影响不流动半固化片粘结因素的探析

不流动PP的流动性很低,与常规FR-4有很大的区别,如采用常规的压合条件,PCB板件经常出现不流动PP粘合不良问题。结合实验验证,详细分析了影响不流动半固化片粘合的因素,为有效提高不流动半固化片粘结强度提供了若干建议。     

No-Flow半固化片固化过程及压合性能研究

采用差示扫描量热法(DSC)研究了no-flow半固化片的固化过程,利用全动态DSC研究了该类型半固化片内树脂体系的固化反应动力学,通过经验方程的拟合获得了固化反应的动力学参数,并建立了固化反应动力学模型,通过模型分析确定了体系的固化工艺。用恒温DSC和动态DSC结合DiBenedetto方程研究了树脂玻璃化转变温度(Tg)和固化度之间的关系,并给出Tg和时间t及温度T之间的数学关系。通过DSC、TGA、SEM等研究了不同压合条件下固化体系的Tg值以及压合可靠性。实验结果表明,固化模型能较好地描述该P片的固化过程,固化程度不同,则材料均在Tg值、耐热性,粘结强度上表现出较大差异。     

低流动度半固化片的压合技术研究及其产品应用开发

随刚挠板、阶梯板与金属基散热板需求量的增大,相对于纯胶片更为便宜的低流动度半固化片的使用量增多,但由于此类半固化片的流胶量较低而往往容易导致压合白斑。本文对比试验了图形分布、半固化片数量、层压辅助材料、拼板工艺边设计及层压工艺参数等的影响,提出了低流动度半固化片的压合模型,此法有效避免了必须采用低流动度半固化片与FR-4半固化片混压或必需采用额外压合辅材的业界做法;试验并成功采用陪板填充阶梯槽的独特的简单工艺,避免了业界报道的操作相对复杂的叠板方式,可成功避免板凹和板件局部变形的质量问题,希望能对PCB制造业同行有所帮助。     

不流动半固化片特性的探讨

随着刚挠板、阶梯板与金属基散热板需求量的增大，作为连接材料的不流动半固化的使用量增多。不流动半固化片与普通FR-4半固化片、纯胶片有很大的差别，苓丈结合实验验证，详细分析了不流动半固化片的测试指标、流动性等特性，为不流动半固化片的加工提供了若干建议。     

不流动半固化片厚铜层压技术探讨

随刚挠板、阶梯板与金属基散热板需求量的增大,相对于纯胶片更为便宜的低流动度半固化片的使用量增多,但由于此类半固化片的溢胶量较低而往往容易导致压合白斑、白点、填胶不足等缺陷。本文通过分析对厚铜层压参数的调整,分析其影响因素,总结出NO-FLOW半固化片的压合技术点,希望能对PCB制造业同行有所帮助。     

盲槽孔板的设计及加工方法探讨

文章主要针对盲槽产品的制作流程及加工方法的控制作探讨,盲槽孔主要是利用已经钻好槽孔板和半固化片与另一张板进行压合形成。压合盲槽板时半固化片上所钻的槽孔大小设计/品质及半固化片本身流胶量严重影响成品盲槽的品质,本次主要以影响盲槽孔品质的几个因素作实验层别:半固化片槽孔大小分别比成品槽孔单边大0.4mm、0.6mm、0.8mm;PP厚度0.0375mm×3张;PP铣槽孔时叠板数为6、9、12。结论:半固化片槽孔单边大0.8mm最优,1.5mil厚的PP铣板叠板数9张时铣出的PP压合后槽孔品质符合要求,叠板数越少铣槽的效果越好;介层总厚度相同时,PP选用的张数越少压合时流胶越少,盲槽孔孔形越好。     

印制板拼版大面积空旷区域层压铜箔起皱的改善

在多层印制电路板层压工序中，容易出现压合后铜箔起皱的现象，导致产品报废。针对12μm薄铜箔在大面积空旷区域压合中，容易起皱这一质量问题展开原因分析，从调整半固化片参数、层压压合参数、拼板方式和铜箔厚度几个角度进行实验论证。通过实验结果得到最佳工艺调整路线，由此提升了印制板生产合格率。     

多层板层压流胶和变形的原因与改善

主要通过对印制电路板层压的研究,探讨一些单层多张PP结构的PCB板,在压合后产生大量流胶及芯板局部变形后导致钻孔孔偏等问题的影响因素。包括对PCB板的结构设计、半固化片的裁切尺寸、压合前的排板方式、压板过程的升温速率及半固化片的凝胶时间等影响因素的对比试验,统计各可能因素的不良率。结果表明：半固化片的凝胶时间是影响流胶大及局部孔偏的主要因素。     

特殊凹腔印制板压合阻胶方案研究

对于一种槽底有导通孔、槽壁非金属化设计的特殊凹腔印制板,采用带有导通孔的母板与带有非金属化槽的子板压合、烧结制作工艺,其关键技术是阻止半固化片流胶污染槽底金属化区域。通过测试半固化片铣空区补偿和PTFE垫片两种阻胶方案,初步探索出特殊凹腔印制板的压合工艺,为此类样板的制作提供了可行的技术方案。     

高可靠性18层刚挠结合印制板制作技术研究

文章通过介绍一款用于航空方面的18层高可靠性刚挠结合印制板在压合、盲槽制作、半固化片开窗、覆盖膜压合等技术点的突破,提出一套适用于此类高层高阶刚挠结合印制板的制作技术。     

无胶单面挠性覆铜板与不流动粘结片结合力的考察

文章对刚挠结合印制板用无胶单面挠性覆铜板与不流动粘结片的结合力进行了考察,结果表明增加PI表面粗糙度和减小PI表面接触角可以提高结合力,但一般不大于0．6N／mm;对PI表面进行等离子处理可以将结合力提高到客户要求的大于0．8N／mm;而提高无胶单面挠性覆铜板与不流动粘结片结合力的最有效的方法是使用高锰酸钾溶液对PI进行表面处理,在合适的条件下,结合力可达到1．15N／mm。     

多层板层压过程中的尺寸收缩分析

在多层板制造过程中,内层芯板的收缩极大地影响了产品的质量。本文通过对多层板制作过程中的尺寸变形的分析,指出导致内层芯板变形的主要因素为材料热胀系数不匹配。通过对半固化片状态变化过程的分析,建立了层压过程各个阶段的数学模型。通过解析计算,得到结构为铜面/半固化片/铜面的一种高Tg芯板纬向菲林补偿系数为1.24668,与实际实验中得到的补偿系数比较接近。     

不流动（低流动度）半固化片及其在刚挠性板和冷板中的应用

介绍了什么是不流动(低流动度)半固化片,以及在PCB行业中的主要应用,特别介绍了在加工挠性板和冷板的工艺注意事项。并通过丰富的图示,介绍了其测试方法,通过玻璃转化温度,导热特性等多方面介绍了不流动(低流动度)半固化片的选择方法。     

Development of environmentally friendly nonanhydride no-flowunderfills

Most no-flow underfill materials are based on epoxy/anhydride chemistry. Due to the sensitizing nature, the use of anhydride is limited and there is a need for a no-flow underfill using nonanhydride curing system. This paper presents the development of novel no-flow underfill materials-based on epoxy/phenolic resin system. Epoxy and phenolic resins of different structures are evaluated in terms of their curing behavior, thermo-mechanical properties, viscosity, adhesion toward passivation, moisture absorption and the reliability in flip-chip underfill package. The influence of chemical structure and the crosslinking density of the resin on the material properties is investigated. The assembly with nonanhydride underfill shows high reliability from the thermal shock test. Solder wetting test has confirmed the sufficient fluxing capability of phenolic resins. Results show that epoxy/phenolic system has great potential for an environmentally friendly and highly reliable no-flow underfill     

Void Formation Study of Flip Chip in Package Using No-Flow Underfill

The advanced flip chip in package (FCIP) process using no-flow underfill material for high I/O density and fine-pitch interconnect applications presents challenges for an assembly process that must achieve high electrical interconnect yield and high reliability performance. With respect to high reliability, the voids formed in the underfill between solder bumps or inside the solder bumps during the no-flow underfill assembly process of FCIP devices have been typically considered one of the critical concerns affecting assembly yield and reliability performance. In this paper, the plausible causes of underfill void formation in FCIP using no-flow underfill were investigated through systematic experimentation with different types of test vehicles. For instance, the effects of process conditions, material properties, and chemical reaction between the solder bumps and no-flow underfill materials on the void formation behaviors were investigated in advanced FCIP assemblies. In this investigation, the chemical reaction between solder and underfill during the solder wetting and underfill cure process has been found to be one of the most significant factors for void formation in high I/O and fine-pitch FCIP assembly using no-flow underfill materials.     

Assembly of lead-free bumped flip-chip with no-flow underfills

Lead-free solder reflow process has presented challenges to no-flow underfill material and assembly. The currently available no-flow underfill materials are mainly designed for eutectic Sn-Pb solders. This paper presents the assembly of lead-free bumped flip-chip with developed no-flow underfill materials. Epoxy resin/HMPA/metal AcAc/Flux G system is developed as no-flow underfills for Sn/Ag/Cu alloy bumped flip-chips. The solder wetting test is conducted to demonstrate the fluxing capability of the underfills for lead-free solders. A 100% solder joint yield has been achieved using Sn/Ag/Cu bumped flip-chips in a no-flow process. A scanning acoustic microscope is used to observe the underfill voiding. The out-gassing of HMPA at high curing temperatures causes severe voiding inside the package. A differential scanning calorimeter (DSC) used to study the curing degree of the underfill after reflow with or without post-cure. The post-curing profiles indicate that the out-gassing of HMPA would destroy the stoichiometric balance between the epoxy and hardener, and result in a need for high temperature post-cure. The material properties of the underfills are characterized and the influence of underfill out-gassing on the assembly and material properties is investigated. The impact of lead-free reflow on the material design and process conditions of no-flow underfill is discussed.     

Study of the fluxing agent effects on the properties of no-flowunderfill materials for flip-chip applications

As one of the key requirements of the no-flow underfill materials for flip-chip applications, a proper self-fluxing agent must be incorporated in the developed no-flow underfill materials to provide proper fluxing activity during the simultaneous solder reflow and underfill material curing. However, most fluxing agents have some adverse effects on the no-flow underfill material properties and assembly reliability. In this paper, we have extensively investigated the effects of the concentration of the selected fluxing agent on the material properties, interconnect integrity and assembly reliability. Through this work, an optimum concentration window of the fluxing agent is obtained and a routine procedure of evaluating fluxing agents is established