• Cabrera, Michel
• Semet, Vincent
• Gerges, Tony
• Charmeau, Jean-Yves
• Lombard, Philippe
• Cauchy-Clerc, Hugo
• Allard, Bruno

Abstract

In-Mold (Structural) Electronics (IME/IMSE) is a 3D Plastronics processes where conductive inks are printed on a thin polymer film and surface mount devices are connected with conductive glue. The circuit is then thermoformed into 3D shapes and overmolded via injection molding. Traditionally Polycarbonate films have been used due to their excellent performances, but the need for more ecological materials led us to investigate other polymers such as PLA, leading to new challenges. One such challenge is that IME inks necessitate curing to evaporate their solvent. Typically, this is achieved through heating in an oven at 120°C for Dupont ME603 ink on PC film. PC's high heat resistance (HDT ~135°C) allows this, but not PLA’s. In our previous research, conductive ink on PLA substrate required a 2.5-hour heating at 55°C, yielding suboptimal conductivity. The same challenge applies to curing conductive glues used for SMD connections, requiring sufficient time and temperature. Here, we present an improved, faster curing method for conductive ink and glue on PLA and PC. This method, known as photonic curing, employs intense, brief flashes of high-intensity light to heat the targeted area. The distinct absorption spectra of the ink (or glue) and the polymer substrate ensure precise curing without compromising substrate integrity. We will present our results on using photonic curing compared to the traditional curing in an oven. We will show how the process improves the conductivity of the ink and how it impacts the thermoformability of the part. Quantitative adhesion tests on photonic curing of conductive glue are reported (to avoid soldering). Potential applications for connecting the SMD with a promising industrial process are discussed.

Topics

• impedance spectroscopy
• surface
• polymer
• injection molding
• curing
• heat resistance