Packaging levels

Prasher RS, Chang JY, Sauciuc 1, Narasimhan S, Chau D, Chrysler G, Myers A, Prstic S, Hu C (2005) Nano and micro technology-based next-generation package-level cooling solutions. Intel Technol J 4(4) 285-296... 

It is often useful to manage dependencies on the package level, checking that the number of dependencies from and to any one package is not too large. 

Section 7.4 discusses package-level decoupling. Design patterns (such as Pattern 16.15, Role Decoupling, or Pattern 16.17, Observer) provide specific techniques for decoupling. 

Within this book, we assume that variables are typed, that access can be controlled at the package level, and that variables contain implicit references—in other words, the scheme followed by Java, Eiffel, and others. 

Figure 7.25 Package-level beta and release versions.

Draw dependency diagrams (see Section 7.4, Decoupling with Packages) between operations, classes, packages, and components. Study the package-level dependencies and seek ways to refactor across packages to reduce coupling. 

Although the primary thermal transport mechanisms and the commonly used heat removal techniques vary substantially from one packaging level to the next, in general, heat removal can be addressed hierarchically. The first level of the hierarchy is at the chip package (IC) level where heat conducts from the chip or component to the package surfaces through interface materials and is then rejected from the outer surfaces (heat sink and the board) into ambient air (Figure 4). 

The analytical requirements in IC processing equal or surpass those of any other industry and present a formidable problem to the analyst. The fabrication of a semiconductor device Involves interaction of materials, processes and environment to produce a complex, geometrical configuration of many materials. When processed through to the package level a typical IC is a composite of semiconductors, metals, ceramics and polymers containing over a dozen distinct materials. 

Design to avoid secondary, tertiary, and additional packaging levels. 

Reduce the rise in temperature and control the variation in the device operating temperature across all the devices, components, and packaging levels in the system. 

Labor costs estimates are normally entered at the work package level. The costs are aggregated successively at the higher WBS levels to provide the total project labor costs in the end. 

Direct costs are also entered at the work package level for items acquired by direct purchases. Direct costs include normally different types of cost items such as material, equipment, or contract workers. 

In order to specify project resource requirements, it is helpfid to examine each work package element in the project work break down structure (WBS) depicted in Fig. 12.7. The elements of the work package level are considered to determine the resource and the effort required to fiilfill specified project work. Project planners start here by attaching different names to the project work packages, specify a resource type, and level of resource qualification required. In order to realize this, three steps are required ... 

First, it is essential to review each WBS work element at the project work package level. This is realizable by determining the type of work required to be accomplished and align a competent resource with the effort. At this level, work efforts are generally separate and distinctive. Afterwards, any resource specified at the work package level is accounted for upwards throughout the project. This first step results in a preliminary resource requirement matrix. 

Upon completion of project resource utilization, the resources are finally entered into the WBS at the work package level. This compilation enables the specification of the total project staff strength for all project elements and activities. Therefore, the number of resources are represented which are requested for the staffing allocation (Barratt 2004). 

It is important to note that a major role of solder in area array solder joints at the chip and package level is to accommodate plastic strain without cracking that is, the solder is a plastic strain absorber. This implies that weak solders are potentially good candidates for this application. It has been demonstrated that solders with low shear strengths exhibit the greatest thermal cycling lifetimes [124], and this explains the lower thermal mechanical fatigue resistance of tin-based solders compared to lead-based solders (Table 5). 

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