印制电子用阻焊油墨及其发展趋势

本文介绍了PCB制造过程中所用阻焊油墨的研究现状及其发展趋势,重点介绍了可喷墨打印阻焊油墨、柔性电路板用阻焊油墨、水溶性碱显影感光阻焊油墨和LED封装用白色阻焊油墨的研究现状及趋势。     

稀土元素对提高镍基喷焊合金层耐磨性的效果

通过在喷焊合金粉末中添加稀土合金及其化合物的方法，研究稀土对镍基喷焊合金层性能的影响，探讨了稀土在镍基喷焊合金中应用的可能性，试验结果表明稀土能够明显提高喷焊合金层的耐磨性，细化喷焊合金层组织，改善喷焊合金层和基体的结合状态。     

焊缝余高对焊接接头疲劳强度的影响

通过测定AQ400NH材料的光滑焊件、余高焊件的疲劳性能、观察断口形貌、绘制S-N曲线以及用AN-SYS有限元程序计算应力分布,研究余高对焊接接头疲劳强度的影响.结果发现,对于光滑焊件,焊接缺陷是影响疲劳强度的主要原因,对于有余高焊件,余高的高度是影响疲劳强度的主要原因,实际应变测量和有限元计算都表明,焊趾部位是应力集...     

纳米Y2O3对Ni-WC合金喷焊层组织和耐磨性的影响

通过在含35%WC的Ni基自熔合金粉末中添加微量的纳米Y2O3,研究纳米Y2O3对合金喷焊层组织、硬度和耐磨性影响规律及其作用机制.实验结果表明,添加适量的纳米Y2O3可细化合金喷焊层组织,提高合金喷焊层硬度和耐磨性,改善合金喷焊层和基体的结合状态,并且经一定温度的后续热处理,可进一步提高合金喷焊层硬度和耐磨性.     

焊锡粉品质对回流焊时焊料球产生的影响

研究了焊粉导致焊料球(回流焊过程中残留在焊点周围的微小珠状焊料)产生的3个因素 氧化度、粒度以及焊粉中是否添加抗氧化元素.通过大量地分析检验证明, 焊粉粒度范围越窄, 氧含量越低, 在回流焊中产生焊料球的机会越少, 焊接质量越好, 且通过对加入微量元素X的焊粉进行检测, 及对此焊粉在回流焊中焊锡球(回流焊中焊料熔化后凝结成的焊点)表面进行成份分析, 表明加入微量元素X可以起到抗氧化作用, 使焊粉初始氧含量降低且放置时间延长.     

稀土对喷焊层耐磨性的影响机制

通过在镍基自熔合金粉未中添加微量稀土,研究稀土对喷焊层耐磨性的影响规律及其作用机制。实验结果表明:稀土元素的微合金化作用使喷焊层的组织细化,并使硬质相数量、尺寸、形状及分布发生变化,从而提高喷焊层的耐磨性能。     

二元羧酸半酯与环氧化合物反应动力学研究

用于印制电路板 ( PCB)的传统的热固化或光固化阻焊油墨是利用屏印的方法把图案印刷在覆铜板上 ,然后固化 .通过这种方法得到的图案不够精细 ,应用上也受到一定限制 .为此 ,近年来国际上研制出一类新型的阻焊油墨——碱液显影型阻焊油墨 [1～ 3] .它是通过曝光、显影及后固化等步骤形成精确的图案 ,可用于制备高密度的电路板 .通常 ,碱水显影型阻焊油墨由碱溶性光敏树脂 (组分 A)、环氧化合物 (组分 B)、光引发剂、热固化剂和稀释剂组成 .组分 A由二元羧酸与含有光聚合性双键的线性酚醛型环氧化合物通过半酯化反应得到 ,羧基的引入使其具…     

往复挤压准晶增强快速凝固Mg92.5Zn6.4Y1.1合金

采用往复挤压工艺将快速凝固Mg92.5Zn6.4Y1.1合金薄带在330℃挤压2道次和4道次,然后正挤压制成Φ10 mm的棒材。用OM,TEM,XRD及DTA研究了往复挤压过程中准晶相I-Mg3YZn6弥散析出及对力学性能的影响。研究表明,往复挤压有利于快速凝固Mg92.5Zn6.4Y1.1合金薄带的焊合,获得组织致密、均匀、高强韧合金。往复挤压2道次,相组成为-αMg和准晶I-Mg3YZn6,脱溶析出纳米准晶相较少;4道次相组成为-αMg和准晶I-Mg3YZn6及MgZn相,脱溶弥散析出的纳米I-Mg3YZn6准晶相及MgZn相较多。往复挤压提高材料的拉伸性能,其主要原因是细晶强化和析出强化。     

无铅焊膏研究进展

用无铅焊膏代替传统的Sn-Pb焊膏是近年来研究的热点。本文比较了Sn-Ag,Sn-Zn,Sn-B i系无铅焊料的优缺点并介绍了国内外对Sn-Ag,Sn-Zn,Sn-B i系无锅焊料研究所取得的研究成果,并详细阐述了助焊剂的分类以及主要活性成分的用途。     

稀土对喷焊层耐蚀性的影响机制

通过在镍基自熔合金粉末中添加微量稀土、研究了稀土对喷焊层耐蚀性的影响规律及其作用机制。实验结果表明：稀土元素的微合金化作用使喷焊试样在腐蚀过程中的表面活性点减少，腐蚀速度下降，从而提高了耐蚀性。     

Cyclic welding behavior of covalent adaptable network polymers

Surface welding effect of covalent adaptable network (CAN) polymers enables self‐healing, reprocessing and recycling of thermosets, but little is known about their welding behaviors during repeated welding‐peeling cycles. In this article, we study the cyclic welding effect of an epoxy based thermal‐sensitive CAN. Surface roughness is generated by rubbing the sample on sandpapers with different grid sizes. The welding‐peeling cycles are repeated on the same pair of samples for five times, with roughness amplitude and interfacial fracture energy measured in each cycle. It is shown that the roughness gradually decreases during the repeated welding cycles, especially when a long welding time or high welding pressure is applied. Even though lower roughness amplitude promotes the contact area, the interfacial fracture energy reduces due to the increased BER activation energy after long‐time heating. A multiscale constitutive model is adopted, where we incorporate an explicit expression of interfacial contact area as a function of root‐mean‐square roughness parameter. The model is able to capture the evolving interfacial fracture energy during repeated welding cycles by using the measured roughness parameter, network modulus and BER activation energy. The study provides theoretical basis for the design and applications of CANs involving cyclic welding‐peeling operations. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 402–413.     

轻稀土对低合金钢焊缝韧性的影响

在低合金高强钢焊条中，通过药皮过渡轻稀土元素，探讨其对焊缝韧性的影响。结果表明：适量的稀土具有脱氢、脱硫、减少夹杂物数量、净化焊缝组织的作用。稀土的加入，对焊缝组织形成有一定的影响，能抑制侧板条铁素体的转变，促进针状铁素体的形成，由于稀土元素净化作用与细化组织的作用，使低合金钢焊缝金属的韧性得到提高。但加入量过大，造成夹杂增多，晶粒长大，疏松组织，使焊缝的韧性下降。本实验轻稀土加入的合适范围为2％。     

基于DOE实验设计方法的聚丙烯焊接工艺优化

采用DOE实验设计方法,对聚丙烯(PP)材料焊接工艺进行了研究,确定了影响PP材料焊接强度的关键因素是气压夹紧力、焊接功率和样品厚度。通过全因子正交试验,对焊接强度和焊接工艺参数进行量化分析,通过优化器结果确定对共聚PP(牌号M60RHC)为原材料,样品厚度为2 mm,控制气压夹紧力为0.3 MPa,焊接功率控制在40 W,得到PP材料的最佳焊接工艺,降低了实验的次数,在该最大工艺条件下,焊接强度达到19.475 MPa。这将有助于其他原材料体系进行高效激光焊接工艺的筛选。     

Numerical Study of a Free-Burning Argon Arc with Anode Melting

Numerical modeling of free burning arcs and their electrodes is useful for clarifying the heat transfer phenomena in the welding process and to elucidate those effects which determine the weld penetration. This paper presents predictions for a stationary welding process by the free-burning argon arc. The whole region of the welding process, namely, tungsten cathode, arc plasma and stainless steel anode is treated in a unified numerical model to take into account the close interaction between the arc plasma and the molten anode. The time dependent development of two-dimensional distributions of temperature and velocity, in the whole region of the welding process, are predicted at a current of 150 A. The weld penetration geometry as a function of time is thus predicted. It is shown also that different surface tension properties can change the direction of re-circulatory flow in the molten anode and dramatically vary the weld penetration geometry.     

Emission of gases and degradation volatiles from polymeric wood constituents in friction welding of wood dowels

Analysis of volatile compounds and gases emitted as smoke at the welding interface during rotational wood dowel welding of a hardwood (beech) and of a softwood (Norway spruce) has shown that the compounds in such a smoke are water vapour, CO₂, degradation compounds from wood polymeric carbohydrates and from amorphous lignin, as well as some volatile terpenes, these latter only for the softwood used, Norway spruce. The main carbohydrates contributing to the volatile compounds are xylans for beech and glucomannans for spruce. Numerous compounds, in very small proportions derived from the degradation and rearrangement reactions of lignin, have also been identified. The proportion of CO₂ emitted is very low, and neither CO nor methane is emitted due to the relatively low temperature of dowel welding. Experiments at temperature slightly higher than that of dowel welding but prolonged in time have shown that the main component of the smoke produced during welding appears to be water vapour.     

Influence of Groove on Metal Vapour Behavior and Arc Characteristics in TIG Welding of High Manganese Stainless Steels

Plasma Chemistry and Plasma Processing - In arc welding, a groove is often used between metal pieces being welded. In tungsten inert gas welding of high-manganese stainless steels with arc voltage...     

Photoprotection by Workwear: Ultraviolet Protection Factors for Artificial Radiation from Welding Arcs

Photoprotection by clothing is one of the most effective protective measures against solar ultraviolet radiation (UVR), and the related concept of UV protection factors (UPF) for fabrics has proven itself for decades. Although immense work has been carried out regarding factors influencing textile sun protection, the idea of UPFs for artificial UVR, if necessary with different action spectra, is payed little attention. In this work, a modified UPF equation is proposed utilizing welding arcs and the ICNIRP action spectrum. These welding UPFs (wUPF) were calculated for some workwear as a function of welding power, technique and welded material. No wUPF welding power dependence existed. By means of normalized standard emission spectra, that were further clustered with regard to welding technique, it was found that the wUPF depends exclusively on the fabric’s transmittance and the ICNIRP weighting function yielding a reduced wUPF formula. Finally, a comparison of solar and welding UPFs, based on either their full or reduced equations, is discussed.     

Electrochemical characterisation of laser welding tracks

The advantages of laser welding are high process velocity, the possibility to joint alloys, which are not solderable, and the high bonding strength. During the laser welding process a high energy input in a very short time and a small area is performed, resulting in possible changes of structure and composition. Direct information of the change of the electrochemical behaviour of dental alloys after Laser welding procedure does not exist. The aim of this work was, therefore, to assess the electrochemical behaviour of laser welded joints in comparison with the bulk material using the mini-cell system. The logI vs. E curves performed on the bulk material show a complete change concerning the characteristic data, the shape and the position in comparison to such curves measured on the laser track. The characterisation of the electrochemical behaviour of laser welding tracks seems to be very easy by using the mini-cell system.     

Contribution to the radioanalytical determination of heavy metals in the working environment of welders

Heavy metals can be the most important toxic substances in welding environments. Their chemical behavior is related to welding aerosols; hence, reliable analysis of these aerosols is quite important. Activation analysis by fast neutrons (14 MeV), and radionuclidic X-ray fluorescence analysis (241-Am source) were used to determine selected metals (Fe, Mn, Cr, Ni, Mo) in aerosols produced during welding of high-alloy steels with MIG technology. Sampling was done by filtration using micro-pore filters. A multichannel analyzer (MCA S80 CANBERRA) and Si/Li, Ge/Li detectors were used to process the analytical signals. Appropriate statistical parameters were calculated.     

Laser welding of polymers using unsymmetrical squaraine dyes

Transmission laser welding of plastic is typically achieved by incorporating a laser absorbing dye into one of the two pieces of plastic one wishes to weld together and mediating the welding process using a laser emitting light at a suitable wavelength. Desirable properties of laser absorbing dyes include: (1) the dye is colorless in the visible region but absorbs strongly in the region at the wavelength where the laser emits, (2) the dye has a good conversion of the energy from the laser to heat, (3) the dye is stable enough to be incorporated into the molten plastic, (4) the dye is soluble in the plastic of choice to give an even distribution in the plastic, and (5) the dye is nontoxic. Here, we explore an alternative approach to achieve laser welding of colorless plastics using a laser dye that is colored, but that can be bleached after the welding process. Nonsymmetrical squaraine dyes were prepared by condensation of squaric acid and two equivalents of various 3,5-dimethoxy-N,N-dialkylanilines. After the incorporation into polyethylene and laser welding, the plastic was bleached either by heat treatment or by irradiation with a high pressure Xe-lamp giving colorless polyethylene. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2245–2254