Applications surface-mount technology

We should not think that heat is lost only from the copper side. The usual laminate (board material) used for SMT (surface mount technology) applications is epoxy-glass FR4, which is a fairly good conductor of heat. So some of the heat from the side on which the device is mounted does get across to the other side, where it contacts the air and helps reduce the thermal resistance. Therefore, just putting a copper plane on the other side also helps, but only by about 10 to 20%. Note that this opposite copper plane need not even be electrically the same point it could for example just be the usual ground plane. A much greater reduction of thermal resistance (by about 50 to 70%) can be produced if a cluster of small vias (thermal vias) are employed to conduct the heat from the component side to the opposite side of the PCB. 

The class of polyester-based liquid crystal polymers (LCPs) represent one of the most attractive materials in the field of engineering thermoplastics because of their superior mechanical properties, heat resistance, accuracy of dimensions, moldability and the excellent balance of these properties [1-5]. LCPs have been recently expanding their applications, in particular, those for precision electronic parts appropriate for surface mount technology (SMT). 

Automotive connectors have many of the same demands of high heat surface mount technology connectors. Examples of blends and alloys in these applications are largely based on PBX and PA-66. Xhe high heat and high solvent resistance requirements make a semicrystalhne resin a suitable choice. Xhese systems include ... 

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. 

Epoxies form the basis of products in the multi-chip module (MCM) bonding and surface mount technology (SMT) repair areas. Two-pack room-temperature products (amine cure) are common in repair applications. Two-pack systems with acid anhydride... 

The development of surface-mounted technology (SMT) using surface-mounted devices (SMD) was a major development. SMD are active and passive electronics components without conventional connecting wires. SMD components can be placed on the solder side of the PCB and their metal caps soldered to the copper pads of the PCB. Both layers of the PCB can therefore be used as active areas. The SMT technique opened advantages and new applications through miniaturisation of components and increased reliability. 

Multilayer technology is exploited just as for multilayer capacitors (see Section 5.4.3) to EIA size specifications, and inductor chips can be bandoliered ready for surface mounting, typical inductance values lying in the range 1 nH to about 20 /rH. They find important applications as EMI suppressors as well as for a wide range of applications as a lumped circuit component in equipment of all types -communications, entertainment , computers, etc. (see Fig. 9.17). 

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