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from Brückner Technology Center
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14 May 2010

Flexible printed circuits & stretching high temperature thermoplastic films


18 May 2010 - The market for flexible printed circuit devices (FPC) is growing fast. These applications are based on high temperature polymer films. In addition to the already established materials, the spotlight is increasingly falling on heat resistant thermoplastic polymer films.

As a polymeric base material for flexible printed circuit the thermoset polyimide (PI) is now predominantly used. The polyimide is characterized by outstanding thermal properties, such as low shrinkage and  coefficient of thermal expansion (CTE). On the other hand there are some disadvantages such as high moisture pickup, low alkali resistance and a comparatively high price. 

While polyimide film is produced from the solution, thermoplastic materials are produced by the flat film extrusion process, which is more economic. Especially for price reasons there is a demand from the industry for alternative materials. Thus, in Brückner`s technology center materials such as PEEK, PEI, PES, PPS, PPSU and PSU have been stretched successfully on the laboratory stretching frame as well as on the pilot line. 

In particular the evaluation has been focussed on the semi crystalline PEEK. In contrast to polyimide this resin has a low moisture pick up, very good chemical resistance and outstanding mechanical properties. By stretching high temperature PEEK thermoplastic film, not only a condiderable improvement of the mechanical properties has been achieved, it was also possible to significantly increase the shrinkage characteristic at high temperature. This leads to a sufficient thermal stability at the reflow soldering process. 

BOPEEK films, which have been oriented simultaneously at our laboratory stretching frame KARO IV, show that the mechanical and thermal characteristics could be improved significantly -  depending on the stretching ratio, temperature, annealing and relaxation conditions (see enclosed table 1). 

If want to get more information about Brueckner`s experience in this field please contact Mr. Roland Lund at our R & D department:



Flexible printed circuit device (FPC)