Surface & Interface Contamination and Cleaning

X-ray Photoelectron Spectroscopy or XPS or ESCA:

  • Quantitative elemental composition of surface contamination
  • Surface chemistry with complete chemical phase identification
  • Extremely high sensitivity with an analysis depth of 8nm and sensitivity for less than 0.1 monatomic layer
  • Verification of surface cleanliness
  • Measure silicone surface concentration and relative chain length to determine effect in weakening adhesive bonding to a surface or interface
  • Provide silicone and fluorocarbon contamination test kits to be examined by XPS for facility contamination evaluation
  • Surface chemistry changes caused by cleaning agents, both improvements and residues left
  • Ion sputter gun removal of surface contamination to judge its thickness
  • Quantitative elemental and chemical phase identification of interfacial contamination after adhesive failure, peel, or pull test
  • Interphase chemistry of interfaces with adhesive bonding – adhesives often have different compositions near interfaces
  • Depth profile through thin layers at a surface for elemental analysis as a function of depth
  • Analyze residues left after evaporating water or other solvents
  • Identify plasticizers, fire retardants, and cross-linking agents in polymers or plastics that migrate to surfaces and interfaces

FTIR or Infrared Spectroscopy:

  • Identification of organic functional groups and some inorganic functional groups in thicker contaminant layers using ATR or specular reflectance for greater surface sensitivity
  • Bulk or near-surface (1 -2 micrometers deep) organic material composition for comparison to surface organic composition
  • Identify plasticizer or fire-retardant segregated to the surface of a plastic/polymer material

Microscopic Examinations:

Classic surface contamination residue left by the evaporation of a solvent on a surface.  The circular shape of the evaporating solvent becomes smaller in diameter as the solvent evaporates and the circumference concentrations of salts or dissolved materials become higher with most of the precipitation of contamination occurring there.  A ring structure in the contamination is left.  The residue material was analyzed with XPS to determine its quantitative elemental and chemical species composition.

A scratch in an anti-reflective coating on a lens allowed an interior layer to react with water vapor and produce contamination.  The image was made using the Nomarski phase interference contrast method on our metallographic microscope.  The residue material was analyzed with XPS to determine that a particular underlayer of the many layer film was being attacked corrosively.  The attacking agent was also identified as water.

This contamination on a printed circuit board was analyzed with XPS and identified.

Effect of interfacial contamination on adhesion to the interface using pull tests.

Surface cleaning technique evaluations:

  • CO2 snow jet cleaning, in-house capability, but learn more about CO2 snow jet cleaning at Applied Surface Technologies
  • Solvent-based cleaning
  • Check cleaning effectiveness with above analytical capabilities
  • Determine changes in surface chemistry of plastics caused by plasma cleaning

Electrochemistry or Corrosion Testing:

  • Determine whether oxide film protects metal surface, which it may not due to contaminants, the attacking chemical agents, or a combination of both
  • Determine breakdown potential of passive film on metal or pitting potential, which is affected by contamination and the corrosive media
  • Determine the corrosion rate of a surface in a given electrolyte
  • Measure the effectiveness of a coating or protective film as a function of time, applied potentials, and corrosive ions

Applications:

  • Electronics contamination
  • Packaging materials contamination
  • Medical device contamination
  • Composite materials fibers and particulates contamination affecting matrix bonding
  • Adhesive bonding preparation and cause of bonding failures
  • Corrosion due to contamination