Laser soldering of small pitch BGAs on Plexiglas substrate PCBs
The paper presents the results of the study and the procedure of soldering 200µm pitch BGAs on circuits on PMMA (Poly-methyl-methacrylate or Plexiglas) substrate, starting from the paste deposition process, fine placement of the BGAs and finally soldering. The novelty in this research is that it had to face two restrictions. The combination of PMMA substrate, transparent to laser, and SnBi, ecologic solder paste, which required a low and very well-controlled soldering temperature, and the small size of the BGAs which needed a punctual soldering. These particularities led the team to use laser for soldering, due to the possibility of highly accurate energy calculation and very small size of the focused beam.
Optimizing laser soldering of SMD components: From theory to practice
The paper presents the results of a study of the procedure of laser soldering chip SMD components, taking into consideration various parameters of the soldering process: type and quantity of solder paste used, energy pumped into the system, etc. There are many situations in modern electronics where the heat for soldering must be controlled very accurately, for example for soldering temperature sensitive components or using different substrates that require a soldering temperature different than the usual ones (PMMA substrates need low temperature soldering). We studied the energy necessary for realizing high quality solder joints even from the first soldering, thus reducing the number of destroyed samples and decreasing the time and costs of development of the electronic module. Based on the theoretical model, we soldered components and performed electrical and mechanical tests, cross-sections, optical and X-ray inspections.
Researches on Structural Factor Involvement in Oral Tribology
This study is focused on two ceramic materials, D.SING (Ivoclar) and VM13 (emphasis the VITA TN), frequently used in restorative dentistry practice and it comes to complete a full set of results obtained by the authors over several years of research on oral tribology with main influence on oral health. In this way there are involved more specific structural aspects of dental restorative ceramic materials quality as is shown in [1].