Solar panel manufacturing steps (Final Product)

Solar panel manufacturing steps

·         Solar Cell Testing

The equipment is developed to an automated work unit which characterizes PV cell efficiency using a current-voltage (I-V) test. I-V test subjects a PV cell to a calibrated light source to generate electrical current at different voltages. Using this data, the cell’s efficiency can be characterized. The system then sorts the PV cells according to eight different efficiency ratings for subsequent use in solar panels where cells with similar efficiencies are grouped to maximize the overall panel efficiency.

·         Solar Cell Cutting

Solar cell standard size is 156mm × 156 mm size, sometime cell having 125 mm × 125 mm size. For making different size panels the cell must be needed to cut in custom size. After cell testing, the cell is cutting in solar cell laser cutting machine. This machine is fully automated machine in which size we want to cut cell that size is logged in automated software system.

·         Solar Cell Tabbing and Stringing

Tabbing and bussing are two applications that link individual solar cells together to form a solar module (or solar panel). These applications also provide a method to transfer power from the solar cells to a power output, the junction box. Solar cell interconnect occurs when individual solar cells are joined together with tabbing ribbon (also called stringing ribbon), forming a cluster of solar cells. This is frequently referred to as cell tabbing (or stringing). The tabbing ribbon carries the solar cell’s current to a larger ribbon, the bus ribbon, which then carries power from the cell clusters to the module’s junction box for final output.

Tabbing ribbons are commonly applied as parallel strips that weave from the top of one cell to the bottom of the next to connect the positive and negative sides of the cells in series. The ribbon is soldered onto the paste that was applied to the TCO. The tabbing application creates a cluster of solar cells. Once all of the cells have been strung together with tabbing ribbons, they are then placed onto a substrate, typically glass. Then the thicker bus ribbon is soldered so that it connects to the tabbing ribbon of each solar cell cluster. The tabbing ribbon collects electric current within its cluster of solar cells and delivers it to the bus ribbon. The bus ribbon then conducts the cumulative electric power from all of the solar cell clusters to a junction box for final output. Imagine tabbing ribbon as a road that travels across the solar cell. The bus ribbons serve as the highways to connect and tie them together. Bus ribbon is larger in cross-section because it has more electrical power to carry.

·         Solar Panel Lamination

Lamination is the major process in solar module manufacturing. In this process, all materials are pressed into laminate as a whole. In the first stage, air in the chamber of the machine is pumped out and turned to vacuumed. Then, heating at 150 ° C and pressing will laminate all the materials together. Normally whole lamination cycle (including loading and unloading time) is approximately 6 minute.

·         Trimming & Framing

Debris and uneven edge surface of panel caused in lamination are trimmed to smooth and even in this process by using knife. Silicon glue is spread on aluminum frames manually, then operators collect the glued frames and fix them onto the panels manually, after that, operators load the panels on the framing machine, and frames are fastened and locked by framing machine.

·         Junction Box Fixing

In this proposal, silicon glue is spread on back side of junction boxes manually, and then the junction box is fixed manually on the back side of the panel.

·         Cable Connection

          Cables are connected from the junction box for output power of the panel. This cable called MC4

          connector.

Solar Cell Process Part-4

Solar Cell Process Flow Chart

First Step of the silicon solar cell processing in cell process lab is wafer inspecting. Through this process we choose the cells which forward for next step.

Second Step of the process is etching. For this purpose D.I H₂O and HCl is used.

Third Step of the cell process is texturing in which KOH is used and cell is ready for next step.

Fourth Step is diffusing. In this process cell is diffused in the furnace with Ar, O₂ and PH₃.

Fifth Step of the cell process is sheet resistivity.

Sixth Step of the process is BSF printing then baking the cell in the furnace.

Seventh Step of the process is edge grinding to remove the paste around the cell.

Eighth Step of the cell process Alloying.

Ninth Step in the cell process lab for cell is residue cleaning for this purpose D.I Water and HCL is used.

Cutting and Slicing of Ingot (Part-3)

Cutting and Squaring of Ingot:  

In the next process the ingot is cut from head to tail and squaring from side to side.

 Slicing of the Ingot:

In the next step the Ingots are sliced into wafers using a Wire Saw machine or other type of saw. De-ionized water is used to cool the blade on this ID (inside diameter) saw. The saw is slicing 120mm thick (minimum) wafers.

Lapping: Lapping is next; in this step the Ingots have now become rough cut Silicon wafers with saw marks and other defects on both sides of the wafer. Also at this point the wafer is much thicker than it will be when it is finished. Lapping the wafers accomplishes several things, it removes saw marks and surface defects from the front and backside of the wafers and it thins the wafer and relieves a lot of the stress accumulated in the wafer from the sawing process. Both before and after the lapping process many in-process checks will be done on the Silicon wafers and more fall-outs will occur. After lapping the wafers go thru several cleaning /etching steps using sodium hydroxide or acetic and nitric acids to remove microscopic cracks and surface damage caused by the lapping process, this is followed by followed by de-ionized water rinses.

Edge grinding or rounding is an important part of the wafer manufacturing process, it is normally done before or after lapping, this rounding of the edge of the wafer is very important! If it is not done the wafers will be more susceptible to breakage in the remaining steps of the wafer manufacturing process and the device manufacturing processes to come. If you look at the edge of a finished wafer you will see the edge rounding even in the notch area of 120mm and 300mm wafers. On the best Prime wafers the edges are also highly polished, this can improve cleaning results on wafers and reduce breakage up to 400%. Process Specialties has seen a notable yield differential between poorly and perfectly edge rounded material.

Polishing: Polishing is the next step in the wafer manufacturing process. Most Prime wafers go through 2-3 polishing steps using progressively finer slurry (slurry is the polishing compound). The polishing is normally done on the front side of the wafer, but sometimes it is done on both sides. Polishing is done on huge precision machines that are capable of extraordinary tolerances. Prior to final polishing some wafers may receive that is called backside damage; two examples would be bead blast and brush damage. The wafers may also receive a backside coating of Poly silicon, all these treatments are done to the backsides of the wafer for the purpose of Gettering defects (later in the device manufacturing process these backside treatments will draw defects in the Silicon towards the backside of the wafer and away from the front side where the devices are being built, this is called Gettering). After polishing the wafers are rinsed in DI water and scrubbed to remove any residual slurry compounds from the wafer. 

Final Cleaning: The next step in the process after polishing is a rather intense regimen of cleans and scrubs to remove trace metals, residues and particles from the surface(s) of the finished Silicon wafers. Normally most wafer manufacturers use a final cleaning method developed by RCA in the 1970's the first part of this clean is called SC1 and consists of Ammonium Hydroxide followed by a dilute Hydrofluoric acid clean followed by a DI water Rinse. Next the SC2 clean which consists of Hydrochloric acid and Hydrogen peroxide followed by a DI water rinse. Many companies modify these cleans to make them even more effective. After all this cleaning and rinsing the finished wafers will now go through a front and backside scrub to remove even the smallest particles.

Final sort and inspection: This is one of the last steps in the long wafer manufacturing process. It is here that the wafers either meet or fail the specifications the customers (IC manufacturers) have asked for. There are many specifications the final prime wafers must meet according to agreements made between the customers and the Silicon manufacturer. We will talk about these specifications in a generalized form here, some specifications are tighter, and some more relaxed depending on the end user and their requirements.

(To be Continue)