Reproducible hot caulking is also possible at low cost

Connection technology

Reproducible hot caulking is also possible at low cost

For effective manufacturing, it is essential to utilize ratio potentials of all processes. The attachment of printed circuit boards to housings or the connection of housing parts are no exceptions. A modern approach to hot caulking opens up potential here.

Ensuring process reliability even for small quantities, and doing so in a short lead time, is the current challenge for many companies in the electronics industry.

"Only the right equipment for detailed processes, such as hot caulking, but also the smooth integration into the process chain ensure high reproducible quality and constant processes."

Nicole Leutz, authorized signatory of Leutz Lötsysteme GmbH

Nicole Leutz pointing out that the individual adaptation of the equipment to the respective project requirements also has a major impact on the economic efficiency of production.

The hot caulking process is used to join printed circuit boards to the housing or housing parts to each other. It is based on thermoforming plastics, especially thermoplastics. For example, a plastic pin protruding through a hole in a printed circuit board is formed into a "rivet head" using a heated tool, thus creating a force-fit connection.

There are several challenges to consider when hot staking: These include the selection of the forming die, as this material must be adapted to the plastic material. Also, the appropriate temperature (process window) must be found without sticking to the tool. Other aspects are the dimensional accuracy of the caulked domes, a reliable process window and also the definition of the dwell time of the dome to be caulked. The optimum shape of the domes (mushroom, elongated dome for spreading, flattened) also plays a role.

Leutz Lötsysteme GmbH has accepted these challenges and develops customer-specific systems and devices for the process of hot staking as well as rotary transfer machines. The aim is always to ensure a reproducible process in order to meet the respective quality requirements. The degree of automation and the associated costs depend on the respective requirements.

The picture shows a simple system for the hot staking process (hot riveting, hot stamp riveting). It works through the following process steps:

  • Manual or automatic feeding of the joining partners in a workpiece carrier with component support.
  • Insertion of the workpiece carrier for the hot staking process.
  • The customized, heated hot caulking head is moved onto the product.
  • Hot staking of one or more pins in one work step.
  • The hot caulking head is moved back to its initial position.
  • The processed component is moved out of the hot caulking station.
  • The result: perfectly form-fitted hot staked parts (from printed circuit boards to housing parts) and visually appealing formed plastic domes.

An extension of this system can be a hot staking unit with a rotary indexing table. Process reliability is also achieved with this process or the systems used by taking a holistic view. It is helpful here that experts accompany all steps - from the conception and realization of the component fixtures to the creation of a control loop and the selection of the suitable stamping material to the use of complex multiple hot staking heads (e.g. staking tasks of ten or more simultaneous forming processes). It is helpful here that the hot staking heads used can be changed, which increases the flexibility of the systems. In addition, linking several process steps, e.g. testing of the electronics, marking of the components or, for example, optical inspection of the caulking result, has proven to be useful. Even if the joining of components by hot caulking looks simple at first glance, it is shown time and again that ratio potentials and the quality of the end products can be found or influenced in each individual process step.

Publishing date

9 July 2021


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