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Electronic Components
Published in Michael Pecht, Handbook of Electronic Package Design, 2018
Denise Burkus Harris, Michael Pecht, Pradeep Lall
With DIPs the leads are typically inserted into plated through holes and soldered to the back side of the PWB. Often a wave soldering process is used, in which liquid solder flows across the bottom of the board and adheres to the leads and the walls of the through holes. This method confines the leaded components to a single side of the board. Chip components can be mounted to the bottom of the board by epoxy attaching them prior to solder reflow, so that their terminations are connected to the PWB by the wave solder; or they are hand soldered after the wave solder process. DIPs can also be surface mounted. This requires leads formed, or bent, into an L shape under the component. The short leg of the L is then soldered to the mounting pads on the PWB. This method does allow for surface mounting of the DIPs; however, with the 100-mil pitch of the DIP package, it also requires a large increase in the needed surface mounting area on the PWB. Other package styles (e.g., chip carriers) offer a much more efficient surface mounting design.
Surface Mount Technology
Published in Jerry C. Whitaker, Electronic Systems Maintenance Handbook, 2017
A type III board will first be inverted, adhesive dispensed, SMDs placed on the bottom-side of the board, the adhesive cured, the board rerighted, through-hole components placed, and the entire assembly wave-soldered. It is imperative to note that only passive components and small active SMDs can be successfully bottom-side wave-soldered without considerable experience on the part of the design team and the board assembly facility. It must also be noted that successful wave soldering of SMDs requires a dual-wave machine with one turbulent wave and one laminar wave.
Structure and properties of Sn-Cu lead-free solders in electronics packaging
Published in Science and Technology of Advanced Materials, 2019
Meng Zhao, Liang Zhang, Zhi-Quan Liu, Ming-Yue Xiong, Lei Sun
Compared with traditional Sn-Pb solder, Sn-Cu solders exhibit the higher melting point [14–18]. However, there is still potential for the further development of Sn-Cu solder alloys with higher properties. The eutectic Sn-0.7Cu alloys have become the focus of research, since the eutectic alloys have the advantages of low melting point, narrow crystallization temperature range, good fluidity and low tendency of hot cracking and segregation. Among the new Pb-free alloy candidates, Sn-0.7Cu solders are inexpensive and exhibit promising characteristics [19]. As the practicability of Sn-Cu solder has been confirmed continuously, Sn-0.7Cu solder has been widely used in wave soldering process [20,21]. In order to research several properties of Sn-Cu solder alloys, a lot of researches have been done, including the structure/interface evolution, the wettability and mechanical properties, by means of alloying, particle strengthening and solidification rate control.
Positive lean: merging the science of efficiency with the psychology of work
Published in International Journal of Production Research, 2018
As a manufacturing example, consider a system that produces personal computers. A key component of a personal computer is the printed circuit board (PCB) that serves as the motherboard. A step in the production of these PCBs, illustrated in Figure 2, is surface mount assembly, in which electronic components are positioned on the board. The main inputs to the surface mount process are the raw circuit boards, components, solder paste and electricity. The resources include one or more pick-and-place machines (chip shooters) and human operators. The outputs are boards with components (‘stuffed’ boards). The customer is the wave soldering stage, in which a reflow oven is used to solder the components in place. The orders are production triggers, which could be kanban signals in a pull system or order releases in a push (MRP) system. If a demand occurs when there is no inventory of assembled boards available, then the order incurs waiting time.