氢化物-原子荧光法测定食品容器及包装材料用聚酯树脂及其成型品中的微量锑

为建立简便、快速、高效测定食品包装材料中微量锑的方法,样品用4%乙酸处理后,利用氢化物-原子荧光法检测食品包装材料中的微量锑.结果表明,锑质量浓度在0～20 μg/L范围内呈现良好的线性,回归方程为y =87.284 C-17.440,相关系数r=0.999 9,检出限为0.028 4 μg/L,相对标准偏差RSD为0...     

连续100 W量子阱二极管激光器封装工艺

为了提高激光器输出功率,对研制的铜微通道冷却器性能进行了测试,分析了其散热能力。设计了一种在软焊料中掺杂金属添加剂的工艺,有效抑制了晶须生长,并利用该冷却器和新工艺封装出了连续100 W大功率二极管激光器,并对封装的器件进行了性能测试。测试结果表明,封装的连续100 W器件在工作电流105 A时,输出功率超过了100 W,中心波长为808.5 nm,光谱半高宽为2.15 nm,器件的smile尺寸小于2 μm,部分值小于0.5 μm。     

Temperature field analysis of IC molding process based on three dimensional finite element model

In the case presented in this paper, the distribution of temperature fields of the molding model during each time interval was obtained as the simulation proceeded along the molding time by using the 3D FEM with a simple division mesh. The simulation results indicate that the most temperature rise is located at the upper right hand corner of the die pad, while the least temperature rise during the molding process is located at the upper right hand corner of the lead frame. Based on the simulation results of the temperature field distribution in the molding model, we obtained the temperature variation trend as a result of changes in the geometric shapes of the molding model. Therefore, the information on the molding model and the analysis of temperature distribution during the integrated circuit molding process presented in this paper can be considered as references for the molding design for integrated circuit packaging process.     

Gas permeabilities of polyurethane films for fresh produce packaging: Response of O2 permeability to temperature and relative humidity

Thermoplastic shape memory polyurethane (SMPU) polymers were synthesized, cast to films, and their gas barrier properties were characterized. In addition, performance of an optical method was assessed by measuring oxygen permeability (P_O2) of the films. P_O2 of the SMPU film was at least two times higher than that of low density polyethylene (LDPE and increased at higher relative humidity. Permselectivity (P_CO2/P_O2) of the SMPU film was 15, which is approximately three times higher than for LDPE. The film absorbed circa 18% water vapor at 98% relative humidity. The optical method agreed very well (maximum 20% deviation) with a standard carrier gas method in P_O2 measurement. Overall our results show that SMPU is an attractive polymer for fresh produce packaging.     

Non-destructive evaluation of the interface between silicon dies and copper leadframes in integrated circuit packaging

The silicon die and copper leadframe in integrated circuit (IC) packaging are bonded together by die attach adhesive, and the quality of the interface is a critical issue in the reliability of IC packaging. Common defects such as cracks and delaminations can be detected using the C-scan ultrasonic microscopy method with sufficient confidence. However, weak interfaces due to weak adhesion and poor cohesion have often gone undetected, to subsequently become potential defective areas. In this paper we present experimental work to evaluate the quality of the interfaces that typically exist in IC packages using longitudinal ultrasonic wave propagation with contact transducers. Three different conditioning processes, varying curing, moisture exposure and pre-curing moisture contamination, are used to degrade the interface bonding the silicon die and copper leadframe. Ultrasonic reflection coefficients from the interface are then measured. The results show that the reflection coefficient depends strongly on the interface quality, and can be used as a quantitative indicator to characterize the bond quality.     

基于三维缺陷检测的DMD数字条纹投影光学系统设计

基于半导体行业中PCB焊膏印刷检测的实际应用,采用0.45 WXGA DMD芯片设计了数字条纹投影光学系统.以LED作为光源,结合透镜阵列照明DMD芯片;同时,为了减小投影三角关系造成的条纹周期不均匀性对检测结果的影响,采用双远心光路结构将DMD生成的条纹成像到待测表面,且适用的最小检测面积为1mm2.光学模拟结果表明,该数字投影系统在被投影表面上的照明均匀性为91%,投射条纹的对比度高于0.8,且条纹周期均匀,为实际应用与后续条纹分析提供了良好保障.     

一种大过载MEMS加速度计新型封装方法

传统的MEMS系统级封装多采用IC标准的封装形式,例如塑料封装形式、陶瓷管壳封装形式、TO 系列金属管壳封装。由于大过载传感器需要工作环境冲击振动比较高,陶瓷管壳容易破碎;塑封采用热塑成型,封装后残余应力大;TO系列管壳体积较大,并且采用直插形式安装,在超过5×103g冲击下,管脚容易折断。针对这种情况,本文提出了一种新型 MEMS 加速度计封装方法,在圆片级采用玻璃-硅-玻璃三层结构,并采用铝金属壳体螺钉安装并在壳体内部双组分环氧树脂灌封。封装之后的大过载加速度计具有体积小,密封性强,残余应力小、抗强冲击、稳定性好、适应于小批量生产等优点。     

Mechanics of DNA packaging and ejection from elastic phage capsid

This study intends to investigate how the elasticity of a bacterial phage can affect the process of DNA packaging and ejection. For this purpose, we propose a unified continuum and statistical mechanics model by taking into account the effects of DNA bending deformation, electrostatic repulsion between DNA-DNA strands and elastic deformation of the phage capsid. Based on such a model, we derive the quantitative relations between packaging force, elasticity of capsid, DNA length remaining in the capsid, osmotic pressure and ejection time. The theoretically predicted results are found to agree very well with in vitro experimental observations in the literature.     

气相色谱-质谱法测定聚氯乙烯包装材料和食品模拟物中的46种增塑剂

建立了46种增塑剂在聚氯乙烯(PVC)食品包装材料中的含量及其在水、3%乙酸、10%乙醇和橄榄油4种食品模拟物中迁移量的气相色谱-质谱(GC-MS)测定方法。食品包装材料、水质模拟物和橄榄油中增塑剂分别采用溶解-沉淀法、正己烷液-液萃取和凝胶渗透色谱(GPC)法提取。采用GC-MS法,在选择离子监测模式(SIM)下对46种增塑剂进行定性,采用外标法进行定量测定。各种增塑剂在0.1～2.0 mg/L质量浓度范围内呈线性,相关系数为0.9910～0.9999,各组分检出限均在0.005～0.05 mg/kg之间。在2种食品模拟物中,3个浓度添加水平下46种增塑剂的加标回收率在69.51%～107.21%之间,精密度(RSD, n=6)为3.53%～18.95%。该方法可满足PVC食品接触制品及4种不同性质的食品模拟物中多种类增塑剂的快速筛查和准确定性、定量测定要求。