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45 Degrees Wiring Layers for a Thin Film Module Package

IP.com Disclosure Number: IPCOM000052646D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Deutsch, A: AUTHOR [+2]

Abstract

This article describes a method of routing interconnecting wires for chips mounted on a ceramic substrate. In the conventional approach, a square array of chips is connected using thin film metal lines buried in an insulator, such as polyimide. The two metal layers (called X and Y) are mutually orthogonal and parallel to the sides of the ceramic substrate, as shown in Fig. 1.

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45 Degrees Wiring Layers for a Thin Film Module Package

This article describes a method of routing interconnecting wires for chips mounted on a ceramic substrate. In the conventional approach, a square array of chips is connected using thin film metal lines buried in an insulator, such as polyimide. The two metal layers (called X and Y) are mutually orthogonal and parallel to the sides of the ceramic substrate, as shown in Fig. 1.

Because of the high wiring density requirements for interconnecting VLSI (very large-scale integration) chips on the module, the transmission lines have very small line dimensions and, therefore, significant resistive losses which limit the maximal allowable transmission line length. Eor example, assume a line pitch of about 25 Mum. The resultant 8 Mum wide line can support pulse propagation with no more delay compared with lossless lines up to 15 cm long. However, for the module to carry 100 chips, it should have a dimension of 10 cm on the side. This implies that the maximum module wire length is 20 cm, and there could be non-negligible delay for signals propagating on those long lines.

In the approach of Fig. 2, X and Y conductors are oriented at 45 Degrees with respect to the side of substrate axes 12, 13. In this case, the chips are also oriented parallel with the interconnecting wires. The center-to-center distance between wires is kept the same so that the total wiring supply remains the same.

The advantage of this approach is that the maximum wiring length is reduced by as mu...