Connected ground and floating plane package design and electrical analysis

Kerr, M.K.; Moore, S.; Lawson, Wayne

doi:10.1109/ectc.1994.367511

Cited by 5 publications

(3 citation statements)

References 2 publications

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“…The floating plane adds to the mutual effect of the ground-signal pair and reduces . This agrees with the finding by Kerr and Moore [8]. According to [8], a floating plane could aid in reducing simultaneous switching noise, but the findings in this paper suggest that a floating plane should be avoided in multilayer packages.…”

Section: Discussionsupporting

confidence: 94%

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Influence of a floating plane on effective ground plane inductance in multilayer and coplanar packages

López

Prince

Cangellaris

1999

IEEE Trans. Adv. Packag.

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The impact of a floating metal layer on the effective ground plane inductance has been investigated in both multilayer (ground planes) and coplanar (ground conductors) packages. For the multilayer case, both thick and thin film geometries were examined, and the results were compared to a thin film coplanar configuration. It was seen that the floating plane actually increases the ground plane inductance in the multilayer case and decreases the ground plane inductance in the lead frame case. Examining the current density in the floating and ground plane and the ground's partial self-inductance and ground-signal partial mutual inductance give a detailed explanation for this phenomenon.Index Terms-Coplanar transmission line, eddy currents, floating metal, package inductance, stripline transmission line.

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Section: Discussionsupporting

confidence: 94%

“…This agrees with the finding by Kerr and Moore [8]. According to [8], a floating plane could aid in reducing simultaneous switching noise, but the findings in this paper suggest that a floating plane should be avoided in multilayer packages. The structure examined in [8] was a lead frame package and not a multilayer package.…”

Section: Discussionsupporting

confidence: 94%

Influence of a floating plane on effective ground plane inductance in multilayer and coplanar packages

López

Prince

Cangellaris

1999

IEEE Trans. Adv. Packag.

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“…The effectiveness of this same floating ground plane was previously shown for both PGA and C4 QFP packages [9]. These data show that the performance of this floating plane structure approaches that of a connected ground plane for both simultaneous switching noise and system clock speed.…”

supporting

confidence: 56%

A low-cost metal ball grid array for flip chip die

Wilson¹,

Moore²,

Laine³

1995 Proceedings. 45th Electronic Components and Technology Conference

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A low cost ball grid array package has been developed for use with flip chip die. The structural "back bone" of this chip carrier is a metal plate which serves as a built-in heat spreader and a floating ground plane as well as the principal structural member of the package.Thin film circuitry is employed to make the necessary connections between the die and the solder balls. The fine line circuitization enables escape of many I/O from the flip chip die and thus a high VO package with only a single layer of circuitry. The circuit lines are separated fi-om the metal plate by means of a thin polymer dielectric layer. The die is attached to the carrier with a conventional high temperature C4 attach process. The ball grid array is on a 1.27 mm pitch.The metal plate that serves as the structural member of this package provides a number of benefits. The coefficient of thermal expansion (CTE) of the metal plate is very close to the CTE of the circuit card. The size of the package is not limited, therefore, in order to prevent fatigue and fracture of solder balls. The metal plate is separated fi-om the circuitry by only a thin layer of dielectric material. The plate thus serves as a very effective floating ground plane and thereby provides improved electrical performance. The plate also serves as an effective heat spreader, again because of the thin dielectric layer separating the metal plate fiom the circuitry, the die and the solder balls. If added thermal performance is desired, a heat sink is easily attached to the backside of the metal plate.The thin film circuitry employed in this package also provides a number of benefits. The die and the solder balls are connected by a single layer of circuitry. Since electrical vias are not required, low cost processing is possible. Circuitization of the thin film metal can produce extremely fine lines and spaces; more than 700 U 0 can be handled in a single layer.

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