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。     

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。     

电子封装用SnAgCuGa钎料的改性

针对SnAgCu钎料存在的熔点偏高、润湿性较差等不足,研究了不同Sb含量对SnAg3.5Cu0.7Ga1钎料性能的影响。结果表明,随着Sb含量的增加,SnAg3.5Cu0.7Ga1钎料的固液相线呈增长趋势,但均低于230℃;Sb含量添加0.5%时,SnAg3.5Cu0.7Ga1合金在240℃无卤素松香助焊剂下润湿性变化不大,当Sb含量达到1.0%以上时,SnAg3.5Cu0.7Ga1合金的润湿性随着Sb含量的增加而提高。添加少量的Sb可以提高SnAg3.5Cu0.7Ga1无铅钎料的抗氧化性,随着Sb含量的增加,产生裂纹时的循环次数依次增加,可以提高钎焊铜合金接头的热疲劳强度。     

电子组装用高温无铅钎料的研制

Bi-Ag合金是一种替代高铅钎料的芯片封装无铅焊料。研制了Bi-2.5Ag、Bi-2.5Ag-0.1RE、Bi-5Ag-0.1RE、Bi-7.5Ag-0.1RE、Bi-10Ag、Bi-10Ag-0.1RE钎料。结果表明,该合金系钎料的熔化温度范围随Ag含量的增加而增大,而且其润湿性能良好,润湿角都处于30o～40o。不同Ag含量的Bi-Ag/Cu接头在界面处发生断裂,剪切强度差别不大,都略大于30MPa。Bi-Ag/Cu界面没有金属间化合物形成,结合强度较弱。     

SnAgCu系钎料的合金组织和力学性能

研究了Cu含量对SnAgCu系钎料合金显微组织及其与化学镀Ni基板钎焊接头力学性能的影响。结果表明:高Cu含量SnAgCu合金会产生较多的(CuxNi1-x)6Sn5金属间化合物,从而减少镀Ni层的消耗,进一步提高钎焊接头的剪切强度。与Sn-3.0Ag-0.3Cu相比,Sn-3.0Ag-1.0Cu钎焊接头剪切强度提高了6.78%。经过150℃时效1000h后,界面Ni3(P,Sn)层的增长率从Sn-3.0Ag-0.3Cu合金的约66%降低到Sn-3.0Ag-1.0Cu合金的约40%。     

Sn对BiSbCu钎料钎焊工艺性能的影响

在BiSbCu钎料中添加Sn,分析Sn对BiSbCu钎料合金钎焊工艺性能的主要指标——钎料熔点和铺展面积的影响。结果表明:在Bi5Sb2Cu钎料合金中加入Sn可以显著降低钎料的熔点和显著增强钎料合金的铺展性能。当Sn的质量分数为10%时,Bi5Sb2Cu钎料的铺展面积为26.22 mm2,钎焊工艺性能最好。     

三种典型Sn-Ag-Cu无铅钎料的组织和性能研究

对比研究了三种典型标称成分的Sn-Ag-Cu钎料(即日本JEIDA推荐的Sn-3.0Ag-0.5Cu、欧盟IDEALS推荐的Sn-3.8Ag-0.7Cu和美国NEMI推荐的Sn-3.9Ag-0.6Cu)的显微组织特征、熔化特性、润湿性以及钎焊接头微焊点的力学性能等。结果表明,三种钎料的组织和性能非常接近。然而从性价比等方面综合考虑,Sn-3.0Ag-0.5Cu为三种钎料中最具优势的替代传统Sn-Pb钎料(共晶和近共晶钎料)的无铅合金。     

Sn对BiSbCu钎料钎焊工艺性能的影响

在BiSbCu钎料中添加Sn,分析Sn对BiSbCu钎料合金钎焊工艺性能的主要指标——钎料熔点和铺展面积的影响.结果表明:在Bi5Sb2Cu钎料合金中加入Sn可以显著降低钎料的熔点和显著增强钎料合金的铺展性能.当Sn的质量分数为10％时,Bi5Sb2Cu钎料的铺展面积为26.22 mm2,钎焊工艺性能最好.     

微量Ni对Sn-3.0Ag-0.5Cu钎料及焊点界面的影响

研究了Ni的含量对无铅钎料Sn-3.0Ag-0.5Cu润湿性、熔点、重熔及老化条件下界面化合物(IMC)的影响。结果表明:微量Ni的加入使SnAgCu润湿力增加6%;使合金熔点略升高约3℃;重熔时在界面形成了(Cu,Ni)6Sn5IMC层,且IMC厚度远高于SnAgCu/Cu的Cu6Sn5IMC厚度。在150℃老化过程中,SnAgCuNi/Cu重熔焊点IMC随着时间的增加,其增幅小于SnAgCu/Cu的增幅,此时Ni对IMC的增长有一定抑制作用。     

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。     

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。     

Intermetallic compounds and adhesion strength between the Sn-9Zn-1.5Ag-0.5Bi lead-free solder and unfluxed Cu substrate

The intermetallic compounds (IMCs) formed at the interface between the Sn-9Zn-1.5Ag-0.5Bi lead-free solder alloy and unfluxed Cu substrate have been investigated by x-ray diffraction, optical microscopy, scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). The melting point and melting range of the Sn-9Zn-1.5Ag-0.5Bi solder alloy are determined as 195.9°C and 10°C, respectively, by differential scanning calorimetry (DSC). Cu₆Sn₅ and Cu₅Zn₈ IMCs are formed between the Sn-9Zn-1.5Ag-0.5Bi/unfluxed Cu substrate wetted at 250°C for 10 sec. The interfacial adhesion strength changes from 10.27±0.68 MPa to 8.58±0.59 MPa when soldering time varies from 10 sec to 30 sec at 250°C.     

Experimental Wettability Study of Lead-Free Solder on Cu Substrates Using Varying Flux and Temperature

The selection of soldering flux plays a critical role in promoting wetting and product reliability of printed circuit board assemblies. In this study, the effects of fluxes on the wetting characteristics of the Sn-3.0Ag-0.5Cu solder alloy on Cu substrates was researched by using various flux systems at different soldering temperatures. Because of the distinct characteristic of the lead-free solder—poor wettability—three kinds of fluxes [no-clean flux with high solid content (NCF), rosin mildly activated flux (RMA) and water-soluble flux (WSF)] were chosen for the wetting experiments. The wetting time and force were the evaluating indicators. The experimental observations indicated that the wettability clearly depended on the soldering temperature and flux system when using the same solder. Furthermore, the corrosion potential of flux residues was measured by surface insulation resistance (SIR) testing. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to determine the contents of the flux residues and corrosion products.     

氮气保护对无铅焊接工艺温度窗口的影响

无铅化电子组装中无铅焊料的高熔点、低润湿性给实际生产带来了很大挑战。为了改善润湿性,可适当提高焊接温度,但由于PCB及元件的工艺温度限制,导致了焊接工艺温度窗口变窄。氮气保护可以改善无铅焊料润湿性、防止氧化、提高焊接品质,更重要的是可以降低焊接峰值温度,扩大焊接工艺温度窗口。     

Microstructures and properties of Bi10Ag high temperature solder doped with Cu element

High temperature Bi10Ag solders with different amounts of Cu were used to investigate the impacts of Cu on the microstructures, melting characteristics, wettability and shear strength of the Bi-10Ag-xCu (x = 0, 0.5, 1, and 2 wt%) solders. A metastable Cu-rich phase was formed due to the addition of Cu. The Cu has negligible effect on the solidus but it can decrease about 6 °C on the liquidus. Doped with 0.5 wt% of Cu, the solders showed the largest melting range in the DSC curves and improved wettability on Cu substrates. When the Cu addition excesses to 0.5 wt%, it will induce negative effects on wettability of the solders on the substrate. Moreover, the addition of Cu has no significant influence on the strength of the Bi10Ag lap solder joints. The Bi-10Ag-0.5Cu solder joint has higher shear strength than that of Pb5Sn.     

Microstructure, solderability, and growth of intermetallic compounds of Sn-Ag-Cu-RE lead-free solder alloys

The near-eutectic Sn-3.5 wt.% Ag-0.7 wt.% Cu (Sn-3.5Ag-0.7Cu) alloy was doped with rare earth (RE) elements of primarily Ce and La of 0.05–0.25 wt.% to form Sn-3.5Ag-0.7Cu-xRE solder alloys. The aim of this research was to investigate the effect of the addition of RE elements on the microstructure and solderability of this alloy. Sn-3.5Ag-0.7Cu-xRE solders were soldered on copper coupons. The thickness of the intermetallic layer (IML) formed between the solder and Cu substrate just after soldering, as well as after thermal aging at 170°C up to 1000 h, was investigated. It was found that, due to the addition of the RE elements, the size of the Sn grains was reduced. In particular, the addition of 0.1wt.%RE to the Sn-3.5Ag-0.7Cu solder improved the wetting behavior. Besides, the IML growth during thermal aging was inhibited.