Effect of surface treatment on fatigue life of postceramic soldered joints

Purpose: This research investigated the effect of surface treatment on the fatigue life of metal-ceramic postsoldering. Materials and Methods: Twenty cylindric specimens were cast in a metal-ceramic alloy. All specimens recei ved appropriate heat treatment simulating ceramic application, although no porcelain was applied. Each specimen was cut in half to form two half speci mens. The 40 half specimens were randomly assigned to one of the four treat ment groups, which differed in the type of surface treatment performed on o ne end of each half specimen (joint surface) prior to soldering: (1) alumin ous oxide pink stone; (2) 50-mum aluminum oxide sandblasting; (3) brown rub ber point; and (4) gray silicone wheel followed by pink silicone wheel. All surface treatments were performed for 30 seconds. The half specimens were then steam cleaned, aligned, indexed, and oven soldered with #650 postceram ic solder. The soldering of two half specimens formed a complete test speci men, and a total of 20 postceramic soldered specimens were prepared. Follow ing soldering, a 241.1 MPa fatigue stress was applied to each solder joint during specimen testing. The test variable was the number of stress cycles required to fail each specimen. Results: All specimens failed adhesively at the joint interface between the solder and parent metal. There were signif icant differences in the number of stress cycles to failure between groups 1 and 2, groups 1 and 4, and between groups 2 and 3. Conclusion: The load c ycle to failure for postceramic soldered joints was affected by the metal s urface treatment.