TUT
Department of Electronics
Projects - Jouste

Kankaanpää Unit - Projects

Flexible electronics "JOUSTE"


  • Work done 11/2006 - 01/2008
  • Project team, Kankaanpää Unit: Emma Kaappa, Sanni Santavirta, Lasse Hahto, Manu Myry
  • Extent of work: 48 person months total, Kankaanpää Unit 24 person months, Flexible electronics integration into textiles
  • Co-operation with Pori Unit
  • Funding: TEKES (Finnish Funding Agency for Technology and Innovation), Clothing Plus ltd, Hexamer Oy, Ama-Prom ltd and Teknikum ltd
  • Results: Technology test samples and report
  • Contact: Emma Kaappa

In Kankaanpää unit the project emphasis is on the designing, protection and encapsulation of flexible electronics. The aim is to encapsulate electronics with textiles and elastomer materials and study textile materials potential to protect electronics. The main idea is to find new technologies to cut and weld textile materials and also find new way to integrate electronics into textiles. The research is carried out by the TUT Kankaanpää Unit and the TUT Pori Unit between 1.11.2006-31.12.2007. The project is funded by TEKES (Finnish Funding Agency for Technology and Innovation), Clothing Plus Oy, Hexamer Oy, Ama-Prom Oy and Teknikum Oy.

Flexible electronics can be manufactured with elastomeric encapsulation and textile surface. Soft textile surface has many advantages when compared to the hard plastic cover of electronic devices. Flexible electronics covered with textile is softer and more comfortable. The most important characteristic is that elastomer encapsulated electronics is easier to integrate in to the garment and new design effects can be used.

In the first part of the project, Design of Flexible Electronics, first objective was to find out existing design rules for flexible electronics and to do research on material selection. The second objective was to confirm some of the rules by computer modeling and to form new design rules concerning component layout at bending zones by computer modeling and bending tests. These new design rules are needed for example in the applications of wearable technology.

In flexible electronics the substrate is made of hard plastic, but because of the thinness of the substrate, it is bendable and so more textile like. The used materials are PET, PEN or PI. Soldered joints between components and copper conductive patterns are made on the flexible substrate. Also conductive pastes and their imprinting methods were investigated by Pori Unit. Encapsulation of flexible electronics is necessary in wearable electronics. The purpose of the coating materials is to improve the mechanical properties and to protect the electronics. The textile and the elastomeric materials were attached together by lamination process.

Elastomeric materials and their suitability for encapsulation were researched in the second part of the project. They were chosen because of their flexibility and dielectric properties. The material needs to protect the electronics from the mechanical stress and also prevent moisture. Polyurethanes and silicones with different hardness are the materials used in this study. When choosing the manufacturing method, the temperature tolerance of the electronics and the mounting of the components are the main concern. The molding to a plastic mold is examined to satisfy all needs and is therefore used in this project. Some of the silicone samples were vulcanized in the oven to speed up the hardening process.

The third part of this project was to encapsulate flexible electronics with textiles using new kind of sealing and cutting technologies. As well as find textiles which can be protective and are durable. The main interest was the possibility to use laser or ultrasound technologies with textiles. The project started by studying the manufacturing methods needed with flexible electronics. To meet the requirements, different welding and cutting methods were studied and compared. Laser cutting of textiles is a fast, accurate and it produces well finished edges especially with synthetic materials. The laser was also used to cut edges of flexible circuit boards (FPC). This way we could minimize the tearing of the FPC under stress.

The conclusion, based on the test results, were that the silicones resist better moisture but have lower mechanic strength and adhesion to the electronics and with the right choice of finishing treatment, the textile endures well as electronic covers and it also has better cleaning and protection qualities. The final conclusion was that, elastomeric encapsulation and textile cover gives electronics new soft feeling and good protection.

Links and other info:

Publications:

  • THE PROTECTION AND ENCAPSULATION OF FLEXIBLE ELECTRONICS, Santavirta and Kaappa (2008)
  • THE PROTECTION AND ENCAPSULATION OF FLEXIBLE ELECTRONICS USING ULTRASOUND AND LASER TECHNOLOGIES, Santavirta and Kaappa (2008)

Updated , Hokkanen Mirja