IEC 61191-2:2017 pdf download

IEC 61191-2:2017 pdf download.Printed board assemblies – Part 2: Sectional specification – Requirements for surface mount soldered assemblies
1 Scope
This part of IEC 61 1 91 gives the requirements for surface mount solder connections. The requirements pertain to those assemblies that are totally surface mounted or to the surface mounted portions of those assemblies that include other related technologies (e.g. through- hole, chip mounting, terminal mounting, etc.).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 601 94, Printed board design, manufacture and assembly – Terms and definitions IEC 61 1 91 -1 , Printed board assemblies – Part 1: Generic specification – Requirements for soldered electrical and electronic assemblies using surface mount and related assembly technologies IPC-A-61 0, Acceptability of Electronic Assemblies
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 601 94 apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: • IEC Electropedia: available at http://www.electropedia.org/ • ISO Online browsing platform: available at http://www.iso.org/obp
4 General requirements
The requirements of IEC 61 1 91 -1 are a mandatory part of this specification. Workmanship shall meet the requirements of IPC-A-61 0 in accordance with the classification requirements of this document.
5 Surface mounting of components
5.1 General This clause covers assembly of components that are placed on the surface to be manually or machine soldered and includes components designed for surface mounting as well as through-hole components that have been adapted for surface mounting technology.5.2 Alignment requirements Sufficient process control at all stages of design and assembly shall be in place to enable the post-soldering alignments and solder joint fillet controls specified in 6.3 to be achieved. Relevant factors affecting the requirements include land and conductor design, component proximities, component and land solderability, solder paste/adhesive quantity and alignment and component placement accuracy. 5.3 Process control If suitable process controls are not in place to ensure compliance with 5.2 and the intent of Annex A, the detailed requirements of Annex A shall be mandatory. 5.4 Surface mounted component requirements The leads of lead surface mounted components shall be formed to their final configuration prior to mounting. Leads shall be formed in such a manner that the lead-to-body seal is not damaged or degraded and that they may be soldered into place by subsequent processes which do not result in residual stresses decreasing reliability. When the leads of dual-in-line packages, flatpacks, and other multilead devices become misaligned during processing or handling, they may be straightened to ensure parallelism and alignment prior to mounting, while maintaining the lead-to-body seal integrity. 5.5 Flatpack lead forming 5.5.1 General Leads on opposite sides of surface mounted flatpacks shall be formed such that the non-parallelism between the base surface of the component and the surface of the printed board (i.e. component cant) is minimal. Component cant is permissible provided the final configuration does not exceed the maximum spacing limit of 2,0 mm (see Figure 1 ).5.5.3 Surface mounted device lead deformation Lead deformation (unintentional bending) may be allowed when a) no evidence of a short circuit or potential short circuit exists, b) lead-to-body seal or weld is not damaged by the deformation, c) does not violate minimum electrical spacing requirement, d) top of lead does not extend beyond the top of body; preformed stress loops may extend above the top of the body; however, stand-off height limit shall not be exceeded, e) toe curl, if present on bends, shall not exceed two times the thickness of the lead (2 T), f) coplanarity limits are not exceeded. 5.5.4 Flattened leads Components with axial leads of round cross-section may be flattened (coined) for positive seating in surface mounting. If flattening is used, the flattened thickness shall be not less than 40 % of the original diameter. Flattened areas of leads shall be excluded from the 1 0 % deformation requirement in 6.5.3 of IEC 61 1 91 -1 :201 3. Flattened leads on opposite sides of a surface mount part shall be formed such that the non- parallelism between the base surface of the component and the surface of the printed board (e.g. component cant) is minimal.