[Objectives]This study was conducted to detect the contents of heavy metal lead and chromium in food packaging bags.[Methods]The contents of heavy metal lead and chromium in food packaging bags were determined by micr...[Objectives]This study was conducted to detect the contents of heavy metal lead and chromium in food packaging bags.[Methods]The contents of heavy metal lead and chromium in food packaging bags were determined by microwave digestion-flame atomic absorption spectrophotometer.With concentrated nitric acid and 30%hydrogen peroxide solution as the digestion system,food packaging bags of different materials,plastic packaging bags and paper packaging bags,were ultrasonically digested and then determined for the contents of heavy metal lead and chromium by flame atomic absorption spectrophotometry.[Results]The determination results showed that the linear correlation coefficient of lead was 0.9967,and the linear correlation coefficient of chromium was 0.9977.The method has the characteristics of simplicity,high analysis speed and high sensitivity.[Conclusions]This study provides a theoretical basis for the safety of food packaging bags.展开更多
Soldering experiments of quad flat package(QFP) devices were carried out by means of diode laser soldering system with Sn-Ag-Cu and Sn-Cu-Ni lead-free solders, and competitive experiments were also carried out not onl...Soldering experiments of quad flat package(QFP) devices were carried out by means of diode laser soldering system with Sn-Ag-Cu and Sn-Cu-Ni lead-free solders, and competitive experiments were also carried out not only with Sn-Pb eutectic solders but also with infrared reflow soldering method. The results indicate that under the conditions of laser continuous scanning mode as well as the fixed laser soldering time, an optimal power exists, while the optimal mechanical properties of QFP micro-joints are gained. Mechanical properties of QFP micro-joints soldered with laser soldering system are better than those of QFP micro-joints soldered with IR reflow soldering method. Fracture morphologies of QFP micro-joints soldered with laser soldering system exhibit the characteristic of tough fracture, and homogeneous and fine dimples appear under the optimal laser output power.展开更多
为解决QFN成本较高的问题和进一步提高产品可靠性,华天科技突破了传统思想的束缚,在产品结构的设计上进行了创新。引脚在封装本体内式封装(LIP:Lead In Package)是一种新型的封装形式,它是针对目前QFN(Quad Flat No-lead)在封装高成本...为解决QFN成本较高的问题和进一步提高产品可靠性,华天科技突破了传统思想的束缚,在产品结构的设计上进行了创新。引脚在封装本体内式封装(LIP:Lead In Package)是一种新型的封装形式,它是针对目前QFN(Quad Flat No-lead)在封装高成本问题而重新选择的设计方案。展开更多
基金Supported by Special Scientific Research Project of Shaanxi Provincial Department of Education(16JK1275)。
文摘[Objectives]This study was conducted to detect the contents of heavy metal lead and chromium in food packaging bags.[Methods]The contents of heavy metal lead and chromium in food packaging bags were determined by microwave digestion-flame atomic absorption spectrophotometer.With concentrated nitric acid and 30%hydrogen peroxide solution as the digestion system,food packaging bags of different materials,plastic packaging bags and paper packaging bags,were ultrasonically digested and then determined for the contents of heavy metal lead and chromium by flame atomic absorption spectrophotometry.[Results]The determination results showed that the linear correlation coefficient of lead was 0.9967,and the linear correlation coefficient of chromium was 0.9977.The method has the characteristics of simplicity,high analysis speed and high sensitivity.[Conclusions]This study provides a theoretical basis for the safety of food packaging bags.
基金Project(CX07B_087z) supported by Jiangsu General Colleges and Universities Postgraduate Scientific Research Innovative Plan, ChinaProject(06-E-020) supported by the Six Kind Skilled Personnel Project of Jiangsu Province, China
文摘Soldering experiments of quad flat package(QFP) devices were carried out by means of diode laser soldering system with Sn-Ag-Cu and Sn-Cu-Ni lead-free solders, and competitive experiments were also carried out not only with Sn-Pb eutectic solders but also with infrared reflow soldering method. The results indicate that under the conditions of laser continuous scanning mode as well as the fixed laser soldering time, an optimal power exists, while the optimal mechanical properties of QFP micro-joints are gained. Mechanical properties of QFP micro-joints soldered with laser soldering system are better than those of QFP micro-joints soldered with IR reflow soldering method. Fracture morphologies of QFP micro-joints soldered with laser soldering system exhibit the characteristic of tough fracture, and homogeneous and fine dimples appear under the optimal laser output power.
