SMD package

Fig. 3. Detail measuring setup for pnit optimal distance between optical PIN photodiode in SMD package and output facet of the planar optical pwlymer waveguide...

Presentation of criteria for all the various SMD package types and aU of the possible solder joint problems is beyond the scope of this chapter. The reader is directed to HoUomon (1995), Hwang (1989), Lau (1991), Klein-Wassink (1989), and Prasad (1997) for an in-depth discussion on these issues. 

Broadly speaking, the machines have much the same periphery as those for SMD placement. They can be coupled to component feeders for the common types of SMD package or for special types (e.g., bare die). There are gripping tools for all the various types of package. Most of these tools are variations on the vacuum-pipette principle. The robots have the requisite interfaces and conveyor belts for integration into production lines. 

Pricing as well as reliability considerations have led to an almost exclusive use of Si-based (i.e. Si and SOI) micro machined devices. Packaging and assembly has focused on ceramics (A1203, AIN, Low Temperature Co-fired Ceramics LTCC), Printed Circuit Board (PCB-) and Surface Mount Device (SMD-) technology and multichip modules (MCM s). 

NTCs are available as SMD resistors (surface mounted divices), as well as in special packages like glass-coated or fitted to lead frames. The size of the NTC can be as small as 1 mm x 0.5 mm x 0.6 mm (and smaller) or there are discs of 25 mm diameter [1],... 

Jagt JC, Beric PJM, Lijten GF. Electrically conductive adhesives a prospective alternative for SMD soldering. IEEE Trans Comp, Packaging, Mfg Tech 1995 18(2) 292-298. Part B. 

XyFlexPro / Speedline Technologies (7100) 13 X 10 (7200) 19 X 22 1.0 Single-head dispenser/ 30,000-120,000 (application dependent) Semiconductor packaging or surface mount SMD adhesive Amic[Pg.234]

Jagt, J. C., Beric, P. J. M., and Lijten, G. F., Electrically Conductive Adhesives A Prospective Alternative for SMD Soldering, IEEE Trans. Components, Packaging, andMfg. Tech., Part B 18(2) 292—298 (1995)... 

The new user of surface mount designs (SMDs) must rapidly learn the packaging sizes and types for SMDs. Resistors, capacitors, and most other passive devices come in two-terminal packages, as shown in Fig. 11.17, which have end-terminations designed to rest on substrate pads/lands. 

Basic SMD ICs come in a wide variety of packages, from 8-lead small outline packages (SOLs) to 208-lead quad flat packs (QFPs). Examples ofSO20 and QFP128 packages are shown in Fig. 11.18. 

Plastic leaded chip carrier (PLCC) Shown in Fig. 11.18, it is a mature SMT IC package and is the only package that has the leads bent back under the IC itself Planarity Lying in the same plane. A plane is defined by the exit of the leads from the body of the IC. A second plane is defined at the average of the lowest point aU leads are below the first plane. Nonplanarity is the maximum variation in mils or miUimeters of any lead of an SMD from the lowest point plane. 

FIGURE 58.16 Solder-mask defined (SMD) and non-solder mask defined (NSMD) pad construction. For optimum reliability, the pad size on the PWB should be kept within 80 to 100 percent of the wetted pad area on the package side. This allows the stresses to be vectored equally between both ends of the solder joint, and it the PWB pad is slightly smaller, it allows a slightly higher stand off height, which also tends to enhance solder joint reliability. 

For packages with solder joint pitches less than 0.8mm, a mix of NSMD and SMD pads is sometimes inevitable. At small pitches, it is difficult to route the traces from the pads in the typical dog bone fashion.Thus, to allow routability, the common power and ground pads are bussed together to form one large pad.The connected pads are SMD, whereas the individual signal pads are kept NSMD. 

Typical applications include small parts such as fuel filters, check valves, aerosol cylinders, tubes, and containers. Spin welding is also a popular method of joining large-volume products such as packaging and toys. Spin welding can also be used for attaching smds to plastic parts. 

The MID package is the key to miniaturization of the overall system. Assembly is streamlined by the use of MID technology, because in this case the entire component is an SMD. 

CMCs Chip resistors SMD transistors SO package types QFP package tjqjes Electroplated pure tin... 

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