Surface & Interface Contamination and Cleaning – In-Depth

At Anderson Materials Evaluation, we utilize many techniques to analyze surface & interface contamination and cleanliness.

X-ray Photoelectron Spectroscopy or XPS or ESCA:

  • Quantitative elemental composition of surface contamination
  • Surface contamination chemistry with chemical phase identification
  • Extremely high sensitivity with an analysis depth of 10 nm 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, sealant integrity, wetting problems, or as a source of silicone contamination
  • Provide silicone and fluorocarbon contamination detection test kits to be examined by XPS for facility and oven contamination evaluations
  • 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
  • Examine surfaces after anodization and etching processes to determine if the surfaces were properly cleaned

FTIR or Infrared Spectroscopy for Surface Contamination:

  • 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

GC-MS or Gas Chromatography – Mass Spectroscopy

  • Wipe surfaces with swabs and remove and analyze the contaminants from the swab for high-sensitivity GC-MS analysis at the ppb concentration level.
  • Rinse a surface with a solvent and analyze the rinse solvent to find what was on the surface.

Microscopic Examinations for Surface Contamination:

  • SEM with digital imaging to reveal surface inclusions and surface deposits
  • Inspection microscope, digital imaging
  • Metallographic microscope, digital imaging, Nomarski phase contrast

Profilometry or Surface Roughness and Microscopy:

  • Measure surface roughness
  • 3-dimensional surface topography mapping
  • Detection of defects as small as 500 nm
  • Measurement of 2D and 3D distances
  • Layer thickness measurements

Laser-Induced Breakdown Spectroscopy (LIBS) :

  • Quickly determine the major composition of a material
  • Quickly determine whether a material has such elements as aluminum, calcium, sodium, lead, or boron at elevated concentrations
Surface Contamination Testing - Classic surface contamination residue left by the evaporation of a solvent on a surface.
Classic surface contamination residue left by the evaporation of a solvent on a surface.

Nomarski image of a scratch in an anti-reflective coating on a lens allowed an interior layer to react with water vapor and produce contamination.
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.

PCB Contamination Testing - Contamination on a printed circuit board which was analyzed with XPS
Contamination on a printed circuit board which was analyzed with XPS

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

Corrosion Testing for Surface Contamination:

  • Identify corrosion products and causes.

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

Case Histories

Solving a Polymer Sealing Problem with XPS Analysis

Silicone Detection on the Surface of an Acrylic Adhesive/Polyimide Tape

Silicone Contamination Testing of Facilities and Ovens