Influence of PCBs coatings wettability on lead-free SMT solder joints reliability
The paper presents results of wettability study of PCBs with immersion Sn, Ni/Au and SnCu coatings before reflow soldering process. Furthermore the solder joints were made in the optimal lead-free reflow soldering conditions using chosen materials with different wettability value of PCBs coatings and their reliability assessment was executed. The results of investigations have shown that exist direct influence PCBs coatings wettability on reliability of solder joints. It was find also that by using special procedure of PCBs coatings wettability assessment it is possible to predict future solder joints reliability.
Influence of flux activity on process parameters and solder joints in lead-free wave soldering
Electronics manufacturing has responded well to environmental concerns such as role of CFCs (and related compounds) in stratospheric ozone depletion (Cala and Winston, 1996), and the toxicity of lead. To those who understand these demands the producers of fluxes recommend VOC-free fluxes especially for lead free wave soldering. This paper reports investigation of the influence of the VOC-free flux properties on lead-free wave soldering process. Three commercial no-clean liquid fluxes which based on water were used for PCBs soldering with SnAg and SnAgCu alloys on the wave machines. The influence of fluxes properties and nitrogen atmosphere on wave process parameters and solder joints quality were established. The conclusions important for lead-free wave soldering practice are presented
A New Vacuum Pressure Infiltration CFRP Method and Preparation Experimental Study of Composite
In order to prepare a carbon-fiber-reinforced polymer composite (CFRP) with ideal microstructure and properties, a new vacuum pressure infiltration CFRP method is proposed based on an analysis of existing CFRP preparation process methods. Research on composite material preparation systems was carried out by using this new method principle. The system mainly includes a fiber pre-forming module, a vacuum heating infiltration module, a hot-press curing molding module, and a data acquisition control module. Under the conditions of natural curing at 0 MPa + 6 h + 25 °C, vacuum heating curing at –0.05 MPa + 30 min + 80 °C, and hot-press curing at 0.7 MPa + 5 min + 50 °C, a two-dimensional (2D) CFRP with excellent microstructure and properties was successfully prepared. Observing the microstructure of the prepared composite material, it can be found that the inside of the composite material was sufficiently and uniformly infiltrated, and common preparation defects such as holes and delamination were effectively controlled. Through the performance test, the bending strength of the material reached 790 MPa.