Long-Term Behavior of SMT Components Mounted on Printed Polymer Thick Film Pastes

摘要

In this work the reliability of soldered (SnBiAg) and isotropically conductive interconnections on screenprinted PTF pastes is investigated. The combination of printed circuitry and standard electronic components (HPE) might be a practical solution for high quality and industrial scale production while also saving cost, raw material and reducing process complexity. A commercially available, novel solderable PTF paste was used to mount CR0805-sized SMT components on low-cost PET substrates. By utilizing different accelerated aging tests (high temperature, damp heat and temperature cycling) the influence on electrical and mechanical characteristics is evaluated and compared to freshly produced specimen. Additionally, optical inspection of microsections and the fracture occurrence was investigated. The results for both interconnection materials are very promising. Soldering on the PTF paste resulted in good wettability and solderability. Aditionally, for soldered joints neither electric nor mechanical failures occurred during the test duration of 500 h (250 cycles). For conductively bonded components also no significant decrease in electrical resistance was observed. Both combinations have a contact resistance within 50 mΩ to 150 mΩ. Shear force values increased for HT and TH storage, which might be explained by post-curing of the epoxy resin. For TC storage however, a significant drop (>30% in relation to the initial value) was observed. Further experiments show that the decrease occurs between 100 and 250 cycles. The change in shear force goes along with a change in fracture appearance, which was evaluated in this work. Overall, this study provides significant results which might enable the production of more reliable and high quality MID or HPE products.