Lewis S. Goldmann

An advanced multichip module (MCM) for high-performance UNIX servers

In 2001, IBM delivered to the marketplace a high-performance UNIX?®-class eServer based on a four-chip multichip module (MCM) code named Regatta. This MCM supports four POWER4 chips, each with 170 million transistors, which utilize the IBM advanced copper back-end interconnect technology. Each chip is attached to the MCM through 7018 flip-chip solder connections. The MCM, fabricated using the IBM high-performance glass-ceramic technology, features 1.7 million internal copper vias and high-density top-surface contact pad arrays with 100-?µm pads on 200-?µm centers. Interconnections between chips on the MCM and interconnections to the board for power distribution and MCM-to-MCM communication are provided by 190 meters of co-sintered copper wiring. Additionally, the 5100 off-module connections on the bottom side of the MCM are fabricated at a 1-mm pitch and connected to the board through the use of a novel land grid array technology, thus enabling a compact 85-mm ?? 85-mm module footprint that enables 8- to 32-way systems with processors operating at 1.1 GHz or 1.3 GHz. The MCM also incorporates advanced thermal solutions that enable 156 W of cooling per chip. This paper presents a detailed overview of the fabrication, assembly, testing, and reliability qualification of this advanced MCM technology.

Measurement of solder–flux–vapor surface tension by a modified maximum bubble pressure technique

While it is widely known that flux is needed to maintain an oxide‐free surface during soldering, the fact that flux also reduces the surface tension between solder and ambient is neither widely recognized nor treated extensively in the literature. An apparatus is described which quantitatively evaluates the reduction of surface tension in the presence of flux. Representative data of eutectic lead–tin with water white rosin fluxes are presented.

Product Connector Technology

The use of product connectors has mainly involved high-end applications. Electronic modules normally represent a function, and one or more multichip modules typically are combined on a card or board. It is important that some or all the individual modules be easily separable to permit testing, diagnositcs and field repair, and that the separable connections not functionally degrade the electrical signals [1]. The intent is to preserve the value of a board and its attached components while having the capability to make repairs or upgrades through component exchanges throughout the lifetime of a part. Several early area-array “compression connection” concepts were reported in the mid 1980s/early 1990s that recognized that a disassembly design must also be capable of high I/O density to accommodate ever increasing I/O counts (i.e., extendible to decreasing pitches).

Creep Characterization Of Ceramic BGA

Long term creep of a ceramic ball grid array (CBGA) solder ball under compressive loading was investigated. An experiment was conducted with two levels of loading and four of temperature. Analysis of the data assumed the composite ball structure could be simulated by an interconnection having the same shape, but of a single equivalent material. Curve fitting determined the stress exponent and activation energy of the equivalent material in the Norton creep model; the values were consistent with the range of values of the individual components available in the literature. Nonlinearity of the change in ball height with time was hypothesized to be due to geometric stiffening, a hypothesis which was confirmed by a simplified model. The model may be used to estimate creep behavior of other ball geometries having the same material set. The final result of this work - a closed form equation describing height decrease as a function of compressive force, temperature and time - can be used to simplify complex model...