TC 2.2

Fluid Flow Mechanics: Key to Low Standoff Cleaning

Jimmy Tian, ZESTRON China

In recent years, various studies have been issued on cleaning under low standoff components; most however, with incomplete information. It is essential to revisit and describe the latest challenges in the market, identifying obvious gaps in available information. Such information is crucial for potential and existing users to fully address the cleanliness levels under their respective components. With the emergence of lead-free soldering and even smaller components, new challenges have arisen including cleaning in gaps of less than 1-mil.

This study was initially designed to investigate the impact of mechanical vs. chemical energy contributions during the removal of contamination under 1-2 mil standoff components. To validate the results obtained, extensive studies were conducted, specifically prepared test- assemblies, iterative experimentation, as well as new mechanical innovations that might help users in the future. The latter include, but are not limited to, various flow pattern designs and industry-leading cleaning agents. As a result, the authors will also include experimental data to address fluid flow mechanics, temperature and solvent concentration-related effects.

Initial results obtained indicate that cleanability of residues under low standoff components has become a non-trivial issue. Not only are residues becoming harder to remove, the penetration of the cleaning agent seems to be in direct relationship with the geometry and height of the components in question.

 Key words: Fluid flow mechanics, Low standoff cleaning, Lead-free soldering

 

低间隙清洗工艺中的流体力学研究

田剑,ZESTRON 中国

近年来业界发表了许多关于低间隙元器件底部清洗的论文,遗憾的是大多数论文所包含的信息都不完整。因此笔者认为对于当前行业所面临的挑战需要进行重新分析和更精确的描述,以找到我们手头所掌握信息中的缺漏之处。这些缺漏的信息对潜在客户和现有客户来说都非常重要,因为据此可以了解目前元器件底部清洗的洁净度,并找到恰当的清洗工艺。另外,随着无铅焊接工艺的普及,元器件底部的间隙进一步缩小,如何有效清洗引脚间距小于1-mil的应用给业界带来了新的挑战。

本次研究的最初目的是调查在去除元器件底部间隙为1-2mil的污染物时,物理与化学能量分布的影响。其后又进行了一系列的测试以验证实验结果。在研究的进行过程中应用了专门准备的测试基板、相互关联的DOE以及未来有可能帮助用户的创新型的机械激励方式。在研究的后期引入了多种不同的清洗方式和行业领先的清洗液进行测试。作为研究的结果,笔者将会在本文中提供详细的实验数据以体现流体力学、温度和溶液浓度对清洗工艺的影响。

初始结果说明对低引脚间距元器件底部的污染物进行有效清洗并不容易,且不论清洗液能否对污染物进行有效去除,在元器件的几何结构如此复杂和底部间隙极其细小的前提下,清洗液能否渗透到元器件底部本身已经成为了一大挑战。

关键词:流体力学,低间隙清洗,无铅焊接工艺

 

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8月29日,星期三 09:30-17:00
8月30日,星期四 09:30-16:30
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