Modification of Cu nanoparticles with a disulfide for polyimide metallization

Abstract

Copper metallization on polyimide films was carried out via a wet chemical process. This process included the chemical reaction of KOH with PI to form poly(amic acid) (PAA), ion exchange of doped K(+) with Cu(2+) to form Cu(2+)-doped PAA, doped Cu(2+) reduction by aqueous dimethylamine borane (DMAB) to form copper nanoparticles (CNPs) on PAA, and electroless copper (ELC) deposition catalyzed by CNPs on PAA. An organic additive, namely, bis(3-sulfopropyl)-disulfide (SPS), that can effectively reduce the size of CNPs and significantly enhance the chemical activity of CNPs for ELC deposition was used in this work. For comparison, doped Cu(2+) ions in the PAA were also reduced by hydrogen gas at 350 degrees C. The results show that only aqueous reductants can induce the reduced copper atoms to aggregate on the PAA surface and to form a granular copper layer that acts as a catalyst for the ELC deposition. Mechanisms for the aggregation of copper atoms and for activity enhancement of the CNPs due to SPS addition in the DMAB solution are proposed according to the evidence obtained from Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectrometry (XPS), field emission scanning electron microscopy (FESEM), cross-sectional transmission electron microscopy (TEM), and atomic force microscopy (AFM). The CNP-coated PAA films and the structures of the ELC deposits were characterized by X-ray diffraction (XRD) and UV-visible spectrophotometry (UV-Vis), respectively

Direct Patterning of Copper on Polyimide by Site-Selective Surface Modification via a Screen-Printing Process

“…However, the characteristic absorption of the carboxylate stretching with a slight change in intensity at 1581-1601 cm À1 indicates the formation of copper carboxylate. [15,16] When the ion-exchanged film is subjected to DMAB reduction, for the protonation of the carboxylate anion groups, [17] the spectrum is mostly similar in form ( Figure 1 D) as compared to that of the ion-exchanged film (Figure 1 C), but a slight decrease in intensity at 1601 cm À1 suggests the formation of carboxylic acid groups. It can be concluded, base on IR data, that the surface molecules of the PI film are cleaved to form metal salts of carboxylic acid groups and amide bonds by KOH, and are consequently transformed to carboxylic acid groups by DMAB.…”

Study of Surface Metallization of Polyimide Film and Interfacial Characterization

“…Finally, a Cu layer is electroplated on the electroless Ni layer to accomplish the metallization of polyimide [2]. The base treatment of KOH is a ring-opening reaction which can implant the K + ions into the uppermost sublayer of PI to form a potassium salt poly(amic acid) (PAA) layer [1,4,8,10,32]. The PAA layer plays an important role for the subsequent metallization process.…”

“…Polyimide (PI) is a superior material as a substrate of FPCB and has many advantages such as light-weight, high thermal stability, and good anti-corrosion properties [1,3,6,[8][9][10][11][12][13][14][15][16][17][18][19]. PI also has a high potential in automotive applications [1] as it has a higher glass transition temperature (T g ) at 280-290 • C, which is more sustainable in a high-temperature operational environment. Interestingly, pyromellitic dianhydride-4,4-oxydianiline (PMDA-ODA) PI film shows good sensing characteristics in the detection of ammonia vapors, which has opened a smart application direction for PI [20].…”

“…A common and mature metallization method is copper clad laminate (CCL), which is performed by laminating an electro-deposited (or rolled annealed) Cu foil on a PI film with an intermediate adhesive layer [1,9]. The laminated Cu foil is usually 18-35 µm thick to sustain sufficient mechanical strength; however, this thickness issue may make CCL technology unsuitable for fine-pitched wearable and portable devices.…”

“…Recently, wearable and portable technologies have attracted considerable attention because multiple functions such as communication, internet, sensor, navigation, and media, can be integrated in a small and light-weight device [1][2][3][4][5][6][7][8][9]. The rapid development of wearable and portable devices has driven the microelectronic industries to develop new technologies to meet the demands of scale miniaturization and multi-functionality.…”