A novel manufacturing technology for tensile test specimens for the characterization of copper in plated through holes (PTH)

Plated Through Holes (PTH) in Printed Circuit Boards (PCB) are exposed to high thermal loads during the manufacturing process and in field application. This is due to a significant difference in the coefficients of thermal expansion between base material (epoxy resin) and copper barrel. For the assessment of the PTH reliability, the knowledge of the material properties of the electro-deposited copper is of great importance. In this article the elongated hole specimen technique is introduced as a novel manufacturing technology for tensile test samples. With this simple and inexpensive method, stress-strain curves of copper layers are generated for the first time, with specimens that have similar deposition conditions and roughness as the copper barrel within the PTH. The method can be integrated into the PCB series production without additional cost of material or expenses and is particularly suitable for in-line process control of electroplating. With the film-like sample tensile tests were carried out successfully in an ambient temperature range of 20°C to 140°C. The material data is compared with tensile specimens deposited on the surface of a FR4 substrate.