排序方式: 共有112条查询结果,搜索用时 15 毫秒
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随着欧盟RoHs法令从2006年7月开始实施,印制电路板装配不得不随之无铅化,传统已使用超过50年的63Sn/37Pb焊接材料被SnAgCu(Sn96.5%/Ag3.0%/Cu0.5%)代替,熔点由原来的187℃提升到217℃,相应的焊接温度由220℃。230℃提升到240℃。260℃,印制电路板必须经历熔点以上的焊接时间多出了50多秒,印制电路板吸收热大增,印制电路板必须提高耐热性能与之配合。在过去的一年中,印制电路板分层问题一直困扰着电路板制造商。
印制板分层的机理是电路板吸热后,不同材料之间产生不同的膨胀系数而形成内应力,如果树脂与树脂,树脂与铜箔的粘接力不足以抵抗这种内应力将产生分层,所以解决分层的思路是:
1.生产流程控制尽可能保证板子有最佳的抵抗内应力的能力;
2.使用性能优越的材料减少内应力。
丈章希望通过研究,在成本和品质双重约束下,找到最佳的解决方案,用最低的成本来解决分层问题。思路是从研究分层的原因着手,通过实验设计的方法,对分层的因素从材料选择、印制电路板制造过程控制到电路板装配的整个过程,进行系统分析。
本研究项目耗费25万元的试验材料成本,历时三个多月,最终从成本和品质控制,提升公司竞争力的角度,提出解决分层的三套方案。
在将实验结果运用到A公司的实践中后,产生了良好的经济效益,每月减少客诉成本约30万元,减少成本浪费约80万元,取得超过预期效益。 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(34):10204-10208
A hexagonal phase in the ternary Ge–Se–Te system with an approximate composition of GeSe0.75Te0.25 has been known since the 1960s but its structure has remained unknown. We have succeeded in growing single crystals by chemical transport as a prerequisite to solve and refine the Ge4Se3Te structure. It consists of layers that are held together by van der Waals type weak chalcogenide–chalcogenide interactions but also display unexpected Ge–Ge contacts, as confirmed by electron microscopy analysis. The nature of the electronic structure of Ge4Se3Te was characterized by chemical bonding analysis, in particular by the newly introduced density of energy (DOE) function. The Ge–Ge bonding interactions serve to hold electrons that would otherwise go into antibonding Ge–Te contacts. 相似文献
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Jaime García-Melendrez Walter M. Warren-Vega Ana I. Zárate-Guzmán Francisco Carrasco-Marín Linda V. González-Gutiérrez Luis A. Romero-Cano 《Electroanalysis》2021,33(8):1952-1962
Carbon Paste Electrodes (CPE) modified with Grapefruit-Peels (GP) functionalized with Urea (GPU) and, Melamine (GPM) were designed for the detection of Ag+ in water. Taguchi L9 methodology was used to determine the optimal graphite-Active material ratio. The best electrochemical response was for CPE-GPU with an 80 : 20 ratio. The results obtained showed a linear detection range between 0.5 to 28 μg L−1, with a detection limit of 0.73 μg L−1 and a limit of quantification of 1.04 μg L−1. Attributable to CPE-GPU characteristics: electroactive surface area 0.175 cm2, roughness factor 3.87, resistance 0.09 Ω and, mostly −NH2 groups on its surface. The composite material offers a viable option to be used for the determination of silver traces in situ in industrial processes. 相似文献
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Riter LS Vitek O Gooding KM Hodge BD Julian RK 《Journal of mass spectrometry : JMS》2005,40(5):565-579
This Tutorial is an introduction to statistical design of experiments (DOE) with focus on demonstration of how DOE can be useful to the mass spectrometrist. In contrast with the commonly used one factor at a time approach, DOE methods address the issue of interaction of variables and are generally more efficient. The complex problem of optimizing data-dependent acquisition parameters in a bottom-up proteomics LC-MS/MS analysis is used as an example of the power of the technique. Using DOE, a new data-dependent method was developed that improved the quantity of confidently identified peptides from rat serum. 相似文献
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半导体封装超声波压焊的工艺参数优化 总被引:3,自引:1,他引:2
简要介绍了半导体封装过程中的关键工艺--超声波压焊工艺的原理,应用范围和主要关键技术;并针对具体焊接过程的关键参数分析其效果,在理解原理的基础上提出了一套参数优化的方法。 相似文献
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一种用于光束整形的衍射光学元件设计算法 总被引:2,自引:1,他引:2
在光束整形衍射光学元件的设计中,为同时减小输出光束的均方根误差和顶部不均匀度值,提出了模糊控制迭代算法(IAFC)。在盖师贝格-撒克斯通(Gerchberg-Saxton,G-S)算法的基础上,提出了平滑修正法,可有效改善输出光束的顶部均匀度,但却增大了均方根误差值。模糊控制迭代算法依据模糊控制理论,通过有效结合盖师贝格-撒克斯通算法和平滑修正法来同时降低均方根误差和顶部不均匀度值。计算机设计的结果表明,利用模糊控制迭代算法可以得到非常理想的输出光束,其均方根误差和顶部不均匀度值分别为0.75%和0.46%,能量转换效率可达94.91%。为光束整形衍射光学元件的设计提供了一种有效的新算法。 相似文献