Purpose

In surface mount assembly (SMA) process, small components are subjected to high temperature variations, which result in components’ deformation and cracking. Because of this phenomenon, cracks are formed in the body of carbonyl powder ceramic inductor (CPCI) in the preheat and cooling stages of the reflow oven. These cracks become the main cause of board failure in the ageing process. The purpose of this paper is to ascertain the thermal stress, thermal expansion of carbonyl iron ceramics and its effects on crack commencement and proliferation in the preheat stage of reflow oven. Moreover, this paper also categorized and suggested important parameters of reflow profile that could be used to eliminate these thermal shock failures.

Design/methodology/approach

In this paper, two different reflow profiles were studied that evaluate the thermal shock of CPCI during varying ΔT at the preheat zone of the reflow oven. In the first profile, the change in temperature ΔT at preheat zone was set to 3.26°C/s, which has resulted in a number of device failures because of migration of micro cracks through the CPCI. In the second profile, this ΔT at preheat stage is minimized to 2.06°C/s that eliminated the thermal stresses; hence, the failure rates were significantly reduced.

Findings

TMPC0618H series lead (Pb)-free CPCI is selected for this study and its thermal expansion and thermal shock are observed in the reflow process. It is inferred from the results that high ΔT at preheat zone generates cracks in the carbonyl powder-type ceramics that cause device failure in the board ageing process. Comparing materials, carbonyl powder ceramic components are less resistant to thermal shock and a lower rate of temperature change is desirable.

Originality/value

The proposed study presents an experimental analysis for mitigating the thermal shock defects. The realization of the proposed approach is validated with experimental data from the printed circuit boards manufacturing process.

中文翻译：

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羰基粉末功率电感器回流过程中开裂的实验研究

目的

在表面安装组装（SMA）工艺中，小型零件会经受高温变化，从而导致零件变形和破裂。由于此现象，在回流炉的预热和冷却阶段，羰基粉末陶瓷电感器（CPCI）的主体中会形成裂纹。这些裂缝成为老化过程中电路板故障的主要原因。本文的目的是确定羰基铁陶瓷的热应力，热膨胀及其对回流炉预热阶段的裂纹萌生和扩散的影响。此外，本文还对回流曲线的重要参数进行了分类并提出了建议，这些参数可用于消除这些热冲击故障。

设计/方法/方法

在本文中，研究了两种不同的回流曲线，以评估CPCI在回流炉预热区变化ΔT期间的热冲击。在第一个曲线中，预热区的温度变化ΔT设置为3.26°C / s，由于微裂纹通过CPCI的迁移，导致了许多器件故障。在第二个曲线中，该预热阶段的ΔT最小化为2.06°C / s，从而消除了热应力。因此，故障率显着降低。

发现

本研究选择了TMPC0618H系列无铅（Cb）CPCI，并在回流过程中观察到了其热膨胀和热冲击。从结果可以推断出，在预热区的高ΔT会在羰基粉末型陶瓷中产生裂纹，从而在电路板老化过程中导致器件故障。比较材料，羰基粉末陶瓷组分对热冲击的抵抗力较小，并且期望较低的温度变化率。

创意/价值

拟议的研究提出了减轻热冲击缺陷的实验分析。印刷电路板制造过程中的实验数据验证了该方法的实现。