Microwave Engineering Europe - March 2008 - (Page 22)

22 BENEFITS OF BeO Bonding of copper to BeO improves the performance of a ceramic. In addition to conventional metalizing techniques, copper can be applied to BeO via the Direct Bond Copper (DBC) process, which further enhances the thermal performance of the BeO while allowing high power transmission. Transistor packages produced via the DBC process exhibit less than 1 dB of insertion loss through 8 GHz. New and improved Improvements to BeO have occurred steadily over the years, and several recent developments have expanded its performance in RF and microwave circuits. For example, Brush Ceramic Products has recently achieved an increase in thermal conductivity to 325 W/ mK, which places BeO even further ahead of other materials and makes it appealing for RF power devices with higher outputs that have even more heat to dissipate. Other enhancements include the ability to produce BeO plates up to 4.5- x 4.5-inches (11.4- x 11.4-cm) , which reduces cost by allowing a greater number of patterns to be created on a single plate. In addition, the new BW1000 substrates from Brush Ceramics increase material strength by up to 25 percent to 38,000 lb./inch2 (2671.7 kg/cm2), which is achieved by adding proprietary additives while maintaining a purity level of 99.5 percent, and by precisely controlling grain growth and grain distribution during sintering. An obvious question This article makes a strong case for the use of BeO in RF and microwave systems and RF power transistor packages in particular. So the obvious question is: Why is BeO not ubiquitous (as it once was) in high-power RF transistor packaging, even though it is increasingly popular in other applications? There are two primary reasons for this. First as stated earlier, BeO is comparatively expensive, and especially in commercial wireless applications, cost reduction is a paramount concern. BeO is more costly than alumina and in some applications can be more costly than AlN. If power dissipation and other performance parameters of a device can be accommodated by AlN or alumina, BeO will be the loser. In addition, Laterally-Diffused Metal Oxide Semiconductor (LDMOS) devices do not require die attached to a dielectric, which eliminates the need for BeO (or any other material). Silicon-based LDMOS is the predominant device architecture for RF power applications below 4 GHz. The other issue concerns potential health effects arising from contact with BeO. These concerns are often exaggerated and have inaccurately portrayed BeO as hazardous to end-users, with the result that many design engineers believe they should not use components that contain BeO. However, the truth lies elsewhere. It is true that ﬁne BeO particulates (powder) can cause serious health effects in a small percentage of the population. However, the material in powder form is found only in ceramics manufacturing, where its handling is strictly controlled. Almost all BeO is supplied to end customers as a ﬁnished part that requires no special handling and is no more hazardous (and often less so) than other materials commonly used to create electronic products. Brush Ceramic Products is the world’s largest manufacturer of BeO products, and has long been a world leader in the health and safety of beryllium workers. The company has taken and continues to enhance procedures to ensure worker safety within its facilities. BeO is now and will continue to be available worldwide without legislative restriction such as RoHS or WEEE. Summary Despite challenges from competing materials, high-power RF and microwave applications that require the best possible thermal characteristics, stability, and resistance to hostile operating conditions, BeO remains the best (and perhaps only) choice. BeO also continues to ﬁnd new uses throughout the electronic, scientiﬁc, aerospace, and industrial communities, where its properties provide unique beneﬁts. In addition, after 50 years of development and experience in millions of circuits, BeO’s thermal properties and metallization technologies have proven to be extremely consistent. Although other insulating materials have achieved impressive results in a broad swatch of RF and microwave applications, in many applications only BeO will do. About the author John E. Scheatzle CPIM, CIRM, has been employed by Brush Engineered Materials for 11 years and has been general manager of its Brush Ceramic Products subsidiary since 2004. He was formerly operations manager for bulk products in Brush’s Alloy Division, and earlier was a senior manager with Anderson Consulting (now Accenture). He received his MBA degree from Case Western Reserve University. Company Information What’s new in BeO As the main article describes, BeO was once ubiquitous through microwave and RF applications. Over time, primarily because of cost pressures, other lower-cost solutions have been developed. However, despite the overall decreased usage of BeO in the microwave and RF market, it continues to thrive in new markets as the evolution in electronics continues to demand high power and smaller size. The number of diversity of these applications is quite large. For example, BeO has long been the only solution in the gas laser market where the material is used in laser bores. It is quickly attaining dominant position in the high-powered solid-state laser world as well, where it is used as a substrate for laser diode submounts. BW3250, Brush’s new material with improved thermal conductivity will further cement the material’s strong position. BeO is also ﬁnding a home in the renewable energy marketplace where it is being used as a packaging material in concentrated photovoltaic cells (CPVs). The high thermal conductivity of the material as well as the robustness of its metallization systems make BeO the ideal material to withstand the extreme conditions faced by solar cells. In addition to BeO’s outstanding electrical properties, new formulations of BeO are providing solutions to many problems in the vapor deposition market. BeO’s thermal conductivity and chemical stability make it very desirable material for the manufacture of chamber components. Durox, Brush’s new crucible material, is proving to be an excellent choice for the melting and deposition of aluminum, in which a more efﬁcient method of melting aluminum is required for future display technologies. – John Scheatzle Brush Ceramic Products www.brushceramics.com Microwave Engineering Europe ● March 2008 ● www.mwee.com 020_021_022_MWEE.indd 22 21/02/08 11:12:52 http://www.brushceramics.com http://www.mwee.com

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Microwave Engineering Europe - March 2008 News Contents Comment Wireless Infrastructure: A Direct Conversion I/Q Demodulatordrives Favorable Basestation Cost-performance Metrics Wireless Infrastructure: Mobile World Set to Reshape the Internet RF Amplifiers: Latest Advances in RF Amplifiers Include a CMOS PA Operating at 77 GHz and Significant Advances in PAs for WiMAX and Broadband Applications Many Applications Still Require Unique Performance Benefits of BeO ACE Automated Circuit Extraction Returns to Real Design by Exploring Design Alternatives and Changes in Seconds Exceeding the Standard for Wireless Sensor Networks Products Calendar

Microwave Engineering Europe - March 2008

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