ESPOO, FINLAND -- A new roll-to-roll overmolding manufacturing process turns components into durable electronics products such as wearable sports solutions, toys and, for even household appliances equipped with an overmolded solar cell, a new report says.

The jointly funded project coordinated by and developed at VTT Technical Research Centre of Finland combines printing, component assembly and overmolding of components. The process can print conductors, circuit boards and sensors onto a film, with the resulting electronic components then assembled by an assembly machine. The structure is then overmolded with plastic.

"The results we achieved show that it is easy to overmold components assembled onto a flexible film into durable products," said project manager Tapio Ritvonen from VTT.

Oulu University of Applied Sciences carried out extensive series of tests on the products manufactured using this process, investigating the durability of the structures by means of salt spraying and various mechanical tests, for example.

A printable and modeled transistor was also developed with the roll-to-roll printing process during the project. Precision printing was tested at the same time, achieving 2-micrometre line widths and spaces. During the project, the University of Oulu developed a measurement method for the quality assurance of industrial production, based on synchronized thermography, where a thermal camera locates any defects in a printed, conductive structure.

One of the corporate partners involved in the project, the measurement equipment supplier Focalspec, found that its front row seat in the development and testing of cutting-edge technologies brought it concrete product development benefits.

"The optical scanner solution developed during the project can measure 3D contours of a surface and determine, for example, the layer thickness of a printed pattern with sub-micrometre precision," says Karri Niemelä, Vice President, Research and Development.

"For us, the joint project offered a smooth entry into the TEKES project," says Hannu Valkonen, CEO of Ultracom, the developer of the accurate and lightweight Novus dog tracker. Clothing+, in turn, focused on the data transfer properties of printed conductors in wearable products. "Our development work continues, and we intend to utilise the research results obtained now in future customer projects to a larger extent," said Project Manager Anni Varis.

Flexbright, a manufacturer of flexible LED light foils, was another project partner. The technology it uses was developed in cooperation with PrintoCent and VTT's Oulu unit. "Our involvement has reinforced our own product development, and the groundwork done by the research institutes strongly supports the production prospects of the companies," said CEO Pekka Makkonen. During the project, Flexbright also developed a functional demonstration combining intelligence and wireless control with light foils for prospective Internet of Things applications.


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