Overview

This part 2-83 of IEC 60068 provides methods for comparative investigation of the wettability of the metallic terminations or metallized terminations of SMDs with solder pastes. Data obtained by these methods are not intended to be used as absolute quantitative data for pass-fail purposes. Decisive definitions used in this standard are wettability, that is the ease with which a metal or metal alloy can be wetted by molten solder, the wetting balance method, a method to measure wetting performance and solderability by measuring vertical force to the specimen and recording as a function of time, when the specimen is immersed into molten solder, starting point of heating, that is the time of the start of temperature rise by heating the solder paste applied to a testing jug. The terms and definitions from IEC 60068-1, IEC 60068-20:2008; IEC 60068-2-58, IEC 60194 and IEC 61190-1-3 apply in addition. During the test, the specimen is attached to a suitable holder and hung onto a sensitive weighing instrument. The specimen is immersed into the solder paste applied to a testing jug; subsequently the solder paste is heated until it melts. The resulting force from buoyancy and surface tension acting on the immersed solder termination is detected by a transducer and transformed into a signal. This is continuously recorded as a function of time and recorded on a high speed recorder or shown on a screen. The wetting force can only be evaluated for specimens of the same shape and size. An absolute evaluation cannot be achieved with this method. Three methods are described whereby the method to be applied shall be specified in the applicable regulation: - quick heating method: the solder paste is melted during a quick temperature rise and wettability of the electronic component terminations is evaluated. The specimen is immersed into the solder paste prior to the temperature rise. - synchronous method: the solder paste is melted by means of a quick temperature rise and wettability of the electronic component terminations is evaluated. The specimen is immersed into the solder paste at the beginning of the temperature rise. - temperature profile method: the solder paste is melted analogously to a temperature profile used in manufacturing and wettability the electronic component terminations is evaluated. This test (Tf) can also be used on electronic components for surface mounting with leads. In order to achieve comparable and repeatable test results, test Tf should be carried out on straight terminations. This standard does not specify solder pastes to be used. During the test the vertical force acting on the specimen is recorded. An upward force (compressive force or buoyancy) is represented as a negative value; a downward force (wetting force) is represented as a positive value. In Annex A the equipment for the quick heating and synchronous methods is described. This includes the measurement system, the heating system and the lifting device; Annex B describes the reading of the output data and correction of the results in the quick heating test. In Annex C the test equipment for the temperature profile method and in Annex D the reading of the output data and correction of the result in the temperature profile test are explained. Annex E contains caveats/notes on the influencing factors, such as solder pastes, electronic components and provides information regarding the assessment of the results. Different solderability test methods for SMD are described in IEC 60068-2-58 and IEC 60068-2-69. IEC 60068-2-58 prescribes visual evaluation (solder bath and reflow method), IEC 60068-2-69 wetting balance evaluation (solder bath and solder globule method). The responsible committee is K 682 "Montageverfahren für elektronische Baugruppen" ("Electronics assembly technology") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.

Document: references other documents

Responsible national committee

DKE/K 682 - Aufbau- und Verbindungstechnik für elektronische Baugruppen