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What is bill of material?The bill of material(BOM), often referred to as the BOM or electrical BOM, is simply a list. In PCB design, it is a list of all the parts needed to make a particular printed circuit board during the manufacturing process.
What is included in a Bill of Materials?
There are many types of information that can be in a PCB BOM, but parts must have a core set of elements to start with. Here is a list of some of the more core elements you will see in a PCB BOM:
Notes:Each part type on a printed circuit board needs to have a unique identifier, or part number, listed as a note on the bill of materials. Often a company-assigned part number is used as the comment, but this is not required. Supplier component part numbers or other designations may be used as an alternative. An example of a comment could be the company part number “27-0477-03”.
Description:This is a basic description of the part. In the 27-0477-03 comment listed above, the description could be “CAP 10uF 20% 6.3V”.
Indicator: Each individual component on the board has its own unique reference indicator. In the case of a 10uF capacitor, it might be “C27”.
Footprint: This is the name of the physical CAD footprint used by the part. For example, C27 could use a CAD memory named “CAP-1206”.
DIP package (DualIn-linePackage) is also called dual in-line packaging technology, which refers to integrated circuit chips packaged in dual in-line form. Most small and medium-sized integrated circuits use this packaging form, and the number of pins is generally not Over 100.The DIP packaged CPU chip has two rows of pins, which need to be inserted into the chip socket with the DIP structure.
Through dip encapsulation, high-level modules no longer directly call specific methods and attributes in low-level modules, but through the definition of abstract interfaces to access the functions of low-level modules. This is conducive to decoupling, which can avoid code bloat and maintenance difficulties and improve code reuse and scalability.
DIP encapsulation has the following characteristics:
Dependency inversion: the high-level module does not depend on the underlying module, but both depend on the abstraction.
Interface-oriented: high-level modules access the functionality of the underlying module through the interface, rather than directly accessing its concrete implementation.
Loosely coupled: the system becomes loosely coupled as the dependencies between the high-level modules and the underlying modules are lifted. This reduces the impact between modules in the system and facilitates the expansion and modification of functions.
Easy to maintain: Through DIP encapsulation, all modules depend on the abstraction, so when we need to modify a module, we only need to modify the corresponding abstraction without involving other modules.
What is smt?Surface mount technology, called "SurfaceMountTechnology" in English, or SMT for short, is a circuit assembly technology for attaching and soldering surface mount components to a specified position on the surface of a printed circuit board.Specifically,it is to first apply solder paste on the printed circuit board, and then accurately place the surface mount components on the solder paste-coated pads, and heat the printed circuit board until the solder paste melts and cools down. After that, the interconnection between the component and the printed circuit board is realized. In the 1980s, SMT production technology became more and more perfect. The mass production of components used in surface mounting technology resulted in a significant drop in prices. Various types of equipment with good technical performance and low prices appeared one after another. Electronic products assembled with SMT were small in size.
With the advantages of good performance, complete functions and low price, SMT, as a new generation of electronic assembly technology, is widely used in aviation PCBA, aerospace PCBA production, communication PCBA production, computer PCBA production, medical electronic PCBA production, automobile PCBA production, Electronic products smt patch in various fields such as office automation PCBA production and home appliance PCBA production. SMT features, high assembly density, small size and light weight of electronic products. The volume and weight of patch components are only about 1/10 of that of traditional plug-in components. Generally, after SMT is adopted, the volume of electronic products is reduced by 40% to 60%, and the weight is reduced. 60%~80%.
SMD surface mount devices (SurfaceMounted Devices), "In the initial stage of electronic circuit board production, the via assembly is completely completed manually. After the first batch of automated machines are launched, they can place some simple pin components, but complex components are still Manual placement is required for wave soldering. Surface mount components were introduced about twenty years ago, and a new era was created. From passive components to active components and integrated circuits, they eventually became surface mount devices ( SMD) can be assembled by pick-and-place equipment. For a long time, people thought that all lead components could finally be packaged in SMD.
