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Solder Ball Joint Reliability with Electroless NI-PD-AU Planting
Solder Ball Joint Reliability with Electroless NI-PD-AU Planting
The influence of Pd film thickness in electroless Ni/Pd/Au plating on the solder ball joint reliability after reflow cycles and thermal aging was investigated.
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Authored By:
Yoshinori Ejiri, Takehisa Sakurai,
Yoshinori Arayama, Yoshiaki Tsubomatsu, Kiyoshi Hasegawa
Hitachi Chemical Co., Ltd.
Ibaraki, Japan

Summary
The influence of Pd film thickness in electroless Ni/Pd/Au plating on the solder ball joint reliability after reflow cycles and thermal aging was investigated by conducting a high-speed solder ball shear test. Sn-3.0Ag-0.5Cu (SAC305) was used as the solder ball in this study. On the basis of the solder joint reliability obtained after multiple reflow cycles and thermal aging, the optimum thickness of the Pd film was found to be 0.05-0.2 microns.

The covering property of electroless Pd plating film on the electroless Ni plating film was also investigated. We found that an electroless Pd plating film with a thickness of 0.02 microns or more covered the electroless Ni plating film adequately, and the solder ball joint reliability in this case was better than that with electroless Ni/Au plating. We consider that the shape of the intermetallic compounds (IMCs) is one of the factors that influence the solder joint reliability after multiple reflow cycles. Consequently, we inferred that the high adhesion at the dendrite layers of IMCs/solder interface resulted in excellent solder ball joint reliability after the reflow cycles. We consider that the thickness of the IMCs is one of the factors that influence the solder joint reliability after thermal aging. In (Cu, Ni, Pd)6Sn5 IMCs that contained trace amounts of Pd, the growth of the IMCs is prevented by Pd, resulting in excellent solder ball joint reliability after thermal aging.

Conclusions
The influence of Pd film thickness in electroless Ni/Pd/Au plating on the solder ball joint reliability was investigated. The following conclusions were obtained.

(1) Based on the solder joint reliability obtained after multiple reflow cycles and thermal aging, the optimum thickness of Pd film was found to be 0.05-0.2 microns. (2) The shape of the IMCs is considered to be one of the factors that influence the solder joint reliability after multiple reflow cycles. We estimated that the high adhesion at the dendrite layers of IMCs/solder interface resulted in excellent joints after multiple reflow cycles. (3) The thickness of the IMCs is considered to be one of the factors that influence the solder joint reliability after thermal aging. For (Cu, Ni, Pd)6Sn5 IMCs that contained trace amounts of Pd, the growth of the IMCs is prevented by Pd, resulting in excellent solder ball joint reliability after thermal aging.

Initially Published in the SMTA Proceedings

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