盲孔裂缝的成因与改善

盲孔裂缝是高密度互连印制电路板(HDI)在无铅回焊时最常见的盲孔可靠性问题之一,其影响因素多,原因复杂。文章通过盲孔互连测试板,运用实验设计(DOE)手法对材料、激光能量、除胶速率、沉铜前微蚀大小、化学沉铜厚度、电镀前铜面清洗等进行了实验。结果表明,激光能量和沉铜前微蚀控制是造成盲孔裂缝的显著因子,激光能量选用16/14/12(3shot)和微蚀量控制1.5μm时效果最佳,不会产生盲孔裂缝问题。     

Joint estimation of carrier frequency offset, dc offset and I/Q imbalance for OFDM systems

Orthogonal frequency division multiplexing (OFDM) systems with direct-conversion receiver (DCR) are vulnerable to carrier frequency offset (CFO), dc offset (DCO) and in-phase/quadrature (I/Q) imbalance. In this paper, we propose blind estimator for joint estimation of CFO, DCO and I/Q imbalance in OFDM systems with DCR. Simulation results show that performance of proposed estimator approaches Cramér-Rao lower bound (CRLB) asymptotically, which demonstrates its effectiveness.     

基于DCT域的AVS视频盲水印算法

结合人眼的视觉特性,提出了一种基于DCT域的AVS视频编解码标准的视频盲水印算法.算法首先对水印图像进行增强的Arnold变换,得到置乱的二值水印图像;然后根据嵌入公式替换嵌入点的系数,将水印信息自适应嵌入到Ⅰ帧的DCT系数中.提取水印时不需要原始视频,可实现盲水印.实验结果表明,该算法对高斯、帧剪切、盐噪声等攻击,具有较好的稳健性和不可见性.     

基于模糊酉矩阵TD-SCDMA突发信号组合码的盲估计

针对TD-SCDMA突发信号盲解扰与盲解扩的问题,该文提出了一种基于模糊酉矩阵组合码盲估计的方法。该方法将TD-SCDMA系统中短扩频码与固定长度的扰码一起视为小区的扩频码,即组合码,首先根据用户midamble码自身高度的相关性进行midamble码捕获和载波残余频偏估计;然后根据midamble码所处的相对位置,以扰码长度为周期对数据域信号进行分段截取,最后利用相关函数二阶矩、奇异分解法以及消除模糊关系的酉矩阵法,即可完成组合码的盲估计。仿真结果表明,该算法具有良好的估计效果,而且在估计复组合码前,无需估计组合码的周期。     

高速多层PCB板中过孔的建模、仿真及分析

利用Hyperlynx软件对高速PCB板中所应用到的过孔进行建模与仿真,分析了过孔对流经其上信号的影响,并给出了改进、优化过孔的方法。仿真结果表明,在要求线上信号完整性高的情况下,使用过孔方式连接的电路得到了改善和优化。     

A complete resistance extraction methodology and circuit models for typical TSV structures

Through-silicon via (TSV) is one of the key technologies on three-dimensional integration packaging. In this article, an experimental methodology with circuit models was proposed for electrical characteristic tests on typical TSV structures. To this end, self-developed test patterns such as the via chains, the snake interconnections and the Kelvin structures with different dimensions were designed and manufactured. Suitable electrical measurement methodologies were next employed to characterise the element behaviours of the patterns. Based on the experimental data, electrical circuit models for the TSV structures were introduced and the parameters of the model were exacted. The validity and accuracy of the electrical model were finally verified and the TSV characteristic measurements can be performed through a simpler process.     

有噪复杂度寻踪的新算法

复杂度寻踪是投影寻踪向时间序列数据,即具有时间结构信号的扩展。该方法是和具有时间依赖特性的源信号的盲分离和独立成分分析紧密联系的。在源信号是具有时间依赖特性和存在高斯噪声的情况下,现有的有噪复杂度寻踪算法没有给出自回归系数的估计方法,影响了算法的实际应用,提出了有噪复杂度寻踪的新算法,该算法给出了自回归系数的估计方法。对自然图像和人工信号的仿真表明了提出算法的有效性,和现有的盲源分离算法相比较,提出算法具有好的信号分离性能。      

红外焦平面器件盲元检测及补偿算法

在分析盲元响应特性的基础上,利用红外焦平面阵列对双参考辐射源的响应数据和相邻像元成像数据的相关性,提出了一种基于双参考辐射源的盲元现场自动检测和插值补偿算法,实现了盲元的自动检测和校正.实验结果表明:该方法具有对盲元查找速度快、定位准确率高、补偿效果好及易于软硬件实现等特点.     

一个可处理多种约束的多层布线通孔最少化算法

本文分析了常用的VLSI多层布线图模型线段－相交图SCG的局限性,提出了对SCG模型的修正,并基于该模型用模拟退火算法来解决通孔最少化问题,算法可以处理严格和非严格分层的布线,并考虑了许多物理约束的处理方法.实验证明算法可以较大程度地减少通孔.     

Effect of UV light irradiation on SiC dry etch rates

Inductively Coupled Plasma etching of 4H-SiC under ultraviolet illumination was examined for SF₆/Ar and Cl₂/Ar chemistries. Etch rate enhancements up to a factor of 8 were observed with UV light irradiation during Cl₂/Ar etching. The enhancement mechanism is related to photodesorption of SiCl_x and CCl_x species. Surface morphologies were unchanged as a result of the UV enhancement with Cl₂/Ar discharges. By contrast, there was no effect of UV irradiation on the SiC etch rates in SF₆/Ar plasmas, but the surfaces were typically smoother than those obtained without the ultraviolet illumination. In the SF₆/Ar chemistry the rate-limiting steps are either Si-C bond-breaking or supply of fluorine radicals to the surface, and not desorption of the SiF_x and CF_x etch products.