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A noncontacting scanning photoelectron emission technique for bonding surface cleanliness inspectionMolecular contamination of bonding surfaces can drastically affect the bond strength that can be achieved and therefore the structural integrity and reliability of the bonded part. The presence of thin contaminant films on bonding surfaces can result from inadequate or incomplete cleaning methods, from oxide growth during the time between cleaning (such as grit blasting) and bonding, or from failure to properly protect cleaned surfaces from oils, greases, fingerprints, release agents, or deposition of facility airborne molecules generated by adjacent manufacturing or processing operations. Required cleanliness levels for desired bond performance can be determined by testing to correlate bond strength with contaminant type and quantity, thereby establishing the degree of contamination that can be tolerated based on the strength that is needed. Once the maximum acceptable contaminant level is defined, a method is needed to quantitatively measure the contaminant level on the bonding surface prior to bonding to verify that the surface meets the established cleanliness requirement. A photoelectron emission technique for the nondestructive inspection of various bonding surfaces, both metallic and nonmetallic, to provide quantitative data on residual contaminant levels is described. The technique can be used to scan surfaces at speeds of at least 30 ft/min using a servo system to maintain required sensor to surface spacing. The fundamental operation of the photoelectron emission sensor system is explained and the automated scanning system and computer data acquisition hardware and software are described.
Document ID
19890015252
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Gause, Raymond L. (NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
September 5, 2013
Publication Date
February 1, 1989
Subject Category
Quality Assurance And Reliability
Report/Patent Number
NASA-TM-100361
NAS 1.15:100361
Accession Number
89N24623
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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