Several kinds of ball array packaging techniques are applied in the surface mounting technology, the commonly used ones are plastic ball array ceramic ball array and ceramic columnar array.
Due to the different physical characteristics of these packages, it is more difficult to repair bga.
In the repair, it is necessary to use the latest automation equipment, and understand the structure and thermal energy of these types of packaging on the direct impact of component removal and repasting, which not only saves time and money, but also saves components, improves the quality of the board and realizes the rapid repair service.
In many cases, it is possible to repair a bga package yourself without having to call in a specialist repairman. The repair of the bga package also involves removing other "good" bga components from the defective board.
All bqa repairs follow a basic principle: The number of bqa packages and bqa pads exposed to thermal cycles must be reduced. As the number of thermal cycles increases, the likelihood of thermal damage to the pads, solder masks, and the bqa package itself increases. Current status of bqa technology Ball-grid array technology is attractive due to its high i/0 count. Because of the high cost of X-ray detection equipment, people often blame the detection required by bga, and this technology just has the advantage of no inspection, mount technology has realized the development of independent equipment to be matched with mechanical equipment, and can easily draw the printing and flow curves. However, after the removal of components, to re-add the solder ball to the components, usually can not meet the needs of users.
Unlike many other component technologies, bqa cannot be removed from a pcb component without destroying the interconnecting materials. During the repair process, half of the bga solder ball is retained on the assembly plate, while the other half is carried by the element and drawn into a wire.
For this reason, the whole sphere is required to be repaired and prefabricated pcb pad before repair. Methods used to repair bga One method used is preforming, in which solder balls are embedded in a water-soluble based flux according to array/spacing matrix requirements. The cost of preforming a solder ball is about 1000. Preforming is realized by reflow welding after the bga face down. The entire solder ball is expected to roll so that the water-soluble flux can be rinsed off and the package can then be repaired. Another approach is to mimic the original manufacturing technique, namely printing flux or solder paste on a bt glass substrate and automatically filling the preformed solder balls into a thick template on a downfacing bga. If there are too many solder balls, the formwork should be removed and the components sent to the furnace for re-flow so that the interconnection meets the requirements. However, the application of this method, the cost is lower than the preforming method, its cost is 40/100k sphere, and the use of another method of welding paste, can achieve the advantages of lower cost, in addition, the application of welding paste method, there will be no vibration of the sphere, scattered around the phenomenon.
The solder paste can be printed on the element by combining the solder paste method with the complete tool for refilling the solder ball, so that the template is retained in place and the solder ball is formed in the element during the refilling process. The element was fully repaired when the template was removed. The bga element can be removed by using a hot air repair tool with corresponding curves. The pcb pad must be cleaned and once the excess solder has been removed, the solder should be reprinted prior to mounting the components. The pbga can be welded to the weld area with flux or solder paste. Liquid flux can be applied with hand tools, and sticky flux and solder paste can be applied to the pad either by printing or by spraying. After the component is mounted, the pcb is re-flowed under the appropriate thermal curve. In the re-flow process, each solder ball on the bt substrate, the ball is locally flat and the projection height is about 24mil.
In the process of pbga attached to pcb, a second re-flow and further "collapse" of each solder ball is performed, finally reaching a projected height of approximately 19mil. The solder mask and its hole diameter in the pcb mounting area can determine the height after re-flow. Usually, this tolerance is sufficient for the pbga cleaning process. It is necessary to remove excess solder from the bga. When removing excess solder, use a solder removal tool, solder braid, or soldering iron to complete the removal process by tilting the repair tool to an Angle and touching the area to be repaired.
The residual solder on the bga pad, in the shape of a small crescent, is obviously insufficient to meet the amount of solder required for the sphere. When the excess solder is removed, the center of the element is heated and the heat is transferred to the surface of the element in the form of a spiral to achieve uniform heating. The bqa is then loaded onto the appropriate size template substrate on the downfacing element. After the template has leveled the components, the solder paste can be printed into the holes of the template with a scraper, and the excess solder paste can be removed with a scraper. Use the hot air tool to mount the component, with appropriate nozzles and temperature curves, due to the hot air heating effect, make the component move until the welding sound flow, forming a single ball of solder. The center of the element is heated again, and the radial operation or the outward spiral operation can achieve the purpose of uniform heating.
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