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Variable Grid and Size Stand-Offs

IP.com Disclosure Number: IPCOM000046607D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 97K

Publishing Venue

IBM

Related People

Desai, KS: AUTHOR [+4]

Abstract

A solid power plane screening mask for multilayer ceramic (MLC) applications is designed to have a variable stand-off size and a variable grid arrangement such as to minimize the paste covered area while providing for interlevel contacts and meeting sheet resistance requirements. Solid power plane screening masks for MLC have stand-offs placed in a pattern to prevent collapse of the mesh against the MLC greensheet during screening. Stand-off designs in use involve an array of uniform diameter stand-off dots (on a 0.5 mm grid arrangement, as shown in Fig. 1). This is satisfactory for preventing mesh collapse. In order to prevent delamination or excessive camber, it is desirable to reduce the metal covered area of the sheet.

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Variable Grid and Size Stand-Offs

A solid power plane screening mask for multilayer ceramic (MLC) applications is designed to have a variable stand-off size and a variable grid arrangement such as to minimize the paste covered area while providing for interlevel contacts and meeting sheet resistance requirements. Solid power plane screening masks for MLC have stand-offs placed in a pattern to prevent collapse of the mesh against the MLC greensheet during screening. Stand-off designs in use involve an array of uniform diameter stand-off dots (on a 0.5 mm grid arrangement, as shown in Fig. 1). This is satisfactory for preventing mesh collapse. In order to prevent delamination or excessive camber, it is desirable to reduce the metal covered area of the sheet. However, sheet resistance requirements must be met to assure satisfactory electrical performance, and via contact areas must be present to assure interlevel connections to the power plane.

Fig. 2 shows a design where stand-offs 1 have been removed from paths that are low in metal because of via isolation donuts 3. This improves the sheet resistivity in locally poor areas and allows for reducing the paste covered area to a greater extent elsewhere. Fig. 3 shows a further design where stand-off diameters have been increased.

Note that stand-offs close to contact vias, such as shown at 5, remain small so as to assure contact to the power plane. Stand-off shapes may be other than round. For example, square or hexag...