Defects inspection of the solder bumps using self reference technology in active thermography

With the decrease of solder bumps in dimension and pitch, defects inspection of the solder bumps become more difficult. A nondestructive detection system based on the active thermography has been developed for solder bumps inspection. However, heating non-uniformities and emissivity differences may impede the defects recognition. In this paper, we propose a method using a self reference technology based on a source distribution image (SDI) to eliminate the influence of unevenness in emissivity values and heating power distribution. Three thermograms captured right after the heat pulse are averaged to create the SDI. Then the SDI is subtracted from the original thermograms, and we get the thermal contrast images, in which eight points on the edge of each hot spot are selected as the feature points for the corresponding bump. Thermal difference between the feature points and the central point are adopted to quantify the thermal behaviors of the solder bumps, by which the missing bump is distinguished from the reference bumps. The results show that it is effective using the method to eliminate the impacts of emissivity unevenness and heating non-uniformities on defects identification in the active infrared test.     

浅谈CTE及其对FC—BGA焊点可靠性的影响

PCB对封装行业来说,最关键的莫过不同元器件和PCB之间的热膨胀系数（CTE）匹配性问题。其中FCRGA封装,通过倒装芯片实现芯片焊料凸点与FCBGA基板的直接连接,在FCBGA类产品中可实现较高的封装密度,获得更优良的电性能和热性能。但由于PCB与芯片之间cTE的不匹配,而导致FCBGA焊点的可靠性问题。本文就CTE影响FCBGA焊点可靠性展开讨论。     

Interactions between solder and metallization during long-term aging of advanced microelectronic packages

The reactions between the eutectic PbSn solder and the Au/Ni/Cu tri-layer metallization in advanced microelectronic packages were studied. In this investigation, reflowed packages were subjected to aging at 160°C for times as long as 4000 h. Immediately after the reflow, all the Au had left the Au/Ni/Cu metallization, forming many (Au_1−xNi_x)Sn₄ particles distributed throughout the whole solderjoint. In addition, there was a thin layer of Ni₃Sn₄ (1.4 μm) at the interface. After 500 h of aging, most of the (Au_1−xNi_x)Sn₄ particles regrouped at the interface as a continuous (Au_0.45Ni_0.55)Sn₄, layer over the Ni₃Sn₄ layer. After 2500 h of aging, nearly all the Ni layer had been consumed. A 15 μm layer of (Au_0.45Ni_0.55) Sn₄ and a 20 μm Ni₃Sn₄ were found over the remaining Ni. At 3000 h, the Cu had started to react with both Ni₃Sn₄ and (Au_1−xNi_x)Sn₄, forming a layer of (Cu_1−p−pAu_pNi_q)₆Sn₅, a layer of (Cu_1−r−sAu₁Ni_s)₆Sn₅, and a layer of Cu₃Sn over the Cu layer. A small amount of Cu (2.7–5.7 at.%) was found to dissolve in this Ni₃Sn₄, forming a ternary compound (Ni_1−yCu_y)₃Sn₄. It was revealed that Au diffused up-hill during the reaction. After aging for 4000 h, all the (Au_1−xNi_x)Sn₄ had disappeared and Au atoms had diffused into the (Cu_1−p−qAu_pNi_q)₆Sn₅ and (Cu_1−r−sAu_rNi_s)₆Sn₅ phases. The practical implications for the above findings were pointed out in this paper.     

细微间距器件焊点形态成形建模与预测

基于最小能量原理和焊点形态理论 ,以方形扁平封装器件 (QFP)焊点为例建立了细微间距 (FPT)器件焊点形态成形模型 ,运用有限元方法预测了QFP焊点形态 ,并运用该模型和有限元方法对QFP器件焊点三维形态问题进行了分析。     

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。     

免清洗焊接技术的印刷模板设计及制造技术

印刷模板的合理设计和制造是免清洗焊接技术中的关键 ,也是SMT工艺质量的保证     

JB系列光刻机的原理及维修技术

简述了 JB系列光刻机的基本工作原理以及常见故障的分析和维修 ,同时给出了设备的日常维护保养措施。     

SMT焊点形态成形和焊点可靠性CAD

以ＰＢＧＡ焊点形态成形ＣＡＤ和焊点热疲劳寿命可靠性ＣＡＤ研究为例,提出ＳＭＴ焊点形态成形和可靠性一体化设计思想,并对其实现方法进行了分析研究,给出了具体实现步骤和研究结果．     

Modified form of binary and ternary 3-point subdivision schemes

Binary 3-point scheme, developed by Hormann and Sabin [Hormann, K. and Sabin, Malcolm A., 2008, A family of subdivision schemes with cubic precision, Computer Aided Geometric Design, 25, 41-52], has been modified by introducing a tension parameter which generates a family of C¹ limiting curves for certain range of tension parameter. Ternary 3-point scheme, introduced by Siddiqi and Rehan [Siddiqi, Shahid S. and Rehan, K., 2009, A ternary three point scheme for curve designing, International Journal of Computer Mathematics, In Press, DOI: 10.1080/00207160802428220], has also been modified by introducing a tension parameter which generates family of C¹ and C² limiting curves for certain range of tension parameter. Laurent polynomial method is used to investigate the continuity of the subdivision schemes. The performance of modified schemes has been demonstrated by considering different examples along with its comparison with the established subdivision schemes.     

Correction of a coherent image during KrF excimer laser ablation using a mask projection

Using masks for laser ablation has proven useful in the fabrication of prototypes for the manufacturing of micro-fluidic devices. In this work, an excimer laser was used to engrave microscopic channels on the surface of polyethylene terephthalate (PET), which showed a high absorption ratio for an excimer laser beam with a wavelength of 248 nm. When 50 μm wide rectangular microscopic channels were made using a 500×500 μm square mask and a magnification ratio of 1/10, ditch-shaped defects were found at both corners. The calculation of the laser beam intensity showed that a coherent image in the PET specimen caused the defects. An analysis based on the Fourier diffraction theory enabled the prediction of a coherent shape at the image plane, as well as a diffracted beam between the mask and the image plane. The analysis also showed that the diameter of the aperture was a predominant factor toward the elimination of ditch-shaped defects in the rectangular microscopic channels on the PET produced by an excimer laser ablation.