SMTA International Conference Proceedings

Plasma Based VOC-Free Fluxing for Selective and Wave Soldering

Authors: Andreas Reinhardt, Ph.D. and Sonja Wege, Ph.D.
Company: SEHO Systems GmbH
Date Published: 9/27/2015   Conference: SMTA International

Abstract: For activation of the soldering surface, usually flux based on solvents is used. A new alternative presented in this paper is the plasma based flux deposition. Main component of the system is the plasma nozzle, where short time high voltage pulses generate the nitrogen gas plasma. The fluxing powder is blown into the plasma, melts and is sprayed onto the PCB surface where it solidifies. The challenge for a stable process is the preparation of the powder for uniform delivery to the plasma flame, so that a constant degree of coverage is achieved.

A series of experiments were performed to determine the soldering results for plasma fluxed PCBs. It has been determined that using suitable powders no difference in the results can be determined comparing standard solvent based flux and the plasma technology. Actually, even overaged PCBs could be revived and showed faultless soldering results. The evaluation criteria has been the hole fill of plated-through hole solder joints according to IPC-A-610.

The process can be easily implemented in existing manufacturing as a drop-in solution for both wave soldering and selective soldering. SIR tests have demonstrated that residues after the soldering process have no critical properties. Using this technology, the material logistics can be simplified by eliminating the handling of hazardous materials. Due to reduced creep and reduced residues also the soldering results and need for maintenance of the machines can be improved.

Key Words: 

flux, powder, plasma, soldering, adipic acid

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