PV Ribbon is an important raw material in the welding process of photovoltaic modules. The quality of the PV ribbon will directly affect the collection efficiency of the PV mould current, which has a great impact on the power of the PV module.
How to choose PV ribbon?
The PV ribbon must be welded firmly in the process of connecting the cells in series to avoid the occurrence of false welding. When choosing the PV ribbon, it is important to decide the state of the tape. According to the characteristics of the selected cell. The width of the solder tape should be the same as the width of the main deletion line of the battery. The softness or hardness of the solder tape generally depends on the thickness of the cell and the soldering tool.
Manual welding requires the softer the condition of the welding tape, the better. And the soft state of the solder tape will be well in contact with the cell after the soldering iron walks over it. Then the stress generated during the soldering process is minimal, which can reduce the fragmentation rate. However, too-soft welding tape will have lower tensile strength and can be easily pulled off.
For the automatic welding process, the welding tape can be slightly stiffer, which is conducive to the welding machine straightening. And press the welding tape, too soft welding tape with the machine is easy to deform, thus reducing the product yield.
Leaded solder tape is relatively easy to solder. Generally, as long as you choose the right flux, soldering iron temperature compensation is enough on it.
How to solder lead-free?
But lead-free solder tape is really a lot of trouble when soldering. First, lead-free soldering to choose a suitable soldering iron. For manufacturers, it is a good choice to choose a lead-free soldering station with adjustable power. Lead-free soldering stations are generally DC-powered. Voltage adjustable, DC soldering iron has the advantage of fast temperature compensation, which is incomparable to AC temperature regulating iron. Lead-free soldering tape welding according to the thickness and area of the battery cell should choose 70-100w soldering iron, less than 70w soldering iron will generally have problems in lead-free welding.
How to Lead-free soldering?
In addition, many kinds of lead-free temperature-controlled AC soldering irons (thermal magnet control) on the market are not suitable for soldering large areas of battery cells. Because the silicon of the cell has good thermal conductivity. The heat of the soldering iron tip will be quickly transferred to the silicon. Instantly lowering the temperature of the iron tip to below 300 degrees. And the temperature compensation of the soldering iron is not enough to ensure that the temperature of the iron rises to 400 degrees. It cannot guarantee the solidity of lead-free soldering. The phenomenon that arises is the cracking sound of the cell during the welding process. And the serious one immediately makes the cell crack. It is caused by the shrinkage stress caused by the low temperature of the solder.
Lead-free soldering iron tip oxidation is very fast, to keep the iron tip clean, in the heating state is best to bury the iron tip into the solder. Before use shake off the iron tip excess solder. The contact end of the iron tip and the solder tape should be repaired to the same width as the solder tape as far as possible. Then the contact surface should be flat. The soldering flux should be lead-free and residue-free flux.
How to properly use lead-free solder tape?
How to choose the electric soldering iron?
Lead-free solder tape is divided into many kinds according to the composition of the coated solder. And the most widely used lead-free solder in China is 305 solder, which contains 3% silver and 0.5% copper. The advantage of this type of solder is good solderability, high solder, a melting point is 218 ℃. And it used in the welding of battery cells on the welding temperature requirements are very high. The ordinary internal heating type soldering iron is difficult to meet the temperature requirements. Therefore, the soldering of lead-free solder tape to use high power soldering iron. The general recommended principle is 30-40W higher than the soldering of leaded solder. For example, the original use of 35W soldering iron, then lead-free soldering to use more than 70W soldering iron.
How to weld properly?
Lead-free solder fluidity is very poor, soldering to wait for the full melting of the tin-coated with solder before walking the iron, walking the speed of the iron to slow. And the head of the iron to catch the melting of the solder slowly move. If the solder is found to have solidified or incomplete melting phenomenon. Then the temperature compensation of the soldering iron head is not enough.
The temperature of the soldering iron head has been lower than the melting point of solder. And many lead-free temperature control soldering iron on the market is most likely to occur this phenomenon. When the soldering iron tip with a temperature of 400°C touches the battery cell. The tip temperature suddenly drops below 250°C, making it difficult to continue soldering.
Manufacturers are advised to choose a lead-free soldering station with a large soldering iron head, adjust the temperature of the iron by adjusting the DC voltage. And not choose a thermo-magnetic control of the temperature regulating iron.
Lead-free solder tape will discolor quickly after soldering, this is because lead-free solder is more prone to oxidation which is a normal phenomenon.