上胶工艺及半固化片质量分析

本文阐述了半固化片生产过程中的主要工艺即浸渍胶液的工艺过程及半固化片的表面质量。并分析了产生这些缺陷的因素。     

HDI板埋孔填胶工艺研究

HDI板在生产过程中用LD半固化片填胶的加工工艺。分别通过理论计算分析了LD半固化片(1037)理论含胶量及实际所需胶量的一种量化关系,并以田口-DOE实验法探讨了LD半固化片填胶过程中表面凹陷产生的主要原因,对制作HDI使用半固化片直接填孔选材与工艺有重要的参考意义。     

潜伏性固化剂双氰胺用量探讨

覆铜板生产过程是分段的、间断的过程。它有胶液配制一段,粘结片生产一段及热压成型一段组成。当段与段之间衔接不是很紧凑时,每段制品就产生储存,这就要求配制好的胶液或已生产出来的粘结片应当有一定储存时间,在室温下不会发生固化反应。特别是作为商品用途的半固化片,用户收货后不可能一次用完,它要求半固化片应在数个月时间内保持其技术参数符合使用要求的范围。这就需要一     

HDI板盲埋孔填胶量化分析及模型探索

文章定量分析了半固化片对盲埋孔填胶的影响因素,在此基础上,正交分析确定了盲埋孔填胶的主要控制因素（填胶深度和PP片数量）,为前端工程设计和控制提供依据。最后,建立盲埋孔填胶的胶体流动模型,即在层流状态下的渗流模型,服从达西定律。     

厚铜PCB用高填充性半固化片的研制

一般地,106半固化片的树脂含量（简称RC）只能达到75％左右。因厚铜（铜厚达到105μm及以上）印制电路板的线路间需要更多的树脂来填充,故普通工艺制造的半固化片就很难满足厚铜印制线路板的填胶性。因此,本文研究了提高半固化片RC的新工艺方法,从而改善半固化片对厚铜印制线路板的填胶性能。     

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。     

半固化片浸渍加工技术的新进展

高密度互连印制电路板制造需要高性能可靠性的覆铜板及半固化片基材。为满足这一需求，在覆铜板及半固化片生产中，就要在半固化片（prepreg，简称为PP，或称：预浸粘结片）的加工设备水平上获得提高。当前，在提高环氧-玻纤布基覆铜板及半固化片加工质量和水平的重点之一，是要克服在浸渍加工中出现的半固化片中含有微小气泡、树脂胶浸透性差、漏浸、胶含量不均匀等问题。这些质量问题的存在，会严重影响此工序以后所制出的覆铜板、多层板的可靠性。     

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。     

一种厚铜刚挠结合印制板渗胶改善

厚铜刚挠结合板的生产中一般采用普通流胶半固化片制作,在满足厚铜填胶的同时也导致窗口渗胶的问题越发突出,严重影响弯折性能,本研究选取一款应用于电源模块的105μm厚铜刚挠结合板,结合半固化片类型、压合参数、保护胶带类型、窗口设计等,极大程度的克服了窗口渗胶问题.     

叠层结构对高速板材PCB可靠性影响研究

采用不同类型半固化片设计出多种叠层结构，考察其对高速PCB耐热可靠性的影响，发现扁平玻布（1067、2313等）耐热可靠性较差，无法满足客户无铅焊接要求。同时从理论上分析发现，在耐热可靠性测试过程中，扁平玻布半固化片内应力大和浸胶不完全是引起半固化片分层的主要原因。在生产设计过程中，有耐热可靠性要求的板应禁止或减少扁平玻布半固化片的使用。     

眼部超声Doppler血流计的研制

眼部正常的血液供应是维持眼部组织正常生理功能的基础。该文介绍了一种无创检测眼部血流速度瞬时相对变化和眼部血流状况的超声Doppler血流计,该血流计由超声波信号发生器、超声波换能器、放大器、混频器、A/D转换器和微型计算机等组成,可实时、在体、无创检测眼部血流速度和血容量的相对变化,具有结构简单、使用方便等特点。     

Chemo-rheological characteristics of a self-assembling anisotropic conductive adhesive system containing a low-melting point solder

To achieve the excellent wettability of a solder in an anisotropic conductive adhesive (ACA) in micro-packaging technology, not only the removal of the oxidized layer of the solder but also the chemo-rheological phenomena of the thermally induced self assembly of low-melting temperature solder powders were investigated for ACA applications. Both the optimum kind and amount of reductant were determined in this study to remove the oxidized layer formed on the solder surface in ambient environment. The solder wetting test was performed to observe the chemical and rheological compatibility between the solder, polymer matrix, and reductant. The thermal analysis was done using differential scanning calorimetry (DSC) analysis and rheometer test. Several chemical reactions by the reductant were proposed, and the mechanisms were postulated. It is believed that the reductant reacts with the oxidized layer, amine, and epoxide group, respectively. The relation between conversion and glass transition temperature of the polymer matrix was also obtained from DSC.     

Study on effect of coupling agents on underfill material in flipchip packaging

Coupling agents are widely used in order to improve the adhesion property of underfill. In this study, three different silane coupling agents, two titanate coupling agents, and one zirconate coupling agent were added into an epoxy underfill material. Their effects on the flow behavior and curing profile of the epoxy underfill were studied with a rheometer and a differential scanning calorimeter, respectively. The thermal stability of the cured underfill material was studied with a thermogravimetric analyzer. A thermal mechanical analyzer and a dynamic mechanical analyzer were used to measure the coefficient of thermal expansion, the glass transition temperature (T_g), and the storage modulus (E'). In addition, the adhesion of the underfill on benzocyclobutene passivated silicon die and polyimide passivated silicon die was measured through die shear test. The effects of aging in an 85°C/85% relative humidity chamber were also studied through moisture absorption test and die shear test     

Micro squeeze flow rheometer for high frequency analysis of nano-litre volumes of viscoelastic fluid

In this paper, the design, fabrication and experimental analysis of a piezoelectrically actuated micro squeeze flow rheometer is presented. Being only 30 × 30 × 0.5 mm in size, the micro rheometer is sensitive to very small volumes of the order of 1-10 nL of liquid and light enough to operate at frequencies in the kHz regime, an order of magnitude higher than normally attainable with conventional cone and plate rheometry. Initial experiments show that the response of the rheometer is dependent on the viscoelasticity of the fluid being tested. The prototype was used to measure the moduli of poly(dimethylsiloxane) (PDMS) of viscosity 10 Pa s, a non-volatile viscoelastic fluid, over the frequency range of 10-1000 Hz. Results show good agreement between with the moduli measured using conventional rheometry up to 100 Hz and with values extrapolated up to 1 kHz.     

异步串口通信在转矩流变仪中的应用

介绍了转矩流变仪中异步串口通信的应用,设定串口通信协议的方法,并利用MSComm控件通过VC 语言编写异步串口通信程序,给出程序流程和具体解释。     

Development of no-flow underfill materials for lead-free solderbumped flip-chip applications

No-flow underfill process in flip-chip assembly has become a promising technology toward a smaller, faster and more cost-efficient packaging technology. The current available no-flow underfill materials are mainly designed for eutectic tin-lead solders. With the advance of lead-free interconnection due to the environmental concerns, a new no-flow underfill chemistry needs to be developed for lead-free solder bumped flip-chip applications. Many epoxy resin/hexahydro-4-methyl phthalic anhydride/metal acetylacetonate material systems have been screened in terms of their curing behavior. Some potential base formulations with curing peak temperatures higher than 200°C (based on differential scanning calorimetry at a heating rate of 5°C/min) are selected for further study. The proper fluxing agents are developed and the effects of fluxing agents on the curing behavior and cured material properties of the potential base formulations are studied using differential scanning calorimetry, thermomechanical analysis, dynamic-mechanical analysis, thermogravimetric analysis, and rheometer. Fluxing capability of the developed no-flow formulations is evaluated using the wetting test of lead-free solder balls on a copper board. The developed no-flow underfill formulations show sufficient fluxing capability and good potential for lead-free solder bumped flip-chip applications     

Studies of latent catalyst systems for pot-life enhancement of flipchip underfills

Underfill encapsulant is the material used in flip-chip devices that fills the gap between the integrated circuit (IC) chip and the organic board, and encapsulates the solder interconnects. This underfill material can dramatically enhance the reliability of flip-chip devices as compared to nonunderfilled devices. Current underfill encapsulants generally consist of epoxy resin, anhydride hardener, catalyst, silica filler, and other additives to enhance the adhesion, flow, etc. Catalyst determines underfill properties including pot-life, cure speed, and cure temperature. However, long pot-life and fast cure at relatively low temperature (~150°C) are desirable, as such, it requires a room temperature latent catalyst which would be able to catalyze the epoxy curing efficiently at desirable temperature. Currently, the pot-life of commercial underfills at room temperature is normally less than one day. The underfills have to be stored in the freezer at -40°C and in the dry ice for shipping. The objective of this work was to test various catalyst systems that have the potential to enhance the pot-life of the underfill without adversely affecting its curing. The pot-lives of the underfill with various catalysts were obtained from their viscosity versus time relationships, which were established by measuring the viscosities of the underfill with these catalysts periodically using a stress-controlled rheometer. The curing of the underfills was studied using a differential scanning calorimetry (DSC). The pot-life and curing data of the underfill pre-mixed with each of these catalysts are presented in this paper     

Characteristics of solderable electrically conductive adhesives (ECAs) for electronic packaging

This study investigated the effect of the viscosity of the ECAs using a low-melting-point alloy (LMPA) filler on its bonding characteristics. The curing behaviors of the ECAs were determined using Differential Scanning Calorimetry (DSC), and ECA temperature-dependant viscosity characteristics were observed using a torsional parallel rheometer. The wetting test was conducted to investigate the reduction capability of ECAs and the flow-coalescence-wetting behavior of the LMPAs in ECAs. Electrical and mechanical properties were determined and compared to those with commercial ECAs and eutectic tin/lead (Sn/Pb) solder. In the metallurgically interconnected Quad Flat Package (QFP) joint, a typical scallop-type Cu–Sn intermetallic compound (IMC) layer formed at the upper SnBi/Cu interface after curing process. On the other hand, a (Cu, Ni)₆Sn₅ IMC layer formed on the SnBi/ENIG interface. In addition, the fracture surface exhibited by cleavage fracture mode and the fracture was propagated along the Cu–Sn IMC/SnBi interface. The extremely low-level viscosity of ECAs had a significant influence on the flow-coalescence-wetting behavior of the LMPAs in ECAs and also on the interconnection properties. Stable interconnected assemblies showed good electrical and mechanical properties.     

活性钎焊电子浆料流变性能及丝印质量的研究

研究了固含量及有机载体对电子浆料流变性能及丝网印刷质量的影响。采用流变仪测量钎焊电子浆料的黏度和触变性,并结合丝印后形貌特征,通过优化电子浆料的配方来改善丝印质量,对后续烧结过程形成性能优良的陶瓷覆铜板三明治结构具有很好的指导意义。获得了优化的浆料配方为:固含量为质量分数89%,有机载体成分质量组成为:丙二醇苯醚溶剂93.53%,乙基纤维素粘结剂5.97%及LD-9108型流平剂0.5%。获得的浆料黏度为46.039 Pa·s,触变指数为2.6136。     

Material characterization of fluorosilicone gels for automotive application

Fluorosilicone gel is commonly used in die passivation. This paper studies the characteristics of fluorosilicone gel applied on the manifold air pressure (MAP) sensor die. The cure mechanism and material characterization of the three types of gels were analyzed using differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and rheometer. The temperature and time relationships were derived for each material type. In the process of characterization, it was discovered that characterized material does not always behave as expected in the production confirmation run. It was found that the gel selected interacted with the thermoplastic packaging material hence leading to further findings of cure inhibitation. This paper concludes with the valuable lessons learnt from this material characterization project and explains the importance of these lessons learnt to actual manufacturing experience.