Strain Gauge Adhesive Selection for Structural Strain Transfer
Structural strain transfer requires minimal bondline thickness, high shear modulus adhesives, and precise surface roughness matching to prevent measurement lag.
IEC 60068 2 78
Environmental Specification
Global testing protocols provide a standardized framework for evaluating the resistance of electrotechnical products to high humidity at constant temperatures. Application of iec 60068 2 78 determines how moisture absorption affects the insulating properties of printed circuit assemblies. The document establishes the parameters for damp heat exposure.
Test Execution
Specimens reside in a climatic chamber maintained at a temperature of 40 degrees Celsius and a relative humidity of 93 percent for a duration ranging from four to fifty-six days. This procedure in iec 60068 2 78 forces moisture into the porous structures of the fiberglass reinforced epoxy laminate. Monitoring the insulation resistance during exposure identifies the onset of conductive anodic filament growth.
The chamber must maintain stable conditions to prevent condensation on the surface of the board.
Failure Criteria
Evaluation follows the exposure period to confirm that the physical integrity and electrical performance remain within specified limits. If a sample exhibits delamination or surface tracking after the iec 60068 2 78 test, the manufacturing process or material selection is deemed insufficient for humid environments. Leakage currents often increase due to the presence of ionic contaminants on the surface.
Long term reliability depends on the ability of the protective coating to exclude moisture.