Ask Helena & Leo

Question: We have an application that due to the type of stranded conductor being used, it may be necessary to semi-strip the insulation, flux and dip the conductor with the insulation slug still in place to prevent the conductor from fraying or birdcaging.

I have seen recommendations for litz or magnet wire where the insulation is burned off in a similar method. Is there a concern with contamination of the solder pot by the melted insulation?

Answer: Semi striping the wire with the slug still on the wire is an accepted practice in the industry. Tinning the wire in this condition, however; is not recommended for a variety of reasons, the least of which is the wires beneath the slug may not tin and this may also cause more penetration beneath the insulation eliminating the ability to maintain the wire flexibility. As for the insulation slug, it all depends upon the material it is made from, such as PVC, plastic, and so on. You do not want the insulation to melt into the wire strands as this will impact the soldering of the wire in its final termination.

I would suggest that as the partial strip is remove that it not be pulled straight back off the wire strands of the wire. All the strands within a wire cable are twisted, and the removal of the slug should follow the same twist and rotation to prevent the wire strands from separating. This is a training process and should be included in your training program.

As to whether there may be contamination in the solder pot, the answer is no, as the material is lighter than the solder and will float on the molten solder pot. Although it will have to be removed from the surface of the solder pot, it will not contaminate the solder in the pot.