Sorting of solar cells
1. Purpose
The main purposes of cell sorting are:
(1) Detect unqualified single-cell cells with broken corners, cracks, “watermarks”, etc., and conduct necessary classification of different batches of cells.
(2) The front color of the cell is generally blue-brown, blue-purple, blue, light blue and other different grades of blue (the reverse side is generally gray). Color sorting and grading of the cells ensures that the 72 cells used in a single module are of the same grade color, so that the single module has a beautiful appearance after being produced, and the color difference between the cells is obvious. In addition to the beautiful appearance, the cells with large color difference usually have large deviation in electrical properties.
(3) Match according to the performance of the cells to ensure the maximum power of the produced modules.
2. Bill of Materials
For the cells to be sorted, 72 normal monocrystalline cells need to be prepared and packed into a simple package.
3. Equipment and tools
(1) Cotton gloves.
(2) Finger sleeves.
(3) Sorting table.
(4) Cell I-V tester.
(5) Storage box (customized according to the size of the battery and the plexiglass material used).
4. Process requirements
(1) Color and appearance grading of all incoming cells. After removing the problem cells, the cells are grouped into groups of 72 cells.
(2) Cells that cannot be used on the production line within 4 hours must be sealed, and can be packaged with plastic wrap or thermoplastic.
5. Quality requirements
It is difficult to accurately grade the color by the human eye. The color of a group of cells should be as consistent as possible, and there should be no obvious and strong color difference in the finished product.
6. Precautions
(1) Human eye classification Pay attention to prevent visual fatigue, and rest intermittently as needed.
(2) The battery should be handled with care.
(3) Do not touch the battery with bare hands.
(4) The number of single-chip handovers should be recorded correctly and clearly.
Cutting of solar cells
1. Purpose
According to the process requirements, the cells are cut into the specified size, which is convenient for subsequent production.
2. Bill of Materials
(1) The cell to be cut.
(2) jersey gloves.
(3) Finger sleeves.
(4) Storage box.
3. Process requirements
(1) Cell cutting process requirements
① Write the cell batch number and cell size on the back electrode with a 2B pencil.
② Turn on the compressed air and cooling water, and start the laser dicing machine.
③ Set the size of the battery to be drawn in the program, put the battery on the suction cup, turn on the vacuum, wait for the vacuum gauge to display stable, it means that the battery has been sucked firmly, and the device can enter the scribing state.
④ When scribing, the depth of the cut should be generally controlled at 1/2 2/3 of the thickness of the cell, which is mainly controlled by adjusting the working current of the laser dicing machine. The specific depth is adjusted by the operator and can be determined according to the equipment conditions. (The adjustment range is determined by the craftsman)
⑤ When cutting different batches of cells, it needs to be confirmed by the technician. If the thickness difference is large, pay attention to adjusting the focal length while adjusting the working current of the laser dicing machine.
⑥ All the cut cells need to be tested for reverse leakage current, and the cells that meet the process requirements after testing are regarded as qualified cells. If the test reverse leakage current value index does not meet the process requirements, it needs to be reworked. Usually, it is necessary to remove the silicon chip debris at the mechanical slot, and then test the reverse leakage current value index.
Cutting the cell, sometimes requires a design program. It should be carried out according to the process drawing. It is designed according to the program design requirements of the equipment manufacturer. It should be noted that the use and modification of the program should be recorded accordingly to facilitate tracking.
( 2 ) Requirements for cell breaking process
After cutting, the battery slices cut into two pieces should be broken apart, which is called splitting. The operation steps are as follows:
① Pick up the cut battery, with the gray back facing up, pinch the edge of the battery with thumb and index finger, thumb on top, index finger on the bottom, along the path of the scribe, pull the battery down with both hands at the same time, and divide the battery into two parts.
② According to the type of single-piece grid line and the position of the single-piece in the original cell, the single-piece is classified and placed.
③ After self-inspection of the scribed battery slices, confirm that the size meets the process requirements, and those that do not meet the requirements are the ones to be processed.
4. Equipment and Tools
(1) Laser dicing machine.
(2) Laser safety goggles.
5. Quality requirements
(1) The cut surface after dicing shall not have serrations.
(2) Invisible cracks are not allowed in the cut cells.
(3) The laser cutting depth is visually measured as 1/2~2/3 of the thickness of the cell, and the dimensional tolerance of the cell should meet the requirements of the process drawing, which is ±0.02mm in principle.
(4) The surface of the cut cell should be kept clean.
6. Notes
(1) When a batch of cells is found to have quality problems, it should be reported to the production supervisor in time.
(2) When the cutting requirements or the size and thickness of the cell are changed, the technical personnel must re-adjust the instrument parameters and record them.
(3) Sort and separate the pieces to be processed and the waste pieces during the cutting process.
(4) The battery sheet is extremely fragile, and it is easy to cause invisible cracks that are invisible to the naked eye. Such invisible cracks will cause the battery sheet to be broken in the subsequent production process. Therefore, the number of times of contacting the battery sheet should be minimized during operation to reduce the probability of loss.
(5) The battery slices must be handled with care, and should be neatly stacked in the box. It is forbidden to stack them in the box or on the console.
(6) Cells that are not used for a short time should be sealed or stored in a desiccator.