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We have tested a large number of stretched Cu-Be wires, held with solder alone and with solder/epoxy.
We find that cu-Be wires of 6 mil diameter can be held with epoxy solder alone indefinitely if the shear stress on the wire surface is below 170 psi, limited by creep.
Higher stresses can be supported without significant creep if epoxy blobs are used in addition to the solder. We found, however, a large fraction of electric continuity failures within the epoxy if the boards were oven-cured at 60 C for two days. These failures are not understood.