DIN EN 60068-3-13:2017-04

This Part 3-13 of the 60068 series of standards contains background information and recommendations for authors and users of specifications for electrical and electronic components. Reference is made to the test standards IEC 60068-2-20, IEC 60068-2-54, IEC 60068-2-58, IEC 60068-2-69 and IEC 60068-2-83 as well as to IEC 61760-1, which defines the requirements for the specifications of surface mounting components. After clarifying basic terms such as solderability, solder heat resistance and wettability, an introductory chapter is devoted to the factors that influence the ability to solder. The conditions on which the problem-free production and reliability of a soldered joint depend can be divided into three groups. On the one hand, these are the design of the joint, determined by the choice of the two metallic elements to be joined (their shape, size, composition, etcetera) and the manufacturing method (relative position, initial fixing, etcetera) and, on the other hand, the wettability of the surfaces to be joined and the conditions assumed for the soldering process (temperature, flux, solder alloy, equipment, etcetera). Further clauses deal with the physics of surface wetting, the quality and reliability of soldered joints. The chapter on workability of components in soldering processes or soldering explains that it is not sufficient for a component to have connections that are suitable for soldering (can be wetted by molten solder). Currently, various types of soldering processes and solder alloys are used in the manufacture of electronic equipment. Due to the introduction of lead-free solder, processing temperatures today can vary in a range of more than 100 degrees and can last from seconds to minutes. Due to the wide variety of process conditions, a component can no longer simply be classified as suitable for, for example, "wave soldering" or "reflow soldering" or "lead-free soldering". Particular attention should be paid to the fact that the suitability of a component for "lead-free soldering" cannot be specified due to the variety of lead-free solder alloys and process conditions. Other clauses deal with the solder, the classification of soldering conditions, the suitability for soldering, the moisture sensitivity of the components and the relationship between storage time / storage conditions and solderability. The soldering tests deal with the typical conditions for soldering processes, the function of the tests with regard to industrial soldering processes and the reasons for the choice of test conditions. Industrial soldering conditions in electronics vary considerably, but it is generally not necessary to use different types of components to fulfill the different assembly conditions. It is thus possible to classify the conditions of industrial soldering of components within reasonable, narrow limits. Further clauses are devoted to the topics of solder alloy, flux, test equipment, evaluation methods and acceptance criteria. The purpose of solder tests is explained in the chapter on solder test methods. Components and solder shall be brought together under controlled conditions in such a way that the quality of the wetting can be assessed according to the defined criteria. Basically, soldering time tests are estimates of the time required for the contact angle to reach a uniformly low angle at all points of the solder boundary. For some tests, this condition is only estimated by visual inspection. Others measure the time. Completely quantitative tests are those in which both the time and the force acting on the test specimen due to the surface tension of the solder are measured. If the contact is prolonged, then the contact angle can increase again under certain circumstances and the solder can retract from the surface of the test specimen. This phenomenon is known as dewetting. Some of the test methods include an examination for dewetting. If the possibility of dewetting is a concern, then the relevant specification should require this to be included. Further clauses deal with the topics overview of the test methods, solder bath test, melting test, soldering iron test, solderability and wetting balance. The wetting balance test method allows the vertical forces acting on a test piece to be measured as a function of time when it is immersed in a bath or ball of molten solder. The wettability of the test specimen is derived as the time to reach a specified degree of wetting or as the degree of wetting achieved within a specified time. Some metallic surfaces are easier to solder than others. They differ both in the wetting speed and in the adhesion force of the solder to their surface. The wetting speed depends on the combined effects of the heat requirement and the wettability of the metal surface. These combined properties are known as the solderability of the material. The wettability of the same material can vary considerably as it is highly dependent on the condition of the metal surface. Thin films of oxide, grease or organic contaminants can severely impair the wettability of a metal. With the introduction of lead-free solder processing, many new surface finishes are now in use and these have different wettability characteristics as well as different susceptibility to deterioration under different environmental conditions. A final chapter of the standard explains the requirements and statistical nature of the results. By explaining the basic concept, the guide helps the author and the user of the specification to select a particular method and to understand the exact meaning of the results obtained. DKE/K 682 "Packaging and interconnection technology for electronic assemblies" of the DKE German Commission for Electrical, Electronic & Information Technologies in DIN and VDE is responsible. The responsible committee is DKE/K 682 "Aufbau- und Verbindungstechnik für elektronische Baugruppen" ("Packaging and interconnection technology for electronic assemblies") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.