Extrusion of Solid Wood Impregnated with Phenol Formaldehyde (PF) Resin: Effect of Resin Content and Moisture Content on Extrudability and Mechanical Properties of Extrudate
A new deformation technique of wood flow forming is promising for industrial uses of solid wood. Flow deformability, size stability, and good mechanical properties were obtained by using wood impregnated with low molecular weight phenol formaldehyde (PF) resin. In this study, to clarify the effect of the PF resin and moisture contents in wood on the flow deformability (extrudability) and the mechanical properties of the product (extrudate), a lateral extrusion was conducted by using wood impregnated with various contents of PF resin and three levels of moisture content. The results indicated that the extrudability of wood impregnated with PF resin improved with an increase in both PF resin and moisture content. The mechanical properties of the extrudate worsened with increases in the moisture content of the wood impregnated with PF resin. Because most of the water in the wood remained in the mold during the extrusion process, chemical changes of the wood substance and PF resin occurred due to steam forming under the high temperature and pressure of the extrusion. The steam worsened the mechanical properties of the extrudate.
Effects of resin content and precompression treatment on bulk bamboo extrusion
The use of bamboo, as a natural fast-growing renewable natural resource, contributes to solving resource-depletion and environmental problems such as global warming. We applied a new wood-flow-forming technique to bulk bamboo impregnated with phenol formaldehyde (PF) resin in order to promote the use of bamboo. The influences of resin content and distribution in the bamboo on formability (extrudability) during lateral extrusion were investigated. Moreover, we developed a precompression treatment method during which cracks were introduced in the bamboo prior to resin impregnation, and the effects of this treatment method on the resin permeability of the bamboo were determined. The forming pressure during extrusion decreased linearly with increasing PF-resin content, and this tendency was independent of the presence of cracks or the distribution of the resin. Therefore, increasing the resin content of the bamboo is important for improving the extrudability of bulk bamboo. Precompression treatment was found to effectively improve resin permeability and the formability of bulk bamboo impregnated with PF resin.
Failure analysis for poor solderability of Au surface of PCB
Nonwetting is one of the common problems and is always rejected in electronic assemblies. ENIG pads of a PCBA exhibited nonwetting after lead-free reflow soldering. With the aid of stereomicroscope, SEM&EDS and XRF, a series of analysis was performed. And after visual inspection, surface and cross section analysis, thickness measurement and solderability test, it can be inferred that oxidation of plating surface was the main reason for nonwetting, and corrosion in Ni plating caused an adverse impact on solderalibity.