high speeds. Experimental work is on-going with the Tyndall National Institute and the results will be announced shortly.

 “The applications for the MicroLED are many and varied,” Henry added. “InfiniLED is developing light sources for use in areas such as diagnostics, printing and battery powered consumer electronics. We are particularly focused on applications where the efficient use and control of light is of greatest importance. The first products with MicroLEDs incorporated will be on the market shortly and we look forward to new releases in the near future.” 

InfiniLED will demonstrate this technology at BiOS and Photonic West in San Francisco this February.

Introduction

This year has shown increased innovation, integration, and technical maturity across RF frequency bands. This document outlines emerging RF trends that will be covered at ISSCC 2013.

ISSCC 2013 authors will present an ongoing drive toward increasing levels of integration. This trend can be seen in all areas of RF design from mm-Wave, to cellular, to imaging, to wireless sensors. In mm-Wave designs, higher system complexity (front-end, synthesizer, and baseband) is increasingly being integrated onto a single die. In cellular, the push for integration has led to a strong trend of architectures allowing better linearity and co-existence of these multiple bands and standards. In a related trend, there has been much research the last few years into various ways to remove costly and bulky SAW filters and duplexers. Some of these research areas include highly linear blocker-tolerant receivers, mixer-first receivers, feedback blocker cancellation, feed-forward blocker cancellation, N-path filters, and electrical balance of hybrid transformers. Strong work continues in the effort to integrate CMOS PAs while delivering viable power/efficiency performance. Finally, a clear trend this year was a significant number of chips demonstrated in 65nm CMOS compared to other technology nodes. This observation was noted across all frequency ranges and circuit topologies. The chips presented at ISSCC 2013 confirm that RF devices will continue to see larger levels of integration at the chip- and package level for years to come.

Over the past decade, the papers submitted to ISSCC have indicated clear trends in the continuing push to higher frequencies of operation in CMOS and BiCMOS. This trend has continued this year for oscillators, mm-Wave amplifiers, and PAs. An emerging trend is the increasing complexity of systems operating in the 60-to-200GHz range. The push to ever-higher frequencies is being pursued by both industry and academia for various applications. An important application is high-data-rate communication. With the low-GHz frequency spectrum already overcrowded, researchers are continuing to target frequencies above 60GHz. Two other applications for products operating in these frequency bands are imaging and radar. These frequencies are desirable for such products due to their high spatial resolution and enablement of small antenna dimensions, allowing efficient beam-forming arrays. Another continuing trend is the integration of mm-Wave antennas into silicon substrates.

The combination of these two trends (that is, increased integration and the push to higher frequencies) has enabled a new class of fully-integrated application-driven systems. With the availability of many RF and mm-Wave building blocks in CMOS and BiCMOS, fully integrated solutions for specific emerging domains are appearing, both in the RF and the mm- Wave frequency range. These systems are built on a foundation of circuit-block innovations that have been developed over the past few years. Single-chip radars in RF and mm-Wave frequencies with improved resolution, improved efficiency, showing increasing levels of integration are being demonstrated. Similarly, new systems are being developed for ultra-wideband radar and mm-Wave wireless sensing. Demonstrations in the biomedical field are clearly moving from simple electrical measurements towards real medical measurements in realistic environments using systems-in-package (SiP).

We now discuss these two trends supported with data from chips to be presented at ISSCC 2013.

Complexity and maturity in the mm-Wave and sub-mm-Wave ranges

The high cutoff frequency of bipolar transistors and highly downscaled MOS transistors enables the realization of circuits and systems operating in the mm-Wave range. In the last few years, high-data-rate communication in the 60GHz band and car radar around 77GHz have garnered much attention. While the integration level in these domains is already quite high, we see an improvement of the performance of the building blocks (e.g. output power of PAs, spectral purity and tuning range of VCOs).

The 100GHz barrier for the operating frequency of silicon circuits has been broken a few years ago. Whereas initially elementary building blocks like a VCO and an amplifier operating above 100GHz have been realized, we now witness the trend of increasing complexity in circuits operating above 100GHz. Meanwhile, the electrical performances at the building block level improve: the output power of mm-Wave and sub-mm-Wave sources and PAs increases and VCOs can operate at ever-increasing frequencies with a higher tuning range.

Co-existence and efficiency for cellular applications

RX and TX linearization: In the past few years there has been increasing interest in techniques to improve the linearity of transmitters and receivers. Improved linearity in the receivers will ease the requirements on the RF filtering of out-of-band blockers that can be accomplished, for instance, by placing a programmable notch filter in the RF path. TX linearity improvements will benefit performance parameters such as error-vector magnitude (EVM), ACLR and spectral purity.

Efficiency: PA efficiency improvements demonstrated this year will directly impact the battery life in portable applications. These efficiency improvement techniques include analog and digital pre-distortion, dynamic biasing and envelope tracking.

Digitally-assisted RF: The trend towards digitally-assisted RF continues and is increasingly applied to mm-Wave chips. More digitally assisted calibration techniques are being demonstrated in order to improve the overall performance of the transceiver by reducing the impact of analog impairments at the system level. These techniques include: spur cancelation/reduction, IIP2 improvements, and digital pre-distortion.

VCOs: There is a continuing trend toward improvements in phase-noise figure-of-merit (FOM) and power consumption due to circuit techniques like Class-C and Class-D VCOs. This year’s ISSCC shows clear contributions to this field.

This and other related topics will be discussed at length at ISSCC 2013, the foremost global forum for new developments in the integrated-circuit industry. ISSCC, the International Solid-State Circuits Conference, will be held on February 17-21, 2013, at the San Francisco Marriott Marquis Hotel.

Demand for ubiquitous mobile functionality to achieve enhanced productivity, a better social-networking experience, and improved multimedia quality, continues to drive innovation in technologies that will deliver to these objectives in an energy and cost-efficient manner. While the performance of embedded processors has increased to meet the rising demands of general-purpose computations, dedicated multimedia accelerators provide dramatic improvements in performance and energy efficiency of specific applications. Energy harvesting is another area of growing importance, leading to technologies that leverage non-volatile logic-based SoC’s for applications that do not have a constant power source or handheld devices with very limited battery capacity.

Technology scaling continues to be exploited to deliver designs capable of operating at lower voltages, resulting in reduced energy per operation, as well as reducing the area required to implement specific functions. Processors unveiled at ISSCC 2013 are built on a variety of technology nodes, with best-in-class results accomplished along the axes of integration, performance/watt and functional integration, as well as a few industry-first implementations. These are demonstrated in various process nodes ranging from 0.13μm down to 28nm bulk, and SOI CMOS technologies.

Emerging medical applications require a significant reduction in the standby power over state-of-the-art commercial processors. This drives the exploration of new leakage-reduction techniques in both logic and on-chip memories, targeting orders of magnitude reduction in leakage currents. Fast wake-up time requirements drive the need for saving and restoring the processor state.

In the late 1990s, a GSM phone contained a simple RISC processor running at 26MHz, supporting a primitive user interface. After a steady increase in clock frequency to roughly 300 MHz in the early 2000s, there has been sudden spurt towards 1 GHz and beyond. Moreover, following trends in laptops and desktops, processor architectures have become much more advanced, and recent smart phones incorporate dual and even quad-core processors, running up to 2GHz frequencies. Battery capacity, mostly driven by the required form factor, as well as thermal limits imply a power budget of roughly 3W for a smartphone. From this budget, also the power amplifier (for cellular communication) and the displays have to be powered. The available power budget for everything digital is in the range of 2W (peak) to 1W (sustained). As a result, energy efficiency has become the main challenge in designing application processors, graphics processors, media processors (video, image, audio), and modems (cellular, WLAN, GPS, Bluetooth). For video and image processing, the trend has been towards dedicated, optimized hardware solutions. Some new areas where dedicated processors are particularly needed include gesture-based user interfaces, and computational imaging, to name a few. For all digital circuits, the limited power budget leads to more fine-grained clock gating, various forms of (adaptive) voltage-frequency scaling, a variety of body-bias schemes, and elaborate power management strategies.

Interestingly, cellular links, wireless LAN, as well as short links consistently show a 10× increase every five years, with no sign of abating. With essentially constant power and thermal budgets, energy efficiency has become a central theme in designing the digital circuits for the involved signal processing. Historically, CMOS feature sizes halve every five years. For a brief period in the 1990s, CMOS scaling (a.k.a. Dennard scaling) provided a 23 (α-3) increase in energy efficiency per five years, almost matching the required 10×. During the past decade; however, CMOS scaling offers a roughly 3× improvement in energy efficiency every five years. The resulting ever-widening gap has led to alternative approaches to improve energy efficiency, namely, new standards, smarter algorithms, more efficient digital signal processors, highly-optimized accelerators, smarter hardware-software partitioning, as well as the power management techniques mentioned above.

This and other related topics will be discussed at length at ISSCC 2013, the foremost global forum for new developments in the integrated-circuit industry. ISSCC, the International Solid-State Circuits Conference, will be held on February 17-21, 2013, at the San Francisco Marriott Marquis Hotel.

Ten product categories, led by tablet MPUs and cellphone application MPUs, are forecast to exceed the 6% growth rate forecast for the total IC market this year, according to IC Insights’ 2013 McClean Report.  This report identifies and segments the total IC market into 34 major IC product categories.  Five categories are forecast to enjoy double-digit growth.  The number of categories with positive growth is expected to more than double to 22 in 2013 from 10 in 2012.

Consumer-driven mobile media devices, particularly smartphones and tablet computers, are forecast to keep the tablet MPU (50%) and cellphone application MPU (28%) segments at the top of the growth list for the third consecutive year.  Other IC categories that support mobile systems—including NAND flash (12%) and special-purpose logic devices—are expected to enjoy better-than-industry-average growth in 2013, as well.

Due to increasing demand for higher levels of precision in embedded-processing systems and the growth in connectivity using the Internet, the market for 32-bit MCUs is also forecast to outpace total IC market growth in 2013.  Embedded applications in medical/health systems and smartcards have helped boost the 32-bit MCU market.  In the automotive world, demand for 32-bit MCUs is being driven by “intelligent” car systems such as driver information systems and semi-autonomous driving features such as self-parking, advanced cruise controls, and collision-avoidance systems.  In the next few years, complex 32-bit MCUs are expected to account for over 25% of the processing power in vehicles.

After back-to-back years of steep declines in 2011 and 2012, the DRAM market is forecast to increase 9% in 2013, three points more than the total IC market.  DRAM unit growth is expected to increase only 2%, but the overall average selling price is forecast to jump 7% this year.  In five of the past six years (2007-2012) the DRAM market declined, which took its toll on weaker suppliers.  Fewer suppliers in the marketplace mean fewer competitors trying to undercut each other’s prices in order to gain marketshare and enhances the likelihood of a more stable pricing environment in the coming year.

Interestingly, in a world that is increasingly wireless, two IC categories of “wired” telecom ICs are forecast to grow faster than the total IC market.  Wired telecom—special purpose logic/MPR and wired telecom—application-specific analog are forecast to grow by 13% and 11%, respectively.

Telecom companies and network operators have been upgrading their long-haul and metropolitan-wide communications systems, which require many high-speed transmission ICs and other circuits. New 100Gb/s technology has been ready for deployment since 2009 and is being deployed now. Next-generation transmission technology and ICs for 1 trillion bits per second ("Terabit") networks are in development.

Telecom and network operators say data traffic is increasing more than 50% per year due to growing use of the Internet and video transmissions.  All wireless traffic eventually goes through high-speed cable transmission "backbone" networks—communications are routed over long distance via optical cable before getting to the cellular network on the other end.  All the mobile Internet, data, and video traffic has to go through a cable network and that is driving up the market for wired telecom—special-purpose logic/MPR and wired telecom—application-specific analog.  To a lesser degree, the wired telecom segments are growing on account of developing country markets where the use of landline phones is increasing.

Additional details on IC product markets are included in the 2013 edition of IC Insights’ flagship report, The McClean Report—A Complete Analysis and Forecast of the Integrated Circuit Industry, which features more than 400 tables and graphs in the main report.

large area flexible displaysTechnology directions in the field of large-area and low-temperature electronics focuses on lowering the cost-per-unit-area, instead of increasing the number of functions-per-unit-area that is accomplished in crystalline Si technology according to the well-known Moore’s law.

A clear breakthrough in research for large area electronics in the last decade has been the development of thin-filmtransistor, or TFT processes with an extremely low temperature budget of (<150°C) enabling manufacturing of flexible and inexpensive substrates like plastic films and paper.

The materials used for these developments have for a long time been carbon-based organic molecules like pentacene with properties of p-type semiconductors. More recently, air-stable organic n-type semiconductors and amorphous metal oxides, which are also n-type semiconductors, have emerged. The most popular metal oxide semiconductor is amorphous Indium Gallium Zinc Oxide, or IGZO, but variants exist, such as Zinc Oxide, Zinc Tin Oxide, and so on. The mobility of n- and p-type organic semiconductors has reached values exceeding 10 cm2Vs, which is already at par or exceeding the performance of amorphous silicon. Amorphous metal oxide transistors have typical charge carrier mobility of 10 to 20 cm2/Vs. Operational stability of all semiconductor materials has greatly improved, and should be sufficient to enable commercial applications, especially in combination with large-area compatible barrier layers to seal the transistor stack.

In the state-of-the-art p-type only, n-type only and complementary technologies are available. For the latter, all-organic implementations have been shown, but also hybrid solutions, featuring the integration of p-type organic with n-type oxide TFTs. Most TFTs are still manufactured with technologies from display-lines, using subtractive methods based on lithography. However, there is a clear emphasis on the development of technologies that could provide higher production throughput, based on different technologies borrowed from the graphic printing world like screen and inkjet printing. The feature sizes and spread of characteristics of printed TFT technologies are still larger than those made by lithography, but there is clear progress in the field.

The prime application for these TFT families are backplanes for active-matrix displays, including in particular flexible displays. Organic TFTs are well-suited for electronic paper-type displays, whereas oxide TFTs are targeting OLED displays. Furthermore, these thin-film transistors on foil are well-suited for integration with temperature or chemical sensors, pressure-sensitive foils, photodiode arrays, antennas, sheets capable of distributing RF power to appliances, energy scavenging devices, and so on, which will lead to hybrid integrated systems on foil. Early demonstrations include smart labels, smart shop shelves, smart medical patches, etc. They are enabled by a continuous progress in the complexity of analog TFT circuits targeting the interface with sensors and actuators, to modulate, amplify and convert analog signals as well as progress in digital TFT circuits and non-volatile memory to process and store information.

In line with this trend, ISSCC 2013 features three papers representing the latest state-of-the-art of organic thin-film transistor circuits. A front-end amplifier array for EMG measurement is demonstrated for the first time with organic electronics in paper 6.4. Transistor mismatch and power consumption of the amplifier are reduced by 92% and 56%, respectively, by selecting and connecting the transistors trough a post-inkjet printing. Papers 6.5 and 6.6 present advances in analog-to-digital converters for sensing applications. Papers 6.5 demonstrates the first ADC that integrates on the same chips resistors and printed n and p-type transistors. The ADC achieves an SNDR of 19.6dB, SNR of 25.7dB and BW of 2Hz. In Papers 6.6, an ADC made only with p-type transistors is presented that has the highest linearity without calibration and that is 14 times smaller than previous works using the same technology.

This and other related topics will be discussed at length at ISSCC 2013, the foremost global forum for new developments in the integrated-circuit industry. ISSCC, the International Solid-State Circuits Conference, will be held on February 17-21, 2013, at the San Francisco Marriott Marquis Hotel.

In the second article of the MEMS new product development blog, the importance of the first prototype will be discussed. Theoretical work is valuable and a necessary step in this process but nothing shows proof of principle and sells a design like a working prototype. It’s something people can touch, observe and investigate while distracting them from doubt associated with change. Building multiple prototypes in this first phase is equally important to begin validation early and show repeatability or provide evidence to change design and process directions.

The first prototypes should include both non functional and function samples. The non functional samples are used to test one or more characteristics such as burst strength of a pressure sensor element. Fully functional samples can be used to test multiple performance interactions. An interaction is likely to include how the packaging of a MEMS device influences its accuracy or how exposure to environmental conditions affect sensor performance over life. Let’s look at a few examples of how prototypes can influence proper decision making and expedite new product development.

When working with an OEM on the development of a MEMS sensor, the team hit a road block with the customer pursuing one design direction (for very specific reasons) and the sensor team trying to make a change to improve sensor performance in fluid drainage. The sensor package had two long, narrow ports of specific diameter and the customer was resistant to change because of envelope size constraints and the need to retrofit legacy products in the field. However, the diameter of the ports was the most important factor in improving drainage. Engineers on both sides threw around theories for months with no common ground achieved before a prototype was made. Then a prototype was built with several different size ports and a drainage study was completed. A video was made showing visual evidence of the test results. It turned out that making a 2 mm increase in port diameter resulted in full drainage with gravity where the previous design held fluid until it was vigorously shook.  When the customer saw the results of the prototype testing in the video, a solution to open port diameter was reached in just a days including a method to retrofit existing products in production.   

For another application, the engineering team needed to develop a method to prevent rotation of a MEMS sensor package. The customer requested that rotation be eliminated with a key feature added at the end of a threaded port. One method to achieve this is through broaching. This method involves cutting a circular blind hole, using a secondary tool to cut the material to a slightly different shape such a hexagon and then removing the remaining chip with a post drill operation. When the idea was first introduced, most experts stated it was crazy to attempt such a feature in hardened stainless steel and no quoted the business. However, the team built a prototype to test the idea. Our first prototype successfully broached 3 holes and then the tool failed due to a large chip in the tool’s tip. The team examined the failure and learned that the chip in the tool resulted from a sharp cutting edge. The material was also suboptimal for this broaching process but it was obtained quickly. Learning from these mistakes the team chose a more robust material and slightly dulled the cutting edge. These changes improved tool life from 3 to 92 broaches. This was a significant improvement but not to the point of a robust manufacturing process. Again learning from the prototype the team saw evidence heat was playing a role in the failure. This led the team to change to a more robust lubrication (something similar to the consistency of honey). This single, additional change improved tool life from 92 to over 1100 broaches and it was learned that increased tool life could be obtained with periodic sharpening and dulling the edge slightly. With further development, over 12,000 broaches were obtained in a single sharpening with tool life lasting over 96,000 broaches. Hence a prototype quickly showed proof of concept but also led to process and tool design changes that provided a successful solution.  

The last example is of a fully functional, prototype MEMS pressure sensor. Prior to building a prototype, analytical tools such as finite element analysis were used to predict interactions between the packaging and sense element when large external loads were applied to package extremities. These models are highly complex and often misuse of the tool by non experienced users results in team skepticism of the results. Colleagues may refer to work of this nature as "pretty pictures" but not very meaningful or doubtful at best. However, when performed properly with attention to meshing, material properties, boundary conditions, applied loads and solvers accurate results can be obtained. This allows for multiple design iterations analytically prior to the first prototype to ensure the sensor has the highest probability of achieving the desired performance. After finding a design solution where the packaging had less than 0.1% influence on the MEMS sense element performance, prototypes were built to validate both the optimized (slightly higher cost, better predicted performance) and a non optimized design (lower cost, lower predicted performance).  Upon validation of both prototypes the team found over 90% correlation between experimental and theoretical results. In addition, the first prototype (although having some flaws) was very functional and performed well enough to be used in a customer validation station.  With high correlation between theory and experimentation, the once questionable results were validated as trustworthy and further FEA could be performed for design optimization.

In each of the case studies reviewed above, it was seen that early prototypes led to a wealth of information for the engineering team and proof of principle. In some cases, proof of principle is not obtained and design / process direction needs to change which is equally valuable information. The first prototypes can also be extremely valuable for influencing colleagues, customers and managers to pursue a particular design or process direction when theory can be disputed at length. In the next article of the blog, critical design and process steps that lead to successful first prototypes will be discussed.   

 

Author Biography:

David DiPaola is Managing Director for DiPaola Consulting, a company focused on engineering and management solutions for electromechanical systems, sensors and MEMS products. A 16 year veteran of the field, he has brought many products from concept to production in high volume with outstanding quality. His work in design and process development spans multiple industries including automotive, medical, industrial and consumer electronics. Previously he has held engineering management and technical staff positions at Texas Instruments and Sensata Technologies, authored numerous technical papers and holds 5 patents. To learn more, please visit www.dceams.com.  

Mitsubishi Electric Corporation announced this week that it has developed a prototype multi-wire electrical discharge processing technology to cut very hard four inch square polycrystalline silicon carbide (SiC) ingots into 40 pieces at once. The technology is expected to improve both the productivity of SiC slicing and the effective use of SiC material. Mitsubishi Electric aims to market its multi-wire electrical discharge slicer by fiscal 2015.

SiC is expected to be used increasingly in power semiconductors due to its superior energy-saving and CO2 emissions-reduction properties compared to silicon. Additionally, SiC, along with GaN, zinc oxide (ZnO) and silicon (Si) substrates are considered as the future LED substrates, thanks to low lattice mismatches.

The prevalence of SiC in the semiconductor industry has grown over the past few years, as Si substrates are relatively cheap and benefit from the long process history of semiconductor manufacturing on Si. Currently, Cree is producing epi-wafers using a SiC substrate.

Until now, sliced wafers have been produced through multi-wire saw with diamond particles because SiC is the third hardest compound on earth, but this method requires lengthy machining time and large kerf widths. The new parallel multi-wire electrical discharge machining method utilizes Mitsubishi Electric’s proven electrical discharge technology for difficult-to-cut material, and employs a dedicated power supply specially developed for SiC.

Key technologies of Mitsubishi Electric’s electrical discharge technology

Mitsubishi Electric’s electrical discharge technology provides a method of simultaneously cutting of SiC ingots into 40 pieces.  Forty wire electrodes with a diameter of 0.1 mm aligned at 0.6mm intervals are rotated to cut 40 slices at once, improving productivity. The non-contact, thermal process-wire electrical discharge method slices faster and at closer intervals compared to contact cutting (220 micro meters or less cut at a speed of 80 micro meters per minute). More wafer slices extracted per SiC ingot for improved efficiency.

The power supply dedicated to SiC slice processing allows for simultaneous wire cuts with even energy enabled by 40 electrically independent power feed contacts to wire electrodes. The power supply also means uninterrupted processing with even very thing (0.1mm) wire electrodes, thanks to a newly developed high-frequency power supply tailored to the characteristics of SiC material.