VICTREX® PEEK™ polymer is an ideal substrate for a new durable metallisation process

VICTREX® PEEK™ polymer is the ideal substrate for a new metallisation technique that has been developed by Dr. Ing. Max Schlötter GmbH & Co. Kg of Geislingen/Steige, Germany. The SLOTOSIT KM process has been designed specifically to meet industry needs for highly durable polymer metallisation combined with a high level of mechanical and thermal performance. Companies are successfully using the process to plate PEEK™ polymer with copper, providing a tailor-made material for demanding electronic applications such as flexible circuit boards and parts for moulded interconnect devices.

Electrolytic plating is commonly used to apply metallic coatings to plastics such as ABS and blends of ABS/PC. However, some properties of ABS or ABS/PC, notably mechanical strength, stiffness and temperature performance, limit their suitability for certain applications. Metallised parts made of these engineering plastics withstand a temperature of typically 110°C, which makes a subsequent soldering process impossible.

Dr. Ing. Max Schlötter developed the SLOTOSIT KM process to metallise a range of high performance polymers such as Polyamides, Polyimides, Polyethersulfones and Polyaryletherketones. The best results were obtained using PEEK™ polymer. PEEK™ polymer is a semi-crystalline and aromatic polyketone thermoplastic which is widely regarded as the highest performance engineering polymer. It maintains excellent mechanical performance up to 300ºC and its outstanding electrical properties are maintained over a broad temperature and frequency range. According to UL 746B, PEEK™ polymer has a Relative Thermal Index (RTI) of 260ºC. These properties, in combination with the high adhesion of the metallic coat to the polymer using the SLOTOSIT KM process, provides the electronics industry with a highly durable metallised polymer which can withstand extremely high soldering temperatures.

The Table below shows values of peel force that have been determined after various thermal treatments. Samples of natural PEEK™ 450G and 30% glass fibre filled PEEK™ 450GL30 were coated with 30m copper using the SLOTOSIT KM process and subsequently conditioned as indicated. Adhesion was determined in a peel test according to DIN 53494. The values of peel force after thermal treatment demonstrate that these composites are capable of withstanding common soldering techniques. This was also confirmed by soldering tests on circuit paths generated using a photo resist on copper coated PEEK™ film.

Peel strength of 30 m copper on VICTREX® PEEK™ after thermal conditioning

grade thermal treatment peel force [N/cm]

450GL30 1h/100°C 32  5

1h/220°C 31  5

5h/220°C 31  4

450G 1h/100°C 28  6

24h/220°C 27  6

1h/260°C 25  5

A unique property profile, complemented by consistent ease of processing, has established the use of PEEK™ polymer in diverse applications across a broad spectrum of industries – from aerospace and automotive, electrical and electronics to medical and food. This widespread use, and the success of the SLOTOSIT KM process in the manufacture of flexible circuit boards and parts for moulded interconnect devices, opens up a whole range of exciting opportunities for metallised PEEK™ polymer.

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Helen Swarbrick
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