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Improve the efficiency of SMT Stencil Printer

Time:2019/05/07 丨 Source:未知 丨 Browse times:

Although the current online automatic solder paste screen printer can shorten the production cycle and maximize the pass rate, there is now a new standard called “Double Passage” to help improve the SMT assembly process. Solder paste screen printer machine production efficiency.

Solder paste screen printer is not the longest time-consuming step in SMT production. In many cases, it takes longer to complete the patch than the solder paste. Still, it makes sense to evaluate and adopt new methods to reduce the actual printing process time. The time saved in actual printing operations can be used to perform other steps such as solder paste application, stencil wiping, and post-press inspection. There are several factors that affect the time required for the printing process, which are equally important for reducing process time. Video-aligned Solder paste screen printer is a key factor in achieving fast Solder paste screen printer.
These factors include: the solder paste printer itself; the speed of PCB transfer and the speed with which the vision system adjusts the PCB; and how fast the machine performs the functions of coating, wiping, and post-press inspection. Solder paste itself determines the ultimate speed that can be obtained, which is also a major factor. Even the world's fastest solder paste printer can only print at any printing speed designed with this solder paste when printing any solder paste.
Another major factor affecting Solder paste screen printer speed is the ratio of component pad size to template opening size. In order to ensure the fastest printing speed, the stencil and the component pads on the printed circuit board must be tightly attached or filled, which ensures that the solder paste will not be squeezed under the stencil during the printing process to cause wet bridging. It can be considered that the pads of the component are added by 0.002 inches of the component pitch, and the opening of the stencil template is reduced by about 0.001 inches on each side of the pad. For a 0.020 inch pitch component, the component pad size is 0.012 inches and the template opening is 0.010 inches.
Each of the automation features of the solder paste press has its own advantages.
1. Solder paste applied to Solder paste screen printer machine
A common problem with canned solder paste operation is that there is too much solder paste placed on the stencil template each time. This is generally done because the solder paste printer operator does this to save time and other operations, usually to supplement the patch stock. Doing so will cause a large amount of solder paste to dry on the stencil, causing printing defects or excessive solder paste on the machine, support or camera. Excessive use of solder paste also allows the operator to quickly run out of solder paste, thereby reducing the normal rolling of the solder paste on the stencil and increasing the exposure of the solder paste to the solder paste printer operator and in the air. By placing the solder paste in a container and using an automatic solder paste application system, it is ensured that the solder paste is applied to the template in a timely and appropriate amount. In addition, the use of a container with a coating system also reduces the exposure of the solder paste to the operator and keeps the equipment and other tools as clean as possible.
Second, wipe the Solder paste screen printer machine steel mesh template
Even a PCB with a flat pad of component leads and a well-designed printing process requires regular wiping of the bottom of the stencil. Stencil openings are properly shrunk relative to the component pads, and flat component pads, such as bare copper or Alpha Level, reduce the amount of solder paste that is pushed into the bottom of the stencil, but still do not eliminate the wipe. need. An automated system can be set up to perform this operation at appropriate intervals to ensure that the bottom of the stencil is clean without bridging. Modern Solder paste screen printer machines, such as the Hirose Dessert printing press, have an automatic wiping system that can be used for dry rubbing, solvent cleaning or vacuum wiping. A dry or solvent-filled wipe can wipe off the solder paste on the bottom of the stencil and eliminate bridging. Vacuum wiping can suck out the solder paste in each opening to ensure that the openings are clean and open, so that the shortage of solder paste is not enough.
The automatic stencil stencil can be wiped at the timing of the Solder paste screen printer machine to ensure that the bottom of the stencil is clean without wet bridging.
Third, the Solder paste screen printer machine after printing inspection
As the use of array packages increases, such as ball grid arrays (BGAs), chip scale packages (CSPs), flip chips, and more, the applied solder paste is "observed" before the PCB leaves the solder paste printer. The ability is becoming more and more important. While the array package offers many advantages, it also brings a disadvantage, that is, the actual solder joint can no longer be seen by conventional inspection methods. Post-print inspection ensures that solder paste is applied to each component pad before the PCB exits the solder paste printer. The new version of the software, such as the Hirose Depressor, contains custom BGA inspection capabilities that can be set to check the geometry of the 2D post-printing of any actual package.
The post-print inspection of the solder paste printer ensures that the solder paste is printed on each component pad before the PCB exits the solder paste printer.
Fourth, Solder paste screen printer dual-channel thinking
In addition to technical issues, long-term factors must be considered, such as the benefits of plant and equipment assets. In this respect, many production equipment suppliers have developed the idea of ​​a complete set of production lines based on traditional SMT production equipment such as solder paste printers, placement machines and reflow ovens. It is built on two parallel conveyor belts. Designed on the basis of a new generation of equipment. This idea is called "dual path."
The two-pass idea can be described as follows: In SMT electronics assembly, each path can be independently controlled in a logically ordered sequence to create an effective board flow. This reduces the time lost in the board transport process and extends the time it takes for the SMT equipment to do its job. A two-pass solder paste press can print the second board while loading/unloading one board, saving overall time.
The dual-channel SMT idea can result in higher yields in a given area.
The two-pass concept also shortens the production line, reducing the need for plant space; in addition, many single-piece equipment has been cut, thereby reducing upfront investment, manpower requirements, facility overhead, and overall operating costs. From a device perspective, new assembly systems, including the new model of solder paste presses, offer greater flexibility with two separate channels. With this type of equipment, a two-pass line can handle several boards simultaneously.
In the electronics and PCB manufacturing process, many assembly tasks must be done efficiently to achieve maximum throughput and productivity. Careful planning of the assembly process is critical, and all steps of the SMT process are closely linked to the adjacent upper or lower steps. To address these types of PCBs with different component densities, different layers, different sizes, and different shapes, process engineers must plan the assembly line to meet the type of PCB being machined. Some lines may be set for maximum flexibility (fast line change), while others may be set to have higher yields, and more settings are considered together.
However, while setting up the SMT electronics assembly line, it is necessary to consider other aspects than production. While SMT continues to evolve in all aspects of packaging, manufacturing, and craftsmanship, the idea of ​​“lighter, smaller, faster, and cheaper” is becoming more entrenched. Technologies including high-density internal interconnects will certainly affect the size of the product, and the goal of being an electronics assembly manufacturer is to achieve the best manufacturing process. The result is that regardless of the amount of production involved or the ease of the product, productivity is certainly the most fundamental concern in SMT manufacturing.
Therefore, it is not possible to simply add a solder paste printer, a placement machine, a reflow system, a cleaning machine, or other SMT assembly equipment regardless of the plant area involved and the cost of the investor. Instead, it must be recognized that depending on the minimum requirements for productivity and profitability, the results of different machine or machine combinations can vary greatly.
For this reason, the manufacturing idea like the two-pass method can bring some obvious benefits in the Solder paste screen printer process. The dual path reduces the time required for loading and unloading plates that do not add value, while at the same time producing significant cost savings by bringing more manufacturing potential in a given area, in other words, higher in a given area. Production.
The automation benefits of today's advanced Solder paste screen printer machines, combined with the proper design of the printing process, guarantee the shortest production cycle and the best end product quality, especially in the SMT industry. This is especially true when it comes to the new dual-channel thinking.


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