The solderability of the coating indicates the ease with which solder flows on the surface of the metal to be soldered. Methods to evaluate the weldability of coatings include flow area method, wetting time method and steam test method.

Flow area method: This method is to place a certain mass of solder on the surface of the sample to be tested, add a few drops of rosin isopropyl alcohol, place it on a hot plate and heat to 250℃, keep it for 2 minutes, remove the sample, and then Use an area meter to check and calculate the solder coating area. Evaluation method: The larger the distribution area, the better the coating welding.

Wetting time method: This method distinguishes solderability by the time it takes for the molten solder to completely wet the specified sample. During the test, 10 specimens of a certain specification are first immersed in rosin propyl alcohol flux, and then immersed in 250℃ molten solder. The immersion time is controlled for 1~~10S according to 10 specimens with different numbers, and then taken out immediately. After cooling, check whether the sample is completely wetted. After taking out the sample, evaluate the welding performance of the coating based on the shortest time it takes for the sample to be fully wetted. Generally speaking, it is considered good if everything is wetted within 2s, and worst if it is wetted within 10s.

Steam test method: In this method, the sample is placed on the continuous water surface, and the melter cover is shaped to prevent condensed water on the cover from dripping on the surface of the sample and affecting the test. The distance between the sample and the boiling water is 100mm, and the distance between the sample and the top cover is 50mm. After 240 hours, regardless of whether the sample changes color or not, let the sample dry in the air, and then test it with the flow area method or wetting time method, and evaluate whether it is qualified or not based on the results.