Improved soldering of components with different thermal masses by hybrid printing of solder pastes
In this work are shown the results of an improved Pin in Paste (PiP) technique. With the purpose of soldering of SMD and PTH (Pinthrough Hole) components, the PiP technique is making use of solder paste printing. The problematic PtP soldering due to thermal shading of areas under large size connectors, which results from their big thermal masses, has been considered. The actual temperatures under such connectors differ from the optimum thermal profile needed for the particular solder paste which profile can be monitored by a KIC instrument. A solution of this problem is suggested by making use of a solder paste, whose optimum thermal profile corresponds to the actual thermal profile under the connector components. For that purpose are used two different kinds of solder pastes. The proposed method, named Hybrid Printing, of two kinds of SMD pastes is based on the special design of a rakel which allows depositing of more than one kind of solder paste within one processing step. The effect of the use of Bi containing, Pb containing and Pb-free solder pastes has been investigated. The application of hybrid printing in a real production line has been demonstrated. The results of the X-ray and metallographic assessment of the fabricated solder joints are presented.
Surface Mounting Parallel Tests
This paper presents an approach for parallel testing of materials and processes in surface mounting. The processes of applying paste by means of printing and soldering are discussed. Constructive solutions for the squeegee and stencil are suggested, and technological procedures, and limitations on the processes used are defined. Models for the implementation of test processes and initial results are shown.
Initial Teacher Training: the French view
ABSTRACT This paper, against the background of trends in the development of initial teacher training in Europe as a whole, identifies and explains some of the recent, radical reforms which were introduced in France by a socialist government. These include the need to raise the status and the competence of the teaching profession; the creation of new teacher‐training institutions of university status (Instituts universitaires de formation des maitres); the introduction of common entry qualifications at degree level for both primary and secondary levels; the harmonisation and the extension to 2 years of the post‐degree teacher‐training course and the increase in emphasis placed on professional training, both theoretical and practical. These reforms provoked a storm of protest and an examination of the reasons for this reveals a multiplicity of crucial questions which have far‐reaching implications.