electrical & electronic | Processing
The LPP process in detail. From left, the injection moulded substrate, the part after laser ablation of the lacquer, after plasma deposition of the copper, and the fi nal heat sink with LED installed
Right: An IMKS plastic/metal injection
moulding cell built around a KraussMaffei machine and automation
Below: Low melting point
alloys are used to mould
plastic parts
with integrated conductive
circuits in the IMKS process
deposited 200 micron layer of aluminium oxide was applied to the mounting surface to provide electrical isolation (this would not be required if the substrate was electrically non-conductive). This was followed by application of a 25 micron thick layer of a special lacquer formulated to be non-receptive to plasma- applied metal. The path for the electrical circuits was then created using an LPKF laser system, which selec- tively removed the lacquer from the surface to create the path for the electrical tracks. During the subsequent plasma deposition stage, the metal adhered to the exposed track surfaces to create a fully functional circuit ready for applica- tion of the LEDs and other electronic components. These could be applied using conventional soldering techniques. A 25 micron thick layer of copper was deposited in
the Fakuma exhibit but thicker layers and other metals can be applied, says Mussmann. The demonstration also involved application on a simple 2D surface, but the system is said to be able to handle 3D surfaces making it suitable for production of 3D moulded interconnects. Mussmann says both the laser and plasma systems used in the LPP process are designed for easy scaling to high volume production. LPKF’s laser technology is already well proven in LDS production of mobile phone antennae. The Plasma Innovations plasma applica- tion process is carried out at atmospheric pressure, while the company’s multiple station rotary machines can
be confi gured to process many parts at a time.
Mussmann estimates, for example, that 24 INJECTION WORLD | March 2015
the Fakuma demonstration component could be run at a rate of around 3,000 parts every eight minutes or so on an optimised production-scale system. “We would expect this process to be less costly than LDS,” he says. Elsewhere, engineers at lighting manufacturer
Osram have been working with researchers at the IKV plastics processing institute at Aachen University in Germany to develop a method for integrat- ing metallic electronic circuitry into plastic parts during the injection moulding process. Other partners in the develop- ment of the hybrid integrated metal and plastic injection moulding process (IMKS) include machinery maker KraussMaffei and mouldmaker Krallmann Group.
The IMKS process involves processing of a thermoplastic and a low melting point alloy to create a plastic moulding with
integrated metallic circuitry in a single step on a conventional injection moulding machine. The process has been under development for several years but is now, according to IKV, at a point feasible for industrial manufacturing. In particular, the team claims to have developed strategies to allow integration of the alloy into visible components and to ensure that a reliable contact is made with electrical inserts. The technique was demonstrated at Fakuma by
KraussMaffei on a CX80 moulding machine producing a part with an integrated ‘press-and-hold” switching function. The hybrid drive moulding machine used a specially modifi ed second injection unit from Krallmann for the metal component. The process involved moulding the two halves of the thermoplastic enclosure in the fi rst shot before moving one half into a second moulding posi- tion, where the metal conductor was formed by injection into pre-moulded channels. Process automation was handled by a KraussMafffei LRX50 robot. A schematic of
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