Electronic packaging is the design and production of enclosures for electronic devices ranging from individual semiconductor devices up to complete systems such as a mainframe computer. Packaging of an electronic system must consider protection from mechanical damage, cooling, radio frequency noise emission and electrostatic discharge. Product safety standards may dictate particular features of a consumer product, for example, external case temperature or grounding of exposed metal parts. Prototypes and industrial equipment made in small quantities may use standardized commercially available enclosures such as card cages or prefabricated boxes. Mass-market consumer devices may have highly specialized packaging to increase consumer appeal. Electronic packaging is a major discipline within the field of mechanical engineering.
Design
Electronic packaging can be organized by levels: Level 0 - "Chip", protecting a bare semiconductor die from contamination and damage. Level 1 - Component, such as semiconductor package design and the packaging of other discrete components. Level 2 - Etched wiring board (printed circuit board). Level 3 - Assembly, one or more wiring boards and associated components. Level 4 - Module, assemblies integrated in an overall enclosure. Level 5 - System, a set of modules combined for some purpose.
The same electronic system may be packaged as a portable device or adapted for fixed mounting in an instrument rack or permanent installation. Packaging for aerospace, marine, or military systems imposes different types of design criteria.
Design and productisation of electronic packages is a multi-disciplinary field based on mechanical engineering principles such as dynamics, stress analysis, heat transfer and fluid mechanics, chemistry, materials science, process engineering, etc. High-reliability equipment often must survive drop tests, loose cargo vibration, secured cargo vibration, extreme temperatures, humidity, water immersion or spray, rain, sunlight (UV, IR and visible light), salt spray, explosive shock, and many more. These requirements extend beyond and interact with the electrical design.
An electronics assembly consists of component devices, circuit card assemblies (CCAs), connectors, cables and components such as transformers, power supplies, relays, switches, etc. that may not mount on the circuit card.
Many electrical products require the manufacturing of high-volume, low-cost parts such as enclosures or covers by techniques such as injection molding, die casting, investment casting, and so on. The design of these products depends on the production method and require careful consideration of dimensions and tolerances and tooling design. Some parts may be manufactured by specialized processes such as plaster- and sand-casting of metal enclosures.
In the design of electronic products, electronic packaging engineers perform analyses to estimate such things as maximum temperatures for components, structural resonant frequencies, and dynamic stresses and deflections under worst-case environments. Such knowledge is important to prevent immediate or premature electronic product failures.
Design considerations
A designer must balance many objectives and practical considerations when selecting packaging methods. Hazards to be protected against: mechanical damage, exposure to weather and dirt, electromagnetic interference, etc. Heat dissipation requirements Tradeoffs between tooling capital cost and per-unit cost Tradeoffs between time to first delivery and production rate Availability and capability of suppliers User interface design and convenience Ease of access to internal parts when required for maintenance Product safety, and compliance with regulatory standards Aesthetics, and other marketing considerations Service life and reliability
Packaging materials
Sheet metal
Punched and formed sheet metal is one of the oldest types of electronic packaging. It can be mechanically strong, provides electromagnetic shielding when the product requires that feature, and is easily made for prototypes and small production runs with little custom tooling expense.
Cast metal
Gasketed metal castings are sometimes used to package electronic equipment for exceptionally severe environments, such as in heavy industry, aboard ship, or deep under water. Aluminum die castings are more common than iron or steel sand castings.