The System-level Simulation by Building Macromodels

Numerical algorithms, like FEM, BEM, and FVM, can be used for individual fields, and appropriate iterations are needed between the coupled fields to obtain system performance;

the methods have high accuracy, but with the cost of large and time-consuming calculations.

In practice, designers may not painstakingly search for the local features of the system, but instead focus on overall performance, and input-output properties; therefore, macro models may be used for the simplified analysis of coupled fields and the reduction of the degree of freedom. There is no universal method for the buildup of the macro model. The three methods in common use include:

(1) NODAS (node analysis). The system under consideration is regarded as consisting of multiple basic blocks of identical energy domain or various energy domains, with each block acting as a node, just like the fundamental elements in circuitry, such as resistor and capacitors. By using the VHSI Hardware Description Language (VHDL) languages to unite the nodes with practical circuits to form a network, the differential equations may be constructed and simulated by calling SABER or SPICE. The NODAS method has been developed for micro actuators and sensors and described in a lumped element way, so it is not sufficient for complex microsystems.

(2) Black-box model. Realizing the analysis in various energy domains and selecting a few parameters to depict the system energy will greatly reduce the degrees of freedom, without stressing the localized structure and properties, and thus the coupled field will be converted into a black-box model. The steps are a) reduce the degrees of freedom, b) construct the macromodel of the system, c) convert the dynamic equation into A-HDI, which is inserted into analog circuit simulators as a black box. As long as the complete set of deformation and the energy expressions of the system are rationally constructed, calculations with extremely high precision can be obtained. However, the localized features cannot be taken into consideration, and the effect of the structural dimensions of individual components on the system performance cannot be explicitly revealed, which may not facilitate the design and will come with a large calculation amount.

(3) The VHDL-AMS method is to set up a set of normal differential and algebraic equa-tions depicting the component dynamic properties, on the basis of the law of energy conser-vation. It models large quantities of fundamental components to form corresponding library elements, so that the existing system-level simulator Saber can be used for the simulation on the micromachined elements in tandem with circuitry. If the boundary conditions of the device vary, the VHDL-AMS source code of corresponding devices may be immediately modified and simulated. However, VHDL-AMS is only capable of modeling with normal differential and algebraic equations and is useless for the analysis that involves partial dif-ferential equations representing the dynamics of some devices.

The readers may refer to the literature^[32,36] for further reading on typical case studies of multi disciplinary design, and to the literature^[37−39] for an in-depth analysis of multi disciplinary modeling and simulation methodologies for engineering problems.

Though various methodologies have been presented above, the unified and top-down de-signing, modeling, and simulation solutions for the closely intertwined fields involved in a highly integrated microsystem or SIP are yet to come. However, with the continuous

in-34 Chapter 2 Design Technique for Microsystems Packaging and Integration crease in the calculation power of PCS and workstations and the accumulation of relative knowledge, powerful, versatile, and unified tools will be available in the near future for developers assigned to microsystems or SIP designs.

Questions

(1) What does the design principle for microsystem packaging mainly contain?

(2) What are differences between the design techniques for microsystem and microelec-tronics?

(3) Please describe the design tools widely used for microsystems and give a regular design procedure.

(4) Give the major steps for the multidisciplinary design of a specific microsystem, such as an accelerometer/inertial measuring unit.

References

[1] R. R. Tummala. Fundamentals of Microsystems Packaging. New York: McGraw-Hill, 2001.

[2] J.H. Lau, C.P. Wong, J.L. Prince, et al. Electronic Packaging: Design, Materials, Process and Reliability. New York: McGraw Hill, 1998.

[3] H.B. Bakoglu. Circuits, Interconnections and Packaging of VLSI. Boston: Addison-Wesley, 1985.

[4] W.D. Brown. Advanced Electronic Packaging—With Emphasis on Multichip Modules. IEEE Press, 1998.

[5] H.W. Johnson and M. Graham. High Speed Digital Design: A Handbook of Black Magic.

Upper Saddle River, NJ: Prentice Hall, 1993.

[6] D.M. Pozar. Microwave Engineering. Boston: Addison-Wesley, 1990.

[7] S. Rosenstark. Transmission Lines in Computer Engineering. New York: McGraw-Hill, 1994.

[8] S. Senthinathan. and J.L Prince. Simultaneous switching ground noise calculation for packaged CMOS devices. IEEE Journal on Solid-State Circuits, 26.11 (1991): 1724–1728.

[9] R.R. Tummala and E.J. Rymaszewski. Microelectronics Packaging Handbook. London: Chap-man and Hall, 1997.

[10] A. Kraus. The Use of Steady State Electrical Network Analysis in Solving Heat Flow Problems.

2nd National ASME-AIChE Heat Transfer Conference. 1958.

[11] P.I. Frank and P.D. David. Fundamentals of Heat and Mass Transfer. Fourth Edition. New York: John Wiley and Sons, 1996.

[12] W.H. McAdams. Heat Transmission. New York: McGraw Hill, 1954.

[13] J. Howell. A Catalog of Radioactive Transfer Factors. New York: McGraw Hill, 1982.

[14] Luciana W. da Silva and M Kaviany. Miniaturized thermoelectric cooler. Proceedings of IMECE’02, 2002, 1–15.

[15] A. Bergles, A. Bar-Cohen. Advances in Thermal Modeling of Electronic Components and Systems, New York: ASME Press, 1990.

[16] J. Lau and G. Barrett. Stress and Deflection Analysis of Partially Routed Panel for Depanel-ization. IEEE Transactions on CHMT, 10.3 (1987): 411–419.

[17] A.P. Boresi, O.M. Sidebottom. Advanced Mechanics of Materials. New York: John Wiley and Sons, 1984.

[18] J.H. Lau. Creep of Solder Interconnections under Combined Loads. IEEE Transactions on CHMT, 8 (1993): 794–798.

References 35

[19] K. V. Sharp, R. J. Adrian and J. G. Santiago, et al. Liquid flows in microchannels. Personal Communication, 2001.

[20] Minglun Xue, Zhanhua Li, Some limitations of the digital micro propulsion miniature. Micro-Nanometer Science and Technology, 5 (2000): 125–127.

[21] G.H. Mohamed The fluid mechanics of microdevices—the Freeman scholar lecture. Journal of Fluids Engineering, 121 (1999): 5–33.

[22] A.D. Stroock, M. Weck. D. T. Chiu et al. Patterning electro-osmotic flow with patterned surface charge. Physical Review Letters, 84.15 (2000): 3314–3317.

[23] Yong Li, Min Guo, Zhaoying Zhou, et al., Micro electro discharge machine with an inchworm type of micro feed mechanism. Chinese Journal of Scientific Instruments, 17 (1996): 56–60.

[24] P. Gravesen, J. Branebjerg, and O.S. Jensen. Microfluidics–a Review. Journal of Microme-chanics and Microengineering, 3 (1993): 168–182.

[25] Xiaoning Jiang, Yong Li, Zhaoying Zhou, et al. Experimental Study on Flow Behaviour of Fluid in Micro-Pipe. Proceedings of International Symposium on Manufacturing Science and Technology for the 21st Century (MST’94), (1994): 118–122.

[26] J. Pfahler, J. Harley, H. Bau, et al. Liquid Transport in Micron and Submicron Channels.

Sensors and Actuators, A21–A23 (1990): 431–434.

[27] Makihara Mitsulhiro, Sasakura Kunihiko, Nagayama Akira. The flow of liquids in micro-capillary tubes: consideration to application of the Navier-stokes equations. Journal of the Japan Society of Precision Engineering 59 (3), (1993): (399–404)

[28] Xiaoning Jiang, Zhaoying Zhou, Yong Li, et al. Study on Microfluid Flow Behaviour. Optics and Precision Engineering, 1995, 3(3): 51–55.

[29] Zhanhua Li and Haihang Cui. Characteristics of Micro Scale Flow. Journal of Mechanical Strength, 4 (2001): 476–480.

[30] Xiaoning Jiang, Zhaoying Zhou, Yong Li, et al. Study on Microfluid Flow Behaviour. Chinese Journal of Scientific Instruments. 1995, 16(1), 346–350.

[31] D.S. Xu, A Primary Study on the Chip Preprocessing Blood Sample for Bio-MEMS Applica-tion, Master, thesis, Beijing University, 2007.

[32] Paul Galambos and Gil Benavides of Sandia National Labs. Electrical and Fluidic Packaging of Surface Micromachined Electro-Microfluidic Devices. Proceedings of SPIE, 2000 (4177):

200–207.

[33] www.ansys.com

[34] http://www.simulia.com/

[35] http://www.coventor.com/

[36] Luciana W. da Silva and M. Kaviany. Miniaturized thermoelectric cooler. Proceedings of IMECE’02, 2002, 1–15.

[37] C. A. Felippa, K. C. Park and C. Farhat. Partitioned Analysis of Coupled Mechanical Systems [J]. Computer Methods in Applied Mechanics and Engineering, 2001, 90 (24–25): 3247–3270.

[38] C. Boivin, and C. Ollivier-Gooch. A Toolkit for Numerical Simulation of PDEs II. Solving Generic Multiphysics Problems [J]. Computer Methods in Applied Mechanics and Engineering, 2004, 193 (36–38): 3891–3918.

[39] Michael A. Weaver. Nonlinear multi-discipline analysis of conjugate heat transfer and fluidic-structure interaction, Ph.D. Dissertation, Georgia Institute of Technology, September, 1997.

CHAPTER 3

Substrate Technology

3.1 Introduction

A substrate is a board onto which a number of individual electrical components, de-vices, and modules are integrated into functional electronic systems. It is a critical part of microsystems packaging. The ongoing development of IC chip technology and assembly technology has resulted in increasingly high requirements for the performance of substrates.

Challenges faced by substrate technology mainly come from the following three areas:

(1) Development of microelectronic devices. Microelectronic devices with larger area, quad flat package, surface mount, array pin, I/O, and finer lead pitch are becoming the trend;

(2) Development of passive components. Leadless, miniaturized, SMC technology is re-quired to design, to fabricate together with the substrate, and furthermore to be buried into the substrate. (3) Applications in microsystems. Advanced applications prefer sub-strate with higher wiring density, finer interconnection between layers, and three-dimensional structure.

Substrates used in microsystems packaging mainly falls into the following three categories:

(1) Organic substrates, including paper substrate, woven glass substrate, composite ma-terial substrate, epoxy-resin substrate, polyester resin substrate, or heat-resistant plastic substrate, flexible substrate, multilayer wiring substrate, and so on.

(2) Inorganic substrates, including metal substrate, ceramic substrate, glass substrate, silicon substrate, diamond substrate, and so on.

(3) Composite substrates.

Substrate selection and design requires consideration of a number of factors, mainly in-cluding material parameters, electrical parameters, thermal parameters, and configuration parameters.

(1) Material parameters include electrical permittivity, coefficient of thermal expansion, thermal conductivity, and so on.

(2) Electrical parameters.

(I) To reduce Tpd(time of propagation delay) of substrates, lower electrical permittivity is required.

(II) Matches of various characteristic impedances of different parts within a system should be considered.

(III) To reduce parasitic L, C, and R, it is necessary to minimize leads spacing, use substrate materials with low magnetic conductivity and low electrical permittivity.

(IV) To reduce cross-talk noises, avoid parallel wiring with overdense lines and use of substrate materials of low electrical permittivity.

(V) Prevent signal reflection noise with proper circuit patterns.

(3) Configuration: finer wiring patterns, smaller through-holes for interconnection between layers, and optimization of different electrical parameters are required.

(4) Thermal parameters: key parameters, including thermal-resistance and thermal ex-pansion coefficient of the substrate, should be considered, for example, good thermal match with chip materials such as Si.