Textile electroplating
The dry plating is a process for electrochemical deposition of metals on fabrics and yarns . It represents a special form of plastic electroplating. In order to further increase the flexibility of assemblies in microelectronics and microsystem technology , conductive textile structures are increasingly becoming the focus of interest. In addition to conventionally used metal wires, strands, fiber yarns or thread constructions made of polymer threads and wires, metallized threads are used for this. The interest in metallized thread materials is growing, not least because of their flexibility, resilience and mechanical strength.
Procedure
Since textile materials are generally not electrically conductive, a well-adhering electrically conductive layer must first be applied. Conventional methods of plastic metallization can be used in a modified form for this purpose. Suitable methods of pretreatment are, for. B .:
- Physical Vapor Deposition (PVD),
- Chemical coatings with the aid of palladium activation,
- Chemical etching processes (chemical bonding forces),
- Plasma pretreatment (physical bonding forces),
- Mechanical roughening (mechanical bonding forces ).
After the start layer has been applied, the metal is electrodeposited . Electricity is sent through an electrolyte . The textile forms the cathode . Conventional sacrificial anodes of the respectively deposited metal or dimensionally stable expanded titanium metal anodes can be used as anodes . Electric current density and dwell time are varied depending on the desired metal layer thickness.
The electroplating of textiles is possible both in the form of flat textile structures and on single threads. When galvanizing circular knitted fabrics , the metallized thread can be recovered.
Conductive structured surfaces can also be galvanically treated.
Polyamide and polyester are mainly used as base materials. The process can be adapted accordingly, but can also be transferred to other polymers.
The most common metals deposited on textiles are silver and copper.
properties
With the help of textile electroplating, metal layers of a few micrometers [µm] can be produced. The mechanical and electrical properties of conductive yarns can be specifically influenced by their structure and material composition, whereby the textile character is largely retained. The thinner the metal layer, the more the yarn is characterized by textile properties, but the lower the conductivity.
In contrast to metallic wires and strands, the galvanically metallized threads can be stretched up to 7% without their conductivity decreasing noticeably.
Despite the metal jacket, the textiles are extremely durable and resistant to bending.
In the event of high current loads, the metallized polymer threads interrupt the power supply without creating sparks or heat spots. At higher temperatures they contract, spontaneously and completely tear over all filaments.
application
Textile structures cannot be replaced by any other material with regard to their deformability and flexibility. This is why metallized thread materials are an interesting alternative to the metal threads previously used, because the textile properties of the base material, which largely determine the mechanical behavior, are almost completely retained.
Conductive textiles with lower electrical conductivity are used for antistatic applications and shielding purposes. Higher conductive yarns are used in the textile industry as well as in the electronics industry, electrical engineering and microsystem technology. The advantage of the higher flexibility of conductive textile materials is used.
Through weaving, knitting, embroidery, knitting and sewing, conductive structures can be produced in textiles, which are used for the transmission of energy and information as well as for the integration of electrical components. Because of this, they meet requirements to increase the flexibility of components in microelectronics and microsystem technology.
Over 90% of innovations in automobiles result from the use of electronic components and microsystems. Highly conductive textile materials are already in use today.
The number of textile electronic assemblies used in telecommunications equipment, airplanes and in building services is also growing steadily.
Textile microsystems are used for smart textiles e.g. B. as
- heatable textiles,
- textile electronic components (bus systems, sensors, switches ...),
- Antenna systems for RFID systems
- textile microsystem technology (sensor components, accumulators, solar cells) or
- textile light sources
used.
literature
U. Möhring, A. Neudeck, W. Scheibner: Textile Micro System Technology in H. Matilla (Ed.): Intelligent Textiles and Clothing . Woodhead Publishing Limited, Cambridge (2006)
A. Neudeck 1 , Y. Zimmermann 1 , H. Hellwich 1 , U. Möhring 1 , A. Hacke 2 ( 1 TITV Greiz; 2 WHZ Zwickau): Technology for galvanic and electrochemical modification of pre-structured, partially conductive textile surfaces . UNITEX (2006) 2, pp. 12-14