Process Control

ZESTRON Coating Layer Test

Chemical test for localized detection of protective coating layer defects on PCBs

The reliability of protective PCB assembly coatings, with regard to climate and harmful gas safety, is essentially determined by the uniform application of the coating without interferences or gaps in the protective layer. In particular, common trouble areas such as solder joint edges and pore channels in coating pooling areas, when lacking a proper coating layer, have detrimental effects on the final board assembly.

The ZESTRON® Coating Layer Test utilizes a black color reaction as a visual indicator of the defects in the protective coating, even in the case of μ-coatings. The test thus adds the standardized methods for coating thickness measurement by enabling rapid and non-destructive detection of closed and dense coatings. Therefore, the test can also be used during production for cost-effective sampling.


Key benefits of the ZESTRON® Coating Layer Test:

  • Quick, easy, cost-effective and non-destructive method
  • More precise than black light/ UV inspection ⇒ thinner layers detectable
  • Shows coating defect and missing edge covering
  • Avoids the usage of fluorescent agent

Simple Test procedure in a few steps:

 Application                                                     Rinse and dry                                           Interpretation


  • Detection of protective coating layer defects
  • Solderability testing

Coating types:

  • Solvent coatings
  • µ-coatings
  • Parylene

Application surfaces:

  • Tin, Copper, Nickel/ Nickel containing compounds
  • Other less noble metals and alloys