锡渣的形成特点和减少措施

随着无铅钎料的广泛使用,波峰焊过程将产生更多的锡渣,造成生产成本增加。通过对其分布特点的研究,将锡炉熔融钎料表面氧化物分为A~E5个氧化物区,并分析了各区域氧化物的特点,列举了几种减少氧化渣的办法,分析了他们的实用性。     

无铅波峰焊钎料氧化渣的减少措施

随着无铅钎料的广泛使用,波峰焊过程将产生更多的氧化渣,造成生产成本增加。阐述了液态钎料的氧化行为及无铅波峰焊锡炉中氧化渣的形成特点,并列举了几种减少氧化渣的办法,分析了他们的实用性。     

新型高效湿法锡渣分离技术

随着无铅钎料的广泛使用,波峰焊过程将产生更多的锡渣,造成生产成本增加。阐述了液态钎料的氧化行为及无铅波峰焊锡炉中氧化渣的形成特点,并列举了几种减少氧化渣的办法,重点介绍了一种高效湿法锡渣分离技术及其优劣势分析。     

氮气保护在无铅化电子组装中的应用

无铅钎料的高熔点、差润湿性给SMT传统的焊接工艺带来了很大冲击,并且对焊点质量也产生了很大的影响。为了防止氧化,改善钎料与焊盘、元件引脚之间的润湿性,提高产品合格率,目前在电子纽装中普遍采用氮气保护。针对几种常用无铅钎料进行了氮气气氛中润湿性和焊点组织的分析,并初步研究了氮气保护对焊点质量和氧化渣的影响。结果表明：氮气保护可以改善无铅钎料润湿性,细化焊点组织,减少氧化渣量,而且对焊点外观和成品率也有一定的影响。     

H701型铝钎剂的试制

前言铝波导的火焰钎焊和炉中钎焊,目前较广泛使用的是仿苏34A型铝钎剂,用Al—6Si—28Cu钎料。但由于这种钎料脆性大,抗腐蚀性能较差,所以北大同我厂共同研制了129A、1712B等钎剂[1],和Al—Si—Be钎料[6]。此钎料克服了34A钎料、钎剂的某些缺点,钎料的韧性好,钎剂的流动性好,焊缝表面光滑,易清洗。但由于氯化物钎剂本身的物理化学性质所决定,钎剂易吸潮失效,残留物有吸湿性,放久后有腐蚀斑     

合金元素对Sn-Zn基无铅钎料高温抗氧化性的影响

研究了不同微量合金元素对Sn-Zn基无铅钎料高温抗氧化性的影响。钎料在液态下的表面颜色变化以及热重分析表明,Al、Cr能明显改善Sn-Zn基钎料的抗氧化性能。通过俄歇能谱深度剖析和X射线衍射分析探讨了合金元素的抗氧化机理:Al和Cr在钎料表面或亚表面富集,形成阻挡层,抑制了钎料的氧化。比较了合金元素对Sn-Zn基钎料润湿性能的影响,结果表明Al的加入不利于钎料的铺展。通过实验得出结论:Cr是一种比Al更具有吸引力的Sn-Zn基钎料的高温抗氧化合金元素。     

无铅波峰焊不锈钢锡炉叶轮和喷嘴溶蚀失效分析

常用无铅钎料熔点的升高以及Sn含量的增加使得300系列不锈钢在使用几个月之后就会出现溶蚀现象。Fe-Sn金属间化合物的生长行为特点以及叶轮、喷嘴接触钎料的特点决定了材料表面的溶蚀形貌特征。     

无铅波峰焊钎料抗氧化影响的研究

研究了目前常用的Sn-0.7Cu无铅钎料在手浸锡炉和模拟波峰炉中的抗氧化情况.主要研究了微量P元素的加入对钎料抗氧化性的影响.通过钎料在液态下表面颜色变化和锡渣的产生量的比较可以发现微量P元素的加入可以提高钎料的抗氧化性能.通过比色分析发现微量P元素在钎料表面或亚表面富集,形成"阻挡层",抑制了钎料的进一步氧化.通过实验得出P的最佳质量分数为0.011%.     

Sn-8Zn无铅钎料性能的研究

研究了不同微量合金元素(Bi、Ag)对Sn-8Zn无铅钎料高温抗氧化性能及接头剪切强度的影响,采用氧化质量增加△m值的方法,在高温下观察钎料表面氧化膜形状和颜色的变化并对氧化膜进行X射线衍射分析,探讨了钎料的高温抗氧化性能的机理,通过对钎料的金相显微组织观察和对热处理后钎焊接头的剪切强度试验,分析了提高接头剪切强度的原因.试验结果表明:在Sn-8Zn钎料中加入适量的合金元素(Bi、Ag)均可以改善和提高钎料的高温抗氧化性能和接头的剪切强度.     

廉价钎料Ag4CuP的特性

近年来,出现了使用低银钎料的趋势,尤其是Ag-Cu-P 型钎料。Ag15 CuP 钎料就属于这一类。此种钎料含磷量大(4.5～6.5%),在焊铜时会使铜的氧化物很快还原,因而排除了使用钎剂的必要性,但同时会使钎料中生成脆性磷化物,使钎料难于制成丝状(直径1～2 mm)或片状(厚度大于0.2mm)。根据这种情况,捷克斯洛伐克研制了Ag CuP 新材料。下面介绍这项研究成果。     

共晶烧结贴片氮气保护改进研究

军用陶瓷或金属封装中的共晶烧结芯片贴装工序存在的主要问题是,Sn基焊料极易氧化形成Sn₂O、SnO₂等氧化物,在共晶过程中不断堆积在焊料表面,形成焊料表面悬浮颗粒,造成PIND失效。文章基于氧化膜破裂理论,通过对当前使用的共晶烧结氮气保护的结构进行改进,采用小型半密闭腔体的方式实现了局部高纯度氮气保护环境。在共晶烧结贴片过程中,氧化膜破裂融入焊料体内,同时因氧化膜破裂而流出的熔融焊料在良好的氮气保护环境下形成新的光亮圆润的焊料表面,有效减少了焊料表面悬浮氧化物颗粒。统计数据表明,该改进研究有效降低了PIND失效率和成品筛选电路的成本损失;该改进实现了共晶烧结贴片焊料表面极少产生悬浮氧化物颗粒,极大地降低了可动颗粒导致的电路短路、断路等误动作的危害性和可靠性风险。     

Electrical Interconnection with a Smart ACA Composed of Fluxing Polymer and Solder Powder

The interconnection mechanisms of a smart anisotropic conductive adhesive (ACA) during processing have been characterized. For an understanding of chemorheological mechanisms between the fluxing polymer and solder powder, a thermal analysis as well as solder wetting and coalescence experiments were conducted. The compatibility between the viscosity of the fluxing polymer and melting temperature of solder was characterized to optimize the processing cycle. A fluxing agent was also used to remove the oxide layer performed on the surface of the solder. Based on these chemorheological phenomena of the fluxing polymer and solder, an optimum polymer system and its processing cycle were designed for high performance and reliability in an electrical interconnection system. In the present research, a bonding mechanism of the smart ACA with a polymer spacer ball to control the gap between both substrates is newly proposed and investigated. The solder powder was used as a conductive material instead of polymer‐based spherical conductive particles in a conventional anisotropic conductive film.     

Development of lead-free wave soldering process

Lead-free wave soldering was studied in this work using a 95.5Sn/3.8Ag/0.7Cu alloy. A process DOE was developed, with three variables (solder bath temperature, conveyor speed, and soldering atmosphere), using a dual wave system. Four no-clean flux systems, including alcohol- and water-based types, were included in the evaluation. A specially designed "Lead-Free Solder Test Vehicle", which has various types of components, was used in the experiments. Both organic solderability preservative (OSP) and electroless nickel/immersion gold (Ni/Au, or ENIG) surface finishes were studied. Soldering performance (bridging, wetting and hole filling) was used as the responses for the DOE. In addition, dross formation was measured at different solder bath temperatures and atmospheres. Dross formation with Sn/Ag/Cu bath was compared to that with eutectic Sn/Pb bath. Regarding the connector-type component, a pad design giving the best soldering performance was evaluated based on the DOE results. Finally, a confirmation run with the optimum flux and process parameters was carried out using the Sn/Ag/Cu solder, and a comparative run was made with the Sn/Pb solder alloy and a no-clean flux used in production. The soldering results between the two runs indicate that with optimum flux and process parameters, it is possible to achieve acceptable process performance with the Sn/Ag/Cu alloy.     

塑料球栅阵列（PBGA）焊点三维形态预测与分析

本文应用最小能量原理和有限元方法，建立塑料球栅阵列（ＰＢＧＡ）器件焊点三维形态预测模型。对ＰＢＧＡ焊点三维形态进行预测和分析。并将预测结果与试验结果以及国外学者用数学分析模型所得的预测结果进行了对比验证。     

基于最小能量原理的SMT焊点三维形态预测

本文应用最小能量原理和有限元方法建立表面组装技术（ＳＭＴ：Ｓｕｒｆａｃｅ Ｍｏｕｎｔ Ｔｅｃｈｎｏｌｏｇｙ）形成的焊点三维形态预测模型,并运用该模型对塑料球栅阵列（ＰＢＧＡ：Ｐｌａｓｔｉｃ Ｂａｌｌ Ｇｒｉｄ Ａｒｒａｙ）器件焊点三维形态问题进行了预测和分析。最后将预测结果与试验结果以及国外学者用数学分析模型所得的预测结果进行了对比验证。     

Evaluation of the impact of the physical dimensions and material of the semiconductor chip on the reliability of Sn3.5Ag solder interconnect in power electronic module: A finite element analysis perspective

This paper primarily focuses on an evaluation study for the temperature cycling capability of tin silver solder interconnect in power electronic applications by the impact of die dimensions and die material properties. The study was investigated on finite element analysis perspective on chip/solder/substrate structure. A commercially available chip was chosen in the finite element analysis (FEA) as the nominal base die. Two thermal cycle profiles were utilised. The effect of die area, die thickness and material properties (Si and SiC) on the thermal cycling capability of the solder layer was investigated from FEA perspective. From the FEA, it was concluded that decrease in die thickness resulting in increment of thermal cycling capability of solder layer for both material (Si and SiC). Increase in die area increases the thermal cycling capability of solder. For higher ΔT thermal cycle, solder under SiC die perform better than solder under Si die in terms of thermal cycling capability. When the die thickness become smaller than a threshold value of the thermal cycle regime, solder under Si die have better thermal cycling capability than solder under SiC die. Additionally a parametric study was undertaken for a SiC chip/substrate structure under high ∆ T temperature cycling profile for solder layer geometric parameter (wetting angle, titling angle and thickness). From the parametric study which utilised design of experiments (DoE), a wavelet radial basis surrogate model was generated. A sensitivity analysis was performed on surrogate model in order to identify the most influencing parameter. From the sensitivity analysis, it was concluded that wetting angle and solder layer thickness of solder layer have significant impact on the thermal cycling capability of the solder layer.     

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%...     

Ti/Ag/Cu活性焊料的封接特性

Ti／Ag／Cu活性焊料法广泛应用于陶瓷与金属的焊接中，但该焊料在陶瓷表面的浸润性较差，在金属表面易发生偏析的现象。本文对该焊料的流散特性进行了讨论，对陶瓷与金属的封接界面进行了分析，对封接机理进行了讨论，结果表明在封接界面生成Ti的氧化物主要是TiO2。