Lamination of solar cells

Purpose and requirements of solar cell lamination

1. Purpose

The main purpose of lamination is to encapsulate the laminated battery modules. During the lamination process, the EVA in the module undergoes curing and adhesive modification, so that the laminated module has a certain degree of sealing and water resistance. The internal structure of the laminated module is shown in Figure 1.

Figure 1 - Schematic diagram of the inside of the assembly at the end of the assembly
Figure 1 – Schematic diagram of the inside of the assembly at the end of the assembly

In order to maximize the lamination quality of modules, the selection of lamination parameters must be appropriate, therefore, it is very important to understand the working principle of lamination and the effect of lamination parameter changes on EVA performance. At the same time, it is also very important to understand the performance of the laminator.

2. Bill of Materials

The modules to be laminated that have passed the inspection after lamination.

3. Equipment and tools

1) Laminator.

2) Teflon cloth (high temperature cloth).

3) Cotton gloves (or insulating gloves).

4) Utility knife or heated cutter.

5) 0.8cm wide tape.

4. Process requirements

1) When working, you must wear work clothes, work shoes, work caps, and thread gloves.

2) Do a good job of process hygiene inspection before operation. Before formal lamination every day, check whether the lamination table and the silicone rubber sheet are clean, and check the air tightness of the sealing ring.

3) Turn on the water cooling cycle power supply of the vacuum pump, let the laminator run for 2~3 empty cycles, and during the empty cycle, open the air valve of the vacuum pump for about 5 minutes until the laminator works normally.

4) Test and confirm that the temperature of each point of the equipment is consistent with the temperature displayed by the equipment. Usually, three points are taken for each area of the front, middle and rear areas of the entire machine. For those using a hand-held tester, it is recommended to focus on testing the population and exit of the oil circuit system and the surrounding of the machine.

5) Confirm that the emergency button is in a normal state.

6) Check whether the parameters of the laminator have changed, and adjust to the set parameters if necessary. After putting the stacked modules in, cover with a layer of PTFE cloth, set the laminator to automatic, and close the cover. Since the lamination and curing of the currently used laminator are carried out at the same time, the speed of placing the modules and closing the cover should be as fast as possible, so as to avoid the air bubbles being sealed inside after the EVA melts, and the air bubbles cannot be extracted by vacuuming.

7) Before lamination, check whether the serial number in the module is consistent with the serial number in the “Process Flow Sheet” and whether all the previous processes are confirmed and signed by the relevant personnel.

8) The modules should be placed on the PTFE cloth, and a layer of PTFE cloth should be placed on it.

9) When feeding, two operators help lift the front end of the PTFE cloth on both sides of the equipment so that the modules can enter the laminator smoothly.

10) One of the operators is required to record the vacuum level of the lower chamber every 3 minutes during the operation of the laminator. Another operator is responsible for cleaning the EVA remaining on the Teflon cloth after the lamination of the previous group of battery modules, and de-edges the laminated finished modules that have been cooled to a certain extent. The purpose of recording the vacuum level is to monitor the working state of the laminator at any time and to record the effect of the vacuum level on the lamination quality.

11) When discharging, pay attention to lift one end of the PTFE cloth between the upper cover and the stainless steel baffle, and the range of movement of the hand should be within the area.

12) The edge removal operation should not be carried out when the temperature of the modules has not dropped, otherwise the backplane will be easily separated. When de-edging, the assembly should be turned upside down with the glass facing up.

13) After the laminator is opened, pull out the modules, take out the upper PTFE cloth well to remove the remaining EVA on it, take out another PTFE cloth, and cover it on the heating plate of the laminator. The corners of the tempered glass are relatively fragile and cannot withstand the impact of hard objects. If the EVA residue on the PTFE cloth is not cleaned, it will cause obvious traces on the laminated module backplane.

14) Make a record on the “Process Flow Sheet”, and place the modules whose temperature has dropped to the designated position. The records on the “Technical Flow Sheet” should be entered into the corresponding record files of the computer for future inquiry. Laminated modules are placed as tested to avoid confusion.

15) Laminate the backside of the assembly and place it on the designated tray (note that the bottom piece is face-up) or on the designated curing rack.

16) Sample of basic process parameters (usually, the parameters will be adjusted according to the actual equipment, basically no two equipments have the same working parameters)

5. Quality requirements

1) The single piece in the module has no rupture, element crack, or obvious displacement, and the distance between strings cannot be less than 1 mm.

2) No air bubbles are allowed on the ribbon and the battery, and the remaining parts of the 0.5~1 mm2 air bubble cannot exceed 3, and the 1~1.5 mm2 air bubble cannot exceed 1.

3) There are no impurities and dirt inside the modules.

4) The back panel should be free of scratches and scratches.

5) The gelation rate of EVA should not be lower than 80%. Each batch of EVA should be measured once and tested once a day.

6) The back is flat, and the height of the bumps cannot exceed 1 mm.

6. Precautions

1) The modules should be placed smoothly and quickly, and should be placed in an area where the temperature distribution of the hot plate of the laminator is relatively uniform.

2) The utility knife used for edge removal should be replaced regularly.

3) When the module is pulled out, pay attention to the speed of pulling out not too fast to prevent the edge of the tempered glass of the module from being broken due to collision. Special attention should be paid to the 4 top corners.

4) The laminated assembly process sheet must be glued to the assembly, and be careful not to post it wrongly.

5) Be careful not to damage or lose the process sheet when the modules are stacked together.

6) The operation of the laminator is performed by designated personnel, and other personnel are not allowed to enter the working area of the laminator.

7) Pay attention to whether there is any residual EVA, impurities, etc. on the PTFE cloth when laminating each time.

8) When placing the modules on the machine, they should be placed flat, and fingers should not press the battery.

9) After the modules are put in, they are quickly laminated and taken out quickly after opening the cover.

10) After changing any process parameters, you must go through the operation process to check whether the equipment is abnormal, and then test a module before it can be executed in batches.

11) When there is an abnormality, it should be carried out according to the “Lamination Machine Abnormal Troubleshooting Procedure”.