More Efficient Induction Soldering Through Non-Contact Infrared Temperature Measurement

Temperature Control as a Challenge in Induction Soldering of Copper

In the production of high-performance transformers, generators, and other electrical engineering components, copper wires, copper rods, and multilayer copper busbars must be joined permanently and reliably. One widely used method is induction soldering, in which copper conductors are selectively heated using an electromagnetic field. Precise temperature control plays a crucial role in ensuring the quality of the solder joints and the cost efficiency of the entire manufacturing process.

During the soldering process, several copper conductors are secured in a fixture and heated by an induction coil. Copper-based solder is placed between the individual layers and melts at an application-specific temperature of approximately 650 to 670 °C, allowing it to flow between the contact surfaces. Once the required temperature is reached, the energy supply must be switched off at precisely the right moment. If heating stops too early, the solder does not melt completely, resulting in insufficient joints that require time-consuming manual rework. Excessive temperatures, on the other hand, can cause severe oxidation, material damage, and unusable solder joints.
Non-contact infrared temperature measurement on copper surfaces presents a particular challenge. Copper has a low emissivity that depends strongly on its surface condition. During heating, oxidation and surface discoloration change its radiation characteristics, potentially affecting the readings of an infrared pyrometer. Reflected thermal radiation, changing lighting conditions, and restricted installation positions further complicate reliable measurement.

Manual spot checks using a handheld IR thermometer often fail to provide sufficiently reproducible results because the measurement point varies between readings. Automated industrial soldering processes therefore require continuous temperature monitoring. Permanently installed infrared sensors enable repeatable measurements at defined locations and provide the basis for temperature-dependent shutdown of the induction heating system. This helps reduce critical temperature deviations and maintain consistent process conditions, even at high production volumes.

Optris Pyrometers Improve Process Reliability and Cost Efficiency in Copper Soldering

The use of Optris pyrometers improves process reliability and cost efficiency in the induction soldering of copper conductors. Continuous infrared temperature measurement enables temperature-dependent, reproducible shutdown of the induction heating system. This reduces the risk of incompletely melted solder joints and overheated copper surfaces. As a result, fewer joints require additional soldering, reducing the associated manual workload.

Automated temperature monitoring has a particularly positive impact on manufacturing efficiency at high production volumes. In the described application, approximately 300 to 400 copper conductor assemblies are processed daily in two- or three-shift operations. A complete processing cycle, including clamping, heating, and cooling, takes approximately two minutes. Reducing additional rework enables higher throughput, lower labor costs, and less scrap.

A key advantage of the Optris solution is the combination of compact dimensions, short-wave infrared measurement technology, and straightforward integration into existing machine control systems. Compared with an infrared or thermal imaging camera, the CTi 3M requires significantly less installation space. Since the temperature at a defined measurement point is sufficient to trigger process shutdown, full-field thermal imaging is unnecessary. Point temperature measurement therefore provides a practical solution for this application.

Further optimization is possible using application-specific Optris accessories. A reflection protection tube reduces interference from reflected ambient radiation and improves measurement stability. An air purge attachment with integrated close-focus optics protects the sensor optics and enables smaller measurement spots when the measurement geometry is suitable. Additional mounting brackets facilitate precise alignment of the pyrometers with the solder joints.

The combination of application-specific sensor selection, flexible interfaces, and compatible accessories makes Optris a suitable partner for industrial temperature monitoring. By jointly optimizing the measurement position, emissivity settings, and shutdown threshold, the soldering process can be further stabilized and adapted to different copper geometries and production conditions.