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作为一种新型低温无铅焊料,Sn-Bi基低温无铅焊料具有较低的熔化温度以及优良的焊接性能,在电子封装领域有着广泛的应用。随着电子元器件向微型化方向的发展,对低温无铅焊料的性能提出了更高的要求。添加微量的合金元素及纳米颗粒可以改善焊料的组织性能,满足电子元器件发展的需求。系统介绍了Sn-Bi基低温无铅焊料的组成、结构以及焊接性能,综述了合金元素和纳米颗粒对Sn-Bi基低温无铅焊料组织性能的影响及作用机理,分析了在研制Sn-Bi基低温无铅焊料过程中存在的不足之处,并提出了相应的改进方法。最后对Sn-Bi基低温无铅焊料在发展中需要关注的问题进行了总结与展望。 相似文献
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电子封装无铅化技术进展(续完) 总被引:10,自引:2,他引:8
1.1.2.2Bi对无铅焊料性能影响及Sn-Bi系 在无铅焊料中添加Bi,可以降低熔点,提高浸润性等.对于使用者来说,具有很大的吸引力. 相似文献
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无铅焊料在清华大学的研究与发展 总被引:2,自引:0,他引:2
清华大学材料科学与工程系电子材料与封装技术研究室研制了6个系列的无铅焊料:Sn-3.5Ag添加Cu或Bi; Sn-3.5Ag-1.0Cu添加In或Bi; Sn-Ag-Cu-In添加Bi; Sn-Ag-Cu添加Ga; Sn-Zn添加Ga; Sn-Zn添加多种元素。重点介绍了Sn-Zn添加多种元素。对6个系列无铅焊料的研究取得了较好的实验结果,得到比较理想的低温焊料体系,有的合金熔点已非常接近铅锡共晶焊料熔点183℃。 相似文献
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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。 相似文献
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The influence of temperature and humidity on printed wiring board surface finishes: Immersion tin vs organic azoles 总被引:1,自引:0,他引:1
Substitution of lead-free solders in electronic assemblies requires changes in the conventional Sn:Pb finishes on substrates
and component leads to prevent contamination of the candidate lead-free solder. Options for solderability preservative coatings
on the printed wiring board include organic (azole or rosin/resin based) films and tin-based plated metallic coatings. This
paper compares the solderability performance and corrosion protection effectiveness of electroless tin coatings vs organic
azole films after exposure to a series of humidity and thermal cycling conditions. The solderability of immersion tin is directly
related to the tin oxide growth on the surface and is not affected by the formation of SnCu intermetallic phases as long as
the intermetallic phase is underneath a protective Sn layer. Thin azole films decompose upon heating in the presence of oxygen
and lead to solderability degradation. Evaluations of lead-free solder pastes for surface mount assembly applications indicate
that immersion tin significantly improves the spreading of Sn:Ag and Sn:Bi alloys as compared to azole surface finishes. 相似文献
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While extensive research on the lead-free solder has been conducted, the high melting temperature of the lead-free solder
has detrimental effects on the packages. Thermosonic bonding between metal bumps and lead-free solder using the longitudinal
ultrasonic is investigated through numerical analysis and experiments for low-temperature soldering. The results of numerical
calculation and measured viscoelastic properties show that a substantial amount of heat is generated in the solder bump due
to viscoelastic heating. When the Au bump is thermosonically bonded to the lead-free solder bump (Sn-3%Ag-0.5%Cu), the entire
Au bump is dissolved rapidly into the solder within 1 sec, which is caused by the scrubbing action of the ultrasonic. More
reliable solder joints are obtained using the Cu/Ni/Au bump, which can be applied to flip-chip bonding. 相似文献
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Mohammadreza Keimasi Michael H. Azarian Michael Pecht 《Microelectronics Reliability》2007,47(12):2215-2225
Multilayer ceramic capacitors (MLCCs) are known to experience flex cracking when subjected to bending stresses. An experimental study was conducted to determine the susceptibility to flex cracking of flexible- and standard-termination surface mount MLCCs assembled with lead-free or tin–lead solders and aged at two different temperatures for 200 h. Experimental results showed that MLCCs mounted on printed circuit boards with lead-free solder are less susceptible to flex cracking compared with MLCCs mounted on boards with eutectic tin–lead solder. Two factors which make capacitors assembled with lead-free solder less susceptible to flex cracking were discussed: the lower tensile stresses inside the capacitor body which are a result of the differing elastic–plastic mechanical properties of the solder, and the higher residual compressive stresses after solder reflow assembly which are a result of the higher solidification temperature for the Sn3.0Ag0.5Cu lead-free solder. Flexible-termination MLCCs showed much more resistance to flex cracking in comparison to standard-termination MLCCs assembled with both lead-free and tin–lead solders. Aging at elevated temperatures had little effect on flex cracking susceptibility of MLCCs assembled with tin–lead solder. For MLCCs assembled with lead-free solder, aging at 150 °C increased the susceptibility to flex cracking in comparison with un-aged MLCCs. 相似文献