SnAgCu无铅焊膏用活性物质研究

以SnAgCu无铅焊膏铺展性能为主要指标,通过回流焊接实验,对用于助焊剂的17种有机酸活性物质进行了筛选。选取两种性能较好的有机酸配成复合活性物质,并对该活性物质的组成进行优化。用湿热试验测试焊后残留物的腐蚀性。结果表明:以羧基官能团比例为3:7的丁二酸和一元酸A混合物作为活性物质,并添加质量约0.66%的乙醇胺调整酸度,得到了pH值约为3的助焊剂;此助焊剂性能优良,可使焊点铺展率达到84%。使用含有此助焊剂的焊膏,采用回流焊接工艺在PCB板上贴装片式元件,所得焊点光亮饱满,且焊后残留物无腐蚀性,可以实现免清洗。     

无铅焊膏用无卤素松香型助焊剂的研制

通过筛选试验,调整溶剂、松香和活化剂的含量,确定助焊剂中主要成分的最佳配比。根据国标GB/T9491—2002,测试助焊剂的扩展率、腐蚀性及其他性能,并根据日本工业标准JISZ3198—4—2003进行润湿力测试。结果表明:当助焊剂中有机酸活化剂质量分数为9%、m(水白松香):m(聚合松香)为2:3时,助焊剂具有良好的物理稳定性和润湿性,平均扩展率最高能达到76.00%。焊后铜片无腐蚀,残留物少且成透明膜状。     

无铅松香芯焊锡丝中新型助焊剂的研制

通过扩展率实验对松香芯焊锡丝用助焊剂的成分及配比进行选择及优化,然后通过添加一种天然植物油(C油)对该优化过的助焊剂进行进一步改进,依据行业标准对制备的助焊剂进行了测试。结果表明,这款助焊剂不含卤素、无腐蚀性、表面绝缘电阻高(1.68×10~(11)Ω);无铅SnCu焊锡丝在使用这款助焊剂时,焊接效果好,松香飞溅值为0.3%,扩展率为75.9%。     

无铅钎料用免清洗助焊剂的研制

探讨了免清洗助焊剂的配制及合成工艺,得到两种助焊性和稳定性较好、腐蚀性弱、残留物少的免清洗钎剂,并对所配制的免清洗助焊剂在物理稳定性、黏性、卤化物含量、腐蚀性、酸度和不挥发物含量等方面进行了性能测试.     

无铅钎料用无VOC助焊剂活化组分研究

对无铅钎料免清洗助焊剂用各类活化剂性能及机理进行了分析,通过润湿力研究选择出活化性能较好的丁二酸和戊二酸以及一种羟基酸。以此活化组分为基础配制了两种无挥发性有机化合物(VOC)免清洗助焊剂,并且根据SJ/T 11273—2002《免清洗液态助焊剂》的规定对该助焊剂进行了性能检测。结果表明,两种助焊剂无松香无卤素,固体含量低,润湿力大,腐蚀性小,扩展率达75%,助焊性能良好,可应用到无铅波峰焊中。     

无铅焊锡线中无卤素免清洗助焊剂的研制

研制了一种新的用于无铅焊锡线中的无卤素助焊剂,选取芳香族酸、二元羧酸以及有机胺为活性剂主要成分.并参考日本工业标准JIS-Z-3282-2000和相关国家标准GB/T 9491-2002对其进行了全面的性能测试.结果表明,该助焊剂在可焊性、绝缘性、腐蚀性等方面均符合标准.扩展率大于80%;表面绝缘阻抗大于1011Ω;无腐蚀性.且具有焊接效果良好、无卤素、无毒、环保,焊后免清洗等优点.     

树脂芯助焊剂性能研究

树脂芯助焊剂性能对焊接质量有重要影响,为了解影响其性能的因素,研究了溶剂、活化剂及表面活性剂等的种类和配比对助焊剂性能的影响。结果表明,使用复合溶剂,按w(胺盐)为16.1%,w(有机酸)为2.0%,w(表面活性剂)为0.5%可配制成综合性能优良的助焊剂,其扩展率为80%,w(卤素)为0.07。     

PCB清洗工艺及半水清洗工艺的应用

清洗是PCB组装中的一道重要工序,它对电子产品的质量和可靠性起着极为重要的作用.对于高性能电子产品,不论是通孔插装还是表面组装,在回流焊、波峰焊或浸焊后,基板及其组件都需要进行严格有效的清洗,以去除助焊剂残留物和各种污染物.特别是对于表面组装工艺,由于助焊剂可进入表面组装元器件和基板之间的微小空隙中,从而使清洗显得更为...     

印制板半水清洗技术研究

免清洗焊膏在回流焊接过程中,产生大量透明的固体残留物,分布在焊盘四周.对于军用电子等高可靠性设备,残留物不仅影响印制板表面涂覆质量,而且影响产品的可靠性.研究了助焊剂残留物的半水清洗工艺,通过光学检查和离子浓度检测检查清洗质量.在工艺试验的基础上,掌握了关键要素和控制方法,确定了合适的工艺参数,用于生产作业指导.     

免清洗助焊剂

本文研制的助焊剂是一种无松香的助焊剂，也称免洗助焊剂，它具有以下特点：低固含量，低离子残渣，密度０．８０（２０℃），表面绝缘电阻＞１×１０￣（１２）Ω，卤含量为０％，焊后离子残渣＜１．５μｇＮａｃｌ／ｃｍ￣２，所以焊后不必清洗，节省了清洗设备及工时。免洗助焊剂的使用将会在造福于人类，保护大气臭氧层，维护和改善环境中起重要作用。     

Experimental Wettability Study of Lead-Free Solder on Cu Substrates Using Varying Flux and Temperature

The selection of soldering flux plays a critical role in promoting wetting and product reliability of printed circuit board assemblies. In this study, the effects of fluxes on the wetting characteristics of the Sn-3.0Ag-0.5Cu solder alloy on Cu substrates was researched by using various flux systems at different soldering temperatures. Because of the distinct characteristic of the lead-free solder—poor wettability—three kinds of fluxes [no-clean flux with high solid content (NCF), rosin mildly activated flux (RMA) and water-soluble flux (WSF)] were chosen for the wetting experiments. The wetting time and force were the evaluating indicators. The experimental observations indicated that the wettability clearly depended on the soldering temperature and flux system when using the same solder. Furthermore, the corrosion potential of flux residues was measured by surface insulation resistance (SIR) testing. Scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to determine the contents of the flux residues and corrosion products.     

Surface Insulation Resistance of Conformally Coated Printed Circuit Boards Processed With No-Clean Flux

Printed circuit board (PCB) specimens containing three different IPC-B-25 test structures were exposed to temperature/humidity/bias conditions in order to evaluate the effects of conformal coating, conductor spacing, voltage bias, flux chemistry, and test environment on surface insulation resistance (SIR). Results indicate that conformal coatings improve reliability, provided that sources of contamination on the PCB and within the coating are minimized. The presence of fibrous contaminants within the coating represented a preferential medium for moisture adsorption and ion transport, leading to accelerated reduction of SIR. In the absence of contamination, PCBs with conformal coatings were found to be less susceptible to SIR degradation than uncoated PCBs, with silicone providing better protection than urethane, and acrylic providing the least protection of the three coating materials evaluated. Conductor spacing was observed to represent a factor in the electrochemical migration (ECM) process independent of electric field, indicating that updated test structures are required to predict reliability of today's high-density assemblies. The SIR failure rate with rosin-based no-clean flux was observed to be greater than that with aqueous-based no-clean flux. A higher failure rate was also observed for tests conducted at 40$^circ$C/93% RH than for 85$^circ$C/85% RH. Due to the more rapid evaporation of weak organic acids in the flux residues at higher temperatures, test results obtained at 85$^circ$C/85% RH will not accurately predict reliability at lower temperatures for PCBs processed using no-clean flux. PCB specimens were exposed to temperature/humidity/bias conditions in order to evaluate the effects of conformal coating, conductor spacing, voltage bias, flux chemistry, and test environment on reduction of surface insulation resistance. Results indicate that, in the absence of contamination, conformal coatings improve reliability.     

溶剂对助焊剂性能的影响

选用四种不同的醚与单一醇复配作为溶剂配制出四种助焊剂。通过扩展试验、润湿力试验和表面绝缘电阻测试,评价各种助焊剂的性能。结果表明,溶剂种类对焊料的平均扩展率、润湿性能和表面绝缘电阻均有影响;沸点与焊料熔点相近的溶剂所配助焊剂使焊料具有75.4%的平均扩展率;对活化剂有最好溶解能力的溶剂可提高润湿速率约12.5%。     

Effect of Printed Circuit Board Structures on Temperature-Dependent Gain Characteristics of RF Power Amplifier Chips

We fabricated and characterized heterojunction field effect transistor radio frequency (RF) power amplifier (PA) test fixtures, for wireless applications, with various printed circuit board (PCB) structures. The RF matching and bias circuits of the test fixtures were designed so that they had the same RF characteristics. The only source of the variation of the RF gain (S₂₁) was different thermal characteristics of each PCB. The values of the junction temperature (T_J) and the junction-to-ambient thermal resistance (R _{J A}) of each test fixture were shown to be changed as much as 80deg C and 30deg C / W, respectively, by the change of PCB structures. The change of Rja was shown to be originated from the change of the PCB thermal resistance, assuring that the structure of the PCB was the dominant factor in determining R _{J A} Finally, we obtained a universal relation between S₂₁ of the amplifier and Tj. This work suggests that thermal budget of PCB is as important as that of package in wireless RF equipments.     

The effect of flux chemistry,applied voltage,conductor spacing,and temperature on conductive anodic filament formation

Conductive anodic filament (CAF) formation, a failure mode in printed wiring boards (PWBs) exposed to high humidity and high voltage gradient, has caused catastrophic field failures. This study quantified the effect of flux chemistry, applied voltage (V), spacing (L), and temperature on the failure rate. Test vehicles, which had hole-to-hole spacing of 0.5 mm or 0.75 mm, were processed with one of three water-soluble fluxes (WSFs), and a heated control was also evaluated. The samples were placed in a temperature humidity chamber at 85%RH, at one of three temperatures: 75°C, 85°C, or 95°C. A voltage of 150 V or 200 V was applied to the test vehicle and periodically removed so that a measurement could be taken. A specially designed linear circuit was used to determine when the insulation resistance dropped significantly, indicating a failure. Activation energies were determined. The mean time to failure was a function of L⁴/V².     

Characterizing the weak organic acids used in low solids fluxes

The elimination of chlorofluorocarbons (CFCs) and other chlorinated cleaning solvents due to their long-term environmental impact has lead electronic assemblers to examine soldering fluxes that reduce or eliminate the need for post-solder cleaning. Today, low solids fluxes are replacing more traditional rosin-based and water-soluble fluxes because many of them can be used in a no-clean process. Most low solids fluxes use weak organic acids as active ingredient. It has been reported that some of these weak organic acids leave behind residues that are corrosive to copper. Surface Insulation Resistance (SIR) measurements of flux-processed comb patterns have been the main test method used to determine the corrosivity of flux residues. This test has been performed with test samples exposed to accelerated temperature and humidity conditions of 85°C and 85%RH and a 50 V bias. Recent data on some weak organic acids suggests that they slowly disappear at this temperature and a lower test temperature of 65°C has been introduced into the new Bellco Standard. In Europe, this test is normally performed at 40°C and 93% RH. This paper reports on the application of SIR tests to study the corrosive behavior of three carboxylic acids (succinic, glutaric, and adipic acids) that are commonly used as the active ingredients in soldering fluxes. Coupons treated with equi-molar solutions of the acids were either exposed to reflow-soldering conditions or wave soldered face-up to create partially heated residues. Both tests were run under two different accelerating conditions, 85°C/85%RH for 7 days or 40°C/93%RH for 20 days. This latter condition is being considered for inclusion in an IPC standard. At the end of the test period, both corrosion and SIR test samples were examined under a microscope and any residues or dendritic growth were documented. SEM and EDX characterization was also performed to determine the residue and dendrite composition.     

无铅药芯焊锡丝用非松香基固体助焊剂的研究

针对现有松香固体助焊剂活性温度低和焊后变色的问题,研制了以十八酸、聚乙二醇和少量耐热松香作为载体,以己二酸和癸二酸复配作为活性剂的非松香基固体助焊剂.此助焊剂常温下为白色膏状,熔点范围110℃～130 ℃,满足Sn-0.7Cu无铅药芯焊锡丝灌芯和拔丝工艺.助焊剂中各成分沸点在300℃左右,满足手工烙铁焊高温要求且大大减...     

Neue Erkenntnisse über Oberschwingungsverluste in umrichtergespeisten Käfigläufern

All traditional calculation schemes to determine the harmonic losses of cage induction motors, which are supplied by PWM converters, result in far too low values. Therefore comprehensive experimental investigations have been undertaken to unveil the dependences of the losses and the physical origin. The investigations show that the harmonic losses do not depend on load, however, the harmonic currents are increased very much by load. This effect has been unknown up to now and is interlinked with the change of the flux distribution in dependence on slip. The lines of force of all harmonics comprise the same loop at synchronism as at sinusoidal supply, whereas at small values of slip a high percentage of the harmonic fluxes does not cross the air-gap, but loops as slot quadrature field. The test results form a solid basis for the development of an improved computation method to determine the harmonic losses.     

浅谈改善湿气对CAF测试的影响

湿气对PcB的cAF测试结果影响,往往被大多数人忽视,本文详细研究了影响cAF测试的各种因数及测试结果状况,通过增加线路板烤板流程与改变包装条件基本解决湿气对绝缘性能的影响,从而使得cAF测试结果不因湿气而失效。     

一种醇基低固含量免清洗助焊剂的研制

通过无铅焊料的焊点铺展及润湿力实验考察了活性剂对助焊剂润湿性能的影响,并据此研制出了一种以乙醇为溶剂、以有机酸和有机胺为活性剂并使用复合表面活性剂的免清洗助焊剂.结果表明:使用复合表面活性剂的助焊剂的润湿效果要好于使用单一表面活性剂的助焊剂.其中,以使用Op-4与壬基酚聚氧乙烯醚质量比为8:1的复合表面活性剂的助焊剂的...