PV ribbon is an important raw material in the process of photovoltaic module welding. The quality of PV ribbon will directly affect the collection efficiency of photovoltaic module current and the power of photovoltaic module.

The PV ribbon must be welded firmly in the process of connecting battery pieces in series to avoid false welding. When choosing the PV ribbon, the manufacturer must decide the state of the PV ribbonaccording to the characteristics of the selected battery. Generally, the selection standard is to determine the thickness of the PV ribbonaccording to the thickness of the battery chip and the number of short-circuit current. The width of the PV ribbonshall be consistent with the width of the main cutting line of the battery. The hardness and softness of the PV ribbongenerally depend on the thickness of the battery chip and the welding tools. Manual welding requires that the softer the PV ribbonis, the better it will be. After the soldering iron passes by, the soft PV ribbonwill be in good contact with the battery piece. The stress produced in the welding process is very small, which can reduce the fragment rate. But the tensile strength of too soft welding tape will be reduced, and it is easy to break. For the automatic welding process, the PV ribboncan be slightly hard, which is conducive to the straightening and pressure welding of the PV ribbonby the welding machine. For the too soft PV ribbon, it is easy to be deformed by the machine welding, so as to reduce the yield of the product.

The electric soldering iron used for welding the PV ribbonhas different choices according to different photovoltaic modules. Generally speaking, the requirements for the soldering iron of small photovoltaic modules such as welding lamps and lanterns are low, the area of the small modules is small, and the requirements for the heat of the soldering iron are not high. Generally, the 35W electric soldering iron can meet the requirements for welding the lead-containing soldering PV ribbon. However, when welding the lead-free PV ribbon, the manufacturer is recommended to use the 50W electric soldering iron as much as possible The use of lead-free long-life iron head, because the lead-free solder oxidation fast, the damage to the iron head is quite large.

It is relatively easy to weld with lead PV ribbon. Generally, as long as the appropriate flux is selected, the temperature compensation of soldering iron is sufficient. However, there are many troubles in the welding of lead-free PV ribbon, which many manufacturers feel headache about. First of all, a proper soldering iron should be selected for lead-free PV ribbon welding. For manufacturers, it is a good choice to choose a lead-free soldering station with adjustable power. Generally, the lead-free soldering station has DC power supply and adjustable voltage. The advantage of DC electric soldering iron is fast temperature compensation, which is incomparable to AC temperature regulating electric soldering iron. According to the thickness and area of the battery, the soldering iron of 70-100w should be selected for the welding of lead-free PV ribbon. Generally, the soldering iron of less than 70W will have problems in lead-free PV ribbon welding. In addition, many kinds of lead-free adjustable temperature alternating current soldering iron (controlled by hot magnet) on the market are not suitable for welding large-area battery chips, because the silicon thermal conductivity of the battery chips is very good, the heat of the soldering iron head will quickly transfer to the silicon chip, which instantly reduces the temperature of the soldering iron head to below 300 degrees, and the temperature compensation of the soldering iron is not enough to ensure that the temperature of the soldering iron rises to 400 degrees, which is not enough to ensure lead-free PV ribbon welding The phenomenon of firmness is that the battery chip crackles during the welding process, which seriously causes the battery chip to crack immediately, which is caused by the shrinkage stress caused by the low solder temperature. The iron head of lead-free welding oxidizes very fast. To keep the iron head clean, it is better to embed the iron head in the soldering tin under the heating state. Before use, the excess soldering tin of the iron head should be removed. The contact end of the iron head and the welding strip shall be repaired to be consistent with the width of the welding strip as far as possible, and the contact surface shall be flat. The soldering flux shall be lead-free and residue free.

With the implementation of the EU ROHS directive in June 2006, the export of photovoltaic industry in China is facing the lead free choice. Simultaneous interpreting of lead-free PV ribbon has many shortcomings compared with traditional  lead PV ribbon. How to overcome these shortcomings is a technological problem that many photovoltaic manufacturers urgently need to solve.

There are many kinds of lead-free PV ribbon according to the composition of the coated soldering tin. The most widely used soldering tin in China is 305 soldering tin, which contains 3% silver and 0.5% copper. The advantages of this kind of soldering tin are good solderability, high plasticity and melting point of 218 ℃. It is very difficult for ordinary internal heated electric soldering iron to meet the temperature requirements when it is used in the welding of battery chips. Therefore, the temperature requirements of lead-free PV ribbonare very high ,High power electric soldering iron shall be used for welding, and the general recommended principle is 30-40w higher than that of lead solder. For example, if 35W electric soldering iron was originally used, the electric soldering iron above 70W shall be used for lead-free welding.

The fluidity of lead-free solder is very poor. When welding, it is necessary to wait for the solder of the PV ribbonto fully melt before walking on the soldering iron. The speed of walking on the soldering iron should be slow. The soldering iron head moves slowly with the melted solder. If it is found that the solder has solidified or not completely melted, it means that 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 the solder. Many lead-free temperature adjustments are available on the market This phenomenon is most likely to happen to the electric soldering iron. When the electric soldering iron head with a temperature of 400 ℃ contacts the battery, the temperature of the soldering iron head will suddenly drop below 250 ℃, making it difficult to continue welding. It is suggested that the manufacturer should select the lead-free soldering station with large soldering iron head, adjust the temperature of electric soldering iron by adjusting the DC voltage, and do not select the temperature regulating electric soldering iron controlled by thermal magnetic sheet. The requirements for soldering iron are different for different types of battery chips. Generally, the requirements for soldering iron are higher for thick battery chips and higher for large area battery chips. The problem of welding temperature can be basically solved by selecting direct current lead-free welding platform. The lead-free PV ribbonwill change color quickly after welding, because the lead-free solder is easier to oxidize, which is a normal phenomenon