无铅焊料的研究（2）——机械性质（下）

2Sn-Ag系焊料2.1拉伸特性Sn-Ag焊料是目前被最广泛研究的无铅焊料之一。Lin[4]、Xiao[7]、Plumbridge[8]以及Mavoori[21]等人在室温下以1.0×10-3s-1的拉伸变形速率进行拉伸测试,分别获得Sn-Ag焊料的最大拉伸强度为30MPa、46MPa、24MPa以及33MPa。而Suganuma[17]对Sn-Ag/Cu焊点     

无铅焊料的研究（1）——反应润湿性

针对数种无铅焊料,如Sn-Cu、Sn-Ag、Sn-In与Sn-Ag-Cu四种合金,尤其是具应用潜力的共晶无铅合金与Cu、Ag、Ni三种基材的接触,整理分析了其重要的基础性质——反应润湿,可作为无铅焊料相关研究的参考。     

无铅焊料的选择与对策（未完待续）

通过大量的数据信息分析了各研究机构在无铅焊料方面的研究成果，在目前流行使用的无铅焊料的基础上，进一步研究并比较了其中的Sn-Cu系列与具有专利限制的SnAgCu系列焊料在消费类电子产品组装的波峰焊工艺中使用的可靠性，同时研究并比较Sn-Ag系列焊料与SnAgCu系列焊料在回流焊工艺使用的情况。结果表明，Sn-Cu共晶焊料在消费类电子产品组装的波峰焊工艺中完全可以取代Sn-Ag-Cu系列焊料，同时满足使用要求；而同样技术成熟的Sn-Ag共晶焊料也完全可以取代SnAgCu系列焊料在回流焊工艺使用，焊点的可靠性与成本可以媲美SnAgCu焊料。而且该二元合金在使用维护以及回收利用方面具有相当的优势。     

无铅焊料的研究（4）——电迁移效应

电迁移是金属原子沿着电流方向的移动。阐述了无铅焊料中电迁移的物理特性,由于焊点的特殊几何形状,电流拥挤效应将发生在焊点与导线的接点处;电迁移效应导致无铅焊料中金属间化合物(IMC)的生成与溶解,以及焊点下的金属化层(UBM)的溶解和消耗,使原子发生迁移并会产生孔洞,造成焊点破坏,缩短了焊点平均失效时间(MTTF),从而带来可靠性问题。     

无铅焊互连的板级可靠性（刊中刊）

本主要针对无铅焊料的选择,无铅焊料的工艺性的评估,与封装和PCB耐焊接热量比较,再流焊的优点,界面,润湿,溶解,金属间化合物的特性,描述了所用焊料的物理特性,互连质量取决于再流焊条件,破坏性评估实例,综述了测试件,测试方法,数据读出,标准,中断及中断的位置,用于可靠性研究的测试件,描述开发与可靠性相关的无铅焊点特性的方法;界面（第一和第二级）的显微切片,描述中断和／或非连接特性的典型例子,为描述板级功能稳定性的极限性,实施非破坏性和破坏性测量,开发与电子测试步骤相关的检测缺陷测量方法。     

印制电路词汇（22）

1313 solder metaliaing:焊料喷镀 在陶瓷及有机物表面的粘结部位,用化学镀方法形成焊料层。1314 solder mount:焊接固定 焊接固定是指利用焊料进行完全固定前的元器件的临时固定。它可分为粘结剂固定法和焊膏固定法(如下图所示)。 粘结方式 焊接前临时固定方式     

快速硅通孔（TSV）填充方法

本文提出了一种新的快速低成本硅通孔填充方法。使用该方法,直径为100微米的铜芯焊球被用于硅晶圆上直径110微米、深度150微米的孔的填充。晶圆级孔填充可以在几秒内完成,速度远快于传统填充技术,大大降低了工艺成本。通过对焊料、铜和铜芯焊料三种不同金属材料填充的硅通孔的热机械性能的有限元仿真分析,结果显示在热循环过程中,使用铜芯焊料填充的硅通孔产生的热膨胀和热应力比使用焊料填充的硅通孔更小,从而表明该方法较焊料填充硅通孔具有更高的热机械可靠性。     

员工培训实用基础教程（十七）

第十一章热风整平工艺 11．1概述 热风焊料整平（HASL，又称热风整平HAL，俗称喷锡）工艺，就是将涂有阻焊层（膜）的印制板浸入熔融的低共熔点Sn／Pb比例的焊料锅中，再通过热风将板的表面与孔内多余的焊料吹掉，从而获得一个平滑、均匀又光亮的焊料涂覆层。热风整平又分为垂直式和水平式两种热风整平系统（见图例）。     

新产品与新技术（20）

使用200℃温度焊接的无铅焊料 日立制作所开发了焊接温度200℃的无铅焊料,为锡铜合金焊锡。目前多数无铅焊料选用的是锡银合金焊锡,焊接温度较高而影响印制板和元器件性能,而且在基底镍镀层与焊锡结合会产生镍锡金属氧化物,使得焊接点劣化。锡铜合金焊锡与镍镀层接触会抑制金属氧化物产生,又用较低焊接温度,提高电子设备装配质量。     

高温高铅焊料无铅化的研究进展

微电子封装工业中应用于高温领域的高铅焊料的无铅化是一个国际化难题。对目前高温无铅焊料的研究进展进行了综述,包括80Au-20Sn、Bi基合金、Sn-Sb基合金和Zn-Al基合金。从各种焊料的熔化行为、力学性能、导电导热性能、润湿性、界面反应和可靠性等方面,总结了这些高温无铅焊料的特性以及在应用中各自存在的问题。通过比较,认为Sn-Sb基合金在高温领域取代高铅焊料将有很大的应用前景。     

Lead-free chip scale packages: assembly and drop test reliability

Three underfill options compatible with lead-free assembly have been evaluated: capillary underfill, fluxing underfill, and corner bond underfill. Chip scale packages (CSPs) with eutectic Sn/Pb solder were used for control samples. Without underfill, lead-free and Sn/Pb eutectic drop test results were comparable. Capillary flow underfills, dispensed and cured after reflow, are commonly used in CSP assembly with eutectic Sn/Pb solder. With capillary flow underfill, the drop test results were significantly better with lead-free solder assembly than with Sn/Pb eutectic. Fluxing underfill is dispensed at the CSP site prior to CSP placement. No solder paste is printed at the site. The CSP is placed and reflowed in a standard reflow cycle. A new fluxing underfill developed for compatibility with the higher lead-free solder reflow profiles was investigated. The fluxing underfill with lead-free solder yielded the best drop test results. Corner bond underfill is dispensed as four dots corresponding to the four corners of the CSP after solder paste print, but before CSP placement. The corner bond material cures during the reflow cycle. It is a simpler process compared to capillary or fluxing underfill. The drop test results with corner bond were intermediate between no underfill and capillary underfill and similar for both lead-free and Sn/Pb eutectic solder assembly. The effect of aging on the drop test results with lead-free solder and either no underfill or corner bond underfill was studied. Tin/lead solder with no underfill was used for control. This test was to simulate drop performance after the product has been placed in service for some period of time. There was degradation in the drop test results in all cases after 100 and 250 h of storage at 125/spl deg/C prior to the drop test. The worst degradation occurred with the lead-free solder with no underfill.     

片式元件焊点剪切力比较实验研究

介绍了无铅化推广以来相关行业发生的变化;简述了无铅化进程中,享受"豁免权"的相关行业面临的主要问题,包括可靠性问题和可靠性实验问题等;阐述了无铅与有铅焊点剪切力对比实验的方法;并针对实验数据进行了对比和分析,发现在本试验条件下无铅焊点的剪切力性能明显优于有铅焊点,但焊点间的差异较大;最终给出了进一步开展剪切对比实验研究的实施路线.     

无铅焊接技术最新进展及评述

介绍了国内外相关的无铅焊料的发展状况、无铅设备及其工艺的特殊要求及主要问题。介绍了无铅焊接产品的可靠性检测与评价技术的最新状况以及无铅焊点的寿命理论的最新进展。并对无铅焊接特有的质量问题及解决方法进行了评述。     

Solder Ball Attachment Assessment of Reballed Plastic Ball Grid Array Packages

The ban of lead in consumer-based electronics by many countries has resulted in a dramatic reduction in the availability of electronic components with tin-lead terminations. With the uncertainty associated with lead-free reliability and the issues associated with mixing lead-free solder with tin-lead solder, medical, defense, and aerospace equipment manufacturers are examining and in some cases implementing reprocessing practices to convert lead-free terminations to tin-lead. For area array packages, the practice is referred to as reballing. While reballing has been used for part reclamation, very little information is available on the reliability of reballed parts. This paper presents lead-free ball grid array (BGA) packages subjected to two ball removal and two ball reattachment techniques. Solder attach strength was used as a metric to examine the reballing process. Both the ball shear test and the cold bump pull (CBP) test were used to test solder strength. The impact of isothermal aging was also examined. The solder strength of reballed BGAs remained at the same level when different reballing methods were used and under different aging conditions. The lead-free non-reballed BGAs had higher solder strength and wider strength distribution than reballed tin-lead BGAs. The pull strength increased as the pull speed increased in the CBP test.      

有铅和无铅BGA混装工艺研究

分析比对了有铅和无铅两种焊料的不同温度特性。针对军工产品经常面对的有铅和无铅BGA同时组装在一块印制板上的情况,提出了有铅和无铅BGA混合组装的工艺难点。通过工艺试验列举了混合组装中各个环节所应注意的要点,强调要加强过程控制。最后利用各种可靠性试验和分析证明了混合组装焊点的可靠性。     

元器件无铅化导入技术要求

从电子产品整机厂商的角度,描述了如何保证无铅元器件的可靠性。由于主流无铅锡膏合金为锡银铜系列,其合金的熔点从传统锡铅共晶(锡37%铅)的183℃上升到217℃,随着焊接温度的提高,要求元器件能承受的温度增高,且合金成分也与有铅不同。必须通过对无铅元器件进行相关认证以及可靠性试验验证,如:外观包装要求、元器件耐热要求、可焊性要求、引脚镀层要求、以及相关可靠性试验等方面,以保证从有铅到无铅的成功转换、进而保证产品的长期使用的稳定性和可靠性。     

有铅焊料焊接无铅BGA回流参数探索

航天电子产品尚未允许采用无铅焊接,而航天电子产品中采用的进口元器件多为无铅器件,因此需要对有铅焊料焊接无铅元器件进行研究。通过对无铅焊球和有铅焊料的焊接特性分析,设计数种回流参数,进行回流焊接试验,并对试验结果进行焊接分析,得出回流峰值温度为228℃~232℃,液相线(217℃)以上时间为50s~60s的回流曲线能较好完成有铅焊料对无铅BGA的焊接。     

A reliability study of the lead-free solder connections of miniature chip components on hybrid circuits

The results of the influence of lead-free solder paste, design and process parameters on the attachment reliability of chip surface-mounted components (SMCs) on thick-film conductor pads are presented. The purpose of the investigation was to compare the quality of the soldered joints made with new solder pastes that do not contain lead with joints soldered with standard SnPb solders. The miniature zero-ohm chip resistors were soldered with selected lead-free solder pastes. The visual appearance of the solder joint according to the standards of lead-free soldered components was compared with components soldered with SnPb solders. On the test sample with soldered chip resistors connected in series, the solder-joint resistance was measured before and after temperature cycling. On the same test sample the solder-joint resistance changes were measured with impedance spectroscopy. After temperature cycling the damaged samples were analysed with SEM and EDS. The reliability test results after temperature cycling indicate two lead-free solder pastes that are the most convenient for chip-component soldering on thick-film conductor pads with the reliability of the joints being equal or better than solder joints with Pb-containing solder paste.     

JIS Z 3198无铅钎料试验方法简介与评述

JIS Z 3198是关于无铅钎料及其接合部性能测试的工业标准,由日本焊接协会提出初始提案,经日本工业标准调查会审议,最终由日本经济产业省于2003年6月20日并发布.标准涵盖了无铅钎料熔化温度范围测试、机械特性测试、铺展性测试、润湿性测试、接头的拉伸与剪切强度测试、QFP引线软钎焊接头拉引测试、片式元件软钎焊接头的剪切测试7个方面.依据JIS Z 3198 1-7原文对该标准各部分进行介绍,拟推进我国电子封装与组装的无铅化进程.     

无铅BGA封装可靠性的力学试验与分析

着重研究了机械冲击和应力对无铅BGA封装焊点可靠性的影响,介绍了BGA封装的可靠性力学试验(跌落、弯曲试验)及其分析方法.通过对力学试验中失效焊点的分析以及借助ANSYS模拟工具,找出引起失效的根本原因,为开发性能更好、高可靠性的无铅材料、改进无铅工艺提供依据.