This discussion has been beat around the net more than a tennis ball. I think the best statement on soldering a crimped terminal comes from the Senior Product Engineer Tom Michielutti at AMP. AMP is one of the most widely respected suppliers of crimp terminations to the US Aerospace and military sectors. Below is the statement from the senior engineer at AMP. NOT MY WORDS.


Begin Quote:


"Subject: Soldering Crimped Connections & Solder in Crimps


This subject is discussed in AMP’s internal “Fundamentals of Connector Design” course.


Soldering Crimped Connections


In the minds of some customers, fortunately a diminishing minority, the reliability of crimped connections can be improved by soldering. In fact, soldering can degrade the performance of properly crimped connections. Such degradation can arise from the effects of soldering temperatures, the potential corrosion from improper cleaning of soldering fluxes and the effects of solder wicking on the conductors. Solder wicking causes the multi-strand conductors, which have high flexibility and stability against vibration, to become, effectively, solid which degrades both the performance characteristics mentioned. For these reasons, soldering of crimped connections is not recommended.


Should Solder be Used in Crimps?


Crimps are designed to work without solder or solder-dipped wires. Solder present in a crimp changes the deformation, metal flow, cleaning, welding, and residual force characteristics designed into the crimp. Soldering would be an additional heat producing assembly step. Test results show that soldering or solder-dipping wires before crimping does not produce a termination superior to that obtained in a properly applied crimped termination. Some tests specifically show detrimental effects due to soldering or solder-dipping (e.g. soldered crimp terminations can lose some ability to withstand vibrations and flexing, due to solder embrittlement of the copper wire, and/or due to solder wicking up the strand of stranded wire to form a short length of solid conductor near the
termination). The terminated conductor then does not have the flexure strength characteristic of strand wire, and should behave more like solid wire which fails quickly in flexure testing."


The above is a direct quote from AMP.


PHOTO: The cut open pictured crimp was made with the tool on the left in the bottom photo. An AMP yellow PIDG terminal and an AMP crimp tool. This combination is certified for aerospace use. When crimped with a 12 AWG wire it will also withstand at least 190 pounds of pull out force and do so repeatably within a pound or two every single time. This is 80 pounds beyond Mil Spec!!