Specimen Preparation
Chemical treatment of a polished metal surface reveals the grain boundaries and microstructural features for microscopic analysis. Proper metallographic etching is essential for assessing the quality of copper plating and the integrity of solder joints. The etchant reacts preferentially with different crystal orientations or phases to create a relief that is visible under a microscope.
This process allows inspectors to identify defects that are invisible on a purely mechanical polish.
Contrast Enhancement
Selection of the correct chemical solution depends on the specific metal and the features that need to be highlighted. For copper samples, a mixture of ammonium hydroxide and hydrogen peroxide is commonly used to reveal the grain structure and any plating interfaces. This treatment makes it possible to distinguish between the original foil and the subsequent layers of electrodeposited copper.
It also highlights the presence of intermetallic layers at the base of a solder joint. These layers provide information about the thermal history and the potential reliability of the connection.
Microstructure Identification
Visualizing the internal grain pattern helps to confirm that the plating process has achieved the desired equiaxed or columnar structure. Anomalies like large voids or inclusions become clear after the chemical application.
