Test And Analysis Of Life Extending Technology For Printed Circuit Board Of Electronic Equipment

Though the update cycle of modern electronics is shorter and shorter,the life span of those needing a long service life is still the key technical indicator.Due to the complex strategic patterns at home and abroad,higher requirements for the life of military equipment are proposed.The life span of military equipment is expected to be extended through various life extension measures.To meet the development requirements of military equipment in the new era,the service life of electronics is mainly extended by improving and replacing old models,replacing printed board assemblies,and replacing elements on the basis of the original design life.This thesis,based on the life extension of printed circuit boards of electronics,mainly researches two topics,namely,changing manual welding to wave soldering of printed boards involved in the replacement of printed circuit boards,element desoldering and resoldering involved in the replacement of elements on printed circuit boards.Technical parameters are optimized and improved by theoretical analysis and the reliability of processing methods is checked by technological test.For manual welding,the gap between installation aperture and the lead of elements on printed circuit boards is 0.2mm~0.4mm.For wave welding,the gap is 0.2mm~0.3mm.To solve the wave welding of elements with the gap of 0.3mm~0.4mm between the aperture and the lead of printed boards in manual welding,the thesis,based on welding theory,analyzes the solder wetting,capillarity,dissolution and diffusion,and intermetallic compounds,adjusts technological parameters of wave welding in line with the analysis results to meet welding requirements.To verify the reliability of welding spots after wave welding with new technological parameters,technological test samples are made and subject to temperature cycling test and vibration test,to check the reliability of welding spots by technological test.The results of technological test are analyzed and summarized.As per Technical Requirements of Repair and Modification of Printed Circuit Board Assemblies for Space Use(QJ 2940A-2001),the elements of printed circuit board can only be replaced once,while the elements which will be out of service or suffer degraded performance must be replaced for life extension products.To solve this,the thesis,based on the theory of printed boards,analyzes the base materials,manufacturing process,main parameters of printed boards,sets technological parameters of desoldering elements and resoldering elements as per the analysis results.To verify the reliability of printed board assemblies after welding for several times,technological test samples are made and subject to tensile test,to check the reliability of printed board assemblies after welding for several times by technological test.The results of technological test are analyzed and summarized.