Selection and use of PV Ribbon for photovoltaic modules

1. The role of PV Ribbon

PV Ribbon is an important raw material in the welding process of photovoltaic modules. The quality of the tabbing wire will directly affect the collection efficiency of the PV module current. It has a great impact on the power of the PV module.

The welding tape must be firmly welded in the process of connecting the cells in series to avoid the occurrence of false welding. Manufacturers in the selection of welding tape must be selected according to the characteristics of the selected cell to determine what state of welding tape. The general selection criteria is based on the thickness of the cell and the amount of short-circuit current to determine the thickness of the tape, the width of the tape should be consistent with the width of the main deletion line of the battery, the degree of hardness and softness of the tape generally depends on the thickness of the cell and welding tools.

Manual welding requires the softer the state of the tape the better, soft state of the tape in the soldering iron will be very good, and battery contact after walking together, the welding process produces very little stress and can reduce the rate of fragmentation. But too soft solder tape will reduce the tensile strength, and it is easy to pull off. For the automatic welding process, the tape can be slightly harder. So that it is conducive to the welding machine to straighten the tape and pressure welding, too soft tape with machine welding is easy to deform, thereby reducing the product yield.

2. Soldering photovoltaic tape with the soldering iron

The soldering iron used for soldering PV ribbon has different options according to the different modules. Generally speaking, soldering small photovoltaic modules such as lamps requires less iron. The area of the module itself is small, so the heat requirement of the iron is not high, generally 35w soldering iron can meet the requirements of soldering leaded ribbon. But when soldering lead-free solder tape, manufacturers are advised to use 50w soldering iron as far as possible, and the purpose of using the lead-free long-life iron tip. Because of the rapid oxidation of lead-free solder, the damage to the iron tip is quite large.

Leaded solder tape is relatively easy to solder, generally, as long as you choose the right flux soldering iron temperature compensation enough to use. But lead-free solder tape soldering is really a lot of trouble, many manufacturers feel the headache. First, lead-free soldering to choose a suitable soldering iron. For manufacturers, the choice of the power-adjustable lead-free soldering station is a good choice. A lead-free soldering station is generally DC power supply, with adjustable voltage. DC soldering iron has the advantage of fast temperature compensation. It is unmatched by the AC temperature-controlled soldering iron. Lead-free soldering tape welding according to the thickness and area of the battery should choose 70-100w soldering iron, less than 70w soldering iron will generally have problems in lead-free soldering.

3. Soldering of lead-free solder tape

In the process of welding lead-free solder tape, the manufacturer should pay attention to adjusting the welding habits of workers. Lead-free solder does not flow well. And the welding speed should be much slower. Welding must wait until the solder is completely dissolved before walking the soldering iron, the iron should go slowly. If you find that the process of going soldering iron solder solidification, indicates that the temperature of the soldering iron head is low, adjust the temperature of the soldering iron head. Up to the soldering iron head smoothly move, solder smooth flow until.

4. The correct use of lead-free solder tape

With the implementation of the EU ROHS Directive in June 2006. China’s photovoltaic industry exports are facing the choice of lead-free. Lead-free solder tape has many disadvantages compared with the traditional PV ribbon, and how to overcome these disadvantages is a process problem that many photovoltaic manufacturers urgently need to solve.

Lead-free solder tape is divided into many kinds according to the composition of the coated solder. Our most widely used lead-free solder is 305 solder, which contains 3% silver and 0.5% copper. The advantage of this kind of solder is good solderability solder is high, the melting point is 218C used in the welding of battery cells the welding temperature requirements are very high, and ordinary internal heating type soldering iron is difficult to meet the temperature requirements. Therefore, the soldering of lead-free solder tape should use a high-power soldering iron. The general recommendation 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.

5. Fluidity of lead-free solder

The fluidity of lead-free solder 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. The head of the soldering iron catches the melting of the solder and slowly moves. If the solder is found to have solidified or incomplete melting phenomenon, the temperature compensation of the soldering iron head is not enough. And the temperature of the iron head has been lower than the melting point of the solder.

Many lead-free temperature-controlled soldering irons on the market are most prone to this phenomenon. When the temperature reaches 400C when the tip of the soldering iron touches the battery. The temperature of the iron head will suddenly drop below 250°C, making it difficult to continue soldering. It is recommended that manufacturers choose a lead-free soldering station with a large iron head by adjusting the DC voltage to adjust the temperature of the soldering iron. And do not choose a thermo-magnetic control of the temperature regulating iron. Welding different types of battery cells on the requirements of the soldering iron is not the same. The general thickness of the large battery cells on the iron requirements is higher. And the area of large battery cells on the iron requirements is higher. The choice of DC lead-free soldering station can basically solve the problem of welding temperature.

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.