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Vol.45, No.11, 635 ~ 639, 2007

Title

The Effects of Fatigue Diffusion by Lead Free Solder SnAg3.5Cu0.5Sb2 of BGA Packaging

Kyoung Soo Kim

Abstract

Each layer of metals plated on Ball grid array package (BGA) substrates has its own specific functions. The compound of Sb is used to prevent from diffusing into solder balls. Reliability tests were conducted to investigate the effect of Lead free solder composition on ball fatigue strength. Samples were made using SnAg(3.5)Cu(0.5), SnAg4Cu(0.5) and SnAg(3.5)Cu(0.5)Sb2 solder compositions and were pre-conditioned at moisture resistance test (MRT) level 3. Temperature cycle tests (T/C) were done after pre-conditioning. It was found that two intermetallic layers formed formed when SnAg(3.5)Cu(0.5), SnAg4Cu(0.5) solders were used while only a single intermetallic layer was observed when SnAg(3.5)Cu(0.5)Sb2 solder was used. The effect of the weight ratio of Sb on the ball shear strength under reliability tests becomes very interested. The degradation of shear strength of solder balls after reliability test is discussed.

Key Words

Intermetallic Layer, temperature cycle tests (T/C), Lead free solder

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