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Passive components
Published in Mike Tooley, Electronic Circuits, 2019
Surface-mounting technology (SMT) is now widely used in the manufacture of printed circuit boards (PCBs) for electronic equipment. SMT allows circuits to be assembled in a much smaller space than would be possible using components with conventional wire leads and pins that are mounted using through-hole techniques. It is also possible to mix the two technologies, i.e. some through-hole mounting of components and some SMCs present on the same circuit board. The following combinations are possible: ▶ SMCs on both sides of a printed circuit board▶ SMC on one side of the board and conventional through-hole components (THCs) on the other▶ A mixture of SMCs and THCs on both sides of the printed circuit board.
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.
Interconnection technology
Published in Stephen Sangwine, Electronic Components and Technology, 2018
There are two methods of mounting components on a PCB, as illustrated in Figure 2.10. Through-hole mounting, in which component leads pass through holes in the board, is a technique that has been used from the advent of printed wiring, but has now been superceded for many applications by surface mount technology in which component leads or pads are soldered to the surface of a PCB without passing through the board. Surface mounting was tried during the 1960s, using welding to attach IC leads to copper, but it became feasible using solder jointing in the 1980s and 1990s. The main advantage of surface mounting is the smaller size of surface mount components, which allows greater component density on PCBs. Holes are still needed, of course, to make connections between one side of the board and the other, or to connect to internal layers, but these holes can be much smaller than those needed for component leads. Surface mount technology was driven by the need to make IC packages smaller (because of the large numbers of pins) but ended up contributing to the miniaturization of electronic products as smaller components were developed for surface mounting.
Development and validation of finite element impact models of high-density UAS components for use in air-to-air collision simulations
Published in Mechanics of Advanced Materials and Structures, 2020
Kalyan Raj Kota, Trent Ricks, Luis Gomez, Jaime Espinosa de los Monteros, Gerardo Olivares, Thomas E. Lacy
The FW-UAS laminated composite components are comprised of quasi-isotropic PCBs fabricated using FR4 glass-fiber reinforced epoxy. The firewall in the motor subassembly, battery housing in the battery subassembly, as well as select payload components are fabricated from PCBs. All laminated composite [57–59] components were simulated using the Enhanced Composite Damage material model (MAT_054-055) using properties from [60, 61]. Individual plies were assumed to be locally orthotropic. As an aside, quasi-isotropic PCBs are generally composed of multiple layers of woven glass fiber-reinforced epoxy substrates sandwiched between thin layers of copper foil. Electronic components, connectors, sockets and lead wires are typically attached to PCBs via through-hole connections or soldering joints. The minor reinforcing effect due to the outer layer of copper clad on the PCBs was neglected. Similarly, tiny pass-through holes and nonstructural solder joints were not included in the PCB models.