EN 62739-3-2017 pdf download.Test method for erosion of wave soldering equipment using molten lead-free solder alloy – Part 3: Selection guidance of erosion test methods (IEC 62739-3:2017).
Surface processing is classified as surface diffusion type which Is forming a surface process layer by diffusing nitrogen (for example) into material and coating type which is forming a coating layer on the surface of the mater material. Examples of each type are given below.
a) Surface diffusion type: nitrogen supersaturated solid solution diffusion treatment, diffusion penetration nitriding, gas nitriding, nitrocarburizing. plasma nitriding
b) Coating type: fine ceramic coating by chemical densified process, CrN coating by a Physical Vapor Deposition (PVD) method, and alumina coating by thermal spray.
NOTE The erosion mechanism of the test is explained in Annex C.
6 Common items for each test method
6.1 Specimen preparation
The specimens shall be prepared as indicated below.
a) Basically, specimen shaping shall be carried out by punching, using a press machine. However, for high hardness materials such as titan and cast iron which are not suitable for punching, shaving shall be used.
b) Specimen edge burrs, etc., which are produced during specimen shaping and may cause erosion, shall be removed by chamfering and such:
C) if necessary, surface processing shall be done after processes a) and b).
d) Care shall be taken to handle the specimen after fabrication, so as not to contaminate the specimen by oil, or other contaminants, since this could affect the test result.
6.2 Solder alloy
Unless otherwise specified, Sn96,5Ag3Cu,5 solder alloy specified in IEC 61190-1-3 shall be used. If Sn purity is too high, erosion occurs after a short time and inaccurate results may be the consequence.
6.3 Accelerated stress conditions
6.3.1 Test temperature
The test temperature is specified as 350 °C ± 3 C in IEC 62739-1 and 450 C ± 3 °C in IEC 62739-2. These test temperatures are determined so as to clearly identify the non-erosion area which is used for the baseline of the erosion depth by the focal depth method and to differentiate metal material and surface processing employed by erosion the depth on the specimen. A sufficient test duration for metal material shall be pre-set, suitable for each metal material and surface processing (see Annex A).
6.3.2 Rotation speed
The speed difference between molten solder alloy and the specimen by rotating the specimen is assuming the molten solder flow speed in the wave soldering equipment. A rotation speed of 100 r/mln ± 3 r/min is specified for all test methods. If the rotation speed is slower than the specified value, then the molten solder flow speed is lower than the speed in the actual production process. Thus, this condition is not recognized as an acceleration factor of the molten solder flow speed in the actual production process. If the rotation speed is higher than the specified value, then the molten solder begins to rotate and the relative speed difference between the molten solder and the specimen becomes minimal. This condition is also not recognized as an acceleration factor of the molten solder flow speed in the actual production process.
NOTE An example of a lest result Is shown In FIgure A.3.
6.3.3 Bending stress to the specimen
If it takes too long during the rotation test at 450 °C, further acceleration is needed. During the rotation test at 450 C with 2 mm bending specified in IEC 62739-2. the specimen Is subjected to bending stress as additional acceleration. 1 mm bending stress is not enough to accelerate occurrence of erosion (see Clause A.2), Bending stress exceeding 2 mm gives permanent deformation of the specimen, thus the erosion depth measurement by the focal depth method becomes difficult.
6.4 Dross
6.4.1 Dross generation and removal interval
The higher the test temperature and the higher the rotation speed, the more dross is generated due to the promoted oxidation of molten solder. Compared to the amount of dross produced by the rotation test at 350 °C the rotation test at 450 °C, generates more dross. However, by removing dross every 16 h. both tests can be run without problems such as firing and overflowing.EN 62739-3-2017 pdf download.