电子组装中胶黏剂及其涂覆工艺的选择（待续）

胶黏剂在混装及双面回流焊接工艺中主要是把元器件固定于电路板底面,以便进行波峰焊或双面回流焊工艺.常用的胶黏剂涂覆方法包括针转移法、点涂法和丝网印刷法/模板印刷法.模板印刷法近年来在大批量高速流水线生产中得到了较为广泛的应用.主要介绍了胶黏剂的涂覆工艺及选择、胶黏剂的性能及选择和胶黏剂的相关工艺设计,并对其进行了较为详细的分析.     

电子组装中胶钻剂及其涂覆工艺的选择(续完)

胶赫剂在混装及双面回流焊接工艺中主要是把元器件固定于电路板底面,以便进行波峰焊或双面回流焊工艺.常用的胶赫剂涂覆方法包括针转移法、点涂法和丝网印刷法/模板印刷法.模板印刷法近年来在大批量高速流水线生产中得到了较为广泛的应用.主要介绍了胶私剂的涂覆工艺及选择、胶私剂的性能及选择和胶猫剂的相关工艺设计,并对其进行了较为详细的分析.     

电子组装中胶粘剂及其涂覆工艺的选择（待续）

胶粘剂在混装及双面回流焊接工艺中主要是把元器件固定于电路板底面,以便进行波峰焊或双面回流焊工艺。常用的胶粘剂涂覆方法包括针转移法、点涂法和丝网印刷法/模板印刷法。模板印刷法近年来在大批量高速流水线生产中得到了较为广泛的应用。主要介绍了胶粘剂的涂覆工艺及选择和胶粘剂的性能及选择和胶粘剂的相关工艺设计,并对其进行了较为详细的分析。     

振动条件下的CQFP器件高可靠组装工艺

CQFP器件由于其高可靠性优势已经广泛应用于军事、航天和航空领域,但是在实际使用中,特别是在温度和力学等可靠性试验中容易出现焊点脱落和引脚断裂等问题.分析了出现此类问题的原因并结合工作实际给出了包括焊盘设计、引线成形、器件焊接、敷形涂覆和胶黏剂力学加固处理在内的完整工艺解决方案与具体实施方法.     

模板及其印刷技术

贴片胶印刷工艺是SMT是组装工艺中的第一步，也是关键的一个步骤，因为印刷质量直接影响到后续工艺，因此，必须对印刷工艺加以重视，为后续的组装操作打下一个良好的基础。本文就贴片胶的印刷工艺而对印刷中使用的不同类型的模板以及不同条件下应采用的参数进行了论述，并针对易出现的问题简要说明了防范措施以及模板的清理维护。     

3D阶梯模板在SMT特殊制程及器件上的应用技术

在当前的SMT生产制程中,由于某些电子产品SMD凹腔电路板（CarityPCB）设计、元器件高密度组装与特殊构造需要,以及通孔回流焊（Through—HoleReflow）器件、混合制程器件（HybridProcessComponent）、正反表面焊接连接器（DoubleSurfaceReflowSolderingDevice）等问题,令焊锡膏或胶的印刷与涂覆工艺,变得日益复杂与多样化。而一直来最具主流的普通平面型印刷模板（2DScreenStencil）,便难以满足日新月异复杂工艺需求,于是非共面性阶梯模板（3DStencil）应运而生,它为解决SMT特殊制程及异型器件的焊锡或胶的印刷涂覆问题,正发挥着日益重要的作用。3DStencil的设计多种多样且用途广泛,它适宜各种较为复杂的PCBA组装工艺需求,可用在各种较为前端的特殊而复杂的工艺产品上。传统的非共面性3D模板,通常有局部减薄模板（Step—downstencil）、局部加厚模板（Step—upstencil）或两种工艺同时在一块模板上应用,模板的局部加厚或减薄的阶梯高度,通常需依据PCB板面的凹陷或凸起高度以及元器件的特点灵活应对,且加厚或减薄的阶梯既可放在模板装锡膏的印刷面,也可放在模板的底面。而时下的精密特制3D阶梯型模板,其模板钢片厚度与普通2D模板无异,但阶梯高度可达N20mm它足以避让底部多数己组装的SMD器件或AI器件剪脚后的高度。这种模板通常称之为VectorGuard3DStencil,由于它能够对己贴片组件展示出全方位的立体屏蔽保护而得名。3D阶梯模板在设计制作过程中,需重点关注其脱模性能与模板的使用寿命,力求使其既有良好的印刷效果又能经久耐用。在各种模板的制作工艺中,电铸成形模板和激光切割／电抛光模板的印刷性能较好,而以激光切割加电抛旋光性价比最高;对于印刷工艺的优化,模板的设计是关键的一环。为了使焊锡膏的脱模性能达到最好,模板上的开孔尺寸比率以及开孔性能应当按照行业标准设计,其开口的宽厚比、面积比、开孔梯度、开口侧壁的光洁度等方面都有严格要求。多半情况下,通过3D阶梯模板能够解决的SMT特殊制程及器件的工艺难题,也能通过非接触式喷印（JetPrinting）或针头点涂（Dispenser）的工艺方式解决。不过机器喷印或点涂的方式,不仅前期设备投资巨大,而且它们对于高密度设计的PCB和精细间距器件（FinePitchTechnology）,在组装精度、质量和效率等诸多方面都还受到限制,很多时候还不及3D模板实用有效。     

双面回流焊接过程中掉片问题的研究

针对目前双面回流焊接的日益增多及用户在对双面回流时担心的元件掉落问题，对其进行较为系统的试验验证，为双面回流提供技术支持数据。     

对面回流焊接过程中掉片问题的研究

针对目前双面回流焊接的日益增多及用户在对双面回流时担心的元件掉落问题，对其进行较为系统的试验验证，为双面回流提供技术支持数据。     

减成法制作双面COF印制电路板工艺研究

双面COF基板可以极大地缩小基板面积,满足产品的轻、薄、短小的要求,因此对于双面COF基板的需求也会逐渐增长.减成法工艺是生产FPC产品的主要工艺,技术与设备都非常成熟.本文对减成法工艺制作双面COF印制板进行了初步研究,讨论了微孔清洗方法的选择,比较了化学镀铜与黑孔化工艺的优劣,对应用液态感光抗蚀剂时的参数如曝光能量、显影速度、蚀刻速度及蚀刻压力等进行了优化,得到最佳工艺流程及工艺参数.     

印制板组件的三防涂覆及其去除工艺

对于特殊环境条件下使用的电子产品,三防涂覆可以对印制板组件进行有效的防护.主要介绍了印制板组件的三防涂覆和涂覆后涂层的去除,从涂覆材料的选择到如何正确地实施涂覆工艺以及涂覆过程中的相关注意事项,再到涂覆后如果需要返修,返修过程中如何快速、安全地去除涂层的实用工艺过程.     

基于无铅SMT焊膏印刷参数优化控制研究

无铅表面组装制程是以模板印刷、表面贴装元件放置、回流焊或波峰焊为主要步骤.其中模板印刷制程在生产线中扮演第一个重要的步骤.文章设计了"印刷结果观测数字化实验"方法,并找出模板印刷工艺无铅化生产的最优化工作参数,得出NP-04LP丝网印刷机,0.127mm厚的不锈钢模板在使用Loetite LF320无铅焊膏时,考虑SM...     

插件回流焊印刷模板的设计

根据插件焊接质量的要求 ,按照回流焊工艺设计印刷模板。在设计插件回流焊印刷模板时 ,应尽可能设计成普通模板以简化工艺流程和满足较好的印刷效果。     

Modelling the effect of uneven PWB surface on stencil bending during stencil printing process

In the mass assembly of today’s electronic circuits, solder paste is first printed onto the surface of the assembly boards through a metal mask called a stencil. The possible surface differences in level on the PWB, e.g. marking stickers or other protruding objects keep the stencil away from the PWB during stencil printing, can cause excessive printed volume of the solder paste, and solder bridges or other soldering failures can occur after reflow soldering. If these differences in level are not too high or they are sufficiently far from the soldering pads in lateral direction, the stencil can bend down to the pad during stencil printing and the volume of the deposited solder paste will be as expected.In our research a Finite Element Model (FEM) was created to investigate the stencil deformation and to determine the necessary distance between the pads and the local differences in level to achieve complete stencil contact to the PWB. A simple deformation measuring set-up was designed and fitted together to experimentally determine the mechanical parameters of the stencil and the squeegee, which were necessary for the FEM. PWB surface differences in level in the range of 0–90 μm and stencil foil thicknesses varying between 75 and 175 μm were inserted into the FEM as geometrical parameters and simulations were executed to calculate the minimum distances which are necessary to achieve perfect stencil contact to the PWB. The FEM was verified by comparing simulation results to experimental results obtained by real stencil printing.     

一种BGA封装器件的应急焊接工艺方法

简要介绍了热风回流焊接的常规工艺及影响焊接质量的关键工艺因素;总结了焊接的机理,结合实际工作经验,详细地描述了在没有模板、锡膏及回流焊炉等专业设备的条件下,使用电热板应急焊接BGA器件的过程及注意事项;通过引用大量的研究结论,从温度曲线和助焊剂法这两个最为关键的工艺参数分析了加热板法焊接BGA的可靠性并结合实际经验给出了提高可靠性的具体方法。最终全面总结了采用电热板使用助焊剂高可靠焊接表面贴装器件(SMD),特别是BGA器件的详细工艺流程。     

Understanding the process window for printing lead-free solderpastes

Solder paste is primarily used as a bonding medium for surface mount assemblies (SMA) in the electronics industry, and is typically deposited using the stencil printing process. Stencil printing is a very important and critical stage in the reflow soldering of surface mount devices, and a high proportion of all SMA defects are related to this process. This is likely to continue with the drive toward the introduction of lead-free solder pastes. Work is continuing on the metallurgical properties of these lead-free solders, including solder joint strength and material compatibility. However, the initial challenge for the new Pb-free formulations is in achieving repeatable solder deposit from print to print and from pad to pad. To meet this challenge, new flux formulations are being developed. For a smooth transition to Pb-free soldering formulations, a proper understanding of the solder paste printing performance is necessary. The key parameters that affect solder paste printing have been identified and are the subject of numerous studies. In lead-free solder paste, the replacement of lead with other elements (including Bi, Cu) changes the density of this dense suspension. In this paper, we investigate the effects of printer parameters, i.e. squeegee speed and pressure (defined as the process window) on the printing performance of a variety of lead-free solder pastes. A three-level design of experiment on these factors was used. Comparisons are presented with lead-rich solder pastes. The metal content of the lead-free solders had a significant effect on the process window     

Implementing 0201s On High-Density Lead-Free Memory Modules

The introduction of 0201 components is another step taken in the world of electronics to aid the miniaturization of electronic products. Capacitors and resistors are now being produced in a 0201 package size; in dimensions, it means a length of 0.02 in and a width of 0.01 in. The assembly of miniature components on printed circuit boards (PCBs) poses numerous process challenges. Legislative measures to eliminate the usage of lead from electronics products compel electronics manufacturers to implement lead-free assembly. This mandates the use of lead-free 0201 components and a lead-free soldering process. The current research focuses on high-density lead-free memory module assemblies using a 1.27-mm-thick organic solderability preservative (OSP)-coated boards. The spacing between components is as low as 0.25 mm. The objective of this research is to develop a robust assembly process for lead-free 0201 components used in memory modules. The stencil, PCB land pattern designs, solder paste printing, component placement, and reflow soldering processes were studied. The process and design changes required for achieving a robust manufacturing process for assembling lead-free 0201 components on high-density assemblies have been identified and reported.     

微电子表面贴装关键技术与装备

提出了选择性拖焊工艺,浸焊工艺,在无需制作专门的模具即可完成。确认了采用屏蔽模具波峰焊接工艺,实现双面混装PCB波峰焊生产,大幅度提高双面混装PCB生产效率,减少粘贴阻焊胶的准备时间,降低生产成本,达到与传统波峰焊接兼容以及通孔回流焊接工艺,对提升焊接质量、减少工艺流程的优势。研究了SMT印刷设备的双路输送板发展方向、贴片设备的高速、高精密、多功能、智能化、多悬臂、多贴装头、柔性连接模块化发展方向、以及再流焊设备的多喷嘴气流控制、局部强制冷却、可监测元器件温度的发展方向。     

SMT/THT混装回流焊工艺技术研究

含有大量表面贴装元件和少量通孔插装元件的高密度混装型印制板是电子装联技术的主要类型,这种SMT/THT混装型印制板采用传统的回流焊接无法一次完成印制板的组装。采用波峰焊或手工焊接会增加工序而且可能使印制板翘曲变形,采用SMT/THT混装回流焊则可以较好的解决问题。通过选用可用于回流焊的表面贴装和通孔元件制作样件,对通孔元件的焊膏印刷模板的合理设计,导入SMT/THT混装回流焊工艺,完成试验板的组装和焊接,焊点质量满足要求。     

电子装联三维结构垂直线和面印刷及回流焊工艺研究

在电子装联领域,焊点通常都位于PCB平面。然而,随着散热、信号屏蔽等要求越来越高,器件及通路的分散性要求焊点能够在三维结构上延伸,从而形成了三维结构的焊点。在回流焊时,垂直(Z轴)方向上的焊料必然要受到重力的影响,特别是在要求连续的线、面焊接时,控制焊料的向下流动是保证焊接质量的难点。针对这一问题,从焊膏性能、印刷工艺和回流工艺三个方面进行分析和实验,不仅获得了连续均匀焊点,而且达到了批量印刷、单次回流的工艺要求,同时减少了器件的热冲击次数。