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Browse Prior Art Database

Algorithm to Locate the Seating Plane of Surface-Mounted Devices

IP.com Disclosure Number: IPCOM000039313D
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Blackshear, ED: AUTHOR

Abstract

An algorithm has been proposed to mathematically establish the seating plane of a surface-mounted semiconductor device. A program can then be written so that automatic optical measuring equipment may be used to give coplanarity readings. This method would replace manual techniques using feeler gages. On surface-mounted semiconductor modules the leads must be coplanar within rigid specifications. The conventional method used to measure coplanarity is to place the module lead down on a surface plate. Feeler gages are then used to determine the distance between the lead surface and the plate. The proposed algorithm would establish a seating plane 1 (Fig. 1) with the module 2 on its back. The object is to determine which three leads 3, 4 and 5 comprise the seating plane.

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Algorithm to Locate the Seating Plane of Surface-Mounted Devices

An algorithm has been proposed to mathematically establish the seating plane of a surface-mounted semiconductor device. A program can then be written so that automatic optical measuring equipment may be used to give coplanarity readings. This method would replace manual techniques using feeler gages. On surface-mounted semiconductor modules the leads must be coplanar within rigid specifications. The conventional method used to measure coplanarity is to place the module lead down on a surface plate. Feeler gages are then used to determine the distance between the lead surface and the plate. The proposed algorithm would establish a seating plane 1 (Fig. 1) with the module 2 on its back. The object is to determine which three leads 3, 4 and 5 comprise the seating plane. The criterion for the seating plane is that these three leads form a triangle enclosing the center of the device. The three leads which comprise the seating plane may be determined from three coordinate (XYZ) measurements of each lead by performing a series of coordinate shifts and rotations followed by application of the criterion for the seating plane. The procedures for the method are given in Fig. 2. Coordinate transformations are to be performed in the manner described by [1,2].

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References

L. G. Roberts, "Homogeneous Matrix and Manipulation of

N Dimensional Constructs," MIT document #MS1045, 1965.

R. P. Paul, "Robot...