Ga、Al对Sn-Zn钎料耐蚀及高温抗氧化性能的影响

采用侵蚀失重法研究Ga、Al对Sn-9Zn钎料在3.5%NaCl水溶液中耐腐蚀性的影响.结果表明,添加Ga元素后,腐蚀产物的粘附性提高,均匀覆盖在钎料表面上,提高了钎料的耐蚀性能;添加Al以后,Zn和Al被选择性腐蚀,腐蚀随着Al含量的增加而加剧.采用热重分析(TGA)和俄歇电子能谱(AES)研究Ga、Al对Sn-9Zn钎料高温抗氧化性的影响.结果表明,Ga可在钎料表面形成一层集肤层;Al可在钎料表面形成一层致密的氧化膜,两者均可阻挡空气中的氧向钎料内部扩散,从而大大改善钎料的高温抗氧化性.     

Development of novel brasses to resist dezincification

The effect of alloying Sn, Pb, As, Sb and P on the dezincification of commercial brass 60Cu-39Zn-1Pb has been investigated in 1% CuCl₂ solution by immersion studies and electrochemical measurements. Specimens with a smooth surface finish exhibited more resistance to dezincification. Appreciable inhibitive effect on dezincification was observed for the 55Cu-40Zn-3Pb-2Sn brass composition. The galvanic coupling of lead phase with the matrix accelerated corrosion. To improve the dezincification resistance of the Sn containing brass, As, Sb and P were added at two different levels (0.05% and 0.1%). Brass of composition 48.95Cu-45Zn-5Pb-1Sn-0.05As was more resistant indicating the synergistic effect of Sn and As. The effect of 0.05 and 0.1% of arsenic addition with various concentrations of zinc was also studied. The alloy of composition 57.90Cu-40Zn-2Pb-0.1As showed better corrosion resistance than the alloy containing 1% Sn and 0.05% As (48.95Cu-45Zn-5Pb-1Sn-0.05As). To understand the influence of Sn and As on the dezincification of commercial brass, linear polarization and cyclic voltammetry experiments were conducted for the alloys 60Cu-39Zn-1Pb, 55Cu-40Zn-3Pb-2Sn and 57.90Cu-40Zn-2Pb-0.1As. Linear polarization measurements indicated that the alloys 55Cu-40Zn-3Pb-2Sn and 57.90Cu-40Zn-2Pb-0.1As possessed higher resistance to corrosion than commercial brass. Inspection of cyclic voltammograms revealed that the peak current densities as well as the passive current density were lower for the alloys 55Cu-40Zn-3Pb-2Sn and 57.90Cu-40Zn-2Pb-0.1As than the alloy 60Cu-39Zn-1Pb. The surface layer on the alloys 60Cu-39Zn-1Pb, 55Cu-40Zn-3Pb-2Sn and 57.90Cu-40Zn-2Pb-0.1As after immersion of 72 h in 1% CuCl₂ solution were analyzed by X-ray diffraction and scanning electron microscopy. Higher enrichment of Sn and As at the interface of surface layer and metal was indicated for the alloys 55Cu-40Zn-3Pb-2Sn and 57.90Cu-40Zn-2Pb-0.1As, respectively.     

Effects of Ga,Al, Ag,and Ce multi-additions on the wetting characteristics of Sn-9Zn lead-free solder

An orthogonal method was used to evaluate the effects of Ga, Al, Ag, and Ce multi-additions on the wetting characteristics of Sn-9Zn lead-free solders by wetting balance method. The results show that the optimal loading of Ga, Al, Ag, and Ce was 0.2 wt.%, 0.002 wt.%, 0.25 wt.%, and 0.15 wt.%, respectively. Intermetallic compounds (IMCs) formed at the interface between Sn-9Zn-0.2Ga-0.002Al-0.25Ag-0.15Ce solder and Cu substrate were investigated by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) analysis. The SEM images illustrate that the IMCs can be divided into two portions from the substrate side to the solder side: a planar Cu₅Zn₈ layer and an additional continuous scallop-like AgZn₃ layer. The EDS analysis also shows that Ga segregates in the solder abutting upon the interface. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) of the surface components of Sn-9Zn-0.2Ga-0.002Al-0.25Ag-0.15Ce solder indicate that Al aggregates at the surface in the form of Al₂O₃ protective film, which prevents the further oxidation of the solder surface. On the other hand, Ce aggregates at the subsurface, which may reduce the surface tension of the solder and improve the wettability in consequence.     

Effects of Zn,Zn-Al and Zn-P Additions on the Tensile Properties of Sn-Bi Solder

Effects of Zn, Zn-Al and Zn-P additions on melting points, microstructures, tensile properties, and oxidation behaviors of Sn-40 Bi lead-free solder were investigated. The experimental results show that the addition of these three types of elements can refine the microstructures and improve the ultimate tensile strength（UTS） of solder alloys. The fractographic analysis illustrates that ductile fracture is the dominant failure mode in tensile tests of Sn-40Bi-2Zn（SBZ）and Sn-40Bi-2Zn-0.005Al（SBZA） specimens, while brittle fracture is the controlled manner in Sn-40Bi-2Zn-0.005P（SBZP） and Sn-58 Bi solders. XPS analysis indicates that trace amounts of both Al and P additives in solder can improve the antioxidant capacity, whereas only the additive of Al in solder can reduce the thickness of oxidation film.     

The effect of reflow process variables on the wettability of lead-free solders

A quantitative dynamic solder wettability measurement was utilized to evaluate the effects of reflow processing on the wettability parameters associated with the lead-free solders 96.5Sn-3.5Ag and 58Bi-42Sn. Solder wettability was determined with respect to the final degree of spread and the extent of solder wetting onto the terminal areas of surface-mount components. The solder alloy composition of 96.5Sn-3.5Ag exhibited better wetting characteristics than the 58Bi-42Sn alloy. This wetting behavior was enhanced under the reflow conditions of a nitrogen atmosphere and the use of a gold metallization. The wetting of the conventional 63Sn-37Pb solder alloy was improved over the comparatively processed 58Bi-42Sn alloy. However, the 63Sn-37Pb solder alloy displayed a greater sensitivity to reflow atmosphere than the 96.5Sn-3.5Ag alloy, which generally exhibited better wetting characteristics than the Sn-Pb alloy.     

时效对Sn-Zn无铅钎料焊点可靠性的影响

采用扫描电子显微镜及STR-1000微焊点强度仪器,研究了Sn-9Zn-0.06Nd/Cu钎焊接头在150℃时效过程中界面组织形貌和力学性能的变化.结果表明,Sn-9Zn-0.06Nd/Cu接头焊接后的界面生成了较为平坦的金属间化合物层Cu5Zn8,随着时效时间的增加,金属间化合物层不断增厚.经过时效处理,钎料中的稀土元素Nd向界面富集并在界面附近生成了Nd3Sn相,同时微焊点的拉伸力不断减小,当时效720 h后,焊点的拉伸力下降了近50%.时效后焊点断裂方式由韧性断裂向脆性断裂转变.     

ZL102合金用低温软钎料的研究

Sn-9Zn共晶钎料可以用于钎焊钎焊性极差的铸造铝合金ZL102，在Sn-9Zn钎料的基础上添加In元素，以提高钎料对ZL102合金的润湿。本文对Sn-9Zn和Sn-9Zn-5In两种软钎料对ZL102合金润型，界面结合等方面进行研究，分析实验结果可知，Sn-9Zn-5In钎料的性能优于Sn-9Zn共晶钎料。     

CuCGA器件焊点热疲劳行为数值模拟

基于蠕变模型构建 Sn3.9Ag0.6Cu 和 63Sn37Pb 钎料的本构方程,分析铜柱栅阵列封装(CuCGA)器件在不同温度循环载荷下焊点的应力-应变分布.结果表明,不论温度循环如何变化,距器件中心最远处焊点的等效蠕变值总是最大,且均有明显的应力集中现象,在热循环作用下,很容易在该焊点处最先产生裂纹,导致器件失效,是整个器件最脆弱的焊点.同样温度载荷下,Sn3.9Ag0.6Cu 焊点的应力应变总是小于 63Sn37Pb 焊点,而随着温度循环范围的减小,两种钎料的应力和蠕变值均有所降低.另外,预测发现同样温度循环载荷条件下 Sn3.9Ag0.6Cu 焊点具有较高的疲劳寿命.

Abstract：

The constitutive equation of Sn3. 9Ag0.6Cu and 63Sn37Pb were established based on creep law, and the stress-strain distribution of soldered joints in copper column grid array (CuCGA)devices was analyzed under the loadings of different temperature cycles. Results indicate that no matter how the change of temperature cycle range, the maximum creep strain is located in the soldered joint where the location from the device center is foremost, in which the stress concentration is found and cracks appear, therefore, the comer soldered joint is the most fragile area in the whole device.Creep strain of Sn3.9Ag0. 6Cu soldered joints is smaller than that of 63Sn37Pb soldered joints. Low er stress and creep strain are exhibited for both Sn3.9Ag0.6Cu and 63Sn37Pb when the temperature cycles range is shortened. Sn3.9Ag0.6Cu soldered joints show higher thermal fatigue life than 63Sn37Pb soldered joints under the same temperature cycle.     

The Inhibition of Tin Whiskers on the Surface of Sn-8Zn-3Bi-0.5Ce Solders

Through the refinement of the (Ce, Zn)Sn₃ intermetallic phase, the formation of tin whiskers, previously observed on the surface of a Sn-3Ag-0.5Cu-0.5Ce solder, was prevented in a Sn-9Zn-0.5Ce alloy. However, whisker growth can still occur on the surface of Sn-8Zn-3Bi-0.5Ce solder after air storage at room temperature and at 150 °C due to the formation of large (Ce, Zn)Sn₃ intermetallic clusters. Further experiments showed that decreasing the Bi-content in this Sn-8Zn-0.5Ce alloy to 1 and 2 wt.% can recover the beneficial effects of Zn additions on the refinement of the (Ce, Zn)Sn₃ phase and obviously reduce the appearance of tin whiskers. In addition, alloying the Sn-8Zn-3Bi-0.5Ce solder with 0.5 wt.% Ge, which increases the oxidation resistance of the (Ce, Zn)Sn₃ intermetallic clusters, can also effectively inhibit tin whisker growth.     

稀土铈在Sn-Zn无铅钎料表面的高温氧化行为

通过俄歇电子能谱法和X射线光电子能谱法研究了Sn-9Zn-0.15Ce和Sn-9Zn-0.002Al-0.2Ga-0.25Ag-0.15Ce两种钎料表面Ce元素的分布和存在形式.结果表明,铈在Sn-9Zn-0.15Ce钎料表面0~40 nm范围内的富集区浓度达到30%(原子分数)左右,是基体内部的250倍,主要以CeO2和Ce2O3形态存在.在Sn-9Zn-0.15Ce钎料中复合添加镓和铝后,Ga元素在钎料表面0~6 nm范围内富集,Al元素在表面2~20 nm范围内富集并主要以氧化态形式存在.Ce元素富集在距离钎料表面2~60 nm的范围内,处于Ga,Al元素富集层的下方;由Ga,Al元素富集层构成的致密保护膜可显著降低表面铈被氧化的概率.     

Sn whisker growth in Sn-9Zn-0.5Ga-0.7Pr lead-free solder

The spontaneous growth of Sn whisker in Sn-Zn series solder is newly reported in this work. It is found that during the exposure of Sn-9Zn-0.5Ga-0.7Pr bulk solder to ambient conditions for a few hours, many different lengths of needle-like Sn whiskers originate spontaneously from the Sn-Pr intermetallic compounds of the solder and grow rapidly at a rate of about 3.5 Å/s. It is proposed that the driving force for whisker formation is the compressive stress resulting from the oxidation of Sn-Pr compounds, and that the free Sn atoms released from oxidation reaction feed the whisker growth during exposure.     

复合添加Ga,Al,Ag对Sn-9Zn钎料性能的影响

采用润湿平衡法研究了合金元素Ga,Al,Ag复合添加对Sn-9Zn钎料润湿性的影响.结果表明,Ga,Al,Ag的最佳添加量分别为0.2,0.002,0.25(质量分数,%);添加合金元素后钎料的高温抗氧化性能显著提高.俄歇电子能谱分析表明,Sn-9Zn-0.2Ga-0.002Al-0.25Ag钎料表面Al高度富集并形成一层致密的氧化膜,可阻挡氧向液态钎料内部扩散,减少钎料的氧化.Sn-9Zn-0.2Ga-0.002Al-0.25Ag钎料与Cu/Ni/Au基板之间的金属间化合物由一层平坦的AuZn3和颗粒状的AuAgZn2化合物组成.另外,微焊点力学试验表明,采用Sn-9Zn-0.2Ga-0.002Al-0.25Ag钎料时,电子元器件与基板间微焊点的力学性能比Sn-9Zn钎料略有提高.     

无铅焊料在NaCl-Na_2SO_4-Na_2CO_3模拟土壤溶液中的腐蚀浸出行为

研究了Sn-3.5Ag-0.75Cu和Sn-0.75Cu焊料合金在NaCl-Na_2SO_4-Na_2CO_3模拟土壤溶液中的腐蚀浸出行为,并与Sn-37Pb焊料合金的腐蚀浸出行为对比分析。研究表明,这3种焊料合金中Sn的浸出量随时间的延长趋于平缓,且Sn-0.75Cu焊料合金中Sn的浸出量最高,添加Ag元素后明显抑制了Sn-3·5Ag-0·75Cu焊料合金中Sn的浸出;Ag,Cu,Pb的浸出量随时间的延长呈线性增加,且Ag,Cu的浸出量较少。3种焊料合金浸出后表面产物层较厚,主要由Sn_4(OH)_6Cl_2和SnO组成,其中Sn-0.75Cu焊料合金的表面产物层有裂纹和孔洞,Sn-3.5Ag-0.75Cu焊料合金的表面产物相对致密,而Sn-37Pb焊料合金的表面产物局部出现剥落现象。这3种焊料合金浸出动力学行为存在差异,主要与表面产物的相组成和形貌有关。     

Sn-Zn-Bi-(P,Nd)无铅钎料的微观组织及性能

研究了复合加入P,Nd元素的Sn-8Zn-3Bi钎料的微观组织、力学性能、抗氧化性及润湿性.结果表明,单独加入元素P会导致Sn-8Zn-3Bi钎料组织中出现初生Zn相,而同时加入元素P和Nd不仅能够抑制初生Zn相的形成,钎料组织也能够得到细化,因此钎料的塑性提高,断后伸长率达到48%.P,Nd元素的复合添加能够在钎料表面形成稳定的扩散阻挡层,抑制P元素在长时间加热条件下的烧损,进一步降低表面的氧化速度.由于钎料的抗氧化性提高,Sn-8Zn-3Bi-0.1P-0.05Nd钎料呈现出更好的润湿性.     

Sn-9Zn钎料与内加Cu质点和Cu基体界面生长行为

在Sn-9Zn无铅钎料中加入Cu金属质点,研究在长时间钎焊条件下钎料/Cu质点、钎料/Cu基体界面金属间化合物（IMCs）的生长行为。结果表明：在钎料/Cu质点和钎料/Cu基体界面处都生成Cu-Zn相（IMCs）,其组成为Cu5Zn8＋CuZn或Cu5Zn8,而且钎料/质点界面处IMCs的生长速度明显快于钎料/基体处;同时发现,Cu质点的加入大大减小了钎料/Cu基体界面IMCs的厚度。由于Cu质点原位生成Cu-Zn IMCs,消耗了焊点中的Zn,因此Sn-9Zn/Cu接头的可靠性得以提高。     

Sn-9Zn系无铅焊料钎焊接头剪切性能的研究

利用扫描电镜及万能材料实验机研究了Sn-9Zn/Cu钎焊接头的界面形貌及Sn-9Zn焊料微合金化前后钎焊接头的剪切性能变化。结果表明,Sn-9Zn/Cu界面金属间化合物为Cu5Zn8,界面层呈平整的锯齿状。由于焊接时没有保护气氛,以致Sn-9Zn氧化而使剪切性能变差,而同时添加微量RE和Ag或RE和Al元素后剪切强度大幅度增高,尤其是添加0.025%RE和0.3%Ag时剪切强度可提高46.47%,同时添加元素后剪切断口韧性断裂趋势增大。     

Oxidation of liquid solders for die attachment

This study deals with thermal oxidation behaviour in the liquid state of a commonly-used die-attach solder, Pb–Sn, and its potential Pb-free alternatives (Bi–Ag and Zn–Sn) from viewpoints of thermodynamics and kinetics. The characteristics of the oxidation reaction layers were investigated using XPS, XRD and AES. The superior performance in oxidation prevention of the Zn based alloys can be ascribed to their stable oxidative product, ZnO, which exhibits low free energy of formation, as well as slow growth rate.     

Electrochemical corrosion behaviour of Pb-free Sn-8.5Zn-0.05Al-XGa and Sn-3Ag-0.5Cu alloys in chloride containing aqueous solution

The electrochemical corrosion behaviour of Pb-free Sn-8.5Zn-0.05Al-XGa and Sn-3Ag-0.5Cu alloys was investigated in 3.5% NaCl solution by using potentiodynamic polarization techniques. The results obtained from polarization studies revealed that there was a negative shift in the corrosion potential with increase in Ga content from 0.02 to 0.2 wt% in the Sn-8.5Zn-0.05Al-XGa alloy. These changes were also reflected in the corrosion current density (I_corr) value, corrosion rate and linear polarization resistance (LPR) of the four element alloy. However, for Sn-3Ag-0.5Cu alloy a significant increase in the corrosion rate and corrosion current density was observed as compared to the four element alloys. SIMS depth profile results established that ZnO present on the outer surface of Sn-8.5Zn-0.05Al-0.05Ga alloy played a major role in the formation of the oxide film. Oxides of Sn, Al and Ga contributed a little towards the formation of film on the outer surface of the alloy. On the other hand, Ag₂O was primarily responsible for the formation of the oxide film on the outer surface of Sn-3Ag-0.5Cu alloy.     

Solderability and intermetallic compounds formation of Sn-9Zn-xAg lead-free solders wetted on Cu substrate

The eutectic Sn-9Zn alloy was doped with Ag (0 wt.%-1 wt.%) to form Sn-9Zn-xAg lead-free solder alloys. The effect of the addition of Ag on the microstructure and solderability of this alloy was investigated and intermetallic compounds (IMCs) formed at the solder/Cu interface were also examined in this study. The results show that, due to the addition of Ag, the microstructure of the solder changes. When the quantity of Ag is lower than 0.3 wt.%, the needle-like Zn-rich phase decreases gradually. However, when the quantity of Ag is 0.5 wt.%-1 wt.%, Ag-Zn intermetallic compounds appear in the solder. In particular, adding 0.3 wt.% Ag improves the wetting behavior due to the better oxidation resistance of the Sn-9Zn solder. The addition of an excessive amount of Ag will deteriorate the wetting property because the glutinosity and fluidity of Sn-9Zn-(0.5, 1)Ag solder decrease. The results also indicate that the addition of Ag to the Sn-Zn solder leads to the precipitation of ε-AgZn₃ from the liquid solder on preformed interfacial intermetallics (Cu₅Zn₈). The peripheral AgZn₃, nodular on the Cu₅Zn₈ IMCs layer, is likely to be generated by a peritectic reaction L + γ-Ag₅Zn₈ → ɛ-AgZn₃ and the following crystallization of AgZn₃.     

Influence of stress on the creep behavior of Cu particle enhancement SnPb based composite solder joints

1. Introduction Mechanical fracture of solder joints is a major cause of failure and it decreases the reliability in electronic systems. With the increased functionality, miniaturization of electronic components, broad op-eration temperature ranges, and increased stress re-quirement, good mechanical properties are de-manded on solder joints. The eutectic tin-lead solder, which has a low melting point (183°C), plays an important role in SMT (surface mount technology). The working temperature…