5/1/2023 0 Comments Reflow stationUsing semiautomated or fully automated machinery.įor the PS3 and Xbox mentioned above, the time is about 120 minutes if all goes well.Using a BGA "preform" with embedded balls corresponding to the device pattern, or.Using a stencil for both the balls and the solder paste or flux,.The new balls can be placed via several methods, including: Reballing involves dismantling, heating the chip until it can be removed from the board, typically with a hot-air gun and vacuum pickup tool, removing the device, removing solder remaining on the device and board, putting new solder balls in place, replacing the original device if there was a poor connection, or using a new one, and heating the device or board to solder it in place. While such methods can cure some problems, the outcome is likely to be less successful than is possible with accurate thermal profiling achieved by an experienced technician using professional equipment. Reflowing can be done non-professionally in a domestic oven or with a heat gun. On a forum where professional repair people discuss reflowing of laptop computer graphics chips, different contributors cite success rates (no failure within 6 months) of between 60 and 90% for reflowing with professional equipment and techniques, in equipment whose value does not justify complete reballing. For typical devices ( PlayStation 3 and Xbox 360) one repair company estimates that the process, if there are no unexpected problems, takes about 80 minutes. This may or not resolve the problem and there is a chance that the reflowed board will fail again after some time. Reflowing as a rework technique, similar to the manufacturing process of reflow soldering, involves dismantling the equipment to remove the faulty circuit board, pre-heating the whole board in an oven, heating the non-functioning component further to melt the solder, then cooling, following a carefully determined thermal profile, and reassembling, a process which is hoped will repair the bad connection without the need to remove and replace the component. Devices can be recovered from scrapped assemblies for reuse in the same way. Imperfect connections of devices which are not themselves faulty, which work for a time and then fail, often triggered by thermal expansion and contraction at operating temperature, are not infrequent.Īssemblies which fail because of bad BGA connections can be repaired either by reflowing, or by removing the device and cleaning it of solder, reballing, and replacing. Bad connections produced during assembly can be detected and the assembly reworked (or scrapped). Connecting pins are not accessible from the top for testing, and cannot be desoldered without heating the whole device to the melting point of solder.Īfter fabrication of the BGA package, tiny balls of solder are glued to the pads on its underside during assembly the balled package is placed on the PCB and heated to melt the solder and, all being well, to connect each pad on the device to its mate on the PCB without any extraneous solder bridging between adjacent pads. The surface tension of the molten solder, which is on the board's solder pads, tends to pull the device into precise alignment with the pads if not initially positioned totally correctly.īall grid arrays (BGA) and chip scale packages (CSA) present special difficulties for testing and rework, as they have many small, closely spaced pads on their underside which are connected to matching pads on the PCB. High quality demands or specific designs of SMDs require the precise application of solder paste before positioning and soldering the unit. Reliable solder joints are facilitated by use of a solder profile which preheats the board, heats all the connections between the unit and the PCB to the melting temperature of the solder used, then properly cools them. The smaller the pitch and size of the components, the more precise working must be.įinally the newly placed SMD is soldered onto the board. The precise placement of the new unit onto the prepared pad array requires skillful use of a highly accurate vision-alignment system with high resolution and magnification. A soldering iron or hot air gun can be used with desoldering braid. It is quite easy to remove these residues by heating them to melting temperature. The pad array on the conductor board should then be cleaned of old solder. Heating a single SMD with a hot-air gun to melt all solder joints between it and the PCB is usually the first step, followed by removing the SMD while the solder is molten.
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