新型低银无铅焊料的研究论文

1、新型低银无铅焊料的研究论文 10213 国内图书 分类号:TB34 学校代码 : 国际图书 分类号:620 密级: 公开 工学硕士学位论文新型低银无铅焊料的研究 硕士研究生 : 马新波 导师 : 李明雨教授 申请 学位 : 工学硕士 学科、专业 : 材料物理与化学 所在 单位 : 深圳研究生院 答辩 日期 : 2010 年 6 月 授予学位单位 : 哈尔滨工业大学Classified Index: TB34 U.D.C: 28 Dissertation for the Master Degree in EngineeringSTUDY OF A LOW-SILVER LEAD-FREE SOL

2、DER ALLOYCandidate: Ma Xinbo Supervisor: Prof. Li Mingyu Academic Degree Applied for: Master of Engineering Materials Physics and Chemistry Speciality: Shenzhen Graduate School Affiliation: Date of Defence: June, 2010 Degree-Conferring-Institution: Harbin Institute of Technology哈尔滨工业 大 学工学硕士 学 位论文摘

3、要 出于保护 环境和保 护人类自 身健康的 要求, 电子 产品的无 铅化已经 进入实 施阶段。 出 于降低现 有无铅钎 料的成本 , 提高其 抗高温时 效性能的 要求, 低 银型 无铅钎料的 研究具有 十分重要 的意义。 一种低银 型无铅钎 料SAC0307正在使 用 中,但是此种 钎料合金 的熔点较 高,润湿 性较差, 而SAC305 钎料合金 的价格昂 贵,为此本论 文在此基 础上研究 了一种新 型的低银 型无铅钎 料SAC0507X。 通过对比性试验 , 研究银和X 元素不同 含量对钎 料熔点 、 润湿性及 溶铜量的 影响, 找 到具有最佳综 合性能的 钎料合金 成分, 以 及开发出 具

4、有低成 本、 低熔 点, 良好 的润 湿性,低溶 铜量等综 合性能优 异的无铅 钎料。 对钎料熔 点的研究 结果表明 :低银型 SAC0507X 无铅钎 料合金的 熔点范围是 217.24225.97 , 基本上和 目前国际 上推荐的 高银型 Sn-Ag-Cu 钎 料合金的 熔点一致。 对钎料润 湿性的研 究结果表 明:由于 低银型 SAC0307 无 铅焊料合 金的润湿力较差。 而 SAC0507X 在增 加 了银的含 量及 X 合 金元素的 添加之后 ,润湿时 间降低到 1.293s , 已经 远远满足 了工业实 际机械化 生产 t2.5s 的需 求 , 并且此种 成分的钎料 合金最大 润

5、湿力达 到 3.687mN, 具有很 好的润湿 性能。 对焊接接 头剪切力 的研究结 果表明: 低银型 SAC0307 无 铅钎料的 剪切力为25.948N,而 SAC0507X 钎料合 金的剪切 力略有提 高,最大 剪切力为 28.673N,低于高银型 SAC305 钎 料合金。 对无铅钎 料合金的 微观组织 观察结果 表明: X 合 金元素的 添加能够 降低钎 料中原子的 扩散速度 , 细化晶 粒, 阻碍 钎料中金 属间化合 物的生长 ; 在焊接 接头 的- I - 哈尔滨工业 大 学工学硕士 学 位论文截面图中 可以看到 ,X 合金元 素的加入 降低了金 属间脆性 化合物的 生长速度 ,

6、 提高了接头 的力学性 能。关 键词 :低银焊料 ;润湿性 ;剪切力 ;微观组 织 - II - 哈尔滨工业 大 学工学硕士 学 位论文ABSTRACT For environmental protection and the protection of human health requirements, lead-free electronic products have entered the implementation stage. For reducing the cost of the existing lead-free solder, to improve their req

7、uirements of high temperature aging performance, the research for low-silver lead-free solder has a very important significance. A low-silver-based solder SAC0307 is in use, such a high temperature solder alloy has a poor wettability and SAC305 solder alloys are very expensive. For this recearch bas

8、ed on a kind of new low-silver lead-free solder SAC0507X. By comparing the test datas to study the influence of silver content and the X element on solder melting point, wettability and dissolution of copper content and find the best overall performance of the solder alloy composition, and to develo

9、p a low cost, low melting point, good wettability, low amount of dissolved copper with excellent properties lead-free solderSolder melting point of the study results show that: low silver type SAC0507X lead-free solder alloy melting point range is 217.24 225.970C, basically, the same with internatio

10、nally recommended high-silver-type Sn-Ag-Cu solder alloy melting point line Wettability of the solder results show that: Because of low silver lead-free solder alloy SAC0307s poor wettability, The SAC0507X increasing the silver content and the addition of alloying element X, the wetting time reduced

11、 to 1.293s, has been far from meeting the mechanization of the industrial production of t 2.5s - III - 哈尔滨工业 大 学工学硕士 学 位论文actual demanded, and such a solder alloy composition of the largest wetting force is 3.687mN, has good wetting propertiesShear stress on the solder joints results show that: low

12、silver lead-free solder alloy SAC0307 shear force is 25.948N, but SAC0507X solder alloy slightly higher than that, the imum shear force is 28.673N, less than High silver type SAC305 solder alloyLead-free solder alloy on the microstructure observation showed that: X alloy elements added will reduce t

13、he rate of diffusion of atoms diffuse, refine grains and thus hinder the growth of intermetallic compounds; from the cross-sections of soldered joints can be seen X alloying elements decreases the brittle intermetallic compound growth rate and improve the mechanical properties of joints Keywords: lo

14、w-silver, solder alloy wettability, shear force, microstructure- IV - 哈尔滨工业 大 学工学硕士 学 位论文- V - 哈尔滨工业 大 学工学硕士 学 位论文ACKNOWLEDGEMENTS The author welcomes this opportunity to acknowledge the support accorded to Prof. Li Mingyu and my work supervisor Wang Yong for encouraging and guiding me to finish thi

15、s project. Their unreserved commitment to this role and patience is deeply appreciated. The author expresses sincere gratitude to other members of the examination committee and friends in the company, Yang Ming, Zhang Zhihao, Li Zhuolin, Pan Jianmin, Qiu Dayong, for their beneficial discussion, cons

16、tructive suggestion, help and support in my experimentsI am forever grateful for the support and love of my family. Thank you for the unfailing support in all that I do- VI - 哈尔滨工业 大 学工学硕士 学 位论文LIST OF FIGURES 1Fig.1. 1 Overview of silicon IC assembly process. 33Fig.1. 2Cross-section of a flip-chip

17、connection. 3 Fig.1. 3 Cross-section of a pin through hole connection of a microelectronics4component on a printed wiring board4 Fig.1. 4 Cross-section of a surface mount connection of a microelectronics component 18with leads on a printed wiring board4 19Fig.1. 5 Cross-section of a ball grid array

18、BGA microelectronics component4 Fig.1. 6 Secondary electron micrographs of a Sn?3.5Ag; b Sn?3.5Ag?0.5RE by slow cooling 12 Fig.1. 7 Secondary electron micrographs of a Sn?0.7Cu; b Sn?0.7Cu?0.25RE12 Fig.1. 8 Secondary electron micrographs of a Sn?3.5Ag?0.7Cu; b Sn?3.5Ag?0.7Cu?RE. 13 Fig.1. 9Microstru

19、ctures of solder alloy. 14 Fig.1. 10 SEM images of the creep fracture solder joints 15 Fig.1. 11 Shear strength of solder bumps as a function of Co content. 16 Fig.1. 12 Interfacial cross-sections of a 0, b 0.1, c 0.5, d 1.0, and e 2.0 wt.% Co-added Sn?3.5Ag solder on Cu and f EDS results on the fac

20、etted needle-like shaped Cu,Co Sn IMCs 17 3 2Fig.2. 1 The picture of smelting furnace19 Fig.2. 2 a solder checker b Standard copper piece c clamp. 19 - VII - 哈尔滨工业 大 学工学硕士 学 位论文Fig.2. 3 Typical heating and cooling curves for Sn in a differential scanning calorimeterThe peak labeled 1 represents the

21、endothermic event during heating while the peak labeled 2 represents the crystallization event for Sn23Fig.3. 1 The dsc curve of Sn-0.5Ag-0.7Cu alloy Fig.3. 2 The dsc curve of Sn-1.0Ag-0.7Cu alloy 26 Fig.3. 3 The melting temperature range for the alloy with different Ag content. 26 Fig.3. 4 Schemati

22、c of a wetting force balance27 Fig.3. 5 The change of wetting force according to Ag content. 29 Fig.3. 6 Relation between copper dissolve and Ag content 29 Fig.3. 7 Relation between Wetting Time and Ag content 30 Fig.3. 8 The influence of A alloy content to Wetting Force and Wetting Time31 Fig.3. 9

23、The influence of B alloy content to Wetting Force and Wetting Time31 Fig.3. 10 The influence of P element content to Wetting Force and Wetting Time32Fig.4. 1 Fracture surfaces of the SAC0507X solder alloy at different aging time39 Fig.4. 2Fracture surfaces of the SAC0307 solder alloy at different ag

24、ing time 41 Fig.4. 3 Fracture surfaces of the SAC305 solder alloy at different aging time. 42 Fig.4. 4 SEM of SAC0507X solder alloy under 500 times: a aging for oh, b aging for 50h,43 Fig.4. 5 SEM of SAC0507X solder alloy under 4000 times: a aging for oh, b aging for 50h,44 Fig.4. 6 IMC growth and m

25、orphology changes subject to thermal aging: a aging for oh, b aging for 50h,c aging for 100h, d aging for 150h, e aging for 200 h45 - VIII - 哈尔滨工业 大 学工学硕士 学 位论文Fig.4. 7 SEM of SAC0307 solder alloy under 500 times: a aging for 5oh, b aging for 100h, 47 Fig.4. 8 SEM of SAC0307 solder alloy under 4000

26、times: a aging for 5oh, b aging for 100h, 48 Fig.4. 9 IMC growth and morphology changes subject to thermal aging: a aging for 5oh, b aging for 100h, c aging for 150h, d aging for 200h 49 Fig.4. 10 SEM of SAC305 solder alloy under 500 times: a aging for oh, b aging for 50h,51 Fig.4. 11 SEM of SAC305

27、solder alloy under 4000 times: a aging for oh, b aging for 50h,52 Fig.4. 12 IMC growth and morphology changes subject to thermal aging: a aging for oh, b aging for 50h,c aging for 100h, d aging for 150h, e aging for 200 h53- IX - 哈尔滨工业 大 学工学硕士 学 位论文LIST OF TABLES24Table 1. 1 Elemental composition of

28、 Lead-free alloys. 6Table 2. 1 Raw materials18Table 4. 1 Physical properties of SAC0507X ally36 Table 4. 2 Shear force of three solder alloys38- X -哈尔滨工业 大 学工学硕士 学位论文 CONTENTS摘 要 I ACKNOWLEDGEMENTS. VI LIST OF FIGURES VII LIST OF TABLESXChapter 1 Introduction. 1 1.1 Significance of the selected topi

29、c 1 1.2. Pb-free solder alloy compositions 4 1.2.1 Tin. 5 1.2.2 Sn-Zn8 1.2.3 Sn-Cu8 1.2.4 Sn-Bi8 1.2.5 Sn-Ag. 9 1.2.6. Sn-In. 10 1.3 Solders with minor alloy elements 10 1.3.1 Sn0.6Cu0.05Ni SN100C10 1.3.2 Rare-earth additions to lead-free electronic solders. 11 Chapter 2 Experimental procedure 18 2.

30、1 Raw materialS. 18 2.2 Experimental equipments and methods. 18 2.2.1 Smelting furnace. 18 2.2.2 Wetting balance19 2.2.3 Direct reading spectrometer. 20 2.2.4 Hardmeter 20 2.2.5 Densitometer. 20 2.2.6 Electrical conductivity test21 2.2.7 Thermal conductivity test 21 2.2.8 The Scanning Electron Micro

31、scope SEM. 21 - XI -哈尔滨工业 大 学工学硕士 学位论文 2.2.9 Differential scanning calorimeter DSC 22 Chapter 3 Alloy design and selection. 24 3.1 Optimizing the content of Ag25 3.1.1 Solder melting point test. 25 3.1.2 Wettability test27 3.2 Chapter summary33 Chapter 4 SAC0507X properties and microstructure analys

32、is. 35 4.1 Introduction35 4.2 Physical properties 36 4.3 Mechanical property 37 4.4 Fracture surface morphology38 4.5 Microstructure of the solder alloy. 43 4.5.1 Microstructure of SAC0507X solder alloy 43 4.5.2 Microstructure of SAC0307 solder alloy 46 4.5.3 Microstructure of SAC305 solder alloy50

33、4.5.4 Chapter summary 53CONCLUSION 55 REFERENCES 58 哈尔滨工业大学硕士学位论文原创性声明 64 哈尔滨工业大学硕士学位论文使用授权书 64- XII - 哈尔滨工业 大 学工学硕士 学位论文 Chapter 1 Introduction 1.1 Significance of the selected topic Soldering is a well-known metallurgical joining method that uses a filler metal,1the solder, with a melting point be

34、low 425In the immense electronic materials world, solder plays a crucial role in the assembly and interconnection of the silicon die or chip. As a joining material, solder provides electrical, thermal and mechanical continuity in electronics assemblies. The performance and quality of the solder are

35、crucial to the integrity of a solder joint, which in turn is vital to the overall functioning1-6of the assemblySolders are used in different levels of the electronic assembly sequence, as shown in Fig.1.1 As a die bonding material; the solder provides the electrical and mechanical connection between

36、 the silicon die and the bonding pad. It also serves as a path for dissipation of the heat generated by the semiconductorBonding of the die to a substrate and its encapsulation is referred to as Level 1 packaging. While the predominant method of providing electrical connection to the silicon chip is

37、 through wire bonding, the use of solder bumps on the surface of the Si die, instead of wire bonding, has been gaining acceptance recently, due to the higher number of input/output terminals that can be attached to a given area. The flip chip configuration, a cross section is shown in Fig.1.2, which

38、 is such an approach. The Si die is turned upside down, hence flip chip, and mounted on an appropriate substrateThe next level of assembly and interconnect, referred to frequently as Level 2 packaging, is where the component encapsulated silicon die is mounted on a printed wiring board PWB. Solder i

39、s the primary means of interconnect in Level 2 - 1 -哈尔滨工业 大 学工学硕士 学位论文 packaging. Practically all microelectronic devices also known as packages are mounted on PWBs using solders. There are two primary means of attaching electronic components to PWBs, pin-through-hole PTH or surface mount technology

40、 SMT, illustrated in Figs.1.3. and 1.4, respectively. Surface mounted electronic components can either be leaded, i.e. with leads, as shown in Fig.1.4 or have solder balls that are called ball grid arrays BGAs, as shown in Fig.1.5 the locations where solders are used are also shown 8The microelectro

41、nics industry is extremely cost consciousThe history of the industry has been to continuously produce higher performance at lower costsSince cost of the product is the resultant of the cumulative cost of the components, the cost of Pb-free solder alloys can impact the cost of the finished product. C

42、ost competitiveness in the electronics industry is maintained by reducing the cost of individual components to a minimum, in order to imize the overall cost reduction. Purely from a cost and availability standpoint, an unpatented solder alloy, with multiple suppliers and a stable price structure, an

43、d no geopolitical concerns,7would be most desirable11The assembly and soldering of Printed Circuit Board Assemblies PCBAcan involve pure surface mount components or mixed technology assemblies where both SMT and PTH are used, either in single- or double-sided PCBA configurationSoldering of surface m

44、ounted devices, commonly called reflow soldering is done by application of solder paste on one of the mating surfaces, usually on soldering pads located on the PCB, and heating the assembly to melt the paste, which upon 9-11solidification forms the jointThe solder paste is a mixture of solder powder

45、, flux and other additives forming a thick cream. Additives are included in the paste to promote wetting surfactants and to control the property of the paste tackiness, slump, viscosity, etc. Reflow soldering is defined as the joining of mating surfaces - 2 -哈尔滨工业 大 学工学硕士 学位论文 that have been tinned

46、and/or have solder between them, placing them together, heating them until the solder fuses, and allowing them to cool in the joined 12 13-17positionAs shown in Fig.1.3 PTH soldering is done by wave soldering, where the assembly is transported over a molten solder bath from which the solder rises an

47、d forms solder joints by capillary action. The properties of the solder that are1Fig.1. 1 Overview of silicon IC assembly process3Fig.1. 2Cross-section of a flip-chip connection- 3 -哈尔滨工业 大 学工学硕士 学位论文Fig.1. 3 Cross-section of a pin through hole connection of a microelectronics component on a4printed

48、 wiring board important are invariably process dependent. The formulation and printability of the solder paste are critical parameters for reflow soldering, while viscosity and density of the molten solder significantly influences the performance of the wave soldering process Fig.1. 4 Cross-section

49、of a surface mount connection of a microelectronics component with leads 18on a printed wiring board19Fig.1. 5 Cross-section of a ball grid array BGA microelectronics component 1.2 Pb-free solder alloy compositions A relatively large number of Pb-free solder alloys have thus far been proposed,21and

50、are summarized in Table1 , with their elemental compositions. The solder - 4 -哈尔滨工业 大 学工学硕士 学位论文 alloys are binary, ternary and some are even quaternary alloys. A total of 69 alloys were identified from the literature. It can be noticed that a very large number of these solder alloys are based on Sn

51、 being the primary or major constituent. The two other elements that are major constituents are In and Bi. Other alloying elements are Zn, Ag, Sb, Cu, and Mg and in one case a minor amount of Pb. In reviewing the compositions listed in Table 1, it can be seen that some compositions are variations of

52、 one basic composition. For example, there are four Sn-10Bi compositions, with variations in the ternary additive-either Cu or Sb, and with or without Zn. A brief description of Sn, and other major binary systems is provided in this section1.2.1 Tin The ability of Sn to wet and spread on a wide range of substrates, using mild fluxes, has caused it to become the principal component of most solder alloys used 18-20for electronic applicationsElemental Sn melts at 231. Tin exists in two different forms with two different crystal str