Dressers have many different styles and functionalities. However, the most popular are all dressers, chest dressers, media chest dressers, and dressers with mirrors. All dressers and chest dressers are the most traditional type of this furniture and provides an ample amount of space to store your clothes and belongings.
On the other hand, if you are looking to maximize the available space in your room, media chest dressers and dressers with mirrors will provide additional storage. Media chest dressers are designed to provide plenty of space for a TV on top and may include a cubby area that can hold your cable box or other device. If you choose one with this feature, they also include a hole in the back to allow wiring to easily connect to your wall. In order to prevent tipping, we recommend that the dimension of the TV should not exceed the width of the dresser.
Darren Brown, DEK International
There are many factors that affect the productivity and cost-effectiveness of manufacturing solar cell modules. The metallization process may be the best way to solve these problems. The metallization of a silicon chip substrate is a key connection process for manufacturing crystalline silicon (cSi) solar cells. It is very important to collect the current generated by the solar cell, which directly affects the energy conversion efficiency of the battery. Metallization of silicon chips using screen printing technology is best suited for solar cell production and is the preferred process technology for the next generation of solar cell manufacturers.
Screen printing is a sophisticated printing technology used in various industries, from product labels to embedded passive electronic components and conductive inks, conductive inks and cSi solar cells. The production of crystalline silicon solar cells has been around for decades. For a long time and not too long ago, this fast-growing industry has already challenged screen printing technology and demanded the use of small, negligible errors in the slender conductors. Precise and repeatable printing on the substrate. Some material properties, such as thixotropy and rheology, must also be considered when manufacturing solar cells.
At present, the relationship between the screen printing technology and the solar cell process is very close, thereby promoting the screen printing technology to improve the printing accuracy and repeatability, exceeding the general requirements for printing conductive patterns on the dopant silicon chip. For example, surface-mount circuit board assemblies often require ultra-fine-pitch printing to print solder paste onto many pads with a pitch of 0.3 mm or less and a diameter of 0.3 mm. The chemical substances contained in the solder paste contain more chemicals than the materials used for screen metallization of the solar cell silicon chips. The earliest solder paste consisted of tiny solder balls and shot balls suspended in flux. Today's lead-free solder paste contains copper, silver, and indium. The solder paste is generally printed on the conductive copper pad of the bare circuit board, and then the lead or pin of the electronic device or component is precisely placed on the copper pad printed with the solder paste, and the circuit board is then reflowed into the soldering furnace. , Forming a solid electrical and mechanical connection.
Other metallization processes and materials were explored, such as hot-melt technology, but most solar cell manufacturers chose wire mesh technology as the preferred method. The choice of materials used was very small. Silver paste was used to form the front side of the silicon chip. The finger conductive strips are formed with aluminum paste to form a surface coating on the backside of the silicon chips.
Manufacturers face challenges
Manufacturing a new generation of solar cells presents a series of new challenges to every part of the manufacturing process. These challenges are not new to similar industries, such as electronic components manufacturing.
The key to the company's requirements for the production of solar cells is two requirements for metallization: First, to improve the performance of hardware and equipment, first, to strengthen the process development and improve the efficiency of the solar cell itself. Improving the performance of hardware and equipment is related to increasing production and improving yield. This is a problem that manufacturers are familiar with - that every chip coming out of the production line is qualified by reducing chip breakage and controlling the process. Strengthening process development requires increased requirements for equipment providers. Equipment suppliers are no longer simply providing productive machines. The designers of the equipment must understand the requirements of the solar cell manufacturers and the technological level of the process, and develop new technologies so that solar cell manufacturers can maintain high yields and high yields and produce better solar cells.
Productivity-oriented solar cell manufacturers require production of more than 2,400 chips per hour per metallization line. At present, typical metallurgical production lines produce between 1,200 and 1400 chips/hour, and doubling production is a very high demand, not to mention increasing the delivery of fragile substrates and at the delivery speed without increasing breakage. Solar cell manufacturers also want smaller plant space to have greater production capacity and lower overall costs.
The screen printing technology must develop towards the metallization production line, require it to exceed the output target of the solar cell producer, and also satisfy the manufacturer's consideration of the actual area of ​​the production workshop. A technology developed to meet these requirements, a production line can produce 3000 chips per hour, its length is the same as the production line of 1200 blocks per hour, and the width is only 25% wider than the conventional production line. This technique uses multiple print heads operating in parallel, which is beneficial for production, if the print head stops on the production line, the other print heads continue to work.
If the conventional 1200 block/hour line is stopped and production stops completely, a pause of 5 minutes will mean that 100 chips will be produced less, which is equivalent to an 8.3% loss of productivity per hour. If a conventional production line produces 3,000 chips per hour, the production line will pause for five minutes and produce 250 chips less. Using multiple print head technology, 3000 chips per hour were printed, only one print head was paused, but other print heads continued to print, suspending production of 84 chips in 5 minutes. Therefore, the output per hour for only one print head when suspended is 2916 chips, and the productivity loss is only 2.8%, which is still acceptable.
The area occupied by equipment is now a matter of great concern to solar cell manufacturers. This issue is also a problem that other electronics assemblers have long been concerned about. The reason they care about this issue is the same: the overall cost. Making full use of the plant will make manufacturers' investments faster and more rewarding (ROI), and they do not need to build new plants to increase productivity. As a result of this need, a new generation of small and compact metallization solutions has emerged. It is designed to be modular and expandable. It can easily and quickly expand production as the market demand increases, but the production line is very compact. It takes up very little space.
The material used for the material metallization process seems to have become simpler. Interest in hot-melt technology has declined and people have focused their attention on a simple set of conductive chemical formulations. Therefore, suppliers with process expertise can strengthen the metallization process and focus their development on improving the efficiency of solar cells instead of dealing with decentralized material supply.
For metallization process experts, the key challenge is to generate enough conductive finger patterns on the front side of the silicon chip to conduct the current generated by the silicon chip without covering the chip surface with too much area. Part of the surface of the chip that is covered by sunlight, including overprinted conductive strips, cannot generate current, which reduces the maximum efficiency that the battery may achieve.
Contrary to this, too few conductive strips printed on the chip will reduce the efficiency of the battery. This is because silicon is a semiconductor and its natural surface resistance is large. When there are too few conductive strips, the actual current generated on the surface of the silicon chip is large, but the collected current is very small.
On the silicon chip, receiving the sunlight portion and the covered portion to achieve the best balance will help improve the energy conversion efficiency. The small finger-like conductive strips printed on the chip cover a relatively small area, but the conductive strips are relatively thick in the vertical direction and can effectively conduct electricity. The purpose of this is to make the conductor have a relatively large aspect ratio, usually 50 microns wide and 22 microns high. This issue is currently receiving much attention. Other factors, such as latex screens used in screen printing, also affect the energy conversion efficiency. Among the various technologies currently being developed, there is a new template technology, and the conductive strips may be formed by several layers or electroformed, like a hybrid screen.
Self-manufactured screens and stencils Screen-printing equipment manufacturers are developing metallization at three levels:
Determine the standard latex screen and optimize the printing process with a set of printable materials; use the latest latex screen technology where a stronger alloy is used, the wire of the mesh is finer, and combined with new optical imaging technology Get up; make sophisticated hybrid templates.
As people can form finer conductive strips on silicon chips, part of the problem has shifted to avoid creating defects in the printing process. A very narrow conductive strip must be printed perfectly. However, a smaller width and height of the conductive strip will increase the impedance and reduce the energy conversion efficiency of the solar cell.
Of course, poor printing can cause the conductor to break. No matter how small the breakage, it will break the circuit and make the part of the solar cell that contains the circuit breaker inoperative. To solve this problem, you can use the experience and knowledge of solder joint reliability in SMT components.
in conclusion
For solar cell manufacturers, to achieve high productivity, the screen printing process and materials must be optimized according to the required yield, and the performance of the metallization line must be controlled to avoid chip damage and production line shutdown. All of these need the production line to be kept in a small area. To solve these problems, solar cells and final solar modules and arrays that are more efficient and have higher energy conversion efficiency are just around the corner. 
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