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Redundant Circuit Personalization at the Module Level

IP.com Disclosure Number: IPCOM000051586D
Original Publication Date: 1981-Feb-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Coullahan, JP: AUTHOR [+3]

Abstract

A technique is described that enables the use of redundancy in memory chips but requires only a single part number. By removing solder balls when no connection is desired between the chip and the module substrate, redundancy can be used to increase yields with no increase in the number of part numbers. Consider the chip wiring and pad array shown in Fig. 1. The diagram is illustrated for a three-bit memory chip with one bit of redundancy. The technique may readily be extended to a chip having a larger number of bits. The chip is depicted with pads down.

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Redundant Circuit Personalization at the Module Level

A technique is described that enables the use of redundancy in memory chips but requires only a single part number. By removing solder balls when no connection is desired between the chip and the module substrate, redundancy can be used to increase yields with no increase in the number of part numbers. Consider the chip wiring and pad array shown in Fig. 1. The diagram is illustrated for a three-bit memory chip with one bit of redundancy. The technique may readily be extended to a chip having a larger number of bits. The chip is depicted with pads down.

Fig 2 shows the associated module wiring to accommodate the chip of Fig. 1. Let one assume, for example, that bit 1 of the three-bit array was defective. Fig. 3 shows a composite drawing of how a good three-bit array is provided using redundancy.

Fig. 3 depicts a connection from the bit 1 chip pads to the module in a manner that substitutes the redundant bit for the bad bit. This is accomplished by selectively removing solder pads at the proper locations on the chip. Note that external to the module it appears that bit one is good, even though it has been replaced by the redundant bit. The chip module combination produces a single part number equivalent to a like part number not employing the redundant bit.

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