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VISION STENCIL INSPECTION TO ENSURE SOLDER PRINT QUALITY

IP.com Disclosure Number: IPCOM000006663D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2002-Jan-21
Document File: 1 page(s) / 53K

Publishing Venue

Motorola

Related People

Richard Mangold: AUTHOR [+3]

Abstract

One of the main variables in effective PC board assembly is the solder paste print quality. Methods of reliably inspecting solder print quality have historically been elusive. A common solder print defect is insutli- cient solder deposition, which is caused by solder paste remaining in the stencil openings upon snap-off, as opposed to being transferred to the PC board. This prob- lem becomes more pronounced with tine pitch solder printing.

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M-LA INC. Technical Developments Volume 17 December 1992

VISION STENCIL INSPECTION TO ENSURE SOLDER PRINT QUALITY

by Richard Mangold, Chris Becher, and Reed George

  One of the main variables in effective PC board assembly is the solder paste print quality. Methods of reliably inspecting solder print quality have historically been elusive. A common solder print defect is insutli- cient solder deposition, which is caused by solder paste remaining in the stencil openings upon snap-off, as opposed to being transferred to the PC board. This prob- lem becomes more pronounced with tine pitch solder printing.

  With the recent advent of vision equipped solder printers, the facilities are provided to inspect the stencil openings subsequent to printing to ensure that all sten- cil openings are free of solder paste. The idea is to use

the camera that finds the solder stencil fiducials for align- ment to inspect the stencil openings to ensure that they are free of paste alkr the printing cycle. In this way, it is possible to inspect either 100% of the stencil openings, or suspect openings such as those for very tine pitch components. This method may also be used to trigger automatic or manual stencil cleaning as determined by the stencil status.

  In conclusion, this method offers a simple solution to the problem of passing insticient solder printed PC boards into the automated assembly line, which will lead to any number of defects at subsequent stages in the assembly process.

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