BiAgSbCu系高温无铅钎料制备及焊接性能研究

研制开发熔点在260 ℃以上的高温无铅钎料来代替传统的高铅钎料运用于电子封装一直是钎焊领域的一大难题。熔点约为272 ℃的Bi-2.6 Ag-5 Sb钎料合金因润湿性和焊接可靠性不良在运用上受到限制。文中通过在Bi-2.6 Ag-5 Sb钎料合金中添加微量元素Cu来改善B-i2.6 Ag-5 Sb合金的润湿性及焊接可靠性。研究结果表明,Cu含量对BiAgSbCu系钎料合金熔点影响较小,当Cu含量为2 %时,润湿性及焊接可靠性最佳。     

微量Sn添加对BiAgSb系高温无铅钎料焊接性能的影响

通过在Bi-2.6Ag-5Sb钎料合金中添加微量元素Sn来改善Bi-2.6Ag-5Sb合金的润湿性和焊接可靠性。研究结果表明:Bi-2.6Ag-5Sb钎料合金中添加质量分数0.5%~3.0%的Sn,随着Sn含量的增加,钎料的熔点呈下降趋势,熔点仍然在260~280℃,能明显改善其润湿性和焊接可靠性。     

Sn-Sb-Cu(Bi)系无铅钎料的研究

本文研究了Sn-Sb-Cu(Bi)系无铅钎料的润湿性、显微组织以及熔化特性,对Sb、Cu、Bi等元素在Sn基钎料中的作用进行了阐述,发现了几种有应用潜力的合金,有望取代现有广泛使用的SnAg(Cu)系钎料.     

Sn-Cu、Sn-Ag-Cu系无铅钎料的钎焊特性研究

制备了Sn-0.7Cu、Sn-3.5Ag-0.6Cu钎料,用润湿平衡法测量了钎料对铜的润湿曲线,研究了温度、钎剂活性、钎焊时间对润湿行为的影响,并与Sn-37Pb钎料进行了比较。结果表明:升高温度能显著改善无铅钎料对铜的钎焊性。当温度<270℃时,Sn-0.7Cu的钎焊性明显低于Sn-3.5Ag-0.6Cu钎料;而当温度≥270℃时,两种钎料对铜都会显示较好的润湿性,而Sn-0.7Cu略优于Sn-3.5Ag-0.6Cu钎料。提高钎剂活性能显著增强钎料对铜的润湿性,其卤素离子的最佳质量分数均为0.4%左右。随着浸渍时间的延长,熔融钎料与铜的界面间产生失润现象。无铅钎料的熔点和表面张力较高,是钎焊性较差的根本原因。     

P元素对Sn-0.3Ag-0.7Cu钎料抗氧化性、润湿性以及显微组织的影响

为改善Sn-0.3Ag-0.7Cu钎料抗氧化性和润湿性差的问题,在钎料中添加了P元素,研究了微量P元素对Sn-0.3Ag-0.7Cu钎料抗氧化性、润湿性以及显微组织的影响。制备了含不同质量分数P元素的Sn-0.3Ag-0.7Cu-xP (x=0%, 0.005%, 0.010%, 0.015%, 0.020%)钎料。以实验的方式测试了钎料的抗氧化性以及润湿性,并使用扫描电镜(SEM)和能谱仪(EDS)观察了显微组织。结果表明：随着P含量的增加,钎料的抗氧化性和润湿性显著提高。当P含量达到0.020%时,与不添加P元素的钎料相比,在250℃保温30 min后的氧化渣质量由2.25 g减少到0.79 g。此时,钎料的铺展面积和润湿力也达到最大,分别为65.74 mm²和5.04 mN,润湿时间为0.96 s。添加微量P元素未改变钎料的相组成,其显微组织主要由β-Sn、Ag₃Sn与Cu₆Sn₅三种相构成。随着P含量的增加,Ag₃Sn的形态由粒状向片状转变。     

BiSbCuSn高温无铅软钎料物理性能及润湿性能研究

研制开发熔点在250～450℃之间的高温无铅软钎料一直是钎焊领域一大难题。熔点为300℃左右的Bi5Sb2Cu钎料因润湿性能和导电性能不良而受到限制。本文通过在Bi5Sb2Cu中添加不同含量Sn形成新型BiSbCuSn四元合金,来改善Bi5Sb2Cu合金的润湿性能和物理性能。结果表明：在Bi5Sb2Cu钎料合金中添加2-↑10wt．％Sn,BiSbCu钎料合金熔点呈下降趋势且幅度较大,但仍在250～450℃之间,润湿性能和导电性能明显改善。当Sn含量为10wt．％时,（Bi5Sb2Cu）10Sn钎料合金润湿性能和导电性能最好。     

新型无铅焊料的研制

由于目前使用的Sn3.5AgCu无铅焊料,温度较高、润湿性较差.在Sn3.5AgCu无铅钎料中添加金属元素Ga、Bi,并改变Ag的含量,对其合金进行熔化温度、润湿性、力学性能和微观组织研究.研究表明,添加Ga、Bi并改变Ag含量有利于降低Sn3.5AgCu合金的熔化温度和改善其润湿性,并提高了力学性能.     

微量元素对Sn-0.7Cu无铅钎料抗氧化性能的影响

以Sn-0.7Cu系无铅钎料合金为基础,添加微量的P、Ge、Ga、RE元素,进行了280℃大气环境下氧化试验,通过对含有不同微量元素的无铅钎料表面氧化状况的对比及分析,研究了不同微量元素对Sn-0.7Cu无铅钎料抗氧化性能的影响。发现当P和Ga同时添加时,得到Sn-0.7Cu-(0.001~0.1)P-(0.0001~0.1)Ga无铅钎料的抗氧化性能高于Sn-0.7Cu-(0.001~0.1)P和Sn-0.7Cu-(0.0001~0.1)Ga的抗氧化性能。     

Ga元素含量对305钎料组织及性能的影响

通过在Sn-3Ag-0.5Cu钎料中添加不同含量的Ga，并采用差示扫描量热法（DSC）、万能试验机测试方法配制合金材料的熔化特性曲线、力学性能、金相结构、焊接润湿扩展率等性质，研究Ga含量对Sn-3Ag-0.5Cu钎料的熔化过程、焊接润湿扩展性以及组织和力学性能方面的影响。结果表明，Sn-3Ag-0.5Cu钎料中加入Ga元素以后，随着Ga增加，钎料的熔点显著降低，熔程也逐渐增大；适量的Ga元素可以改善Sn-3Ag-0.5Cu钎料的润湿性能；当Ga元素的添加量质量分数达到0.5%时，Sn-3Ag-0.5Cu钎料的组织均匀，晶粒明显细化，钎料的力学性能最佳，但Ga元素含量进一步增加时，在晶界处析出黑色富Ga相，对钎料力学性能产生了不利影响。     

稀土对Zn20Sn高温无铅钎料组织与性能的影响

向Zn20Sn高温无铅钎料中添加微量铈镧混合稀土（RE）,研究了RE的添加量对该钎料合金显微组织及性能的影响。结果表明,添加微量RE的合金显微组织中出现含RE的金属间化合物（IMC）。随着RE的添加,形状各异的IMC的数量显著增加。RE质量分数为0.5%~1.0%的合金的固相线温度不变,而液相线温度略有降低。当RE质量分数为0.5%时,钎料在Cu基板上的铺展面积最大,比Zn20Sn钎料提高了57.6%。但随着RE的继续添加,钎料的润湿性降低。当RE质量分数超过0.1%时,钎料的显微硬度和电阻率随着RE含量的增加而增大。综合考虑,合适的RE添加量为质量分数0.5%。     

Sn-0.3Ag-0.7Cu-xBi低银无铅钎料的润湿性

以Bi为添加剂对低银型Sn-0.3Ag-0.7Cu无铅钎料进行改性,应用SAT—5100型润湿平衡仪对Sn-0.3Ag-0.7Cu-xBi(x=0,1,3和4.5)钎料的润湿性能作了对比分析。结果表明:适量Bi元素的加入可以改善Sn-0.3Ag-0.7Cu钎料合金的润湿性能,且在240℃下Sn-0.3Ag-0.7Cu-3.0Bi无铅钎料具有最佳的润湿性能,在250℃其润湿力达到最大值3.2×10–3N/cm。     

Ti对Sn0.7Cu无铅钎料润湿性和界面的影响

研究了Ti的加入对Sn0.7Cu无铅钎料润湿性能以及钎料/Cu界面微观组织的影响.结果表明:在Sn0.7Cu中添加微量Ti,提高了钎料的润湿性能,可使铺展面积提高5％左右,当钎焊时间为3s时,界面金属间化合物(IMC)形貌由原来的扇贝状变为锯齿状;随着钎焊时间延长,Sn0.7Cu/Cu和Sn0.7Cu0.008Ti/C...     

Effect of alloying elements on properties and microstructures of SnAgCu solders

Recent years, the SnAgCu family of alloys has been found a widely application as a replacement for the conventional SnPb solders in electronic industry. In order to further enhance the properties of SnAgCu solder alloys, alloying elements such as rare earth, Bi, Sb, Fe, Co, Mn, Ti, In, Ni, Ge and nano-particles were selected by lots of researchers as alloys addition into these alloys. Rare earth (RE) elements have been called the ‘‘vitamin” of metals, which means that a small amount of RE elements can greatly enhance the properties of metals, such as microstructure refinement, alloying and purification of materials and metamorphosis of inclusions. In addition, a small amount of Zn addition has the ability to reduce undercooling efficiently and suppress the formation of massive primary Ag₃Sn plates, and Bi/Ga has the ability to enhance the wettability of SnAgCu alloys as well as Ni. Moreover, adding Co/Fe/Ge can effectively refine microstructure, modify interfacial Cu-Sn compounds and increase the shear strength of joints with Cu. This paper summarizes the effects of alloying elements on the wettability, mechanical properties, creep behavior and microstructures of SnAgCu lead-free solder alloys.     

Wetting reaction of Sn-Ag based solder systems on Cu substrates plated with Au and/or Pd layer

The wetting behavior of SnAg based Pb-free solders on Cu and Cu substrates plated with Au, Pd, and Au/Pd thin films have been studied. The wetting angle and kinetics of interfacial reaction were measured. The Au-plated substrates exhibit better wetting than the Pd-plated substrates. In the case of SnAg on Pd-plated Cu, SEM observation revealed that the solder cap was surrounded by an innerring of Cu−Sn compound and an outer ring of Pd−Sn compound. This implies that the molten SnAg solder had removed the Pd and wetted the Cu directly in the equilibrium state. The effects of pre-doping Cu in the SnAg solder on wetting behavior were also investigated. We found that wettability decreases with increasing Cu content in the solder. We also observed that the SnAgCu solders have a lower Cu consumption rate than the SnAg solder.     

Reactions of lead-free solders with CuNi metallizations

We have done experimental research on the dissolution rate and intermetallic growth on Cu, Ni, and CuNi-alloy substrates as a function of time and Cu/Ni ratio of the substrate. Reactions that occur when CuNi metallizations are soldered with lead-free solders were investigated. The experiments were performed using Sn-3.5Ag and Sn-3.8Ag-0.7Cu solders and different CuNi alloys. To determine the rate of dissolution of the substrate material into the solder, CuNi foils of different concentrations were immersed in Sn-3.5Ag and Sn-3.8Ag-0.7Cu solder baths for soldering times ranging from 15 sec to 5 min at 250°C. In addition, reflows of solder balls were made on top of bulk substrates to study the reaction when there is a practically infinite amount of CuNi available compared to the amount of solder. Thin film experiments were also done, where Ni containing under bump metallizations (UBMs) were fabricated and reflowed with eutectic SnAg solder balls. The nickel slows down the dissolution of the UBM into the solder and the formation of intermetallics during reflow compared to Cu metallizations. The solder/UBM interfaces were analyzed with SEM to find out how Ni concentration affects the reaction, and how much Ni is needed to obtain a sufficiently slow reaction rate.     

Morphology and growth kinetics of intermetallic compounds in solid-state interfacial reaction of electroless Ni-P with Sn-based lead-free solders

A comparative study of solid/solid interfacial reactions of electroless Ni-P (15 at.% P) with lead-free solders, Sn-0.7Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, and pure Sn, was carried out by performing thermal aging at 150°C up to 1000 h. For pure Sn and Sn-3.5Ag solder, three distinctive layers, Ni₃Sn₄, SnNiP, and Ni₃P, were observed in between the solder and electroless Ni-P; while for Sn-0.7Cu and Sn-3.8Ag-0.7Cu solders, two distinctive layers, (CuNi)₆Sn₅ and Ni₃P, were observed. The differences in morphology and growth kinetics of the intermetallic compounds (IMCs) at the interfaces between electroless Ni-P and lead-free solders were investigated, as well as the growth kinetics of the P-enriched layers underneath the interfacial IMC layers. With increasing aging time, the coarsening of interfacial Ni₃Sn₄ IMC grains for pure Sn and Sn-3.5Ag solder was significantly greater than that of the interfacial (CuNi)₆Sn₅ IMC grains for Sn-0.7Cu and Sn-3.8Ag-0.7Cu solders. Furthermore, the Ni content in interfacial (CuNi)₆Sn₅ phase slightly increased during aging. A small addition of Cu (0.7 wt.%) resulted in differences in the type, morphology, and growth kinetics of interfacial IMCs. By comparing the metallurgical aspects and growth kinetics of the interfacial IMCs and the underneath P-enriched layers, the role of initial Cu and Ag in lead-free solders is better understood.     

添加微量高熔点金属对无铅焊料性能的影响

研究了在SnAgCu、SnAgBi、SnZn三个系列无铅焊料中添加质量分数为0.1%的高熔点金属(Ni、Co、Fe)对其熔融特性、力学基本性能和浸润性的影响。结果表明,添加微量高熔点金属对焊料的熔融特性影响小于2%。添加微量Ni能明显改善SnAgCu系和SnZn系焊料的力学性能,并能使SnAgBi系焊料在铜表面的接触角降低约10%~14%。添加微量Co或Fe后的新焊料仅少部分性能指标有所提高,而部分性能参数则严重下降。