Thermomechanical analyses of laser precision joining for optoelectronic components

Thermomechanical analyses in laser-spot-welding (LSW) technique for a dual-in-line (DIP) type package has been studied experimentally and numerically to predict post-weld-shift (PWS). Experimental results show that the PWS of optoelectronic component changes sensitively depending on process parameters such as laser energy, beam delivery position, weld joint design and so on. This indicates that the PWS in laser packaging can be minimized by properly controlling the process parameters. A finite element method (FEM) has been carried out on the analysis of the effect of laser parameters and geometry of joint variation on PWS in laser packaging. And experimental studies of laser spot welding and electronic speckle pattern interferometry (ESPI) have also been conducted to validate the numerical model. A satisfactory agreement between the experimental results and FEM calculations suggests that the FEM provides one of the effective methods for predicting the PWS and optimizing package design in LSW technique for optoelectronic packaging. By using the numerical method above this work has led to an understanding of the effect of laser energy variation and joint design on thermal distortion. Hence the PWS can be controlled to produce a reliable laser module with high yield and high performance.     

光电器件激光焊接封装焊后位移的有限元分析和实验观测

建立了晶体管外形罐(TO-can,transistor outline-can)型LD激光焊接封装的三维有限元模型,利用热-结构耦合分析方法,对焊后位移(PWS)进行数值模拟.分析结果表明:焊点位置对称时,其能量差别越大,PWS越大,PWS朝向能量合成的方向;3个焊点的位置不对称引起的PWS较小,主要是轴向位移.PWS特征的理论分析得到了实验结果的证实,因此有限元方法可以有效预测PWS.     

A novel fiber alignment shift measurement and correction technique in laser-welded laser module packaging

A novel measurement and correction technique employing an ultra-high-precision laser displacement meter (LDM) with a 20-nm resolution to probe the postweld-shift (PWS)-induced fiber alignment shifts in laser-welded laser module packaging is presented. The results show that the direction and magnitude of the fiber alignment shifts induced by the PWS in laser-welded laser module packaging can be quantitatively determined by four parameters: the lateral position (r), the position angle (/spl alpha/), the swing angle (/spl theta/), and the tilt angle (/spl psi/). Further studies show that the deformation of the lateral shift and the position angle are the dominant mechanisms that determine the fiber alignment shifts induced by the PWS. This clearly indicates that the PWS can be quantitatively corrected timely by applying a single weld spot on the negative lateral shift and the position angle to compensate for the fiber alignment shifts. In comparison with previous studies of the PWS correction by a qualitatively estimated technique, this LDM technique has significantly provided an important tool for quantitative measurement and correction to the effect of the PWS on the fiber alignment shifts in laser-welded laser module packaging. Therefore, the reliable laser modules with high yield and high performance used in low-cost lightwave transmission systems may be developed and fabricated.     

光电器件激光焊接封装的建模与分析

介绍了激光焊原理和有限元分析过程,建立了激光二极管封装组件的3-D有限元模型,利用Ansys有限元分析程序对激光二极管在不同焊接条件下激光焊封装的温度场进行了计算模拟,仿真分析了激光锤作用下激光二极管封装尾纤的焊后偏移（PWS）。在增加功率和脉冲时间的条件下,激光锤引起的焊后偏移量也相应的增加,但是在校正量相同的情况下,增加脉冲时间比增加功率对材料的热应力影响区要大。高功率低脉冲的焊接参数是完成焊接封装的首选参数。     

A novel inspection of fiber post-weld-shift in butterfly laser module packaging

Butterfly packaging technology with a fiber pigtail is widely used in packaging optical modules, and laser welding is used to join components in a butterfly package. During laser welding, the rapid solidification of the welded region and the associated shrinkage of material are expected cause relative movement between prealigned components. Such a post-weld-shift (PWS) might significantly reduce the efficiency of light coupling. The laser hammer technique can be used to realign fiber that shifts during laser welding, and it requires that the fiber shift be measured in three directions. Measuring the shift along the Y axis is difficult because space is limited. In this paper, a reflector placed near the fiber during laser welding was used to determine the shift along the Y-axis. The fiber images obtained using the charge-coupled device (CCD) camera were sometimes deformed, so digital image processing was used to calibrate the deformed images and calculate the fiber shift along three axes. The experimental results indicate that the fiber shift along the Y-axis, when captured using reflector inspection could be measured precisely, and more strongly influenced power coupling loss than shifts in the other two directions. The results are useful in implementing the realignment method after butterfly packaging.     

Fiber-alignment shifts in butterfly laser packaging by laser-welding technique: Measurement and finite-element method analysis

The post-weld shift (PWS)-induced fiber-alignment shifts of fiber-ferrule clip (FFC) joints in butterfly laser packaging by using laser-welding techniques and a high-magnification, video-probe camera system were studied experimentally and numerically. The measured results show that the fiber shifts of FFC joints with a 5-μm gap between the clip and ferrule exhibited shifts less than that without a gap. This suggests that the 5-μm gap design may be more suitable for FFC joints in laser packaging. The experimental measurements of fiber shifts in FFC joints were in reasonable agreement with the numerical calculations of the finite-element method (FEM) analysis. The major fiber-shift formation mechanisms of FFC joints in the laser-welding process may come from the mismatch of the thermal expansion coefficient, the solidification shrinkage, and the residual stresses within the FFC joint, but solidification shrinkage is the dominant cause. This study demonstrates that the FEM is an effective method for predicting PWS-induced fiber-alignment shifts in laser-module packaging.     

Laser welding induced alignment distortion in butterfly lasermodule packages: effect of welding sequence

Welding-induced-alignment-distortion (WIAD) is a serious issue in fiber-optic component attachment using laser welding, which can significantly affect the packaging yield. Elimination or minimization of WIAD is expected to be possible if the laser welding process and all relevant packaging parameters can be optimized. The effect of laser welding sequence on WIAD for butterfly laser diode packages is reported for the first time in this work. The results demonstrate that WIAD deduction can be as high as 96% if an appropriate welding sequence is employed     

Effect of welding sequence on welding-induced-alignment-distortion in packaging of butterfly laser diode modules: Simulation and experiment

Controlling welding-induced-alignment-distortion (WIAD) and maintaining coupling efficiency is obviously the most challenging issue in assembling of fiber-optic components using laser welding. WIAD is the dominant barrier to having high packaging yields. Previous investigation has revealed that the WIAD in butterfly laser diode module packaging could be mitigated by properly choosing weld process parameters such as welding sequence. In this paper, the effect of welding sequence on WIAD is studied numerically by finite-element method (FEM) with a more realistic physics based laser welding model and experimentally by welding prototype butterfly packages. Results from both methods are compared. It is shown that the influence of welding process parameters on WIAD is significant and WIAD control is possible if proper welding sequence is employed.     

同轴型激光器焊后偏移的理论与实验研究

为了研究同轴型激光器激光焊接产生的焊后偏移(PWS),采用基于有限元热-结构耦合理论的分析方法,建立了同轴型激光器3束激光焊接模型,分析了激光焊接工艺参量对焊后偏移的影响规律,并进行了激光锤校正实验研究,获得了同轴型激光器激光焊接前后及校正后的耦合光功率值。结果表明,同轴型激光器的焊后偏移受到3个焊点功率分布和位置分布等因素的影响;耦合光功率在激光锤校正后整体呈上升趋势,最大耦合光功率可恢复至94%,有限元仿真分析对PWS的方向预测合理。这一结果对激光焊接同轴型激光器的生产具有一定的指导意义。     

汽车板激光扫描焊接工艺研究

为了研究激光扫描焊接汽车板的工艺方法,采用4kW光纤激光器对0.7mm镀锌板与0.8mm冷轧板SPCC两类汽车板的激光扫描焊接工艺进行了理论分析和实验验证,得到了板间间隙、激光功率、扫描速率等对焊缝成形及强度的影响规律。结果表明,当选取板间间隙0.1mm~0.2mm、激光功率3000W~3400W、焊接速率不小于3m/min等适当参量进行焊接时,焊缝质量可满足电子束及激光焊接接头欠缺质量分级指南C级标准,且强度高于母材。选取合适的工艺参量时,激光扫描焊接在无保护气的作用下可得到高质量的焊缝。     

一种应用于二次平行封焊的工艺方法

实现二次平行封焊并达到气密性标准是气密性产品返修的关键。该文介绍了一种应用于二次平行封焊的工艺方法,通过对平行封焊后的气密性元器件进行激光开盖,在控制多余物产生后,利用机加工铣平壳体围框表面进行二次平行封焊。测试并分析了气密性元器件系统集成封装(SIP)模块二次平行封焊后的检漏。结果表明,细检漏率＜1.01×10^-8 Pa·m³/s,粗检漏无连续气泡产生,气密性满足电子与电器元件试验方法(GJB 360B-2009)要求。根据该文介绍的工艺方法可为多余物可控的气密性元器件实现二次平行封焊提供一种有效的解决方案。     

Reduction of fiber alignment shifts in semiconductor laser modulepackaging

The thermally induced fiber alignment shifts of fiber-solder-ferrule (FSF) joints in laser module packaging have been studied experimentally and numerically. From direct measurements of the metallographic photos with and without temperature cycling, fiber displacement shifts of up to a 0.8 μm were found after undergoing 500 temperature cycles. Experimental results show that the fiber shifts increase as the temperature cycle number and the initial fiber eccentric offset increase. The major cause of fiber shift may come from the plastic solder yielding introduced by the thermal stress variation and the redistribution of the residual stresses during temperature cycling. A finite-element method (FEM) analysis was performed to evaluate the variation of thermal stresses, the distribution of residual stresses, and fiber shifts of the FSF joints. Experimental measurements were in reasonable agreement with the numerical calculations. Both results indicate that the initial offset introduced in the fiber soldering process is a key parameter in causing the thermally-induced fiber shift of FSF joints in laser module packaging. The fiber shift, and hence fiber alignment shift under temperature cycling tests can be reduced significantly if the fiber can be located close to the center of the ferrule     

工艺参量对铝合金复合焊接接头耐蚀性的影响

为了保证船舰在海水环境中拥有足够的焊接强度和耐久性，选用船用铝合金（5083-O）进行焊接试验，模拟焊接接头在海水中的耐腐蚀性能。采用高适应性的激光-熔化极惰性气体保护焊复合焊接系统，分别分析研究了激光功率、焊接电流、光丝距对铝合金焊接接头耐腐蚀性能的影响；利用型号为CHI760D三电极化学工作站对不同焊接工艺参量下的铝合金焊接接头进行了腐蚀测试。结果表明，自腐蚀电流密度随激光功率的增加呈先增大后减小再增大的趋势，随焊接电流和光丝距的增加均呈"V"形规律变化，即先减小后增大的趋势；当激光功率为3.0kW、焊接电流为200A、光丝距为3mm时，接头组织以等轴晶为主，且气孔等缺陷较少，此时接头微观闭塞原电池效应微弱，自腐蚀电流密度最小，接头耐腐蚀性能相对较好。该研究对深入理解铝合金焊接过程中缺陷形成机理及提高接头耐腐蚀性能是有帮助的。     

Effect of thin film coating of Au on joint strength in invar-invar packages

The effect of a thin film coating of Au on the joint strength, weld width, and penetration depth in laser welding techniques for Invar-Invar packages is investigated experimentally. It is found that the joint strength, weld width, and penetration depth are strongly dependent on the coating of Au thickness on the Invar material. The welded joints with thick Au coating show narrower weld width, shallower penetration, and hence less joint strength than those of the packages with thin Au coating. The increase in both the thermal conductivity and the vapor volume in the welded joints as the coating of Au thickness increases are the possible mechanisms for the reduction. Detailed knowledge of the effect of thin film coatings of Au on the welded materials, which gives both the highest joint strength and good adhesion, is essential for practical design and fabrication of reliable optoelectronic packaging.     

铝合金连续-脉冲激光焊接工艺对比实验研究

为了研究5052铝合金激光焊接工艺,采用脉冲激光和连续激光分别对1.5mm厚的5052铝合金板进行了焊接,并对工艺参量进行了优化。通过对两种不同类型激光焊接试样的焊缝形貌的对比、微观组织的分析、抗拉强度和显微硬度测试,可知脉冲激光焊接对焊接接头气孔的控制更为理想,使得脉冲激光焊接所获得的焊接质量更加优异,与连续激光焊接相比,其接头的抗拉强度增加了10%。结果表明,脉冲激光焊接和连续激光焊接均可以使焊接试样得到较为理想的焊缝形貌和较高的抗拉强度。     

5A06 铝合金的激光填丝焊接头组织与性能

为了研究5A06铝合金焊接接头的显微组织和力学性能,采用3kW的Nd:YAG激光器填充SAl-Mg5焊丝,对2mm厚的5A06铝合金板进行对接拼焊。焊缝的化学成分基本和基材相同,显微组织在靠近熔合线附近为细小致密的柱状晶,焊缝中心为细小的枝状晶,热影响区宽度为50μm～100μm,晶粒粗化不明显;接头的拉伸强度达到母材的93%以上,延伸率为基材的58%左右;断口位置为热影响区,断裂特性和母材相似,均为韧窝和撕裂棱昆合型韧性断口。结果表明,在铝合金的激光焊接过程中,填充合适成分焊丝可以消除铝合金激光自熔焊时的凹陷、咬边等宏观缺陷,接头的综合力学性能得到极大改善。     

压接式GCT封装的热特性分析

电力半导体器件的散热性能和热可靠性与其封装结构密切相关,选择合适的封装结构对改善器件的散热性能和提高热可靠性非常重要。文中根据压接式GCT器件封装结构特点,采用ANSYS软件利用有限元法分析了单芯片封装和多芯片封装结构的温度及热机械应力分布,并与常规的焊接式封装进行了对比。结果表明,压接式封装结构的散热效果比焊接式封装结构稍差,但其芯片上产生的热机械应力明显减小。多芯片封装采用常规的风冷散热器时芯片温度已经超过了器件的安全工作温度(125℃),应该采用热管散热器才能保证器件可靠地工作。     

Direct evidence of au segregation in laser welded au-coated invar material

Evidence of the Au segregation within the crack region in laser welded Au-coated Invar material for semiconductor laser packaging is investigated. Results obtained from the metallography, scanning electron microscope (SEM) mapping, energy dispersive spectrometer (EDS) line profile, and Auger electron spectroscopy find that the cracks in the welded joints occur around the Au rich boundaries. The SEM Au mapping and EDS line profiles show that Au accumulates at the crack region. This direct observation indicates that one of the primary causes of cracks in laser welded Au-coated materials is due to the segregation of Au in the final stage of solidification. Detailed knowledge of the defect formation mechanisms in laser welded Au-coated materials is important for the practical design and fabrication of reliable optoelectronic packaging.     

6061铝合金激光-MIG复合焊中能量比影响的研究

为了研究激光-熔化极惰性气体保护焊（MIG）复合法焊接铝合金时激光、电弧两种热源各自的作用,得出二者最佳耦合效果,采用观察接头显微组织、焊缝截面形貌等手段,分析了激光、电弧各自对焊缝的影响。在此基础上,进一步测定焊缝气孔率、力学性能等参量,探索了能量分配比例对焊接接头性能的影响规律。结果表明,激光-MIG复合焊接6061铝合金时,控制电弧、激光能量比在0.9附近,辅以合适工艺,获得的焊接接头气孔率仅为1.5%,抗拉强度291MPa,达母材的82.9%,符合工程需求。此研究对不同厚度的铝合金复合焊具有普遍指导意义。     

YAG脉冲激光焊接的光致等离子体机理研究

针对 YAG脉冲激光焊接 Al及 4 5#钢时产生的光致等离子体 ,采用空心圆电极探测等离子体电信号 ;建立探测器内等离子体区域分析的理论模型 ,并用试验加以验证。研究结果表明 ,在负电压段 ,等离子体电信号的电流随电压增加呈现饱和趋势 ;理论与试验曲线比较证明 ,等离子体温度高于被焊材料气化温度约 30 0 K。