铜框架表面氧化过程及氧化膜厚度测量

在集成电路封装过程中,表面氧化是制约铜框架大批量应用于生产的主要原因,而框架表面氧化程度的测量和管控是铜框架应用于封装的关键点。本文运用金属氧化理论阐述了铜框架表面氧化过程及机理;进行铜框架烘烤氧化实验后测量框架表面的氧化膜厚度,通过对测量数据拟合得到铜框架氧化膜生长曲线,从而可以预测铜框架在封装过程中的氧化程度,为集成电路封装工艺的设计和管控提供依据。     

浅析环氧塑封料性能与器件封装缺陷

简要介绍了环氧塑封料可靠性、流动性、内应力等性能及影响因素：对环氧塑封料与铜框架失效机理进行了分析,包括试验方法等内容,并对封装器件中产生的气孔、油斑问题,从环氧塑封料性能改进方面作了分析,这些都是为了保证最后成品的质量和可靠性,另外对其他器件封装缺陷也作了简要叙述．     

铝纳米薄膜对铜纳米薄膜的防护作用

铜纳米薄膜在微电子器件中应用广泛。然而,纳米尺度的铜表面极易发生氧化,影响铜纳米薄膜的电学性能。利用物理气相沉积方法制备了铜纳米薄膜,研究了基底粗糙度对铜纳米薄膜电学性能退化的影响,发现基底粗糙度越大,铜的电学性能退化越快。通过在铜纳米薄膜的表面蒸镀铝纳米薄膜对铜纳米薄膜进行防护,研究了铝纳米薄膜厚度对其在不同环境下防护效果的影响,结果显示铝膜厚度越大,对铜纳米薄膜的防护效果越好。通过高温破坏测试,发现铝纳米薄膜能有效地提高铜纳米薄膜的极限工作温度,当铝纳米薄膜厚度为10 nm时,可将铜纳米薄膜的极限工作温度提高2.5倍。     

直接敷铜技术中铜箔预氧化层的检测与控制

通过控制氧化的方法对制备敷铜陶瓷基板(DBC基板)的铜层进行预氧化处理。研究了预氧化温度、氧分压对铜箔氧化层物相和厚度的影响,采用拉曼光谱仪测试铜箔氧化膜物相组成,采用紫外-可见分光光度计测试铜箔氧化膜的吸光度,确定了铜箔表面氧化物层吸光度与厚度的关系。结果表明:预氧化温度在400~800℃,氧分压控制在100×10~(–6)~700×10~(–6),铜箔表面生成一层氧化亚铜(Cu_2O)层;在过高的预氧化温度和氧分压条件下,铜箔表面就会生成Cu O物相,而且氧化膜层变厚,表面疏松、局部出现氧化膜脱落,不利于DBC基板的制备。当氧分压为500×10~(–6),预氧化时间为1 h,温度为600℃时,铜箔表面可以获得均匀致密的Cu_2O薄膜,并且氧化膜与基体Cu结合紧密,有效提高DBC基板的结合性能。     

FC传递成型封装的可行性分析

对于FC封装来说,一次成型的生产效率具有无可比拟的优势,而且固态塑封料相对于液态塑封料在性能上也具有很明显的优点,因此塑封料的制造商一直都在研究一次成型的FC用封装材料。本篇文章主要就目前所使用液态灌封材料和固态塑封料之间的性能进行比较,并就目前传统的封装工艺及其他专用材料、封装设备如何改进才能够适应FC封装进行简单的分析。     

DFN封装翘曲和应力分析与优化

回流焊过程中,双边扁平无引脚(DFN)封装会因为巨大的温度变化产生翘曲和应力,影响超高频射频识别(RFID)芯片的性能和可靠性.选取DFN3封装为例从理论方面分析结构和材料参数对封装翘曲和应力的影响,发现减小环氧塑封料(EMC)热膨胀系数(CTE)、增大其杨氏模量均能减小封装翘曲;通过有限元仿真分析得出的结论与理论分析相一致.为了减小封装翘曲和应力,选定具有更小CTE的9240HF10AK-B3(Type R)作为新型EMC.通过有限元仿真结果对比发现,在25℃时,采用新型EMC的封装翘曲增大了 16.8％,应力减小了 4.1％;260℃时,其封装翘曲减小了 45.7％,应力减小了 9.2％.同时,新型EMC的RFID芯片标签回波损耗较之前优化了 6.59％.     

IC环氧塑封料性能及其发展趋势

材料是微电子工业和技术发展的粮食，随着IC封装技术的发展，对材料特性的要求也愈来愈严格，也顺势带动封装材料发展。环氧塑封料(Epoxy Molding Compound，简称EMC)是IC后道封装三大主材料(塑封料、金丝、引线框架)之一，用环氧塑封料封装超大规模集成电路(VLSI)在国内外已成为主流，目前95％以上的微电子器件都是塑封器件。本文将简要介绍EMC配方组成、反应机理、性能之间关系及其发展趋势。     

无铅回流焊后跨线碳膜裂纹的探讨

针对PCB在过无铅回流焊后跨线位碳膜出现裂纹问题进行分析探讨,通过从调整碳膜参数、不同碳膜厚度对比、不同碳膜性能对比的结果,得出结论:碳膜开裂与油墨性能和设计有直接的关系。最终调整碳膜工艺参数和更改线路设计等方案,能有效改善碳膜裂纹的问题。     

耐高温耐湿性环氧树脂封装材料的制备

以双酚型液体环氧树脂作为基体环氧树脂,具有疏水性支链的芳香胺作为固化剂,疏水型熔融二氧化硅为填料,并配以触变剂、消泡剂、促进剂等助剂,通过DSC、TGA、TMA、回流焊等热分析手段以及高压蒸煮试验来对封装材料的性能进行表征,并对配方优化,获得了具有良好耐水性以及耐热性的单组分液体环氧树脂封装材料。结果表明:该封装材料具有良好的耐湿性和耐高温性能,可以满足COB(Chip on Board)封装客户对高压蒸煮及回流焊等可靠性测试的性能要求。     

大尺寸LTCC器件在铝合金封装模块中的可靠性设计

在军用铝合金微波模块中焊接尺寸较大的LTCC器件时,由于热失配的存在,易出现应力过大甚至开裂。当采用陶瓷基板时问题更为突出。在此采用有限元分析方法研究了这类结构在温度循环过程中应力变化和分布的特点。研究结果表明,当采用陶瓷基板时,封装盒底厚度与其上各层结构(包括过渡层垫板,陶瓷基板和陶瓷元件)厚度的不合理匹配会导致陶瓷器件产生过高应力,可靠性降低。合理的设计应是减小过渡层垫板和陶瓷基板厚度,同时增加封装盒底厚度。     

Properties of molding compounds to improve package reliability ofSMDs

Package cracking during reflow soldering process is the great problem in the reliability of plastic packages. The technique of lowering the glass transition temperature (Tg) of a molding compound is very effective for improvement of the package cracking resistance because of the properties of low moisture absorption and high adhesion strength for a molding compound. But the package reliability except for the package cracking resistance is also important. In this study, the effects of the Tg for molding compounds on the package reliability was discussed. It was confirmed that decreasing the crosslinking density was an important factor to improve the package cracking resistance. There was no problem in thermal resistance, even if the molding compound has low Tg. However, decreasing the crosslinking density by the lowering of Tg may not satisfy humidity resistance in some cases. It was found to be important to decrease the crosslinking density of molding compounds without lowering Tg in order to improve both the package cracking resistance and the humidity resistance. It was also confirmed that the introduction of rigid structural segments into the matrix resin molecules of the molding compound was a useful technique for achieving excellent package reliability     

Copper lead frame: an ultimate solution to the reliability of BLPpackage

Copper lead frame was chosen as an on-board reliability enhancement for the BLP (bottom leaded plastic) package. Adopting the copper lead frame needed a verification process for the package reliability because of its high affinity with oxygen that degrades package reliability. A series of tests were performed to select the best copper material and to determine the adhesion index parameter. The experimental results showed that the adhesion strength between the copper lead frame and EMC (epoxy molding compound) was affected by alloy composition, oxide layer thickness, and cupric/cuprous oxide ratio, Among them, the adhesion index parameter proved to be the cupric/cuprous oxide ratio. When it falls between 0.2-0.3, the highest adhesion strength was obtained regardless of alloy composition and oxide thickness. From the adhesion test results, the Cr-Zr-Cu copper alloy was employed as the lead frame for the 54-pin BLP package. The package reliability and on-board reliability tests including surface mountability, mechanical robustness, and solder joint reliability were carried out to compare the 54-pin BLP package, with Cr-Zr copper alloy and alloy 42 lead frame     

Adhesion strength of leadframe/EMC interfaces

Cu-based leadframe sheets were oxidized in alkaline solutions to produce brown and/or black oxide on the surfaces, and molded with epoxy molding compound (EMC). The adhesion strength of leadframe/EMC interface was measured using sandwiched double-cantilever beam (SDCB) specimens and pull-out specimens. Results showed that the adhesion strength of leadframe/EMC interface was inherently very poor but could be increased drastically with the nucleation of acicular CuO precipitates. The presence of smooth-faceted Cu₂O on the surface of the leadframe gave close to zero fracture toughness (G_C) and suitable pull strength (PS). A direct correlation between G_C and PS showed that PS can be a measure of G_C only in a limited range.     

Cu diffusion in Ag-plated Cu leadframe packages

Cu diffusion onto an Ag-plated Cu leadframe surface was detected by Energy Dispersive X-ray (EDX) after de-capsulating the molded package. However, no Cu was detected by EDX on the Ag surfaces of bare leadframe, leadframe after die attachment including die attachment curing, or leadframe after wire bonding. Temperature simulation of molding and post-molding curing show that the temperature and its duration have some impact on the Cu diffusion, which is as expected. Interestingly, this study shows that the Cu diffusion onto the interface of the Ag-plated surface and mold compound is very much dependent on the type of mold compound used, which has never been reported in the literature so far. The Cu diffusion was detected by EDX only for certain types of mold compounds used. It is concluded that the mold compound is a major contributor to the Cu diffusion observed. This is possibly because S and O in the mold compound react with Cu and form copper sulfides and copper oxides, which accelerate the Cu diffusion from the Cu leadframe substrate onto the interface of the Ag surface and mold compound.     

Study on the different procedures for debleeding of plastic dip

Inevitable wear on encapsulation molds and small variances in the leadframes cause a small amount of the molding compound or resin to leak out. The leakage results in either excess flash around the body of the plastic package or a thin transparent film on the leadframe and leads, which subsequently affect the solder-dipping that protects the leadframe from corrosion. Thus, effective debleeding procedure must be performed before the solder-dipping process. In this study, nine different flow procedures are designed. The results of the study show that the resin bleed can be more effectively removed by a debleeding procedure carried out immediately after molding rather than post-cure. The wet blasting process used for the debleeding purpose is also found not suitable as it causes side effects to the package surface and leadframe.     

A novel high performance adhesion enhancing Zn-Cr leadframe coatingfor popcorn prevention

A novel adhesion enhancing Zn-Cr (A2) leadframe coating has been reported to be a highly effective solution for popcorn prevention in plastic surface mount packages. In this paper, we report our recent understanding of the adhesion and degradation mechanisms of such a coating system. TEM and TOF-SIMS were employed to study the structure of A2-coating and the molding compound/leadframe (MC/LF) interface. The A2-coating was found to be a partially thin, crystalline layer comprised of a continuous interfacial layer and a network of whiskers. Zn silicate compound, ZnO and Cr oxide(s) were identified as possible phases present in the A2-coating. The adhesion enhancing and degradation mechanisms of the A2-coating were investigated by lead pull test to study the influence of temperature cycling, pressure cooker testing, moisture preconditioning, and leadframe oxidation. The adhesion data showed that the A2-enhanced MC/Cu LF interface is not susceptible to thermomechanical stress and moisture degradation. The wetting of the molding compound coupled with mechanical interlocking mechanism offered by the whiskers are believed to be key contributing factors of adhesion enhancement. Degradation of the A2-enhanced MC/Cu LF adhesion was observed after 100 min exposure at 300°C by Cu oxide formation from Cu outward diffusion through the A2-layer and was validated by AES analysis operated in the depth profiling mode. Lead pull test specimens were cleaved to have access to the MC/Cu LF interface for RBS analysis to identify the locus of failure     

利用PⅢ技术改变框架与EMC间附着力的研究

利用等离子体浸没式注入(PⅢ)技术,使用O2,N2,CO和CO2做气体源,对镀镍铜框架表面进行处理。拉力测试实验结果表明,与未经处理的空白框架相比,经过CO和CO2等离子体注入处理的镀镍铜框架与环氧塑封料(EMC)间的附着力分别提高了约35倍和12倍,而在使用O2和N2等离子体注入处理的情况下,附着力基本没有变化。通过扫描电子显微镜(SEM)对处理前后的框架表面观察,发现PⅢ处理并未引起表面粗糙度的显著变化。利用X射线电子能谱(XPS)分析,可以发现在经过CO或CO2等离子体注入处理后的框架表面有羰基出现。基于这些结果,分析了导致附着力提升的机理。     

PBGA封装的可靠性研究综述

通过传统BT类型的PWB材料与独特的PWB材料来PBGA封装的可靠性。相关的研究结果表明,后者同样具有相同的热循环稳定性和回流焊期间的疲劳强度,并具有较低的封装翘曲特点;模塑料的低吸湿性及粘片材料的高粘附强度和高断裂强度特性,有利于提高回流焊期间的疲劳强度和防止剥离现象的扩散。     

Reliability of plastic ball grid array package

The reliability of plastic ball grid array (PBGA) package is studied for different materials. The reliability of the PBGA packages using conventional Bismaleimide-Triazine type PWB and our original product PWB that is made of high Tg epoxy resin is evaluated. The PBGA package using our original PWB has a feature of lower warpage for the package, and has similar performance regarding the thermal cycling stability and the endurance during reflow soldering as compared with the PBGA using the conventional PWB. The endurance during reflow soldering for each PBGA is JEDEC STD Method A112 level 3. In order to improve the endurance during reflow soldering, not only PWB materials but also other factors are investigated. As a result, the molding compound with the property of low moisture absorption and the die attach material with the properties of high adhesion strength and fracture strength are effective to improve the endurance property during reflow soldering. The package crack mechanism during reflow soldering is briefly described as follows