Assembly process Surface-Mount technology

Piracci, A. F., Advantages of Non-Contact Dispensing in SMT Assembly Processes, Surface Mount Technology Assoc./ATE, Chicago, IL (Sep. 2000)... 

Surface-mount technology replaces previous methods of inserting component leads into plated through-holes of PWBs, wave soldering from the back side to flow solder into the holes, and simultaneously forming both mechanical and electrical connections. SMT is highly automated and currently the most widely used production process for the assembly of single-layer, double-sided, and multilayer circuit boards. 

The need to use lead-free solder in surface mount technology applications where soldering temperatures of between 220 °C and 240 °C are likely to be encountered has necessitated the use of such high temperamre polyamides as DuPont s Zytel HTN LX resins for board assembly. It is interesting to note that some Japanese companies have been using lead-free solders in their flow soldering processes since 1997. 

Of course, various levels of automation may be considered, depending on production volumes and capital expenditure costs. However, with continued miniaturization of surface-mount products as well as the strict requirements for the repeatable placement of specific solder paste volumes and accurate placement of components, will be a foregone necessity to assemble surface-mount technology with a fuUy automated assembly process. 

FIGURE 53.1 Generic manufacturing process for surface-mount technology printed circuit assemblies, including the possible locations within the process for inspection or testing of mechanical or structural attributes and electrical characteristics of an assembly. 

Electronic packages are composed of complex materials that are assembled via intricate processes and then subjected to a wide range of service environments. It is crucial to note that both the die-packaging processes and surface-mount technologies can impart stresses and create residual stresses in the final packaged assembly that impacts its interconnect reliability. Assessing the rehabihty of package devices requires that all variables that can hinder or enhance reliabihty be considered. 

For nearly 30 years, SMT has remained the only dedicated resource for the surface mount technology industry. Recognized as the leader in comprehensive knowledge base for assembly of printed circuit boards, electronics and the materials critical to the process, readers represent the core and leadership of the surface mount industry. 

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