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SolderTips: Avoiding the Creation of Splices Via Wire Twisting

Question: The IPC lists different splices for wires including wrap, hook, mesh, and lap. We have all seen wires spliced together by twisting the two wires together forming a gentle twist before soldering. This splice would not have the physical strength of a wrap or hook splice, but it seems like it would offer at least the same strength as a lap splice with less aggravation, since the splice would stay in place during the soldering process. Why does the IPC not recommend creating this type of splice?

Answer: The IPC/WHMA-A-620, Chapter 8 – Splices (as you stated) includes the criteria for the various splice processes.  Section 8.1.2 Soldered Splices – Wrap, includes the statement: “Strip wire to allow a minimum of 3 wraps (not twists) of each wire around the other.”  There are other sections throughout the standard where the “twisting of wire” is a Defect Condition for all 3 classes.

The reason we do not twist wires to create splices is that it may affect the reliability of the solder joint.  Over stress may crack and separate this type of splice.  One recommendation, if you are having a difficult time during the soldering process, might be the “lash” process even though the 620 states; “ . . . a lash splice, does not provide a significant increase in strength to the connection, it may facilitate forming the splice.”  The lash will hold the wires together during the soldering process.