MCM Design Research Articles

Thermal placement algorithm based on heat conduction analogy

A thermal force-directed placement algorithm, called TFPA, based on heat conduction analogy, is proposed for MCM design. TFPA begins with the transformation of the real substrate with chips into an unbounded substrate with an infinite number of chips. Then, each chip pushes every other chip with a force based on the heat conduction analogy. Thus, each chip will move in the direction of the force until the system achieves equilibrium. TFPA generates high quality placement results and maintains a cooler and uniform thermal profile, by distributing chip powers as evenly as possible. Unlike conventional force-directed algorithms, which might have serious component overlapping problems, TFPA places chips apart and only little or even no overlap occurs. In practice, the initial placements obtained by TFPA are very close to final placements.

MCM technology and design for the S/390 G5 system

MCM technology and design for the S/390 G5 system

Design standards for effective MCM design

MCM design requires many elements of both IC and printed circuit board (PCB) design. The combination of industry standards and well developed processes is yielding excellent design systems for leading electronics firms. The MCM industry, however, is lacking many of the standards necessary for creating effective design systems. Significant efforts need to be made to overcome major shortcomings in industry infrastructure, concurrent engineering, staff expertise, and design tools. The current state of MCM design is assessed using the IC design process as an positive example. Significant industry investment has yielded enormous gains in IC design productivity, time-to-market, and functional costs. The electronic packaging industry can benefit from similar approaches. Successful MCM design first requires a standard method for modeling all of the elements in a design, including the components, substrates, assembly processes, and performance requirements. Data for these models must be gathered from a wide range of sources; it is not unusual on a single design to receive information from 20 manufacturers. Since data gathering is very time-consuming, these models should be available before starting actual designs. The paper gives detailed examples of specific issues concerning modeling components, substrates, and assemblies. Systems for capturing die data, substrate design rules, and assembly design rules are described. These systems are being used in work conducted as part of the IMAPS' Ceramic Interconnect Initiative. The results of developing and using design standards will be significant: better products built at lower cost and brought to market quickly.

The Intelligent Multichip Module Analyser: A Thermal Design Tool

The Intelligent MCM Analyser (IMCMA) is a software tool which allows the designer to concurrently assess the reliability of an MCM design based on operational parameters. Traditionally, this type of assessment takes days to accomplish and is performed after the design phase. The Intelligent MCM Analyser does not require the designer to be a thermal/reliability expert and gives an assessment in minutes depending on the complexity of the design and the speed of the computer. IMCMA assists and designer in achieving a robust design which will improve both quality and reliability. The software uses object‐oriented data representation, a blackboard architecture and heuristic expertise to perform lower level reasoning associated with finite element thermal analysis techniques that are normally very tedious and labour intensive. A test case is presented comparing results from IMCMA with the results from a general purpose finite element code. The ultimate pay‐off will be the manufacturer's ability to build higher quality, higher reliability MCMs at a lower cost.

M/sup 2/R: multilayer routing algorithm for high-performance MCMs

We introduce a new multilayer routing strategy for high-performance MCMs whose objective is to route all nets optimizing routing performance and to satisfy various design constraints (e.g., minimizing coupling between vias as well as between signal lines and minimizing discontinuities such as vias and bends). First we introduce the Pin Pre-wiring and Redistribution Problem, which redistributes the pins or prewired subnets uniformly over the MCM substrate using pin redistribution layers. Pin redistribution is very important in MCM design. Our experience shows that it not only provides a global distribution for the pins congested in the chip site over the chip layer so as to ease the future routing difficulty, but also reduces the capacitive coupling between vias induced by many layers (up to 63 layers) by separating the pins far apart. The goal of the problem is to minimize the number of layers required to redistribute the entire set. An effective approach is proposed for solving this problem. Next we develop four effective algorithms for signal distribution, i.e., two variations on both single-layer routing and xy plane-pair routing paradigms. Based on these algorithms, a mixed version of single-layer routing and xy plane-pair routing techniques is proposed to establish a good trade-off between them to favor circuit performance and/or design objective instead of overemphasizing on the area minimization. One strategy is to apply single-layer routing iteratively until /spl alpha/ % of the nets are routed, then route the remaining (100/spl minus//spl alpha/)% nets by xy plane-pair routing process. This provides the designer with a trade-off (e.g., between the number of layers and total number of vias) and shows the versatility of the proposed techniques. Various strategies are compared using practical MCM examples (each MCM has 25-100 ICs, 25-60 I/Os per IC, and 50-1,200 nets).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A computer aided design tool for robust multichip module package design

A novel methodology for design assessment of MCM packages is presented using finite element analysis and a Taguchi based design of experiments technique. This methodology enables the design engineer to rapidly estimate the quality of candidate designs and thereby select better designs. The proposed method allows the designer to generate a robust finite element model of the physical process which is also numerically efficient, to identify the design parameters that are critically important to the performance of the design and also to investigate the effect of tolerances on the significant design parameters. A detailed description of the methodology is presented along with a MCM design example to illustrate the proposed method. >

DESIGN AUTOMATION FOR MULTICHIP MODULE — ISSUES AND STATUS

In this paper we will review the current state of commercial electronic design automation (EDA) tools for the design of multichip modules. MCM can be classified in terms of its substrate technology. The choice of substrate technology has important implications for the selection of design automation tools. A PCB EDA system seems more appropriate for MCMs with stacked via substrate which closely resembles the through-hole printed circuit board (PCB). A chip layout system may be more appropriate for MCMs with low-cost thin-film silicon substrate which typically uses staircase vias. The cofired ceramic substrate MCM which evolved from the hybrid integrated circuit technology may use the specialized hybrid EDA software packages available for the designing of hybrid integrated circuits. Historically, printed circuit board and integrated circuit design automation software evolved separately. There exists a boundary between the printed circuit board and integrated circuit design automation tools in the physical design hierarchy. This boundary can be an important limitation for the repartitioning of the physical design hierarchy within the MCM. We shall discuss in detail the impact of MCM on various aspects of EDA. In the area of physical design, we must face the traditional placement and routing problem for any high speed design. Problems such as system clock skew and tight timing requirements must be considered. As one push clock frequency higher, one also must consider discontinuities due to vias and bends besides the classical transmission line effect due to long wires. Other traditional physical design problems such as ground and power plane generation, physical design verification and mask tooling must be revisited in the context of various MCM substrate technologies. The thermal aspects of MCM design are strongly influenced by the placement of chips on the MCM substrate. Thermal design is especially important for high density MCMs using the flip-chip mounting technology. Here, the heat must be dissipated through the back of the substrate via thermal pillars or bumps. We still need to deal with the traditional coupled transmission line problems. Due to the small cross section, high performance MCM substrate interconnects are resistive and the transmission lines they form are lossy. Noise is another main problem for MCM design. For high speed MCM with many CMOS buffers, the ground bouncing noise resulting from simultaneous switching of a large number of CMOS drivers must be controlled through proper substrate and package design. We will conclude the paper by comparing existing VLSI and PCB EDA tools for MCM design.