The metallurgy of fillet wiped soldered joints

THE seriousness of the present tin scarcity has stimulated large consumers of this vital metal to develop drastic conservation measures in order to extend the available supplies to cover the emergency period. By devising new soldering methods and alloys the Bell System has contributed a substantial share in the tin conservation effort. Fortunately, the changes, as far as can now be determined, have not introduced weakness into the soldered joints. Some of the new procedures now used were already in the process of development at the onset of the emergency, while others were devised under its stress. In some instances, the newly developed solders were found to be more difficult to use than the alloys previously available, and would not have been introduced under normal conditions. One major change made that previously had been under consideration will result in large tin savings. Unless service difficulties are encountered, this modification gives promise to remain after the emergency has passed. The change involves a reduction in the amount of solder placed on a wiped joint between the cable sheath and the sleeve. Instead of the customary full size wiped joint a wipe of fillet proportions is formed. Through this change, a solder saving of over 60% per joint can be realized.