Originally Posted by Nessism
That blurb from Spectrum is full of inconsistencies. For example regarding the UCD study, first they say "They concluded that all three joining techniques (TIG, Lug, Fillet Brazed), done properly, are clearly of sufficient strength for the purpose of bicycle frame construction." Next they go to say, "Frames built with silver soldered lugs will last longer than those that are fillet brazed and considerably longer than those that are welded."
Honestly, the joining technique does not matter as long as the joining is done properly. TIG is very popular since it's cheapest. It's also slightly lighter which is important to many people. Frame will ride the same either way - it's mostly about looks and cost.
That's not an inconsistency.
Sufficient strength is different from longevity.
In what I've been reading and from what I can add from the mechanics of materials engineering classes I've taken, fillet brazed joints do not create stress risers, unlike the highly heterogeneous surface and interface of TIGed joints. Also, the transition from lug to tube will create a stress riser but seems far away enough from the joint to be less of a problem. However, I've seen several older racing frames broken at the edge of the lug on the chainstay, seat tube and downtubes all at the bottom bracket.
I don't think TIGed frames have been around long enough for failures to really start occuring yet and there just weren't nearly as many racing frames with thin tubes and fillet brazed joints for a good comparison to lugs.