Surface-mounted packages

Table A-3 Typical Surface Mount Package Thermal Resistances...

Vishay-Siliconix (1992). Low voltage motor drive designs using n-channel dual MOSFETs. In Surface Mount Packages. Application Note AN802, ( htq> //www.vlshay.com/doc 70592) Vishay Intertechnology Inc., Malvern, Pa. 

Introduction Surface Mount Packages Chip-Scale Packaging... 

Plastic surface mount packages result in a device that is light, small, able to withstand physical shock and g forces, and inexpensive due to a one-step manufacturing process. The plastic is molded around the lead frame of the device. Work is still continuing on developing coatings for the die, such as polyimide, which may resolve hermeticity problems and coefficient of thermal expansion mismatches between the die and the plastic package. 

Surface mount packages (and related packaging terms) include the following. 

Flatpack (or quad flatpack), one of the oldest surface mount packages, used mainly on miHtary programs. Typically, flatpacks have 14—50 leads on both sides of the body on 0.050-in centers. 

FIGURE 40.11 Photographs of (a) peripherally leaded and (b) area-array surface-mount packages. (Courtesy ofSandia National Laboratories.)... 

The laser has proven to be a versatile tool in many industries. For circuit board assembly, it can be used for marking, single-point soldering, or rework. Lasers can accommodate bonding of the finest or coarsest peripherally leaded surface-mount packages, and its performance and applicabUity are independent of device population density on the board, the thickness of the printed circuit board, or the presence or absence of package heat sinks. It can be used with most any component lead or PWB pad surface finish and any solder, including Pb-free alloys. 

JEDEC JESD-51-3 Low Effective Thermal Conductivity Test Board for Leaded Surface Mount Packages... 

JEDEC JESD-51-9 Test Boards for Area Array Surface Mount Package Thermal Measurements... 

If components are exposed to a chemically hostile environment, the leakage path will be extremely important because it enables ionic species to reach the die. Users of the increasingly popular surface mounted packages are likely to have to pay particular attention to this hazard. For these packages, the leadframe is shorter than in the... 

Electrolytic capacitors are very susceptible to high-temperature damage, as are wound components, such as relays [2]. Surface mount packages are not rated for temperature exposures beyond 230°C, but some survive up to about 250°C, and a few beyond that temperature. Pin-in-hole components are typically rated to survive up to 260°C. In standard reflow assembly practice, the solder liquidus temperature is less than 200°C (e.g., eutectic Sn-Pb, mp = 183°C) and the reflow temperature is t5q)icaUy below 230 °C. 

Peripherally leaded, surface mount packages use lead materials of Cu or an Fe-Ni alloy with a Ni solderable finish and an electroplated Pb n or Sn protective layer. Leadless chip devices have terminations comprised of a fired-on Ag thick film conductor that is overplated with a Ni or Cu solderable coating, followed with an electroplated Pb-Sn protective finish. Leadless ceramic chip components (LCCC) use castellated terminations with a thick-fihn Au finish. 

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