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What Are the Soldering and Handling Recommendations for Ultracapacitors?

Tecate Group carries a variety of different ultracapacitor cells. Most of these products are designed to be mounted to PC boards by way of soldering, and all of them are RoHS-compliant and thus have lead-free preparations that require adjustments in the processes used to interconnect them with their substrates.

Please note that the process and parameters described here were developed on specific equipment and apply most fully to that equipment. It is very likely that alternative pieces of equipment will require fine-tuning of those parameters to achieve optimal results.

General Precautions

There is a risk of the ultracapacitor cells deteriorating due to excessive heat exposure during soldering, and there may also be a buildup of internal pressure. Depending on the type and size of the board, overheating the ultracapacitor cells may also cause the safety vent to burst. These outcomes will greatly shorten the life of the cells and may cause leaking problems.

Be sure not to dip the entirety of the ultracapacitor cell bodies into melted solder and to only flux the leads of the cells. Ensure that there is no direct contact between the sleeves of the ultracapacitor cells and the PC board or any other component as excessive heat during soldering may cause sleeves to shrink or crack. Similarly, do not touch the sleeves with the soldering rod, as that can cause them to melt or crack.

Hand Soldering

In order to solder ultracapacitor cells by hand, good soldering practices must be used. The solderer should have experience with hand soldering of electronic components and understand fundamental soldering processes. In general, lead-free soldering by hand requires higher heat and more active fluxes than solder containing lead as a constituent. Therefore, new thermal profiles must be adopted and new cleaning agents should be used.

The recommended temperature of the soldering rod tip is no more than 350°C. The soldering duration should be shorter than 3 seconds. Minimize the time that the soldering iron is in direct contact with the terminals of the ultracapacitor cells, as excessive heating of the leads may result in higher ESR.

Wave Soldering

In order to wave solder components, special attention must be paid to the dwell time and total time at temperature, since ultracapacitors are temperature-sensitive components. Preheat the board from the bottom side only, bringing the top of the board to 100°C, maximum, immediately before soldering. The preheat time will depend upon the heating efficiency, but use a maximum preheating time of 60 seconds.

The recommended conveyor speed is 2.8cm per second, and the soldering duration time should be shorter than 2.5 seconds. Minimize the time that the soldering iron is in direct contact with the terminals of the ultracapacitor, as excessive heating of the leads may result in higher ESR.

Due to the relatively high thermal masses of the components, and especially if the total number or density of the components is high, the use of a standard thermo-profiling device is strongly recommended to avoid excessively high temperatures.

Automated Soldering

Soldering may be automated with a hot-bar soldering jig, with soldering irons mounted on an automated raise-lower device with time and pressure controls. It is also possible to mount cells using conductive adhesive, ultrasonic welding, or laser welding.

Washing

Do not use solvent cleaners, as these may damage the device packaging; improper solvents include acetone, benzene, isopropyl alcohol, and halogenated solvents. Instead, use only aqueous cleaning solutions based on deionized water.

Washing should take place at elevated temperatures not exceeding 70°C. Spray pressures should not exceed 50psi.

Drying

Post-wash drying should be kept to the minimum necessary duration, at temperatures not exceeding 80°C. Rapid airflow around the modules during drying will assist in the removal of moisture trapped in the packages.