Jun. 05, 2019
Rapid repair application of SMT circuit components
Custom PCB prototype China shares that repair is usually to remove components that have lost function, damaged leads or misaligned components and replace them with new ones. It is to recover the unqualified circuit components into qualified circuit components consistent with specific requirements. In order to satisfy the electronic equipment smaller, lighter and cheaper, more and more electronic products with precision micro components, such as flip chip, CSP, BGA, new packaging components for assembly process put forward higher request, is to improve on the requirements of the repair process, therefore, should pay more attention to the correct repair technology, method of repair and repair tools. Part of the repair technology of SMT components was introduced in the last section. What are the application of repair technology?
(1) laser welding. This kind of system has the heat focused on point, is not affected by device packaging material properties and not on the substrate heating, hot melt the characteristics of short time, can obtain higher quality of solder joint, but there are also slow, easy to produce welding ball, the welding temperature characteristic consistency are harder to control, the price is expensive and other shortcomings, thus more used in special fields. In addition to the laser welding can be used in SMT repair system has the basic control system, laser and optical and infrared detection device used to real-time monitor laser welding joints heat state, so in shaft under the help of a computer system, thermal characteristics of the specific solder joint inspection, to ensure the consistency of spot welding, at the same time direct feedback control, welding and inspection in sync.
The above characteristics of laser repair device is especially suitable for the repair process to add components, especially high density printed circuit components repair, and some is not suitable for gas welding and hot air reflow soldering heat sensitive components are also very accord with the characteristics of laser welding, a new type of components such as BGA, CSP, flip chip, can under the east light scanning laser energy of fast enough, don't use other Xiang help finish point welding device. Under the special control, also can do short circuit correction of high density circuit components, even the PCB printed wiring can be revised, cutting, marking, such as work, although the mountain to the device and complex manufacturing cost cause there is no special equipment to get essence applications, but the laser welding technology in SMT circuit components of fast repair applications extremely promising.
(2) welding process materials. Flux is an essential process material in the welding process of all printed circuit components. Liquid flux can be applied with a needle drop or with a sealed or rechargeable flux pen. Flux pen can be applied to effectively control the amount of flux used. Common solder wire can also carry a solid flux core, this form of welding material contains both flux and solder alloy, when using flux-cored solder and liquid flux, in the process control to ensure that the two flux compatibility.
(3) manual welding process. Normally, there are five steps in the manual welding procedure, including preparation, heating, inserting the tin wire, removing the tin wire, and leaving the soldering tip five steps away. Quickly contact the heated and tinned soldering tip with the cored tin wire, and then contact the welding area. Use the melted solder to realize the initial heat transfer from the soldering tip to the components, and then move the tin wire away from the soldering tip that will receive the soldering surface. In some application environments, for example, lead-free solder manual welding, due to the characteristics of solder and flux composition requirements, most enterprises recommend such a welding procedure. First, heat the electric soldering tip to contact the pin or pad, put the tin wire between the electric soldering tip and the pin to form a thermal bridge; The wire is then quickly moved around the solder joint area to form a perfect solder joint.
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