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Screen printing sintering process white paper

Public number: Moore photovoltaic Source: Time: 2020-02-21 01:51:58

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1

Influence of basic parameters

1.1 Influence of printing parameters

a) Snap-off: The larger the screen pitch is, the thicker the printing thickness is, and vice versa; b) Pressure: The larger the printing pressure is, the thinner the printing thickness is, and the thicker it is; c) Down-stop: the blade thickness is larger when printing The thinner it is, the thicker it is; d) Printing speed: The faster the printing speed, the thinner the thickness, and the thicker it is.

1.2 Influence of sintering parameters

a) The loss of the open circuit voltage Uoc is mainly recombined in the body, so reducing various recombination centers (various defects, shadows, stains, etc. on silicon wafers) is an effective way to improve Uoc; b) Factors affecting the short-circuit current Isc include: 1 ) Textured anti-reflective effect; 2) Diffusion PN junction structure; 3) Post-cleaning edge removal effect; 4) PECVD coating anti-reflective effect; 5) Shading area of printed grid lines; 6) Dirt. c) Series resistance Rs includes: P-type silicon wafer base body resistance, diffusion layer resistance, front electrode and back aluminum metal material resistance, ohmic contact resistance formed on the front and back; d) shunt resistance Rsh is mainly affected by material defects, various Effects of impurity contamination and post-cleaning removal of the edge PN junction effect; e) Fill factor FF is a comprehensive reflection of the best operating point, which is closely related to the incident spectral light intensity, short-circuit current, open-circuit voltage, and series-parallel resistance. Offset of back electrode printing and broken grids will also cause FF to a certain extent.

2

Common problem handling


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2.1 Printing common problems

a) 网版高度太低或网版形变量不够,调节方法:抬高网版高度、加大压力;b) 如果抬高网版和改变压力没有效果,可将印刷头顶部限位螺丝松动,将旋钮逆时针旋转,然后重新调节压力和网版高度。 2.1.1 Adhesive sheet a) The screen height is too low or the screen deformation is not enough. Adjustment method: raise the screen height and increase the pressure; b) If raising the screen and changing the pressure have no effect, you can set the top of the print head The limit screw is loose, turn the knob counterclockwise, and then readjust the pressure and screen height. a) 印刷不全通常表现为网版高度太高,此时适当降低网版高度;b) 适当降低回料板高度,切忌调节幅度过大导致网版破损;c) 虚印是印刷不全的一种形式,虚印的产生主要是浆料渗透性不好或者网版局部堵塞,可适当的增加印刷压力和降低印刷速度;d) 印刷不良品的处理:背电极和背电场轻微印刷不全时可用碎硅片沾取浆料补全未印全位置,然后轻压平整;印刷不全面积较大时用废硅片尽量铲掉背面所印刷浆料,重新印刷;正电极印刷不全较严重时直接重新印刷。 2.1.2 Printing incompleteness / virtual printing a) Printing incompleteness usually manifests as the screen height is too high, at this time, the screen size should be appropriately reduced; b) The height of the return plate should be appropriately reduced, and the adjustment plate should not be too large to cause screen damage; c) Virtual printing is a form of incomplete printing. The production of virtual printing is mainly due to poor permeability of the paste or partial blockage of the screen, which can appropriately increase the printing pressure and reduce the printing speed; d) Treatment of poor printing products: back electrodes and When the back electric field is slightly incomplete, the chip can be used to pick up the paste to fill the unprinted position, and then flatten it gently; when the area of the incomplete print is large, use a silicon wafer to scrape off the paste printed on the back and try to print again; positive electrode Reprint directly when printing is incomplete. a) Item1和Item 2漏浆时可以用胶带补全网孔,严重直接更换新网版;b) Item3印刷漏浆时直接更换网版。 2.1.3 Leakage a) When Item1 and Item 2 leak, you can use tape to complete the mesh, and directly replace the new screen. B) Item3 directly replace the screen when leaking. a) 一般轻微断栅使用无尘布擦拭网版即可恢复正常;b) 浆料的渗透性导致虚印而表现的断栅可延长搅拌时间、改变浆料稀释度,印刷时可先使用松油醇擦拭网版再用无尘布将虚印点上下网版对擦;c) 网版太高也是断栅的一个方面,情况类似印刷不全。 2.1.4 Broken grids a) Generally, using a dust-free cloth to wipe the screen can restore normal screens; b) Broken grids which are caused by the permeability of the paste can cause prolonged stirring, change the dilution of the paste, and print. You can use terpineol to wipe the screen first, and then use a dust-free cloth to wipe the printed dots up and down the screen. C) The screen is too high, which is also an aspect of the broken grid. The situation is similar to incomplete printing. 所谓毛边是指边缘栅线印刷不平滑,呈毛绒状,毛绒处为多余浆料印刷。 2.1.5 Roughness The so-called burr is that the edge grid line printing is not smooth, and it is fluffy, and the plush is printed with excess paste. a) 所有台面均表现为栅线过宽时抬高网版、降低刮刀高度;栅线过细则调节方向相反;b) 刮条局部区域被磨损更换刮条,此情况在调节参数和设备无效的情况下进行;c) 回料板位置太低也会导致栅线过宽,原因是回料板在回料过程中因为压力较大又印刷了一次,此情况类似印刷模式中的“double squeegee”;d) 如果几个台面的栅线宽度粗细不一致或者同一电池片的不同区域粗细不一致可查看台面是否平整以及网版的形变量是否发生变化。 a) Adjustment method: raise the screen, and it needs a large range of movement, and the effect of slight adjustment is not obvious; b) too low screen will also cause burrs, the difference lies in the direction of the fluffy deflection, which is usually biased towards the inside of the battery sheet. Raise the screen, and the height of the screen can be appropriately reduced if it is biased towards the outer edge of the battery slice; 2.1.6 The grid line width is unqualified a) All the table tops show that the screen is raised when the grid line is too wide, and the height of the scraper is reduced; Detailed instructions The adjustment direction is opposite; b) the wiper strip is worn and replaced in the local area, this condition is performed under the condition that the adjustment parameters and equipment are invalid; c) the position of the return plate is too low will cause the grid line to be too wide because of the return material The board was printed again during the return process due to the high pressure. This situation is similar to the “double squeegee” in the printing mode; d) If the thickness of the grid lines on several tabletops is inconsistent or the thickness of different regions of the same cell is inconsistent, you can view Whether the table is flat and whether the deformation of the screen is changed. 背场印刷存在的几个问题:厚度不均匀,边缘印刷偏厚;a) 此处厚度不均匀表现在背电极附近印刷湿重较大,目前主要的手段是保持印刷均匀性,另外设备电极的稳定也是重要的方面即保证印刷过程中印刷台不抖动;b) 边缘印刷偏厚的调节方法包括抬高网版(降低刮刀高度和加大压力有相同效果)和更换刮条。 2.1.7 Back-field printing quality There are several problems with back-field printing: uneven thickness and thicker edge printing; a) The uneven thickness here is manifested in the large wet weight near the back electrode. At present, the main method is to maintain printing Uniformity, in addition, the stability of the electrode of the equipment is also an important aspect, that is, to ensure that the printing table does not shake during the printing process; b) adjustment methods for thicker edge printing include raising the screen (reducing the blade height and increasing the pressure have the same effect) and replacing Scraping. 开始印刷时需要使用游标卡尺来确定是否偏移以及偏移方向和偏移量,根据测量情况调节X、Y、T补偿。 2.1.8 Printing offset When you start printing, you need to use a vernier caliper to determine whether it is offset, and the direction and amount of offset. Adjust the X, Y, and T compensation according to the measurement. During the printing process, it can be observed whether the back electrode is offset after the back electric field printing and sintering. The current back electrode design includes a symmetrical zigzag area on both sides of the electrode. If the offset occurs, the zigzag area is no longer symmetrical, showing a large area and a small area. The back electrode is silvery white, which is clearly distinguished from the back field color. , Can be carefully observed with backlight. 印刷过程中的漏浆、碎片等导致台面纸洁净度下降,台面纸沾污必须及时更换,防止对电池片造成污染。 2.1.9 Contamination of tabletop paper during the printing process will cause the cleanliness of the tabletop paper to decrease, and the contamination of the tabletop paper must be replaced in time to prevent contamination of the battery chip. 一旦从烧结炉出来发现隐裂则立即停止印刷段所有印刷,从item3开始向前逐步排查台面、网版、真空等是否异常。 2.1.10 Hidden cracks Once the cracks are found out of the sintering furnace, all printing in the printing section is stopped immediately, and item3, screen, and vacuum are checked for abnormalities starting from item3. a) The crack is usually the unevenness of the table paper or there are fragments, particles, etc., so it is necessary to keep the table paper flat and clean the printing press table; b) the suction pressure is not balanced due to insufficient or unstable table surface; c) the equipment is prolonged The operation of the elevator caused the lifter of the ejector rod to become loose or tilted. 判断网版印与刮条印的主要方法是看印迹图形的形状。 2.1.11 Screen printing and scratch printing The main method for judging screen printing and scratch printing is to look at the shape of the print. If the graphic is a straight line, it is mostly a scratch printing and the scraping bar needs to be replaced; if the graphic is a curved line or an irregular area is a screen printing, the screen printing should be replaced in time when the situation is serious.

2.2 Treatment of sintering common problems

造成弯曲度过大的几个因素:a) 来料片源太薄,可适当降低背电场的印刷湿重;b) 湿重(印刷量)过大:降低背电场的印刷湿重;c) 温度过高:降低烧结炉4-6区背场烧结温度,效果不明显时可降低8、9区温度,但要防止对效率造成影响;d) 印刷厚度不均匀。 2.2.1 Excessive curvature caused by several factors: a) The source material is too thin, which can appropriately reduce the wet weight of the back electric field; b) Excessive wet weight (printing amount): reduce the back electric field. Printing wet weight; c) Excessive temperature: reduce the back-field sintering temperature in the 4-6 zone of the sintering furnace. If the effect is not obvious, the temperature in the 8 and 9 zones can be reduced, but the effect on the efficiency should be prevented; d) The printing thickness is uneven. 烧结炉因履带带速或者温度波动较大(超过设置值±10℃)时报警,立即停止放片,及时消除报警,然后回到主界面升温。 2.2.2 Sintering furnace alarm The sintering furnace alarms when the crawler belt speed or temperature fluctuates greatly (more than the set value ± 10 ° C), immediately stops filming, promptly eliminates the alarm, and then returns to the main interface to heat up. Alarm resolution steps: a) Remove the alarm signal in the upper right corner of the unregistered monitoring interface; b) Log in to the monitoring interface and select Alarm Status on the interface to enter the alarm interface to eliminate the alarm; c) Exit to the monitoring interface and click on the System Status adjustment Heater The Disable button on one line performs temperature adjustment. a) Uoc、Isc偏低,Rs、FF正常,考虑来料异常;b) 查看生产流程单确认扩散方块电阻和少子寿命无异常;c) 浆料污染会导致Isc偏低,Uoc变化不大,同时FF会降低,Rsh会很小。 2.2.3 Uoc and Isc are low a) Uoc and Isc are low, Rs and FF are normal, and consider incoming materials abnormal; b) Check the production process sheet to confirm that there is no abnormality in the resistance of diffusion block and minority life; c) slurry contamination will cause Isc On the low side, Uoc does not change much, at the same time FF will decrease, and Rsh will be small. a) Rs小,Rsh大,正常现象;b) Rs偏大,Rsh正常,升高温度;c) Rs正常,Rsh偏小,漏电严重;d) Rs偏大,Rsh偏小,考虑浆料是否污染或者烧穿。 2.2.4 The abnormal relationship between Rs and Rsh a) Rs is small, Rsh is large, normal phenomenon; b) Rs is large, Rsh is normal, temperature rises; c) Rs is normal, Rsh is small, leakage is serious; d) Rs is large , Rsh is too small, consider whether the slurry is contaminated or burned through. a) 烧结温度不足,可以适当的升高烧结温度;b) 烘干温度过高,可适当的降低烘干温度;c) 测试台探针压片不准、接触不好或者探针使用时间过久需更换。 2.2.5 Rs is too high and FF is too low a) The sintering temperature is insufficient, and the sintering temperature can be appropriately increased; b) The drying temperature is too high, and the drying temperature can be appropriately reduced; c) The test table probe is not allowed to be pressed 2. The contact is not good or the probe needs to be replaced for too long. 2.2.6 Isc decreases, Rs decreases, Ncell decreases. This phenomenon is most common when the screen's service life reaches the upper limit or the screen's tension decreases; the main reason is that the increase in the width of the grid line leads to the increase in the light-shielding area. The decrease in resistance reduces Rs, which leads to a certain reduction in efficiency. a) 背场颜色一般铝背场烧结后呈龟裂状,颜色的灰色(或青色);背场颜色发白或者无龟裂状很有可能未烧结充分;背场呈焦黄色有可能烧过。 2.2.7 Common problems in back-field sintering a) The back-field color is generally aluminum. The back-field sintering is cracked and gray (or cyan). The back-field color is whitish or crack-free. The field may be burnt yellow. b) Aluminum clad aluminum clad adjustment is judged according to the number, size and position of aluminum clad. The number is 1-3, the position is fixed, and the shape is convex. You can check whether there are nodes in the back field aluminum paste printing. When there are a lot of aluminum bags and the position is not fixed, it is mostly caused by the temperature being too high or too low. High or low can be referenced according to Rs and FF. The most accurate and reliable is to use a thermometer to determine the current temperature. In addition, the adjustment of hot exhaust air and cooling water, and the drying temperature of the oven also have a certain effect on the adjustment of the aluminum bag. c) Aluminum thorns are mainly affected by temperature and track. Most of the aluminum spikes caused by the track are on the back-field sintered track marks, which can be seen by reflective observation, and the shape is a long and narrow blade shape. The difference between the aluminum package and the aluminum spike caused by temperature is not much, compared with aluminum The ruptured form of the package can be adjusted by cooling. d) The large leakage caused by the large leakage current Irev2: 1) There are many impurities or defects in the incoming film source. Test EL can see that there are more dark spots on the image or the image is dark overall; 2) insufficient edge etching It is necessary to pay attention before and after cleaning and changing the liquid and immediately after production; 3) slurry contamination, in this case, Rsh will become very small, and Isc and FF are also significantly reduced; 4) pulp leakage at the printing edge, in this case Less, it is a problem that should be found and corrected in time within the scope of print quality monitoring; 5) The leakage change is an order of magnitude, which is manifested by the presence of breakdown on the grid line when C10X is observed. Factors that cause breakdown include the contamination of metals and oily substances. Contamination, probe crushing, breakdown, cracking, etc. The specific situation needs to be carefully observed and tested by EL to assist judgment.

2.3 Common solutions to common problems in the screen printing process

现象描述:测试台线间效率差异大于0.08%,或线内差异大于0.03%;或丝印各线测试效率均较低时,应立即启动工艺排查机制。 2.3.1 Description of the difference inspection phenomenon: The efficiency difference between the test bench lines is greater than 0.08%, or the intra-line difference is greater than 0.03%; or when the test efficiency of each screen printing line is low, the process inspection mechanism should be started immediately. Solution: When a difference occurs, it should be immediately reported to the quality control and equipment personnel. When there is a difference between lines, the value of the difference in electrical performance of each line should be compared to find the most important parameter that affects efficiency. Adjust the voltage compensation or recalibrate the target when Uoc is low; recalibrate the target when Isc is low; test bench probe troubleshooting can be performed when Rs is large and FF is low. FF is sometimes biased due to glitches in the IV curve Large or low; cleaning the test bench when Rsh is low. When in-line differences occur, you can view the specific data of the different battery slices, observe whether there are individual battery slices with higher or lower efficiency tests, and then re-measure the different battery slices. If the difference still exists after re-measurement, you can check whether the upper and lower probes on the test bench are loose or fall off, and notify the equipment personnel to perform related tasks such as probe reset or probe test position adjustment. When the test efficiency of each line of silk screen printing is low, you can check the target for contamination or chipping, and observe whether the calibration method of the target calibrator has any problems. 现象描述:正面电极经烧结后出现主栅线两头翘起现象。 2.3.2 Description of main grid line shedding phenomenon: After the front electrode is sintered, two ends of the main grid line are lifted up. Solution: The main influencing factors of the main grid line falling off are mainly too high drying temperature or too large electrode printing thickness. If the drying temperature is too high, the inorganic substances or glass oxides that have an adhesion effect on the electrodes in the slurry will be volatilized in advance, and the electrodes will warp during sintering, so reducing the drying temperature in the first three zones is the direction of adjustment. In addition, increasing the printing pressure of the front electrode (2 to 4N) and reducing the screen height can reduce the printing thickness and effectively solve the problem of the main grid line falling off. The main grid line dropout usually occurs immediately after the third pass of the screen is changed or the parameters related to the increase in printing thickness are adjusted. Therefore, the first inspection must be performed after the third pass of the screen is replaced (no less than 5 battery cells) ) Mass production can only be carried out after normal. Technicians must also follow up when adjusting the parameters during the production process, and leave after confirming that the printing quality is correct after the parameters are adjusted. The main gate line shedding phenomenon is generally common in PV159 slurry. 现象描述:浆料污染是指印刷第三道Ag浆受到污染,尤其是受到Al浆污染后,电池各项电性能参数连续发生异常,主要表现在Isc下降明显,Rsh突然降低(约在60ohm左右),伴随着Rs、Irev2明显增大,Ncell较低。 2.3.3 Description of slurry contamination phenomenon: The slurry contamination refers to the contamination of the third Ag paste during printing, especially after the Al paste contamination. The battery's various electrical performance parameters continue to be abnormal, which is mainly reflected in the obvious decrease in Isc, and Rsh suddenly Decrease (about 60ohm), with Rs and Irv2 increasing significantly, Ncell is lower. Solution: If you suspect that the slurry is contaminated, you should immediately notify the production department to stop the third printing and immediately start the process inspection mechanism. An effective method to confirm whether the slurry is contaminated is to verify the cross-contrast of the two production lines. For example, if there is doubt that slurry contamination occurs in the third lane of # 1, 5 to 10 battery cells that are not being printed with the front electrode are being produced on # 2 and printed on # 2. After printing, take back # 1 for sintering and testing, and observe Whether the electrical performance parameters are normal. If the electrical performance is normal, it can be basically determined that slurry contamination has occurred in # 1. At this time, the production department should be immediately notified to replace the screen, slurry, scraper, and carefully clean the scraper, return knife and other objects that are in close contact with the slurry. Before the new screen is installed, the process hygiene of the third printing station must be carefully carried out to ensure that the slurry pollution is completely resolved. When the production is just resumed, pay close attention to the changes in the electrical performance parameters of the battery. The slurry that is suspected to be contaminated must be labeled and placed in a designated position to prevent the production staff from receiving it. Afterwards, the slurry pollution accident should be submitted to the relevant leaders and the silk screen process report. Slurry contamination generally occurs during transfer shifts or when operators are lacking. Improper slurry agitation, operator incorrect operation, and mixing of scraper blades are all possible causes of slurry contamination. 现象描述:当发生以下情况之一时,工艺人员需立即启动工艺排查机制: (1) 高阻密栅线单批效率低于15.60%时,需要提交排查报告;(2) 高阻密栅线平均效率低于15.70%时,需要提交排查报告;(3) 高阻密栅线单批效率低于15.80%时;(4) 高阻密栅线平均效率低于15.80%时;(5) 电性能参数Uoc连续多批低于0.610V时;(6) 电性能参数FF连续多批低于77.50%时;(7) 电性能参数Rsh连续多批低于100ohm时;(8) 电性能参数Irev2连续多批高于0.3A时;(9) 同批电池片电性能参数Uoc或Isc有分层现象时;(10) 同批电池片电性能参数Rs(或者FF)持续增加(或者持续降低)时;(11) 同批电池片电性能参数Rsh、Irev2有明显恶化趋势时。 2.3.4 Description of low-efficiency inspection phenomenon: When one of the following situations occurs, the process technician must immediately start the process inspection mechanism: (1) When the single batch efficiency of the high-resistance gate line is less than 15.60%, an inspection report needs to be submitted; (2) When the average efficiency of high-resistance grid lines is less than 15.70%, an investigation report needs to be submitted; (3) When the single batch efficiency of high-resistance grid lines is less than 15.80%; (4) When the average efficiency of high-resistance grid lines is less than 15.80% (5) When the electrical performance parameter Uoc is less than 0.610V in successive batches; (6) When the electrical performance parameter FF is successively less than 77.50%; (7) When the electrical performance parameter Rsh is successively less than 100ohm; (8) ) Electrical performance parameter Irev2 when multiple batches are higher than 0.3A; (9) When the electrical performance parameter Uoc or Isc of the same batch has delamination; (10) The electrical performance parameter Rs (or FF) of the same batch of battery cells continues to increase (Or continue to decrease); (11) When the electrical performance parameters Rsh and Irev2 of the same batch of cells have a significant tendency to deteriorate. Solution: General method: The general method to solve the above problems is called reverse troubleshooting, which is the most common method for troubleshooting by screen printing. For example, when one of the above problems occurs in silkscreen 1 #, if the electrical performance parameters of 2 # battery cells are normal, you can compare 1 # and 2 # for troubleshooting, and check in reverse order from back to front, that is, check the two first. If there is a test difference in the line test bench, then check the sintering furnace, then item3, then item2, and finally item1. When a certain segment was checked, it was found that the two lines were significantly different, and abnormal electrical performance had been found. At this point, the troubleshooting was completed, and problem-solving measures were carried out for the segment where the problem occurred. (1) If problems are found on the test bench, you can check the probes of the test bench, clean the test bench, recalibrate the target, and other measures; (2) If you find a problem with the sintering furnace, you can compare the temperature between the lines by drawing. (3) If there is a problem with item3, you can check whether the wet weight is normal, the screen line width expansion, printing quality, and whether the slurry is abnormal; etc. (4) If there is a problem with item2 You can check whether the wet weight is normal, whether the printing is good, whether there is offset, whether there is inequality in the printing; (5) If there is a problem with item1, you can check whether the wet weight is normal, whether the edge printing is good, whether there is offset, etc. . Weight measurement method: Because the reverse inspection method takes a long time, the adjustment effect cannot be known immediately, and the impact on production is large, so the process personnel can carry out the weight measurement method according to the actual situation. (1) Uoc is low, you can check whether the wet weight of item2 is normal, test whether the temperature is high, or EL test is obvious whether dark streaks are obvious; (2) Isc is low, you can check whether the unevenness of the resistance of the diffusion block is relatively high Large, whether the life of the minority child is low, check whether the line width of the front grid line is large, whether the wet weight of item3 is normal, whether the print quality of item3 is good, whether the dark lines are obvious on the EL test, whether the surface of the battery is stained, No pollution, whether the process hygiene is up to standard; (3) When Rs is large or FF is low, you can focus on the sintering furnace to check the difference between the lines by drawing temperature. Generally speaking, when Rs is large, the temperature of the sintering zone can be increased Or reduce the temperature in the drying zone. When the FF is low, the temperature in the eight or nine zones can be increased; (4) When the Rsh is low, the temperature of the sintering furnace can be appropriately reduced; The slurry condition, whether there is slurry residue on the battery transmission walking beam, whether the battery etch line is clear, whether the sintering furnace temperature is high, whether the EL test has more dark streaks, etc. (6) If the electrical performance parameters do not change significantly after the above-mentioned methods are checked, a reverse check method shall be used for troubleshooting.

Source: Network

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