PV ribbon tin coating process, including the following steps:
(1) substrate selection: selecting an oxygen-free copper strip as the substrate, which is either a bi-plane solder strip or a heterogeneous copper strip;
(2) plating: the selected substrate is placed in a silver plating solution, tin-lead alloy or pure tin plating solution for plating, the thickness of the alloy plated on 0 to 8 μm, that is, the bottom solderable layer;
(3) Solder paste coating and printing: the substrate plated with a good bottom solderable layer in step (2) is coated and printed with solder paste, the specific process of which is:
Preparation of solder paste: select 4 to 6 levels of particle size, viscosity range of 150 ± 5% Pa.s or 190 ± 5% Pa.s of solder paste modulation spare;
Application of solder paste layer: the prepared solder paste is applied to the plated substrate plane by means of roller, printing, spraying or pad printing; a solder paste layer of 20μm to 50μm is formed, which can form a solderable layer;
Black photovoltaic solder tape process steps: for the substrate with embossing, require the solder paste coating and the shape of the substrate plane consistent, not in the groove; for the substrate with oblique V groove, require the solder paste coating and non-oblique edge of the substrate plane consistent, not on the oblique edge; for the double plane of the solder tape, require the solder paste coating on the substrate plane to form a regular pattern, the shape is not limited, the area occupied by the plane part of 30 to 60 per cent;
Preparation of solder joints: the substrate coated with solder paste in step (3) is heated and melted by a high-temperature furnace or by hot air, with the peak heating maintained at 160°C to 230°C. After 15s to 20s, a solder joint with a thickness of 10μm to 25μm is formed in the plane area, i.e. the entire tin coating process is completed.
As a preference, in step (2) plating link, the specific tin coating process is:
Placing the selected substrate in a silver plating solution, a tin-lead alloy plating solution, or a pure tin plating solution;
Plating tin or tin-lead for 60s to 90s at a temperature of 30°C and a current density of 20ASD to 26ASD;
To cover the surface of the substrate with a dense tin or tin-lead alloy plating layer with a thickness of 0 to 8 μm and a bright surface;
After the plating is done, the solder tape is cleaned, dried and ready for use.
Preferably, in step (2), the surface of the substrate is plated with a bright silver layer, and the thickness of the layer is 1μm to 4μm.
Preferably, in step (3), the solder paste is selected: tin-lead solder paste, tin-silver-copper solder paste, tin-bismuth silver solder paste or tin-bismuth solder paste. And each of its components according to the mass percentage are:
said tin-silver-copper solder paste of each component according to the mass percentage of Sn3Ag0.5Cu;
Preferably, each component of said tin-bismuth silver solder paste is Sn35Bi1Ag by mass percentage;
Preferably, the components of said tin-bismuth solder paste are Sn37Pb by mass percentage; wherein Sn is a residual amount.