Electroless Plating Cycle Process for High-Conductivity Flexible Printed Circuits

Abstract

In this work, a non-formaldehyde electroless plating cycle process was successfully applied to prepare the flexible copper printed circuits on poly (ethylene terephtalate) (PET) films.Copper nanoparticles (Cu NPs) were employed as catalytic seeds, and dimethylaminoborane (DMAB) was used as the reductant. Cu NPs were directly printed on the PET surface modified by 3mercaptopropyltriethoxysilane (MPTES) to serve as the seeds to trigger the electroless deposition. MPTES modification can dramatically improve the adhesion of the PET and Cu layer. Cu NPs can ideally substitute noble metals Ag, Pt, and Pd to catalyze electroless deposition. DMAB, as an innocuous reductant can replace formaldehyde in an alkalescent plating bath. The amount of Cu NPs with different sizes on the per area of the PET surface was investigated to determine its appropriate dosage. Various times, temperatures, concentrations of reactants in the electroless plating process were researched to obtain optimal deposition. The minimal sheet resistance of the copper pattern was 6 mΩ/sq with a resistivity of 2.01 μΩ•cm, which is 1.18 times that of bulk copper. These results demonstrated that the prepared Cu pattern had excellent conductivity. The kinetics of the electroless plating process was researched to quantify the thickness of the Cu layer and the consumption of reactants. The electroless plating bath can well be cycled after compensating reactants, while the sheet resistance of the Cu pattern fluctuated very little. The cycling electroless plating bath will greatly reduce the discharge of waste and is of vital significance for the large-scale and cheap manufacturing of flexible printed electronics.

Efficient and Simple Fabrication of High-Strength and High-Conductivity Metallization Patterns on Flexible Polymer Films

“…Moreover, in Figure b, the resistivity of the obtained copper circuit is smaller than the conductive metal circuit with the liquid-phase printing/coating process and comparable with electroless copper plating. The specific values are listed in Table S2 (Supporting Information). − As shown in Figure c, the resistance value increases slightly even after 1000 bending cycles, mainly due to the excellent adhesion property between the copper pattern and the PI film. Based on the resistance heat generation properties of the metal itself, the rectangular and circular copper patterns were designed, which can be used in wearable heaters for the human body.…”

Autocatalytic Laser Activator for Both UV and NIR Lasers: Preparation of Circuits on Polymer Substrates by Selective Metallization

“…In the past decades, the selective metallization technology has attracted enormous attention due to its wide applications in communication equipment, − electronic devices, − medical appliance, energy storage devices, , light-emitting displays (LED), and wearable devices . At present, the commonly used metallization methods include photolithography, − ink printing, − micro-contact printing, screen printing, and laser-induced selective metallization (LISM). LISM is the technology that uses lasers to activate the polymer surface and then conducts electroless plating to deposit the metal layer on the activated area.…”

Laser Direct Structured 3D Circuits on Silicone

“…Other recent work has been published recognizing the value of copper as a highconductivity circuit material for flexible applications, deposited by electrospinning or wet chemical plating. 29,30 The process of direct-ink writing a catalyst material followed by electroless copper plating is also being developed (commercial catalyst inks are available), which takes advantage of the highconductivity and robustness of plated copper but will still suffer from adhesion problems of the DIW catalyst without laser microroughening. 30 In this Research Article, an LDS process will be presented that incorporates functional copper circuit traces onto planar and contoured superflexible silicone bodies (30 hardness on Shore 00) with exceptional adhesion and bulk copper resistivity.…”

“…29,30 The process of direct-ink writing a catalyst material followed by electroless copper plating is also being developed (commercial catalyst inks are available), which takes advantage of the highconductivity and robustness of plated copper but will still suffer from adhesion problems of the DIW catalyst without laser microroughening. 30 In this Research Article, an LDS process will be presented that incorporates functional copper circuit traces onto planar and contoured superflexible silicone bodies (30 hardness on Shore 00) with exceptional adhesion and bulk copper resistivity. This is achieved by modifying the silicone with LDS-enabling copper chromite (Cu 2 Cr 2 O 5 ) dopant and developing the LDS process on the new material (Figure 1).…”

“…Since the rigidity was higher than human skin, this type of silicone could not be used for biocompatible, skin-interfacing electronics and sensors and has limited sensitivity for elastomeric sensors and actuators. Other recent work has been published recognizing the value of copper as a high-conductivity circuit material for flexible applications, deposited by electrospinning or wet chemical plating. , The process of direct-ink writing a catalyst material followed by electroless copper plating is also being developed (commercial catalyst inks are available), which takes advantage of the high-conductivity and robustness of plated copper but will still suffer from adhesion problems of the DIW catalyst without laser microroughening …”