Browse Prior Art Database

Coupled Noise Reducer

IP.com Disclosure Number: IPCOM000050635D
Original Publication Date: 1982-Nov-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Bilodeau, L: AUTHOR [+3]

Abstract

It has been found that electrically "coupled noise" between metal lines on a dielectric substrate for packaging I/C chips, which is associated with long line lengths, can be reduced by providing material with a high dielectric constant (Epsilon(r)) in close proximity over the lines, while leaving an air gap between the lines.

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Coupled Noise Reducer

It has been found that electrically "coupled noise" between metal lines on a dielectric substrate for packaging I/C chips, which is associated with long line lengths, can be reduced by providing material with a high dielectric constant (Epsilon(r)) in close proximity over the lines, while leaving an air gap between the lines.

Fig. 1 shows one technique for providing such a high dielectric material. In this figure, a ceramic substrate 10 has conventional metal lines 12 formed on the surface thereof. A cap 14 of high dielectric material, such as silicon (Epsilon (r) =12.0), is connected by means of solder joints 16 and pads 18 on the substrate 10, the lower surface of the cap 14 being positioned to closely overlie the lines 12, preferably at a distance of no more than about 4 mils. Preferably, but not essentially, grooves 22 are formed in the cap 14 to increase the air gap (Epsilon(r)=1.0) between adjacent lines 12 on the substrate.

For very high performance applications, reference planes may be required, as shown in Fig. 2. This embodiment is similar to Fig. 1, but the silicon cap 30 has a flat bottom surface, and a ground plane 32 is diffused therein. Also, a ground plane 34 is buried in the ceramic substrate 10.

Figs. 3A and 3B illustrate a two-step process for forming yet another embodiment of this technique. In Fig. 3A, a substrate 10 with metal lines 12 formed therein is shown with a high dielectric material 40, such as polyimide filled ...