波峰焊接工艺技术的研究

介绍了波峰焊接技术的原理,以及一种新型波峰焊接技术的特点,与传统波峰焊情况不同,它可以保护表面贴装元件来实现对通孔元件焊接。并分别从焊接前的质量控制、生产工艺材料及工艺参数方面探讨了提高波峰焊质量的有效方法。     

无铅再流焊设备配置工艺性评估

无铅钎料的高熔点和低润湿性给再流焊设备带来了新的挑战。从无铅焊接工艺角度出发,论述了加热系统、制程控制、助焊剂管理系统、冷却系统和氮气保护等五个方面对焊接设备提出的要求。     

纳米无铅焊料的研究进展

电子封装互连过程中,无铅锡基焊料是常用的连接材料。然而,由于其较高的熔点(210~240℃),在电子器件连接过程中需施加较高的回流温度,这不仅增加了电子组装过程中的能耗,也大大降低了器件的可靠性。纳米无铅焊料具有热力学尺寸效应,其熔点较块体材料有大幅度的降低,从而受到了越来越广泛的关注。综述了近年来国内外纳米无铅焊料的发展动态,介绍了常用的纳米无铅焊料的制备方法及影响纳米颗粒尺寸的因素,总结了纳米无铅焊料在应用和存放过程中所产生的问题,同时也对纳米无铅焊料未来产业化的实现提出了建议。     

PCB手工焊接温度问题探讨

电子元器件装联过程中焊接温度对产品的可靠性有着很大的影响.焊接温度不但影响着元器件的寿命和可靠性,更重要的是决定了焊点的形成和内在质量.高可靠焊接对焊点的焊接温度有着严格的要求,但是受到各种因素的影响,在手工焊接中温度控制比较困难.从焊接理论出发,在对焊点温度的实测试验基础上,对该问题进行了分析,给出了焊接时的指导建议...     

如何以热饱和效应克服晶圆凸块回焊制程的问题

以热板式回流炉所特有之高速热饱和的优势,改善晶圆级封装中回焊制程热补偿不足之问题     

Accelerated popcorn testing of high solder-reflow crack resistant molding compounds

In testing the resistance of a molding compound to popcorn failures after solder reflow, there are two basic options for shortening the moisture absorption phase: varying the severity of moisture exposure by varying the temperature and percent relative humidity or maintaining a constant humidity/temperature profile and varying the length of time the compounds are exposed. In addition, the total testing time can be accelerated by the choice of test method. There are three major measurement techniques for evaluating the extent of popcorn cracking: SAM testing; bubble chamber testing; and visual crack inspection. In this paper we will explore the effects of differing lengths of exposure time and the merits of different measurement techniques.A variety of epoxy resins, filler mixtures and adhesion additives were examined in semiconductor molding compounds for solder-reflow crack resistance (popcorn crack resistance). A limited comparison of molding compound high-temperature strength properties and extent of popcorn cracking suggests no strong positive correlation. On the other hand, factors that might have an impact on adhesion properties of the molding compound, such as low melt viscosity resins and putative adhesion additives, appear to have the greatest impact. A molding compound developed with these factors showed no internal or external cracks on 84 lead QFPs (29.2 × 29.2 × 3.68 mm) after 72 h of 85°C/85% R.H. and one 10 s solder dip at 260°C. Nor were any external cracks observed after 168 h of 85°C/85% R.H. and one solder dip. However, minor internal cracks were observed.The most data can be obtained by using bubble chamber testing for large numbers of parts and evaluating a smaller sample of the best of those compounds via SAM testing with crack extension analysis. The length of exposure time affected the parts as expected, with longer times being more severe. There did not appear to be a gradient effect or a threshold level. In general, 72 h allowed the greatest differentiation among the compounds tested for internal defects; external defects were not fully developed until 168 h of moisture exposure.     

无铅焊料的新发展

传统焊接技术使用锡铅焊料,对环境造成严重伤害。文章从环保角度出发,阐述了应用无铅焊料的必然性,并介绍了无铅焊料近几年的发展,指出现阶段无铅焊料离市场要求还有一定差距, 需进一步加强研究与开发。     

基于加热因子的回流曲线的优化与控制

回流焊形成的焊点质量与回流焊过程密切相关。基于加热因子Qη对回流焊接过程进行优化控制。根据焊点疲劳寿命随加热因子分布的特点,提出了对冷点加热因子取最优范围下限值控制策略(冷点代表回流过程中经历的加热因子最小焊点),以使所有焊点的加热因子尽可能都在最优范围之内。冷点下限控制策略满足了大部分焊点的高可靠性,而少部分超出最优范围上限的焊点的可靠性虽略微下降,仍可形成良好焊接。由于加热因子理论不对回流曲线形状做严格要求,定义了两个组合参数:形状参数Ht和移动参数Hb,对冷点的加热因子进行控制。并且根据统计学原理利用实验建立Qη与Ht和Hb的回归关系,发现Qη与Ht、Qη与Hb大体上成线性关系,其为Qη的预测和控制带来了极大的便利,从而使焊接可靠性易于得到保证。     

SMT/THT混装焊接技术综述

电子组装的高密度给传统波峰焊接技术提出了新挑战。为了应对挑战,新的混装焊接技术不断涌现。与传统波峰焊情况不同,这些新型焊接技术可以保护表面贴装元件来实现对通孔元件焊接,大幅度降低生产工序和周期时间,印刷线路板的焊接质量也被提升。新的焊接工艺允许充分有效利用SMT贴装设备,消除对点胶机的使用。介绍了几种新型混装焊接技术的特点,可以确信这些新型焊接技术将会被更多地应用于电子组装上,并将非常具有竞争力。     

免清洗型助焊剂的研究进展

根据助焊剂的发展趋势,介绍了免清洗助焊剂的概念、分类及可靠性评价的方法,综述了国内外科研工作者对制备免清洗助焊剂的研究进展状况,并指出了免清洗助焊剂在使用时急需注意的事项,最后阐述了无铅焊料用免清洗型助焊剂是近年来的研究热点.