Accession Number : ADA180436

Title :   Holographic Detection of Latent Defects.

Descriptive Note : Final rept. Aug 84-Mar 86,

Corporate Author : SPECTRON DEVELOPMENT LABS INC COSTA MESA CA

Personal Author(s) : Arunkumar,K. A. ; Trolinger,J. D.

Report Date : OCT 1986

Pagination or Media Count : 87

Abstract : This project was aimed at seeing whether holographic interferometry (H.I.) could be used in evaluation standard environmental stress screening methods currently used to select and qualify printed circuit boards (PCB). To do that it should be proven that H.I. is capable of detecting defects in a PC board that have been brought about by the stress screening procedures. Hence, the objectives of this project were to determine: a) if holographic interferometry and identify the most common circuit board defects before the components fail (component failure due to internal flaws excluded), b) if holographic interferometry can locate defects which have evolved into failure, and (c) if holographic interferometry can locate and detect the onset of defects on PC boards (sensitivity). To achieve the objectives, introduced defects and defects induced by thermal and vibrational stressing were used in the study. Defect identification was through the perturbations in the H.I. fringes on the boards. Some of the defects were detected when the circuits were electrically functional. These defects were solder cracks (cuts), partial trace separation and trace separation at solder joints. H.I. also succeeded in revealing components that have been disconnected either through snipping or desoldering. This displays H.I.'s ability to pinpoint failed components as well. Another important feature of H.I. that was revealed in this study is its capacity to expose simultaneously more than one defect if present in the examined region of the PC board.

Descriptors :   *DEFECTS(MATERIALS), *HOLOGRAPHY, *PRINTED CIRCUIT BOARDS, *PHOTOGRAPHIC ANALYSIS, CIRCUIT BOARDS, CRACKS, DETECTION, DORMANCY, FAILURE, IDENTIFICATION, INTERFEROMETRY, INTERNAL, LABORATORY PROCEDURES, PERTURBATIONS, SEPARATION, SOLDERED JOINTS, SOLDERING, STRESSES, VISIBILITY, FAILURE(ELECTRONICS)

Subject Categories : Photography
      Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE