Circuits Assembly - September 2008 - (Page 54) Materials World 环氧树脂助焊剂为器件保护 提供新方法 虽然焊剂型或非流动型底部填充剂在市场上已 有一段时间了，但这些材料的缺点阻碍了它们的 普遍推广。组装工艺及可靠性能的挑战经常抵消 了这些材料在生产过程上的工艺优势。使用非流 动型底部填充剂时，填充剂首先被应用于基板之 上，然后进行元件贴装。组装件在经过回流工序 时，材料同时固化。但此工艺会受到来源于基板 的湿气蒸发的影响而产生空 洞。为缓解这个问 题，制造商经常选择其它的回流固化材料如边角 加固材料（cornerbond），或回流后固化材料 如周边加固材料（edgebond），因为这些材料 不会填满整个器件底部，所以不存在空洞问题。 虽然边角加固底部填充剂对某些器件是一种有 效的选择，但它们对于许多其他应用并不适合。 因此，为提供一个完全底部保护并具有有效工艺 流程的回流固化粘结剂，环氧树脂助焊剂得以研 制。这种材料可以回流固化，同时具有助焊剂和 底部填充剂的功能。助焊剂 功能确保焊点的形 成，环氧树脂系统则为单独 的焊点提供与底部 填充剂类似的保护。该系统最初为大型的CSP和 BGA器件而设计，用以弥补传统底部填充剂的流 率低及固化时间长的缺点，从而提高在线产率。 环氧树脂助焊剂还可有效用于器件堆叠（PoP） 和值球等工序。除了它的应用多样性外，环氧树 脂焊剂还具有使用方式的灵活性，它可以通过丝 网印刷、浸渍、点胶或喷射等方式使用。 对于PoP组装，环氧树脂助焊剂是一种用于解 决PoP器件装配问题的很有前途的办法。底部封 装件使用相对例行的表面贴装程序，但上部封装 件的组装及后序的长期可靠性并不这么简单。当 前，最常见的方法是在助焊剂上浸渍上部封装件 的底部锡球，器件贴装，然后回流，在回流炉中 形成焊点。但不幸的是，焊点并没有得以保护， 将会受到来源于冲击、跌落 和振动等应力的影 响。相对而言，环氧树脂助 焊剂作为一种替代 方式，虽然上部封装件的组 装使用同样的工艺 流程，但却可得到胶粘剂的额外保护。在此工艺 中，环氧树脂助焊剂被用来代替传统的助焊剂来 浸渍焊球。贴片完成后，组装件被送入回流炉， 回流过程中，助焊剂中的焊剂成分帮助形成牢固 的焊点联接，同时，环氧树脂组分包裹每个焊球 并固化。除了这种新材料提供的额外保护之外， 它可在线使用的好处和成本的节省也是非常显著 的。由于不需要后序的点胶和固化程序，单位产 出量显著提高，产率提高及省去特定的点胶设备 也进一步减少了生产成本。在最近的测试中，与 常规的助焊剂相比，环氧树脂助焊剂具有最好的 跌落测试结果，在初次失效之前，它可承受更多 次的跌落。这表明，环氧助焊剂比单纯的助焊剂 提供了更多的保护。 类似的结果显示，当环氧树脂助焊剂用于植球 工艺时，它再次胜出传统的水溶性助焊剂或非清 洗助焊剂，其可靠性和强度被证明更优秀。用四 种不同的助焊剂对三种锡球合金进行植球并做抗 剪强度测试，环氧树脂助焊剂以明显优势胜出。 图1、2及3中，助焊剂A和B分别是两种水溶性助 焊剂，C是非清洗助焊剂，D是环氧树脂助焊剂。 对于每个焊锡合金，环氧树脂助焊剂都提供了最 强的焊点。 如前所述，新一代环氧树脂助焊剂的多功能特 性是显著的。对于新型的封装形式如PoP的器件 级的植球，当然加之大型的BGA 和 CSP的二级 组装，环氧树脂助焊剂为制造商提供了以一种材 料用于多种应用并有多种使用方法的能力。这种 新型材料以提高供应链效率、节约成本、增加产 出率、简化制造流程、增强可靠性能等优点，提 供了取代老一代工艺的创新途径。 n Dr. Renzhe Zhao is technical manager, applications engineering at the electronics group of Henkel (henkel.com); renzhe. zhao@us.henkel.com. For the English version, visit circuits assembly.com. Flux A B C D 图1. 不同助焊剂在SAC-1合金上的测试结果 1. SAC-1 54 Circuits Assembly SEPTEMBER 2008 circuitsassembly.com http://henkel.com http://circuitsassembly.com http://circuitsassembly.com http://circuitsassembly.com
Table of Contents Feed for the Digital Edition of Circuits Assembly - September 2008 Circuits Assembly - September 2008 Contents Caveat Lector Industry News Market Watch Talking Heads Focus on Business Global Sourcing On the Forefront Screen Printing Better Manufacturing Reflow Soldering with a SnCu Eutectic Pb-Free Alloy Improving OEE in High Mix Facilities Effectively Managing RF Design in Utility Metering Applications Solder Joint Reliability of Different BGAs Reworked Using Low Melting Point Pb-Free Alloys Tech Tips Wave Soldering Pb-Free Lessons Learned Materials World Process Doctor Equipment Advances Product Spotlight Ad Index Assembly Insider Technical Abstracts Circuits Assembly - September 2008 Circuits Assembly - September 2008 - Circuits Assembly - September 2008 (Page Cover1) Circuits Assembly - September 2008 - Circuits Assembly - September 2008 (Page Cover2) Circuits Assembly - September 2008 - Circuits Assembly - September 2008 (Page 1) Circuits Assembly - September 2008 - Circuits Assembly - September 2008 (Page 2) Circuits Assembly - September 2008 - Contents (Page 3) Circuits Assembly - September 2008 - Contents (Page 4) Circuits Assembly - September 2008 - Contents (Page 5) Circuits Assembly - September 2008 - Caveat Lector (Page 6) Circuits Assembly - September 2008 - Caveat Lector (Page 7) Circuits Assembly - September 2008 - Industry News (Page 8) Circuits Assembly - September 2008 - Industry News (Page 9) Circuits Assembly - September 2008 - Industry News (Page 10) Circuits Assembly - September 2008 - Industry News (Page 11) Circuits Assembly - September 2008 - Industry News (Page 12) Circuits Assembly - September 2008 - Industry News (Page 13) Circuits Assembly - September 2008 - Industry News (Page 14) Circuits Assembly - September 2008 - Industry News (Page 15) Circuits Assembly - September 2008 - Industry News (Page 16) Circuits Assembly - September 2008 - Industry News (Page 17) Circuits Assembly - September 2008 - Market Watch (Page 18) Circuits Assembly - September 2008 - Market Watch (Page 19) Circuits Assembly - September 2008 - Talking Heads (Page 20) Circuits Assembly - September 2008 - Talking Heads (Page 21) Circuits Assembly - September 2008 - Talking Heads (Page 22) Circuits Assembly - September 2008 - Talking Heads (Page 23) Circuits Assembly - September 2008 - Focus on Business (Page 24) Circuits Assembly - September 2008 - Focus on Business (Page best1) Circuits Assembly - September 2008 - Focus on Business (Page best2) Circuits Assembly - September 2008 - Global Sourcing (Page 25) Circuits Assembly - September 2008 - On the Forefront (Page 26) Circuits Assembly - September 2008 - On the Forefront (Page 27) Circuits Assembly - September 2008 - On the Forefront (Page 28) Circuits Assembly - September 2008 - On the Forefront (Page 29) Circuits Assembly - September 2008 - Screen Printing (Page 30) Circuits Assembly - September 2008 - Screen Printing (Page 31) Circuits Assembly - September 2008 - Better Manufacturing (Page 32) Circuits Assembly - September 2008 - Better Manufacturing (Page 33) Circuits Assembly - September 2008 - Reflow Soldering with a SnCu Eutectic Pb-Free Alloy (Page 34) Circuits Assembly - September 2008 - Reflow Soldering with a SnCu Eutectic Pb-Free Alloy (Page 35) Circuits Assembly - September 2008 - Reflow Soldering with a SnCu Eutectic Pb-Free Alloy (Page 36) Circuits Assembly - September 2008 - Reflow Soldering with a SnCu Eutectic Pb-Free Alloy (Page 37) Circuits Assembly - September 2008 - Improving OEE in High Mix Facilities (Page 38) Circuits Assembly - September 2008 - Improving OEE in High Mix Facilities (Page 39) Circuits Assembly - September 2008 - Improving OEE in High Mix Facilities (Page 40) Circuits Assembly - September 2008 - Improving OEE in High Mix Facilities (Page 41) Circuits Assembly - September 2008 - Effectively Managing RF Design in Utility Metering Applications (Page 42) Circuits Assembly - September 2008 - Effectively Managing RF Design in Utility Metering Applications (Page 43) Circuits Assembly - September 2008 - Effectively Managing RF Design in Utility Metering Applications (Page 44) Circuits Assembly - September 2008 - Effectively Managing RF Design in Utility Metering Applications (Page 45) Circuits Assembly - September 2008 - Solder Joint Reliability of Different BGAs Reworked Using Low Melting Point Pb-Free Alloys (Page 46) Circuits Assembly - September 2008 - Solder Joint Reliability of Different BGAs Reworked Using Low Melting Point Pb-Free Alloys (Page 47) Circuits Assembly - September 2008 - Solder Joint Reliability of Different BGAs Reworked Using Low Melting Point Pb-Free Alloys (Page 48) Circuits Assembly - September 2008 - Tech Tips (Page 49) Circuits Assembly - September 2008 - Tech Tips (Page 50) Circuits Assembly - September 2008 - Wave Soldering (Page 51) Circuits Assembly - September 2008 - Pb-Free Lessons Learned (Page 52) Circuits Assembly - September 2008 - Pb-Free Lessons Learned (Page 53) Circuits Assembly - September 2008 - Materials World (Page 54) Circuits Assembly - September 2008 - Process Doctor (Page 55) Circuits Assembly - September 2008 - Equipment Advances (Page 56) Circuits Assembly - September 2008 - Product Spotlight (Page 57) Circuits Assembly - September 2008 - Product Spotlight (Page 58) Circuits Assembly - September 2008 - Product Spotlight (Page 59) Circuits Assembly - September 2008 - Product Spotlight (Page 60) Circuits Assembly - September 2008 - Ad Index (Page 61) Circuits Assembly - September 2008 - Assembly Insider (Page 62) Circuits Assembly - September 2008 - Assembly Insider (Page 63) Circuits Assembly - September 2008 - Technical Abstracts (Page 64) Circuits Assembly - September 2008 - Technical Abstracts (Page Cover3) Circuits Assembly - September 2008 - Technical Abstracts (Page Cover4)
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