SMT007 Magazine

SMT007-Sept2019

Issue link: http://iconnect007.uberflip.com/i/1161956

Contents of this Issue

Navigation

Page 69 of 117

70 SMT007 MAGAZINE I SEPTEMBER 2019 There is another option for a company if you want to use a standard as a specification. You can use industry standards as specifica- tions for most of your requirements to keep your costs down and use your custom specifi- cations to meet requirements for your specific applications. IPC makes this easier for having the standards meet three classes of require- ments: Class 1, 2, and 3. Class 1 is for non-crit- ical consumer applications. Class 2 is recom- mended for industrial and office applications and is the most common class used. Class 3 is for very critical applications such as military and space. Again, you can add custom require- ments to any of these classes if you want to use them as a specification for your company, but it is important to remember that industry organizations do not develop specifications; the user develops their own specification for use by them and their suppliers. As noted earlier, since it is required to get the input from IPC members across the globe, standards take time; they can take two to three years. By the time they are released, the tech- nology may have changed. To address those changes, it is not uncommon to proceed with the next revision of that standard. Some of the most common standards are now in their ninth and tenth revisions; IPC-610 is a good example. Meanwhile, specifications can be released very quickly. They are developed by a single company to meet and address their particu- lar requirements but not to solve world hun- ger or fit the entire industry, as is the case for a standard. However, if your specification strays away too far from the standards, you better be prepared to pay for it. And you will have fewer and fewer suppliers who may be able to meet your unique requirements. Common Standards in the SMT Industry: IPC, EIA, and J-STD There are various types of standards in the SMT industry, but the most commonly used are IPC, EIA, and JEDEC standards. IPC, with membership from users across the globe, sets standards for PCBs, assemblies, interconnect designs, and manufacturing processes as well as acceptability and process control. There are over 300 active IPC standards covering almost every stage of electronics product manufactur- ing from PCB laminate materials to assembled printed circuit board assemblies (PCBA). IPC standards are accepted worldwide since they are created by participants across the globe. EIA is a trade organization of electronic com- ponent manufacturers. Various committees of EIA establish outlines for passive and electro- mechanical components. JC-11 committee of the Joint Electronic Device Engineering Coun- cil (JEDEC)—part of EIA—is chartered to estab- lish a mechanical outline for packages of active devices. Similarly, various "P" or parts commit- tees of EIA are responsible for setting standards for the mechanical outlines of passive devices. One of the main complaints about EIA and JEDEC standards by user groups tend to be loose tolerances of packages. This makes land pattern design by the users very difficult. How- ever, it is worth noting that to address these and many other issues to promote SMT, both IPC and EIA, to their credit, formed a Surface Mount Council in the mid-1980s. As one of the members of Surface Mount Council, I can say with certainty that the component tolerances today, which are not perfect by any means, are way better than what was the case then. You probably also know about some very popular standards known as J-STDs. In the early days of SMT, both IPC and EIA used to develop some overlapping standards with con- flicting requirements for acceptability, solder- ability, and baking and handling of moisture sensitive components. Conflicting require- ments only confuse users and suppliers and As noted earlier, since it is required to get the input from IPC members across the globe, standards take time; they can take two to three years.

Articles in this issue

Archives of this issue

view archives of SMT007 Magazine - SMT007-Sept2019