Preparation method of aluminum-based brazing filler metal with low melting point

The invention relates to aluminum-based brazing filler metal with a low melting point and a preparation method thereof. The aluminum-based brazing filler metal with the low melting point comprises the following components in percentage by mass: 9.0 to 13 percent of Si, 78 to 87 percent of Al, 4 to 9 percent of Cu, 0.03 percent of Sr and 0.03 percent of La. The method for preparing the aluminum-based brazing filler metal with the low melting point comprises the following steps of: melting the weighed components in a vacuum melting furnace to form a master alloy ingot; rolling the master alloy ingot on a rolling machine to prepare a band with a thickness of 0.1 millimeters and a width of 200 millimeters; cleaning the rolled band in an NaOH groove, an HCI groove and hot water; after a surface oxide layer of the band is cleared, putting the band into a bluestone plating tank at the temperature of between 25 and 30 DEG C and using the band as a cathode; applying a direct current of between2 and 5V to the tank; electrifying for 20 to 30 minutes; making the filler metal surface of the cathode face an anode alternatively during an electrifying process and continuously stirring the solution; and after electrification, taking the filler metal out, putting the filler metal into washing liquid to clean the filler metal and drying the filler metal.