DIN EN 61191-2:2014-02

This part of IEC 61191 describes 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 (for example, throughhole, chip mounting, terminal mounting, etcetera). This standard recognizes that electrical and electronic assemblies are subject to classifications by intended end-item use. Three general end-product classes have been established to reflect differences in producibility, complexity, functional performance requirements, and verification (inspection/test) frequency. These are the following: - Level A: General electronic products - Level B: Dedicated service electronic products - Level C: High performance electronic products The user of the assemblies is responsible for determining the level to which his product belongs. It should be recognized that there may be overlaps of equipment between levels. The contract shall specify the level required and indicate any exceptions or additional requirements to the parameters, where appropriate. Clause Surface mounting covers the 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. Regarding the 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 7.3 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. Clause Surface mounted component requirements describes that 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. Regarding the lead component positioning it shall be taken into account that parts may be flush mounted, without clearance, if they are positioned over protected surfaces or insulated parts. Parts mounted over exposed circuitry shall have their leads formed to provide a minimum of 0,25 mm between the bottom of the component body and the exposed circuitry. The maximum clearance between the bottom of the leaded component body and the printed wiring surface shall not exceed 2,0 mm. The responsible committee is DKE/K 682 "Montageverfahren für elektronische Baugruppen" ("Electronics assembly technology") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.