WHITE PAPER

“Technical & Financial Value Generation through Ceramic Substrates in Electronics Industry”

Hansu Birol

CSEM Brasil

Abstract

Electronics industry continuously seeks ways to cut costs while improving the performance, design and reliability of products. This is a big challenge requiring creative solutions especially at the time of packing tiny circuit components into shrunk volumes. This paper discusses the technical and cost perspectives of electronic substrates, which play an important role in electronic packaging of components. The focus is LTCC (Low Temperature Co-fired Ceramic), which will be compared to other ceramic and organic substrates. Moreover, cost saving through the use of LTCC will be discussed, which is expected to bring a more precise judgment in evaluation and selection of substrate/package material during product development. Centro de Inovações CSEM Brasil Avenida José Cândido da Silveira 2000 CEP: 31035-536 Belo Horizonte-MG, Brazil T +55 31 3326 1600 www.csembrasil.com.br info@csembrasil.com.br 2

Introduction

Electronic packaging is a multi-disciplinary field that connects a broad spectrum of materials, processes and technologies. It has a direct impact on performance, reliability and cost of the final product [1,2]. An electronic package must protect and ensure the functioning of integrated components, minimize losses in signal transmission, provide effective cooling to heat generating circuits and avoid electromagnetic interference between the modules [1-3]. Therefore, the material properties of package are critical in fulfilling product quality. This is particularly important since the size and cost must continuously reduce on the expense of increasing component density [4-6], as shown in figure 1. There are several parameters to consider in selection of package material such as electrical, mechanical, chemical and physical properties of the substrate, the environment it is exposed to, ease of processing (process robustness, yield, and productivity), desired product life time, norms it has to comply with and cost. Among different substrates options, PCB (Printed Circuit Board) is one of the most widely used substrate materials in electronics industry. Low material cost, well established design and production guidelines, vast experience with the use of accompanying materials and processes make these substrates the choice for several applications [7]. However, organic substrates have limited acceptance for harsh environments, where temperature, pressure, humidity, vibration, chemicals pose a serious threat to the integrity and performance of the product [8]. Moreover, PCB has limitations in packaging of high speed and high density components such as RF, analog and digital components [9,10]. Compared to organic substrates, ceramics are immune to these aforementioned factors and they provide significant advantages such as stability of material properties over time and improved thermal management through increased thermal conductivity [8-12]. LTCC extends these advantages further by facilitating flexible design, exhibiting smoother substrate surface critical for high frequency applications and CTE (Coefficient of Thermal Expansion) match to that of IC materials [11,12], which will be explicitly discussed in the next chapter.

LTCC Technology

LTCC is a special material system which is developed to manufacture miniaturized circuits, components and packages, particularly for high-rel applications in hostile and/or sensitive environments [13-15]. A typical LTCC package is manufactured by screen printing circuit elements, which are available as thick film on green LTCC sheets. This step is followed by isostatic lamination of these sheets and firing. The process is completed by mounting the active and SMD (Surface Mount Device) components on the top layer of the fired stack. A typical LTCC green sheet is composed of filler (ceramic such as alumina), glass and organic vehicle and produced by tape casting [16-18]. The filler is the backbone of the sheet composition and it defines the functional properties. The glass, on the other hand, plays a critical role in lowering sintering temperature and in forming high quality factor dielectric phases essential for the high performance of the ceramic. LTCC reaches to full density at 850- 875 °C, which is considerably below the firing temperature of HTCC (High Temperature Cofired Ceramic) around 1500 °C. Low temperature sintering is essential to co-fire LTCC with noble metals such as Au, Ag, which have melting temperatures around 1000 °C [19-25]. Finally, the organic vehicle in tape formulation is a mixture of binder, which gives the mechanical strength of the tape, as well as solvent, surfactant and plasticizer [26]. The other critical component of the LTCC system is the traditional thick films screen printed either on green LTCC tape or on fired LTCC substrate [27,28]. Technically, any granular material (glass, ceramic, metal) can be prepared to screen print after mixing with a suitable organic vehicle. Conductors of different metallurgies (Au, Ag, Ag/Pd, Au/Pt, Cu), resistors (electrical, piezo-resistor, thermistor), inductors and capacitors are developed to print on LTCC. In order to assure the materials compatibility (chemical, mechanical, physical, thermo-mechanical) between the tape and film, manufacturers pay special attention to developing tailored inks for their specific tapes [29-37]. The possibility to co-fire LTCC and thick film is a significant benefit that LTCC technology brings in miniaturization of circuits. This is achieved by printing passive components within LTCC layers (burying), which significantly reduces the footprint area of the circuit through the elimination of passive SMDs on the top layer [38-42]. Once the maximum number of passive components is buried within the stack, the surface area of the circuit is determined mainly by active components. It should be remembered that passives embedding should bring significant benefits such as space saving. If the footprint of a printed passive is larger than that of the SMD option, the latter should be preferred. Insertion of passive SMDs on FR4 (Flame Retardant, image above) into the multilayer LTCC stack. LTCC also provides mounting of ASIC (Application Specific Integrated Circuit), MMIC (Monolithic Microwave Integrated Circuit), bare die on the frame through wire bonding or flip chip. Depending on the application environment, critical components can be confined into open pockets or cavities on the top layer. A typical LTCC package in 3D.

What Makes LTCC an Interesting Choice?

LTCC has several intrinsic material properties, which significantly enhance the circuit performance. This section aims to show these distinctive properties introduced by LTCC in comparison to other substrates.

1.1.Dielectric Loss

Electronic substrates are expected to be perfect dielectric materials in order to confine the signals (current, waves) within the metallization lines interconnecting components. The dielectric loss can be explained as increased conductivity within the substrate, which requires additional energy input into the circuit in order to compensate the dissipated energy through conduction. Therefore, low dielectric loss is a figure of merit for substrates, particularly those used in high frequency circuits operating at high GHz region of RF (Radio Frequency) spectrum [43,44]. LTCC exhibits an order of magnitude lower dielectric loss than mostly used organic substrates including FR4 [5]. The losses in the circuit are also caused by conductors (DC, skin effect, surface roughness). Low-ohmic metals such as Ag, Au, which are frequently used with LTCC, reduce conductor losses significantly compared to refractory metals such as W, Mo. Therefore, the reduced dielectric and conductor losses make LTCC an attractive material choice in fabrication of components operating in a broad range of RF spectra and hence, in fabrication of components such as bluetooth modules, antennas, transceivers, etc .

1.2. Thermal Management

Thermal conductivity of LTCC is not its strongest feature, although it is still a better thermal conductor than FR4 by an order of magnitude [12,48,49]. What makes LTCC a far better thermal conductor than most of the other substrates is not through its intrinsic properties but through the thermal vias, which are constructed under heat generating components on top layer of LTCC such as power semiconductors, chips, etc. Different than vias in PCB technology, which are metallized on the via wall at a thickness of 5 um, vias in LTCC are filled with bulk metal. These vias go through the entire package and connect to the 6 metal sink on the bottom side of the package. Increasing the metallization area (via density) under the chips increase thermal conductivity up to 90 W/m.K as reported in a recent publication [50]. The effectiveness of thermal via solution is probably best-practiced by LED (Light Emitting Diode) applications. A typical LED die generates high thermal energy, which corresponds to 85- 90% of the total generated energy [51,52]. This heat must be dissipated effectively since the die life is strongly impacted by heat. Thermal vias, which can be easily constructed under the die or in special package sections, play a key role in dissipating this heat effectively. Therefore, LTCC becomes a very interesting package solution for LED [52].

1.2.CTE (Coefficient of Thermal Expansion)

CTE of electronic substrates has serious impacts on package performance [1,15]. The reliability of solders, which connect the active components and SMDs to the substrate, is dependent on CTE match between the components and the substrate, particularly when intensive thermal cycling occurs during processing and in the application environment [15]. As a bridge between the two, the solder is prone to thermo-mechanical stresses induced by both materials. In ideal case, it should be exposed to symmetric stresses (contracting and expanding) above (component side) and under (substrate side) simultaneously. This requires the substrate to have CTE as close as possible to the IC (Integrated Circuit) material such as Si, GaAs (Gallium Arsenide), GaN (Gallium Nitride) [15,24,48,49]. CTE comparison of LTCC, FR4 and mostly used ICs is shown in figure 8. LTCC exhibits CTE that is close to that of ICs, whereas, FR4 has higher CTE from Si by an order of magnitude.

1.3.Surface Properties

Surface roughness (Ra) of substrate is a tricky issue impacting the quality of the package. From the electrical performance point of view, it is one of the major causes of signal attenuation [55]. Particularly at higher frequencies (GHz range), the electromagnetic waves decay rapidly with depth inside the conductor and the current flows on the skin or the surface of the conductor. This increases the effective resistance of the conductor [55-57]. Small roughness values, which can be insignificant at lower frequencies, become significant sources for signal attenuation at higher frequencies, since they become comparable with the skin depth [56]. Therefore, roughness and signal attenuation are related through frequency, which becomes a critical topic for fabrication of micro strip transmission lines, high frequency antennas, etc. Under this chapter, it is also important to explain the tradeoff between the undisturbed propagation of signals at higher frequencies (through smoother surfaces) and stronger mechanical bonding between the substrate and the conductor (through rougher surface). There are efforts in PCB industry to optimize roughness through chemical treatment of conductor and the substrate. However, these processes bring the surface roughness of the dielectric to a few microns [56]. 8 In case of LTCC, the surface roughness is in the sub-micron range [12]. This is related to the composition of the material; LTCC is a material that sinters through liquid phase sintering due to glass. This lets the molten glass to fill in the openings between the filler particles facilitating the formation of dense material with even surfaces up on cooling. FR4 on the other hand, is a composite of woven fiberglass and epoxy resin binder, which exhibits a wavy structure due to the suspended fiberglass in epoxy matrix. Moreover, the mechanical bonding between LTCC and conductor is also much superior since traces of glass frits are used in the thick film composition to bond the printed ink to the dielectric chemically.

1.4.Other Distinctive LTCC Features

 Chemical Stability: Being a ceramic material, LTCC is immune to oxidation, chemical attacks (acid/base/oil/dirt), humidity [8,60]. This makes the LTCC package a hermetic platform in which electrical, mechanical, microfluidic functions can be united [8].

Stability of Dielectric Properties: Due to its chemical integrity and compatibility with printed films, LTCC maintains dielectric properties over extended periods. In other words, aging process is extremely limited when compared to organic substrates, which are severely impacted by humidity, temperature, chemical alterations [1,4,7,8,31,61]. 

Ease of Structuring: It is extremely practical and fast to cut an unfired LTCC sheet by laser or puncher. This facilitates manufacturing of the package in the desired form factor easily [8,60]. 

Process Control: LTCC processes are robust and in favor of avoiding critical manufacturing errors [12,61]. An AOI (Automatic Optical Inspection) system that is placed prior to stacking effectively checks, verifies and separates the individual tapes (or layers) with metallization defects before they are laminated. This is a significant difference and benefit when compared to PCB manufacturing, where the laminated PCB stack is tested after metallization is completed. In other words, the metallization defect found in PCB laminate means the loss of the entire stack, whereas the same problem is resolved by separating the single LTCC sheet before it gets into the stack. 

Re-fire stability: Fabrication of several components need consecutive firings when additional functional layers are printed onto the package. The electronic substrates suffer dimensional changes during these processes. LTCC is specially designed to go through minimum dimensional, mechanical and compositional changes during these re-firings [12,61].

Challenges for LTCC

Technology One of the most known difficulties of LTCC technology is optimization of differential shrinkage between the ceramic and the printed metals during co-firing [62-64]. The ceramic sinters (densifies) at a higher temperature than the metal and hence, it is deformed by the previouslydensified metal layer.. Warpage of the ceramic, delamination, local deformations in stack are typical consequences of differential shrinkage. Therefore, the densification behavior of ceramic and metal must be analyzed carefully in order to avoid shrinkage mismatch. Dilatometry analysis is a useful and commonly applied tool in evaluating the densification behavior of ceramics. In this characterization technique, pressed ceramic powder in pellet form is inserted into the dilatometer, and the equipment records the dimensional changes of the ceramic body as a function of increased temperature. Sintering behavior of commonly used LTCC (DuPont 951) and metal thick films (ESL 8837 Au and DuPont 5744 Au) are shown in figure 12 [65]. It is seen that the ceramic starts sintering at 700 °C (onset of dimensional change), whereas, the two metals start densification at 500 °C. The analysis also reveals expansion of 5744 starting from 700 °C, which contributes to extended deformation of the stack.

The effects of differential shrinkage mismatch between the co-fired ceramic and metal can be controlled through post-firing, symmetric design of circuit elements, production of compatible inks with ceramic. Another alternative is alteration of thick film chemical composition so that its densification dynamics are made compatible with the ceramic, which requires a thorough understanding of intrinsic material properties and careful evaluation of tradeoff between the thermo-mechanical materials compatibility and altered electrical properties. Gradual modification of a commercial ink’s composition (DuPont 9473, Ag/Pd) by addition of LTCC and SiO2 (silica) powders is shown in figure 13 [66]. The onset of metal’s shrinkage temperature is increased to 600 and 650 °C from 500 °C by addition of 10% LTCC powder and 20% SiO2 (by weight), respectively. These temperatures are closer to the onset shrinkage temperature of ceramic at 700 °C. The improvement is also macroscopically observable through the ceramic surface, which becomes warpage free at 20% SiO2 doping, as shown in figure 14 [65-67]. This improvement is ascribed to the insertion of networking phases into the glass composition of the ink, as evidenced by microscopic investigation.

Chemical compatibility of the ceramic and printed inks is also a very critical issue as its lack severely impacts the overall quality of the stack. It is mainly the glass component of LTCC and printed inks, which interact and form undesired phases altering desired electrical properties [65,68]. Figure 16 shows the comparison of ceramic-conductor-resistor interface for two conductor systems. The first is DuPont 9473 Ag/Pd conductor and heavily loaded with glass, whereas, the second one is DuPont 5744 Au system that has trace amounts of glass essential to make the metal adhere on the ceramic surface. It is clearly seen that the glass in Ag/Pd interacts with the glass in LTCC extensively and forms a reaction zone (shown as RZ on image), whereas the Au forms a very clean interface between the ceramic and the resistor.

Discussions

 LTCC has been used as a reliable substrate and package material for fabrication of electronic components for more than 3 decades. It is a mature technology and its distinctive features make it very suitable for several applications shown in figure 17 [7,11,41,45,70-73]. Its capability to integrate multiple RF components in a miniaturized, dielectrically stable and hermetic package has extended its traditional use from a simple MCM-C (Multi Chip Module – Ceramic) package in defense and automotive industries to sensors, packages for MEMS (Micro Electro Mechanical Systems) and SiP (System in Package), which are the critical components of several innovative products manufactured over the last 20 years.

The cost is arguably one of the major obstacles in wider use of LTCC. However, it is a frequent mistake to perceive the overall cost as the raw material cost only, neglecting other direct and indirect cost improvements through LTCC. Figure 18 shows a comparison of the total cost per circuit for the most commonly used electronic substrates in electronics industry [74]. This comparison entails the raw materials and processing costs incurred during fabrication. LTCC circuit is manufactured at a price that is approximately 3-5 times more expensive than that of PCB and 50 to 100% cheaper than that of Si depending on volume. However, this is just a part of the story excluding what LTCC can really offer. LTCC can directly improve the cost by reducing the footprint of the circuit through passives integration. A practical example is the Samsung Galaxy Tab 3, which comes with a radio transceiver that is manufactured by integrating Intel’s Smart i4G module and front end components (filters, duplexers, switches) in a single LTCC package (figure 19) [75]. The new LTCC module is reported to reduce the foot print by 40 components, which corresponds to 20% economy in the PCB area. According to BOM (Bill of Material) analysis [76], this space reduction saves ca. US$ 31 per tablet.

When overall parameters are considered in selection of substrate/package material simultaneously, LTCC is seen to offer excellent benefits at reasonable cost, which can be further improved through smart approaches, materials and process combinations and miniaturization. As explained previously, this is the reason why and how use of LTCC has extended from mainstream to emerging applications in the last 2 decades. Table 1 shows quantitative summary of commonly used substrates in light of aforementioned information and discussions.

It is also very important to mention here that the benefits indicated for LTCC are not meant to address LTCC as an alternative to the PCB or any other specific substrate. It is important to realize that the critical component in the product can be packaged effectively, efficiently and reliably by LTCC (e.g. front end module), which can then be soldered on PCB through BGA (Ball Grid Array) so that the product comes with an optimized quality and price by integration of two mature technologies.

Conclusions

 This paper aimed to give a broad perspective about LTCC technology by discussing the benefits, challenges and technical and financial aspects of the technology vividly. Superior intrinsic material properties, ease of structuring, mature materials and processes developed for volume production, miniaturization through intelligent integration of passives within the multilayer stack make LTCC a more complete material option than the traditionally used organic substrates. This is extra meaningful for harsh environments, where dielectric, chemical and mechanical properties of the material are constantly challenged by hostile environment parameters such as temperature, humidity, vibration. Moreover, the possibility to integrate electrical, optical, mechanical and micro-fluidic platforms in LTCC is also discussed, which fosters development of devices with newer concepts. LTCC technology is also analyzed in terms of cost. The cost improvements through LTCC is usually under evaluated since it is perceived as raw material cost only, most of the times. Although the cost of manufacturing an LTCC circuit is 3-5 times more than that of PCB, cost reduction through miniaturization can significantly compensate the difference, which is mostly the case in consumer electronics such as tablets, smartphones, and laptops. As a conclusion, LTCC is an excellent package material in fabrication of electronic components. It is important and wise to consider its use especially for discrete, critical modules or component blocks, keeping the main frame of the product as an organic substrate such as PCB in order to come up with a product that has an optimized combination of superior qualities and reasonable cost.

References

1. U. Chowdhry and A.W. Sleight, “Ceramics substrates for microelectronic packaging”, Ann. Rev. Mater. Sci., 1987, 17, 323-340. 2. C.A. Harper, Electronic Packaging and Interconnection Handbook, McGraw-Hill, 4th Edition, 2005. 3. R.R. Tummala, R.J.Z. Rymaszewski, A.G. Klopfenstein, Microelectronics Packaging Handbook, Subsystem Packaging – Part 3, Kluwer Academic Publishers, 3rd Edition, 2001. 4. G Kelly, J Alderman, C Lyden and J Barrett, Microsystem Packaging: Lessons from Conventional Low Cost IC, Packaging, J. Micromech. Microeng., 1997, 7, 99–103. 5. QY Research, Research Report on Global and China Low Temperature Co-fired Ceramic (LTCC) Industry, 2014. 6. INEMI, Roadmap for High Performance Systems, 2012, available on http://thor.inemi.org/webdownload/2014/High_Performance_Pkg_WS_070914.pdf 7. R. Hartley, Base Materials for High Speed, High Frequency PC Boards, published in PCB & A, 2002. 8. C. Jacq, T. Maeder, P. Ryser, Sensors and Packages Based on LTCC And Thick-Film Technology for Severe Conditions, Sadhana, 34, 4, August 2009, 677–687. 9. A. Khalil, D. Passerieux, D. Baillargeat, S. Verdeyme, L. Rigaudeau, J. Puech, 150 GHz Band-Pass Filter Using LTCC Technology, IEEE Microwave and Wireless Components Letters, 19, 7, 2009. 10. J. Park, J. Kim, A.C. W. Lu, Y. Shim, J. Kim, Noise Isolation in LTCC-based X/Ku-band Transceiver SiP using Double-Stacked Electromagnetic Bandgap Structure, Proceedings of the IEEE International Symposium on Electromagnetic Compatibility, EMC 2007, 1-6. 11. API Technologies Corp., white paper available on http://micro.apitech.co.uk/uk/products/low-temperature-co-fired-ceramic-ltcc/ 12. DuPont, white paper available on http://www.dupont.com/products-andservices/electronic-electrical-materials/low-temperature-co-fire-ceramicmaterials.html 13. J. Bielawski, G. Slama, A.H. Feingold, C.Y.D. Huang, M.R. Heinz, R.L. Wahlers, Low Profile Transformers Using LTCC Magnetic Tape, 2003. 14. L. Devlin, G. Pearson, J. Pittock, B. Hunt, RF and Microwave Components in LTCC, Sea Ceramic white paper available on www.seaceramics.com/Download/Papers/RF3_WS_LTCC_paper.pdf 15. R. Liu, D. Schreurs, A Low Cost Compact LTCC-Based GaN Power Amplifier Module, Workshop on Integrated Nonlinear Microwave and Millimetre-Wave Circuits (INMMIC), 2011, 1-4. 16. R.E. Mistler, “Tape casting: past, present, potential”, Am. Ceram. Soc. Bull., October 1998, 82-265. 17. “Materials Science and Technology, A Comprehensive Treatment, 17A, Processing of Ceramics”, Edited by R.J. Brook, John Wiley and Sons, 1996, “Tape casting”, by H. Hellebrand, 190-260. 18. “Ceramic Powder Science II”, Edited by G.L. Messing, Ceramic Transactions, 1988, 1 (AB), “Basic requirements for tape casting of ceramic powders” by A. Roosen, 675-692. 19. W.S. Hackenberger, T.R. Shrout, J.P. Dougherty and R.F. Speyer, “Real time observations of LTCC substrate and conductor materials”, ISHM’92 Proceedings, 1992, 82-87. 20. W.S. Hackenberger, T.R. Shrout, J.P. Dougherty and R.F. Speyer, “Sintering phenomena and microstructural development in LTCC multilayer substrates”, ISHM’93 Proceedings, 1993, 215-220. 18 21. J.H. Jean and T.K. Gupta, “Liquid-phase sintering in the glass-cordierite system”, J. Mater. Sci., 1992, 27 (6), 1575-1584. 22. T. Rabe, M. Gemeinert and W.A. Schiller, “Development of advanced low temperature co-fired ceramics (LTCC) ”, Key Eng. Mat., 2004, 264-268, 1181-1184. 23. T. Rabe and W.A. Schiller, “Zero shrinkage of LTCC by self-constrained sintering”, Proceedings of the Ceramic Interconnect and Ceramic Microsystems Technologies (CICMT), 2005. 24. H. Jantunen, A. Uusimäki, S. Leppävuori and R. Rautioaho, “Effect of processing route on thermomechanical properties of low temperature firing ceramic for electronic packaging”, Brit. Ceram. T., 2002, 101 (1), 22-24. 25. C.L. Lo, J.G. Duh, B.S. Chiou and W.H. Lee, “Low-Temperature Sintering and Microwave Dielectric Properties of Anorthite-Based Glass-Ceramics”, J. Am. Ceram. Soc., 2002, 85 (9), 2230-2235. 26. US Patent, US4536535, “Castable ceramic compositions”. 27. “Thick-film Sensors”, Edited by M. Prudenziati, Elsevier, 1994, 73-84. 28. M. Prudenziati, B. Morten, P. Savigni and G. Guizzetti, “Influence of the preparing conditions on the physicochemical characteristics of glasses for thick-film hybrid microelectronics”, J. Mater. Res., 1994, 9 (9), 2304-2313. 29. P. Barnwell, W. Zhang, J. Lebowitz, K. Jones, N. MacDonald, C. Free and Z. Tian, “An investigation of the properties of LTCC materials and compatible conductors for their use in wireless applications”, Proceedings of the IMAPS International Symposium on Microelectronics, 2000, Boston, 659–664. 30. R.C. Sutterlin, G.O. Dayton and J.V. Biggers, “Thick-film resistor/dielectric interactions in a low temperature co-fired ceramic package”, IEEE T. Compon. Pack. B., 1995, 18 (2), 346-351. 31. K.B. Shim, N.T. Cho and S.W. Lee, “Silver diffusion and microstructure in LTCC multilayer couplers for high frequency applications”, J. Mater. Sci., 2000, 35 (4), 813- 820. 32. J.H. Jean and C.R. Chang, “Cofiring kinetics of an Ag-metallized ceramic-filled glass electronic package”, J. Am. Ceram. Soc., 1997, 80 (12), 3084-3092. 33. S.F. Wang and W. Huebner, “Interaction of silver/palladium electrodes with lead-and bismuth-based electrocermaics”, J. Am. Ceram. Soc., 1993, 76 (2), 474-480. 34. R. Zuo, L. Ti, Z.Gui, X. Hu and C. Ji, “Effects of additives on the interfacial microstructure of cofired electrode-ceramic multilayer systems”, J. Am. Ceram. Soc., 2002, 85 (4), 787- 793. 35. T. Martin and D. Schroeder, “Reliability analysis of LTCC MCM’s utilizing silver conductives”, ISHM’94 Proceedings, 1994, 295-300. 36. C.J. Ting, C.S. His and H.Y. Lu, “Interactions between ruthenia-based resistors and corderite-glass substrates in low-temperature co-fired ceramics”, J. Am. Ceram. Soc., 2000, 83 (12), 2945-2953. 37. T. Nakano, T. Iizuka, T. Takada and T. Yamaguchi, “Glass/substrate interaction in model RuO5-glass double layer thick films”, J. Am. Ceram. Soc., 1995, 78 (6), 1705-1707. 38. M. Jackson, M. Pecht, Integral, Embedded, and Buried Passive Technologies, Chapman and Hall/CRC, 2000. 39. S. Al-Taei, D. Haigh and G. Passiopoulos, “Multilayer ceramic integrated circuits (MCICs) technology and passive circuit design”, Proceedings of the London Communication Symposium 2001, 10-11 September 2001, 6th Annual London Conference on Communications, 139-142. 40. M. Jackson, M. Pecht, S.B. Lee and P. Sandborn, “Integral, embedded and buried passive technologies”, from the archive of the Calce Electronics and Products Center, 2003. 19 41. R.L. Brown, A.A. Shapiro and P.W. Polinski, “The integration of passive components into MCMs using advanced low-temperature cofired ceramics”, The International Journal of Microcircuits and Electronic Packaging, 1993, 16 (4), 328-338. 42. R.L. Brown and W.R. Smith, “Embedded passive functions for RF and mixed-signal circuits”, 1997, Proceedings of the 1997 IEEE International Conference on Multichip Modules, 351-356. 43. P.C. Donohue, B.E. Taylor, D.I. Amey, R.R. Draudt, M.A. Smith, S.J. Horowitz and J.R. Larry, “A new low loss lead free LTCC system for wireless and RF applications”, Proceedings of the IEEE International Conference on Multichip Modules and High Density Packaging, 1998, 196-199. 44. K.B. Shim, N.T. Cho and S.W. Lee, “Silver diffusion and microstructure in LTCC multilayer couplers for high frequency applications”, J. Mater. Sci., 2000, 35 (4), 813- 820. 45. V.A. Chiriac and T.-Y. Tom Lee, “Thermal assessment of RF integrated LTCC front end module (FEM)”, IEEE Trans. Adv. Pack., 2004, 27 (3), 545-557. 46. R. Kulke, M. Rittweger, PO. Uhlig, C. Günner, “LTCC-multilayer ceramic for wireless and sensor applications”, 2001, IMST GmbH, paper available on: http://www.taconicadd.com/pdf/technicalarticles--ltccmultilayer.pdf. 47. S.X. Dai, R.-F. Huang, D.L. Wilcox, Sr., “Temperature stable, low loss and low fire dielectric for consumer wireless applications”, Proceedings of the First Chine International Conference on High-Performance Ceramics, October 1998, Beijing, 338- 341. 48. T. Tick, J. Mähönen and H. Jantunen, “Ongoing developments in the LTCC technology beneficial for high-frequency components with advanced performance”, Proceedings of the 2004 Annual Meeting of the Chinese Materials Society, Multilayer Ceramic Devices Section, 2004, Hsin-Chu, Taiwan. 49. H. Jantunen, “Low temperature co-fired ceramic (LTCC) materials for telecommunication devices”, PhD thesis, Department of Electrical Engineering, University of Oulu, Finland, 2001, 15. 50. D. Nair, B. Thrasher, M.A. Smith, DuPont GreenTape 9K7 Materials for Millimeter Wave Applications, DuPont white paper, 2013. 51. H. Dieker, C. Miesner, D. Puettjer, B. Bachl, Comparison of Different LED Packages, Proc. of SPIE, 6797, 2007, 1-12. 52. J. Hu, L. Yang, and M.W. Shin, Thermal and Mechanical Analysis of High-Power LEDs With Ceramic Packages, IEEE Transactions On Device And Materials Reliability, 8, 2, 2008, 297-303. 53. http://www.coorstek.com/materials/ceramics/alumina.php 54. J.P. Bertinet, E. Leleux, J.P. Cazanave, Filtering Capacitors Embedded in LTCC Substrates for RF and Microwave Applications, Industry News on Microwave Journal, 2007. Article available on http://www.microwavejournal.com/articles/5610-filtering-capacitorsembedded-in-ltcc-substrates-for-rf-and-microwave-applications 55. A.F. Horn III, J.W. Reynolds, P.A. LaFrance, J.C. Rautio, Effect of conductor profile on the insertion loss, phase constant, and dispersion in thin high frequency transmission lines, DesignCon 2010. Article available on http://www.rogerscorp.com/documents/1669/acm/articles/Effect-of-conductorprofile-on-the-insertion-loss-phase-constant-and-dispersion-in-thin-high-frequencytransmission-lines.pdf 56. http://www.polarinstruments.com/support/si/AP8155.html 57. X. Wu, D. Cullen, G. Brist, O.M. Ramahi, Surface Finish Effects on High-Speed Signal Degradation, IEEE Transactions on Advanced Packaging, 31, 2008, 1, 182-189. 58. Z. Liu and D.D.L. Chung, “Development of glass-gfree metal electrically conductive thick films”, Transactions of ASME, J. Electron. Packaging., 2001, 123 (3), 64-69. 20 59. S.L. Buedo, E. Boemo, Electronic Packaging Technologies, Universidad Autonoma de Madrid, Lecture Notes. 60. T. Maeder, C. Jacq, I. Saglini, G. Corradini and S. Strässler et al. LTCC thermal gas viscometer – heater module. 4th European Microelectronics and Packaging Symposium - IMAPS, 5, 2006. 61. DuPont, white paper available on http://www.dupont.com/products-andservices/electronic-electrical-materials/uses-and-applications/aerospace-anddefense/uses-and-applications/greentape-for-transceiver-systems.html 62. M. Wagner, A. Roosen, A. Stiegelschmitt, D. Schwanke and F. Bechtold, “In-situ shrinkage measurements of LTCC multilayers by means of an optical dilatometer”, Key Eng. Mater., 2002, 206-213, 1281-1284. 63. S.H. Lee, G.L. Messing and D.J. Green, “Warpage evolution of screen printed multilayer ceramics during co-firing”, Key Eng. Mater., 2004, 264-268, 321-330. 64. A. Roosen and M. Wagner, “Characterization of the shrinkage behavior of pure, screen printed thick film pastes and LTCC green tapes”, Proceedings of the International Microelectronics and Packaging Society (IMAPS-CTI) Meeting, 2004, Denver. 65. H. Birol, T. Maeder, C. Jacq and P. Ryser, “Investigation of Interactions Between Cofired LTCC Components”, Journal of the European Ceramic Society, 2005, 25, 12, 2065- 2069. 66. H. Birol, T. Maeder, P. Ryser, Modification of Thick-film Conductors Used in IP Technology for Reduction of Warpage during Co-firing of LTCC Modules, Key Engineering Materials, High Performance Ceramics IV, 2006, 746-749. 67. H. Birol, T. Maeder, I. Nadzeyka, M. Boers, P. Ryser, Fabrication of a Millinewton Force Sensor Using Low Temperature Co-fired Ceramic (LTCC) Technology, Sensors and Actuators A: Physical, v.134, 334-338, 2007. 68. H. Birol, T. Maeder and P. Ryser, "Influence of Processing and Conduction Materials on Properties of Co-fired Resistors in LTCC Structures", Journal of the European Ceramics Society, 2006, 26 [10-11], 1937-1941. 69. H. Birol, T. Maeder, P. Ryser, Materials Compatibility Issues in LTCC Technology and Their Effects on Structural and Electrical Properties, Proceedings of the 1st CICMT Conference on Ceramic Interconnect Technology, Baltimore-USA, 2005, 300-309. 70. LTCC-Based RF Frontends for WLAN Applications and Radio-Over-Fiber Systems, PhD Thesis, Luca Pergola, ETHZ, 2007. 71. S. Francomacaro, D.K. Wickenden, S.J. Lehtonen, F. Tejada, Microelectronic Substrates for Optoelectronic Packages, Johns Hopkins Technical Digest, 28/1, 2008, 41-48. 72. T.Y. Kau, 60-GHz CMOS Micro-Radar System-In-Package for Vital Sign and Vibration Detection, PhD Thesis, University of Florida, 2013. 73. F. Bechtold, Perspective of LTCC Technology for System in Package and MEMS Packaging, Via Electronic, White Paper, 2011. 74. F. Bechtold, Comprehensive Overview on Today`s Ceramic Substrate Technologies, EMPC Proceedings, 2009, 1-12. 75. Intel press release, Intel Announces First Commercial Availability of 4G LTE Modem; Introduces Module for 4G Connected Tablets and Ultrabooks™, available on http://newsroom.intel.com/community/intel_newsroom/blog/2013/10/30/intelannounces-first-commercial-availability-of-4g-lte-modem-introduces-module-for-4gconnected-tablets-and-ultrabooks.76. http://electronics360.globalspec.com/article/3604/samsung-galaxy-tab-10-1-inch-ltetablet-teardown 21

About CSEM Brasil

CSEM Brasil is a tech start up founded by BNDES (Brazilian National Bank for Development), FIR Capital (one of the leading VCs of LATAM in technology), Minas Gerais State Government and CSEM Switzerland in the state capital of Minas Gerais, Belo Horizonte in 2007. The company is an extension of CSEM AG (Swiss Centre for Electronics and Micro-technology) and aims to turn technology into products and services essential for industry and society. The company has exemplar infrastructure and teams to dominate the two business areas: ceramic microsystems with focus on LTCC and OPV (organic photovoltaics). LTCC facility is a state of the art prototyping and production center with a complete LTCC and SMD line. Being strategic partner with several highly-respected companies and institutes all around the world, CSEM Brasil constantly looks for innovative solutions to provide to its clients and partners.