... via Jet Metal technology
For about the last 10 years, a new technology has been available for production of decorative metal coatings over plastics, for example to produce metallised plastic closures for cosmetics packaging. This is based on the spray application of a metal ion -containing solution together with one containing reducing agent onto a given substrate. This results in reduction of the metal ions to the metal itself. The thickness of such deposited layers can be controlled by varying the duration of the spray procedure. The process is terminated by rinsing off the reactant solutions. The process can also be used to form thin electrically conducting layers for use in electrical or electronic applications. With only minor modifications, electrically conductive structures can likewise be formed.
Abscheidung von leitfähigen Zwischenschichten mittels Jet Metal-Technologie
Seit etwa zehn Jahren wird eine neue Technologie zur Herstellung von dekorativen Metallschichten auf Kunststoffen eingesetzt, um beispielsweise Verschlusskappen für Kosmetik herzustellen. Dabei wird durch Aufsprühen einer wässrigen Metalllösung und einer Lösung mit Reduktionsmittel auf ein beliebiges Substrat eine Metallreduktion ausgelöst. Die Dicke der dabei entstehenden Metallschicht lässt sich einfach über die Reaktionszeit steuern, wobei die Reaktion einfach durch Abspülen der Lösung beendet wird. Das Verfahren kann auch für die Herstellung von dünnen leitfähigen Schichten für die Elektrotechnik verwendet werden, wobei mit geringem Aufwand auch Leiterstrukturen erzeugbar sind.
Since the start of the company in 2007, Jet Metal Technologies focused its efforts to place its unique in-line metallization technology by spraying on the market for decorative applications in cosmetic and alcoholic bottle applications. In such decorative applications a layer stack consisting of a base coat varnish (~ 20 µm), a thin silver layer (~ 80 nm) and a protective top coat varnish (~ 20 µm) is used. The many advantages of the Jet metal technology led to great success as nearly 20 industrial lines in Europe and North & Middle America were installed and produce annually millions of metallized spirit bottles, scent bottles and caps for big players like Coty, Hennessy, L’Oréal, Louis Vuitton, Procter and Gamble and Pernod-Ricard (Fig. 1).
But in many industries where metallization technologies like plating, sputtering or evaporation is utilized, users are facing stricter environmental controls on chemical waste and feel continuous pressure to reduce further their costs. Therefore more and more customers are qualifying the Jet Metal technology as a green and cost efficient alternative for existing metallization technologies or to replace intermediate production steps.
Jet Metal’s metallization method is using standard painting to spray simultaneous two aqueous based solutions onto a substrate at ambient pressure and temperature, leading to a chemical reaction, forming a metal layer onto the substrate.
The two solutions, one being the oxidant containing the metal salt of the metal that the user wants to deposit, the other the reductant, are both water based, solvent and palladium free and CMR (carcinogenic, mutagenic or toxic to reproduction) free so completely in line with the REACh legislation. Using compressed air and a double nozzle spraying paint gun, the reducing and oxidising agents are simultaneously sprayed onto the substrate surface, starting an oxido-reduction reaction and instantly forming a thin metal layer as shown in Figure 2.
The ratio of the sprayed oxidising and reducing solutions are adapted to give an optimal stoichiometric electrochemical reaction onto the surface. The end result of this reaction is a compact, dense and high adherent metallic film on the substrate surface. Most commonly via the Jet Metal technology, silver and nickel are deposited in layer thickness from 20 nm up to 5 to 7 µm.
The Jet Metal metallization technology can be applied on many substrate geometries (small/big, easy/complex, 2D/3D shape) and basically all substrate material choices, whether it is an electrically conducting or non-conducting surface. The range of substrates goes from metals, metal alloys (like Zamak), over glass, all types of textiles, ceramics, silicon, to a long list of plastics and composites to even wax. The only prerequisite to apply the technology is linked with the use of water based solutions: in order realize an evenly well distributed metal layer over the surface, a good substrate wettability is needed which can be achieved via a pre-treatment step with the help of a flame, plasma or corona.
Once the required layer thickness is reached, deionized water is sprayed onto the surface to stop all reactions and the substrate is dried with the help of compressed air, so there is no need for a curing step.
Combining the above advantages with the well-known advantages of painting technology like the ease of getting familiar with the technology and the capability to produce parts inline without breaks on an industrial scale, makes the Jet Metal technology an ideal choice where thin metal layers are needed.
3 Use of Jet Metal technology as intermediate conductive layer
In quite some known technologies like electro plating, electroforming, powder coating or cataphoresis, electrical conductivity of the substrate is needed. Using the listed technologies on metal substrates is well known since many years and commonly used worldwide. But as there is in many industries a continuous battle to cut costs in the value chain and to save weight on components, more and more users would like to apply the above technologies on non-conducting surfaces like plastics or composites. The industry developed some solutions but mostly these are complex, expensive and environmentally non-friendly solutions.
Take the example of electroless nickel plating which is frequently used as a first step to plate on plastics or composites for the manufacturing of a. o. decorative automotive parts, printed circuits boards, connector applications and all kinds of EMI shielding components. Even this electroless nickel plating is used frequently, it has a bunch of disadvantages like bath control and limited solutions shelf life, toxicity (contains carcinogen compounds are used) and ecological disadvantages (for example waste treatment or use of chromic etching), difficulty to plate parts with large dimensions, a plating speed which is limited for most of commercial available plating solutions. On top of the above mentioned problems, another very important industrial inconvenience should be taken into account which is the high number of processing steps, particularly during the palladium activation step which is at the same moment also a very expensive step.
Using Jet Metal technology to deposit a 150 nm thick silver layer on plastics or composites, will give enough electrical conductivity (~ 2,5 x 107 S/m) and the necessary adhesion to the substrate (Class 0 in the adhesion cross cut test according ISO 2409 2013) to be able to plate all those non conducting surfaces with the traditional metals like nickel, copper and others as the principle is shown in Figure 3.
One Swiss customer is using a fine JMT silver layer on 3D printed wax which is then later used in an a electroforming process to create complex and high technological components for the micro-electronics industry.
Fig. 3: Principle of using a Jet Metal silver layer as a conductive intermediate primer
The technical advantages of the Jet Metal technology in combination with the Jet Metal business model (design & implementation of industrial process tools, supplying the consumables for the process and offering all necessary support services) offers a green and cost effective, industrial solution for the intermediate process step of giving a non-conductive plastic/composite surface the necessary electrical conductivity.