Direct thermal joining: Connecting metals and plastics directly

Plastics and fibre-reinforced plastics are getting more and more important in production. Properties such as high strength and low weight have made these materials increasingly attractive for designs, especially in automotive engineering.

The challenges lie in the interface to the metal as a conventional material. For a long time, it has not been possible to weld plastics directly to metal. Adhesive has to cure which takes considerable time until further processing can be carried out. The holes or rivets usually required in mechanical joining processes are weak points and may damage the fibres of reinforced plastics.

Direct thermal joining: The effective alternative

Direct thermal joining developed by our research partner ISF now offers an efficient and effective alternative to adhesive bonding or riveting.

The metallic joining part is heated electrically with resistance heating. When brought together with the plastic joining partner, the plastic melts and forms a firm bond with the metal immediately after solidification.

High-strength and reliable connection

High bond strengths between metal and plastic are already achieved by the adhesive bond. If required, the strength can be further increased through pre-treatment of the metal. Moreover, additional material locking is obtained after structurisation using CMT pin structures or electron beams.

As a result, the joint achieves strength values which are higher than those of the used plastic material. Since a connection is created over the entire contact surface and due to the fact that fibres, also of composite materials, are not subject to damage, the transmitted forces are distributed evenly - the best prerequisite for a reliable connection.

High joining speed

The resistance heating used in direct thermal joining allows to obtain a high joining speed. Compared to adhesive bonding, the process steps of adhesive application and curing are completely eliminated. Immediately after direct thermal joining, the joint is fully loadable and the component is, without any restrictions, available for the next production step.

Cost-effective joining of metal and plastic

Once the parameters of direct thermal joining have been optimally configured, the joining process can be reproduced quickly and easily. Expenditure for required investments is comparatively low, in some cases even existing facilities can be used.

A tight grip on process control

The great challenge in direct thermal joining of plastic and metal is the correct process control. We have gained a wealth of experience in the selection of suitable parameters from our intensive research and development activities. This is how we ensure that your production forms connections between metal and plastic with high strength and reliability.