Evaluation of Inductor for Solderability and Drop Damage Susceptibility

Mack Marshall, Edward Huang, Arun Rajaraman, David Grosjean
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引用次数: 0

Abstract

Abstract Lead-free solder joints tend to be more susceptible to brittle fracture, and thus susceptible to drop-damage. Drop testing of handheld ultrasound devices revealed broken solder joints on a large inductor component. Analysis of the cracks showed a dual intermetallic compound (IMC) layer of Ni3Sn4 (closest to the nickel) and (Ni,Cu)6Sn5, with the crack occurring in between the two layers. The inductor had a tinned nickel lead finish; the solder was SAC305 (a common lead-free solder comprising Sn, Ag, and Cu); and the printed circuit board (PCB) had a standard copper finish. The failure occurred very soon after manufacture and had not been enhanced by temperature cycling or aging, but it was not a time-zero failure: mechanical shocks from drops were required to propagate the crack through the joint fully. Strain measurements did not find any large strains after reflow and assembly, and no other components on the board showed cracking. There was no cracking observed at the PCB (Cu) side of the solder joint. The solution ultimately was to redesign the board, replacing the large single component with several smaller ones.
电感的可焊性和跌落损伤敏感性评估
摘要无铅焊点易发生脆性断裂,易发生跌落损伤。手持式超声波设备的跌落测试显示一个大型电感元件上的焊点断裂。裂纹分析表明,裂纹形成了Ni3Sn4(最接近镍)和(Ni,Cu)6Sn5的双金属间化合物(IMC)层,裂纹发生在两层之间。电感器表面镀锡镍铅;焊料为SAC305(一种常见的无铅焊料,包括锡、银和铜);印刷电路板(PCB)有标准的铜涂层。该故障在制造后不久就发生了,并且没有受到温度循环或老化的影响,但它不是零时间故障:需要来自液滴的机械冲击才能将裂纹完全扩展到连接中。在回流和组装后,应变测量没有发现任何大的应变,并且板上的其他组件没有显示开裂。在焊点的PCB (Cu)侧没有观察到裂纹。最终的解决方案是重新设计电路板,用几个较小的组件取代大的单个组件。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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11 weeks
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