SnAgCu无铅焊膏用溶剂的优化研究

以SnAgCu无铅焊膏铺展性能和焊点形貌作为评价的主要指标,通过回流焊接实验,对常用于焊膏的10种溶剂进行了单一溶剂优选,并对两种性能较好的溶剂进行复配优化研究.结果表明:A醇、二缩三乙二醇和B醚作为单一溶剂时焊膏的润湿性较好、焊点外形较饱满,铺展率都大于83%;A醇和B醚按质量比3:2复配时得到的焊膏铺展率达到93%...     

松香树脂对SnAgCu焊膏性能的影响

通过焊膏回流焊接铺展性能及其抗塌落能力测试分析.研究了助焊剂中氢化松香和聚合松香的总含量以及它们的复配比例对SnAgCu焊膏性能的影响.结果表明:当助焊剂中松香质量分数在20%～60%的范围时,增加松香含量可提高焊膏的铺展性能,改善焊点形貌,并显著增强抗塌落能力.当助焊剂中松香总质量分数为40%时,不同松香复配比例的焊膏铺展试验均表现出焊点饱满、表面光亮、周边规则的特征,铺展率基本相当,约为82%,而焊膏的抗塌落性能随聚合松香比例提高而提高.元件试焊表明焊膏具有良好的焊接性能,可用于一般电子产品的焊接.     

焊膏用免清洗助焊剂的制备与研究

根据免清洗助焊剂各组份的特点,分别对其活性剂、溶剂、成膜剂以及添加物进行筛选和处理.在一定温度下对各组份进行均匀化处理并制备出助焊剂,依据标准对所制备的焊剂进行性能测试.以自制的锡银铜系焊粉为基础制备焊膏并做焊接模拟.结果表明:采用有机酸和有机胺复配制备的活性物质满足预期要求;复配溶剂满足沸点、黏度和极性基团三大原则;所制备的免清洗焊剂多项性能满足规范要求,达到了免清洗的要求,解决了助焊性与腐蚀性的矛盾;所制备的焊膏焊接性能良好,无腐蚀,固体残留量低,存储寿命较长.     

无卤助焊膏用活性剂的选择及优化

针对Sn-Ag-Cu系列焊料开发出了一种无卤素助焊膏,着重探讨了无卤助焊膏中活性剂的选择及优化方法。通过对十种活性剂所配制的助焊膏的扩展率、锡珠、焊点情况进行测试,结合各活性剂的热质量损失(TGA)曲线,最终选择了己二酸、癸二酸和苯基丁二酸三种活性剂,并通过正交方法对其进行复配试验。结果表明有机酸的复配能够显著改善焊点铺展情况,当己二酸、癸二酸和苯基丁二酸质量比为1:4:3时,扩展率达75.36%,所得焊点饱满、光亮,且无锡珠产生。     

焊膏回流性能动态测试法及其应用

通过体视显微镜和CCD等视频设备录制、焊膏回流动态测试方法,观察焊膏回流的整个过程,有助于分析焊膏回流过程中出现的问题,弥补了目前焊膏–锡珠试验只能观察最终结果,而不能对中间过程进行评价的缺点。利用该方法研究了保温时间和焊膏活性对焊膏回流性能的影响,对焊膏的收球性能进行了评价。结果表明:焊膏回流的保温时间有一定限制,超过限制,产生缺陷的机会大大增加;对于活性较强的焊膏,可以通过增加焊膏的黏性,减少锡珠和立碑以及元件歪斜倾向;通过对不同焊膏的回流过程进行对比,提出了焊膏收球性能良好的参考标准。     

无卤素低银无铅焊膏的研制

以铺展性能为主要评价指标,探讨无卤素低银无铅焊膏中活性剂的选择。对常用于助焊剂的10种有机酸活性物质进行筛选,从中选取一种性能优异的己二酸与已知两种羧酸配成复合活性物质,并通过正交实验对三种有机酸的复配比例进行优化。通过正交试验,调整溶剂、松香、活性剂和表面活性剂的含量。结果表明：溶剂、松香、表面活性剂和活性物质质量分数分别为36%,35%,5%和6%,羧酸X、羧酸Y与己二酸的比例为1:2:4时,焊膏有良好的润湿性和抗塌陷性,锡珠试验达到标准一级水平。     

焊膏性能与焊接质量

在SMT生产中，焊膏性能对焊接质量的影响很大，本通过对几种焊膏性能的测试分析实验，探讨了焊膏性能对焊接质量所产生的影响，并提出了焊膏选用的主要原则。     

焊膏可印刷性评价方法的研究

焊膏的印刷性能是SMT中最致SMA的各种缺陷.介绍一种焊膏的印刷性能测试方法,其特点是采用了"刀-环"印刷结构,其中模板设计成环形来实现连续的印刷.此外在环形模板内焊膏滚动的切线方向上安装J形探针,监测焊膏的滚动印刷阻力.通过对几种焊膏的滚动印刷试验,并对可印刷性能进行了评价分析,力求获得一个简单的评价焊膏可印刷性能的指标.焊膏印刷阻力呈下降趋势,在滚动停止时跌倒到最小值.以最终的印刷距离作为焊膏的印刷寿命或者耐受值,由此来有效评估焊膏可印刷性.     

无铅焊膏工艺适应性的研究

无铅焊膏是适应环保要求的一种绿色焊接材料,其质量的优劣直接决定着现代表面组装组件品质的好坏,为了检测与评价无铅焊膏的性能,研究影响其焊接可靠性的因素,实验研制了一种Sn-Ag-Cu无铅焊膏,并根据其本身的材料特性和实际工艺性能结合IPC的有关标准设计了整套试验,包括:焊膏黏度测试、塌陷实验、焊球实验以及铜板腐蚀测试等。研究结果表明:焊粉的质量分数与焊膏黏度呈正比关系;高温高湿环境下焊膏的可靠性降低,焊后残留物的腐蚀性增强;焊膏过多暴露在氧化环境中易引起焊料成球等焊接缺陷。     

电子组装中无铅焊膏的选择（待续）

焊膏是焊料合金粉末与助焊剂的混合物,其质量的优劣对印刷效果有极其重要的影响,特别是无铅化工艺中.介绍了焊膏的组成、主要性能要求及其影响因素,对目前常用的焊料合金和助焊剂的性能和使用效果进行总结,并对不同行业所适用的焊膏类型进行了论述.     

无铅焊膏中松香含量对焊点剪切强度的影响

对不同松香含量的助焊剂进行了润湿力性能测试和黏度测试。用这些助焊剂配制成焊膏,并对焊后的焊点进行了剪切试验,以此来测定不同的松香含量下焊点的剪切强度。结果表明:焊膏的黏度随着松香含量的增加而增加,而其润湿力逐渐降低。当松香的质量分数为42.69%时,焊点的剪切强度可达48.36MPa,焊膏焊接性能良好,焊点饱满光亮。     

无铅焊膏用松香型助焊剂活化点的研究

论述了无铅焊膏用松香型助焊剂活化点研究的重要性,探讨了活化点的物理意义及其影响因素.实验结果表明,无铅焊膏用松香型助焊剂的活化点就是松香树脂酸在有机溶剂中电离溶解平衡常数的升温曲线的拐点,松香种类对其活化点没有影响,决定其活化点的影响因素是松香本身的物理化学性质、溶剂以及有机酸的电离常数.     

无铅焊膏的设计与展望

分析了无铅焊膏的构成和技术要求。对无铅焊膏用焊粉及助焊剂配方设计的现状进行了讨论,焊粉的成分多为Sn、Ag和Cu,粒度越来越多地采用20μm;助焊剂多为改性松香、有机酸活化剂等。展望了无铅焊膏的研究与发展趋势。     

无铅焊膏用助焊剂的制备与研究

无铅焊膏用助焊剂需要一定的黏性,选择有机酸和有机胺混合作为活性物质,配合一定量的松香配制出一种助焊剂。通过控制助焊剂中松香的含量,降低不挥发物的含量,减少残留物对元器件的腐蚀。依据标准对所配制的助焊剂进行了性能测试,并与一种松香含量较高的助焊剂比较。结果表明:助焊剂的松香含量降低约10%,在260℃焊接后不挥发物含量降低了近6%,黏度较好,无卤化物,无毒,环保,符合焊膏用助焊剂的要求。     

Solder thickness variation with respect to soldering parameters

This study investigated the growth behavior of solder interconnect on solder bonding pad. The solder thickness was investigated with respect to parameters including bonding pad area, reflow temperature, solder paste volume, loading, and die size (metallization area). Solder thickness was found to have a maximum value with respect to the ratio of solder paste volume to pad size. Loading and the reflow temperature showed no effect on solder thickness. An enlargement in metallization area reduces the solder thickness, while greater solder paste volume increases the solder thickness     

无铅药芯焊锡丝用非松香基固体助焊剂的研究

针对现有松香固体助焊剂活性温度低和焊后变色的问题,研制了以十八酸、聚乙二醇和少量耐热松香作为载体,以己二酸和癸二酸复配作为活性剂的非松香基固体助焊剂.此助焊剂常温下为白色膏状,熔点范围110℃～130 ℃,满足Sn-0.7Cu无铅药芯焊锡丝灌芯和拔丝工艺.助焊剂中各成分沸点在300℃左右,满足手工烙铁焊高温要求且大大减...     

Critical variables of solder paste stencil printing for micro-BGA and fine-pitch QFP

Stencil printing continues to be the dominant method of solder deposition in high-volume surface-mount assembly. Control of the amount of solder paste deposited is critical in the case of fine-pitch and ultrafine-pitch surface-mount assembly. The process is still not well understood as indicated by the fact that industry reports 52-71% surface-mount technology (SMT) defects are related to the solder paste stencil printing process. The purpose of this paper is to identify the critical variables that influence the volume, area, and height of solder paste deposited. An experiment was conducted to investigate the effects of relevant process parameters on the amount of solder paste deposited for ball grid arrays (BGAs) and quad flat packages (QFPs) of five different pitches ranging from 0.76 mm (30 mil) to 0.3 mm (12 mil). The effects of aperture size, aperture shape, board finish, stencil thickness, solder type, and print speed were examined. The deposited solder paste was measured by an inline fully automatic laser-based three-dimensional (3-D) triangulation solder paste inspection system. Analysis of variance (ANOVA) shows that aperture size and stencil thickness are the two most critical variables. A linear relationship between transfer ratio (defined as the ratio of the deposited paste volume to the stencil aperture volume) and area ratio (defined as the ratio of the area of the aperture opening to the area of the aperture wall) is proposed. The analysis indicates that the selection of a proper stencil thickness is the key to controlling the amount of solder paste deposited, and that the selection of maximum stencil thickness should be based on the area ratio. The experimental results are shown to be consistent with a theoretical model, which are also described.     

Ethylene glycol ether free solder paste development

There are growing concerns in the electronics industry for not only finding alternatives to lead but also other potentially hazardous materials as well. This paper summarizes the development of ethylene glycol ether (EGE)-free solder flux for the formulation of lead-free solder pastes. Replacing the toxic components in the flux was only the first challenge, the criteria of commercially proven pastes also had to be met. Both commercial and in-house solder paste formulations were evaluated for printability, reflow, wetting, flux residue removal, and solder void characteristics. Two critical issues, solder bump boids and flux residue removal, were identified and associated with the high temperature reflow of Pb-free pastes. These issues were not effectively improved by the existing commercial EGE-free solder pastes. New solder paste formulations were developed utilizing alternative chemistry than those found in traditional solder paste fluxes. These pastes, some, of which are also water soluble, reduced void frequency and size by more than 4x as compared to vendors' pastes. Solder bump height uniformity of 135 4 m within each die was consistently achieved. Thermal-mechanical reliability tests were performed on various lead-free solder alloys using the new flux formulations. The reliability of flip chip assembled DCA on organic boards with both OSP/Cu and Cu/Ni/au pad metallizations were comparable to eutectic Sn63Pb37 bumped assemblies using commerical pastes.