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Substrate Visual Inspection/Alignment Tool

IP.com Disclosure Number: IPCOM000043074D
Original Publication Date: 1984-Jul-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Bartley, GK: AUTHOR [+4]

Abstract

Top surface metallization patterns are formed on multilayer ceramic (MLC) substrates using repeated operations where accurate alignment to substrate top surface vias is required for each operation. An improved method is provided to facilitate inspection and alignment using an opaque mask. The top surface metallizations are produced using well-known optical and etching techniques and are made relative to vias. Due to the nature of cofired multilayer ceramic, substrate top surface via locations cannot be controlled accurately. The primary problems are variations in shrinkage rate and local distortion during firing. Therefore, any subsequent process requiring accurate alignment to vias becomes a significant problem.

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Substrate Visual Inspection/Alignment Tool

Top surface metallization patterns are formed on multilayer ceramic (MLC) substrates using repeated operations where accurate alignment to substrate top surface vias is required for each operation. An improved method is provided to facilitate inspection and alignment using an opaque mask. The top surface metallizations are produced using well-known optical and etching techniques and are made relative to vias. Due to the nature of cofired multilayer ceramic, substrate top surface via locations cannot be controlled accurately. The primary problems are variations in shrinkage rate and local distortion during firing. Therefore, any subsequent process requiring accurate alignment to vias becomes a significant problem. One obvious method of accomplishing alignment would be to visually align to surface features for each subsequent step in the substrate process. This technique has two serious drawbacks: (1) throughput would be limited, and (2) visual alignment may not be possible if, for example, processing requires a blanket coating of metal, thus hiding the features used for alignment. The present method of accomplishing alignment establishes mechanical alignment references based on surface feature locations. This method has the advantage that once mechanical alignment references are established, they can be used on all subsequent operations and are approximately two to seven times faster than optical alignment techniques. Also, blanket coatings do not affect mechanical alignment capability. Given the mechanical reference, an alignment feature can be machined or a serialization technique can be used to establish alignment from an existing feature, such as an edge. To implement the present method on MLC, it is necessary to first determine if alignment is possible or if the parts are in specification. This is a formidable problem given that there can be several thousand vias on the top surface which could have moved randomly with respect to one another, hopefully within their allowable tolerance range, during the firing or curing steps. A second but...