The selective metallization of nonconductive polymer materials has broad applications in the fields of integrated circuit technology and metallized patterns. This work discusses a methodology to pattern metal tracks on polybutylene terephthalate substrates. The process consists of three steps: 1) surface patterning with picosecond laser pulses (1030 nm) in air, 2) Pd seeding via treatment in PdCl2 solution, and 3) selective metallization via electroless copper deposition. Picosecond laser irradiation promotes not only surface roughening but also chemical modification to enable Pd seeding as the polymer surface acquires the ability to reduce Pd(II)‐chloride species to metallic Pd. The laser parameters, as well as the PdCl2 concentration and seeding temperature, have an influence on the polymer surface morphology, the concentration and distribution of metallic Pd, and the copper layer properties. Homogeneous copper layers with well‐defined geometries, good coating‐substrate adhesion, and high electrical conductivity can be obtained. This is ascribed to the synergistic effect of the chemical surface activation and roughness development (from 0.13 to ≈1.6 μm). As the patterning and surface activation are performed in air, directly on the as‐received polymer substrate, this methodology shows great potential for metallization of electronic devices with 3D complex geometries.

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Abstract3D‐Molded Interconnect Devices enable the placement of electronic circuits on three‐dimensional plastic components. The following article breaks new ground in order to add reasonably to existing 3D‐MID procedures. An essential aspect was the shortening of the process chain of the conventional MID procedures through laser‐direct structuring. Thus the metallising steps are no longer necessary and a 3D circuit carrier structure can be created directly on any plastic component. The research work focused on the space‐resolved modification of the electric conductivity of non‐conductive plastic components through a newly‐developed procedure of laser beam functionalisation. The principle is based on the application of multi‐phase polymer blends with matrix‐disperse phase structures in which carbon nanotubes are located. They cross‐link on the component surface through a partial laser activation and create a conductive area.

The preparation of metallic tracks on non-conductive or semi-conductive substrates is attracting a strong scientific interest due to its useful applications in integrated circuit technology and its potential for miniaturization. The selective metallization on dielectric substrates can be carried out via laser-assisted direct writing techniques These involve processes such as thermally induced deposition, surface modification for subsequent electroless deposition as well as photocatalysis-mediated deposition among others [1]. Furthermore, a well-known methodology for producing metal tracks onto polymeric substrates is the so-called laser direct structuring (LDS) technology and is widely used for producing molded interconnect devices (MIDs). Conventional LDS uses polymeric materials loaded with a small amount of metallic compound (e.g. Pd particles) which after laser ablation can be released for catalyzing a further electroless plating process. Organometallic complexes based on palladium (Pd2+), copper (Cu2+) [2] as well as metal oxide composites of copper−chromium oxide (CuO·Cr2O3) or antimony-doped tin oxide (ATO) [3] have been used as catalyst sources for LDS technology in the last years. The active material is finely dispersed in the polymeric matrix and can be chemically modified by laser ablation in order to play a role as catalyst in a subsequent electroless deposition process. However, although the LDS method offers flexibility and freedom for 3D patterning design, the addition of those special additives (catalyst sources) is required in order to make the polymeric material suitable for LDS. This paper will discuss a simple methodology for patterning metal tracks onto the polymeric substrate polybutylene terephthalate (PBT). The selective metallization process consists of three main steps: (1) surface patterning and activation with picosecond-laser pulses in a dry processing environment; (2) treatment of the substrate in PdCl2 seeding solution, and (3) selective metallization of the substrate via electroless copper deposition. It was found that, besides a significant surface roughening, the use of ultra-short laser pulses promoted the chemical modification of the polymeric surface in a manner that the surface acquires the ability to reduce Pd-ions into metallic Pd clusters during a subsequent treatment in PdCl2 solution. The laser parameters as well as the concentration and the temperature of the PdCl2 solution were investigated and correlated with the surface morphology, the formation of Pd clusters as well as with the characteristics of the copper layers. The copper features were homogeneous and exhibited well defined geometries. Moreover, the adhesive properties of the copper structures were investigated. Tape tests showed that the copper structures exhibited good adhesion to the PBT substrate and this is ascribed to the high roughness obtained via laser patterning. The copper layers exhibit low electrical resistivity values and therefore show great potential for applications in electronic devices even with 3D complex geometries. References: [1] J.H.-G. Ng, M.P.Y. Desmulliez, M. Lamponi, B.G. Moffat, McCarthy, H. Suyal, C. Walker, K. Prior, D.P. Hand, A direct-writing approach to the micro-patterning of copper onto polyimide, Circuit World. 35 (2009) 3–17. [2] M. Huske, J. Kickelhain, J. Muller, G. Eber, Laser supported activation and additive metallization of thermoplastics for 3D-MIDs, Proc. 3rd LANE. (2001) 1-12. [3] J. Zhang, T. Zhou, L. Wen, Selective Metallization Induced by Laser Activation: Fabricating Metallized Patterns on Polymer via Metal Oxide Composite, ACS Appl. Mater. Interfaces. 9 (2017) 8996–9005. Figure 1