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Interlevel Connections For MLC

IP.com Disclosure Number: IPCOM000048772D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Desai, KS: AUTHOR [+2]

Abstract

Improved interlevel connections for MLC (multilayer ceramic) substrates are achieved by providing a contact pad for via-via connections and for via-to-line connections.

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Interlevel Connections For MLC

Improved interlevel connections for MLC (multilayer ceramic) substrates are achieved by providing a contact pad for via-via connections and for via-to-line connections.

MLC substrates have a large number of vias (e.g. 250 K for some modules) that are used to provide interlevel connections. Since a single defective connection can result in an entire substrate being rejected, it is clear that the manufacturing process must produce a product with very little defect count.

Fig. 1A shows a via-via connection where misregistration causes an open circuit condition. Fig. 1B shows the same via-via connection where the contact pad ensures contact. Fig. 2A shows a further arrangement where an open circuit condition exists in a via-via connection due to a partially filled via. Fig. 2B shows the same partially filled via condition as exists in Fig. 2A but where the contact pad acts to complete the circuit.

In Fig. 3, an alternative contact pad scheme is employed in the form of an "end flash". As shown in Fig. 3A, a defect in upper line 1 may cause the via represented by dotted circle 3 to short lines 1 and 5. The condition in Fig. 3A is such that the inspection system employed would consider the distance between lines 1 and 5 sufficient that no short would occur. On the other hand, with the "end flash" shown in Fig. 3B, the inspection system would reject the particular MLC sheet because of the possible shorting condition, and the substrate would...