无铅钎料助焊剂的研究

目录
摘要 1
Abstract 2
前 言 4
1助焊剂作用的基本原理 10
1.1助焊剂的作用 10
1.2助焊剂的作用机理 10
1.2.1助焊剂中活性成分去除氧化膜的机制 10
1.2.2助焊剂中的活性成分的界面活性机理 12
1.2.3助焊剂对钎料润湿性能的影响 14
1.2.4助焊剂的界面活性机制——传质理论 15
1.3助焊剂残留物的反应机理 17
1.3.1助焊剂的腐蚀机制 17
1.3.2助焊剂残留物的反应动力学 18
1.4一般助焊剂的设计要求 20
2低固体含量助焊剂的研制 21
2.1助焊剂的配制 21
2.1.1助焊剂的配制要求 21
2.1.2助焊剂成分的确定 22
2.1.3主要成分的性质 23
2.2钎焊实验 25
2.2.1实验目的及方案 25
2.2.2实验的基本原理 26
2.2.3实验的器材 27
2.2.4实验步骤及操作 27
2.3实验结果及分析 28
2.3.1开发过程及分析： 28
3助焊剂性能评测 30
3.1室温下助焊剂的各项物理性能 30
3.2不挥发无含量测定 30
3.3水溶物电导率 31
3.4酸值测定 32
3.5助焊剂成分及实验的改进建议 33
4总结 35
参考文献 36

摘要
如今，助焊剂技术配合着钎焊技术已经广泛应用于电子封装产业。人们出于对生存环境与自身健康的考虑，封装用的钎料正在进行从有铅到无铅的重要过渡，人们正在努力寻找新的金属或合金来代替传统的Sn-Pb合金，如已开发出的Sn-Ag、Sn-Zn系列以及它们的合金。而目前已研制出和正在投入使用的无钎铅料的焊接性能在很多方面还赶不上传统含铅钎料，例如焊接温度较高，润湿性较差等。因此助焊剂的作用显得更加重要，而且有必要针对无铅钎料开发一种助焊剂来进一步提高铅料的焊接性能。而传统的助焊剂多含有大量的松香以及有毒的卤化物，所以焊后残余较多，污染较为严重，一般需要再清洗，而所用的清洗剂CFC又严重的破坏大气的臭氧层，多种因素决定免清洗助焊剂的开发势在必行。要做到免清洗首先要降低助焊剂中的固体含量以减少焊后残留。通过对已有成果的研究及大量的实验，成功地开发出了一种针对无铅的 Sn-Ag-Cu系钎料的助焊剂，该种助焊剂具有较低的松香及卤化物含量，焊后残余较少，其各项焊接性能均达到国家标准，为今后做到真正的免清洗迈出了关键一步。该助焊剂的主要成分为松香5%，二苯胍氢溴酸盐0.5%，丁二酸1%，苯甲酸3%，乙醇40.5%，乙二醇30%；二甘醇20%。

关键词：无铅钎料；助焊剂；钎焊；润湿性

Abstract
Recently, Flux technology accompanied with soldering technology has been widely used in the field of electronic packaging industry. With more and more care to the environment and health, solders are in the transition, which is from lead-contained to lead-free now. People are trying to find a new metal or a new alloy instead of lead-contained solders, such as Sn-Ag, Sn-Zn solder family or their alloy. But lead-free solders which have been developed or put into use are not as good as conventional solders based on lead in many aspects, for examples, the melting temperature of lead-free solder is much more higher, and the wettability of lead-free solder is poorer. So the effect of flux is more evident than ever before, and it is very necessary to develop a flux towards the new lead-free solder to improve the soldering performances of the solder. The conventional solders always contain a lot of rosin and poisonous halide, so it is a traditional and only way using CFC (chlorofluorocarbon) to clean the PCB (Printed Circuit Board) after soldering. But CFC destroys the ozonosphere and was forbidden. Based on so many factors, it is necessary to develop a flux, which does not need wash after soldering. In order to achieve the washing-free flux the solid content in the flux must be decreased, in the result the quantity of hangover is very small. By research of the exist result and large quantity of experiments, a new flux aiming at the Sn-Ag-Cu family lead-free solders has been developed successfully, and the content of rosin and poisonous halide is low. Many performances of the flux fulfill the national standard, and it makes a great step towards the coming washing-free flux. Its main composition is rosin 5%, succinic acid 1%, benzoic acid 3%, alcohol 40.5%, ethylene glycol 30%, diethylene glycol 20%.

Key words: lead-free solder, flux, soldering, wettability

前 言
所谓钎焊即采用比母材熔化温度低的钎料，操作温度低于母材固相线而高于钎料液相线的一种焊接温度的一种焊接技术。按填入母材间隙中焊料熔点的高低，一般将钎焊分为两大类。一类的钎料熔点高于450℃，这种钎料称为硬钎料（brazing filler metal），采用硬钎料的钎焊称为硬钎焊（brazing）；另一类的焊料熔点低于450℃，这种钎料称为软钎料（solder），采用软钎料的钎焊称为软钎焊（soldering）。钎焊时钎料熔化为液态而母材保持为固态，液态钎料在母材的间隙中和表面上润湿、毛细流动、填充、铺展、与母材相互作用（溶解、扩散或产生金属间化合物），冷却凝固形成的牢固接头、从而将母材联结在一起。与传统的熔焊相比，钎焊最大的特点在于母材不熔化、工作温度低、焊件变形小、焊件尺寸精度高。因此被广泛应用于成型母材或母材难以熔化等领域，如电子工业、仪器仪表工业、航空航天技术、机械制造技术 。
人类使用钎焊技术有着久远的历史，人们最早使用的钎料是Au、Pb或Sn-Pb合金。公元前4000年美索布达尼亚人就开始使用Pb或Sn合金来连接铜。公元前350年罗马人开始使用Sn-Pb合金来连接Pb制水管或Cu制金属工具。我国在春秋中晚期就开始采用Sn或Sn-Pb合金来连接工具 。