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Method and apparatus for locating ball grid array packages from two-dimensional image data

  • US 6,151,406 A
  • Filed: 10/09/1997
  • Issued: 11/21/2000
  • Est. Priority Date: 10/09/1997
  • Status: Expired due to Term
First Claim
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1. A vision system for locating and positioning ball grid array features for placement on an electronic assembly, comprising:

  • a raw feature finding processor receiving as inputs model information of a ball grid array device, captured image information as a two dimensional image of said ball grid array device, and calibration information comprising a two dimensional transform relating image space to physical space, said raw feature finding processor finding ball features in said captured image and generating a list of ball features as an X and Y location of each ball feature in physical space;

    an angle estimation processor receiving said list of ball features from said raw feature finding processor and receiving as additional inputs a user estimated orientation angle and ball-to-ball pitch information from said mode information, said angle estimation processor determining therefrom an estimated grid angle;

    an on-grid check processor receiving said estimated grid angle, said list of ball features and said ball-to-ball pitch information and fitting said list of ball features to a grid to eliminate noise features and refining said estimated grid angle, said on-grid check processor producing a set of on-grid balls as a list of X and Y translation parameters for each ball found on-grid; and

    a correspondence processor receiving said set of on-grid balls and said model information of said ball grid array device, said correspondence processor searching for correspondence between said on-grid balls and model balls of said model information of said ball grid array device and providing a direct mapping of respective two dimensional spatial relationships between said model balls and said set of on-grid ballswherein correspondence between said model balls and said set of on-grid balls provides a mapping of model balls to corresponding balls in image space which is used, along with said two dimensional transform relating image space to physical space to position/align balls of said ball grid array device in physical space in accordance with model balls in model space.

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