The PCBRM100 is the latest in an impressive line of solder rework systems to remove defective parts from circuit boards after their initial build.
PCB Solder Fountain Technology
Using the proper motion controllers helped one company design their latest product, which is used to remove, site clean, and replace through hole components on large printed circuit boards.
As a manufacturer of flexible machines for high-quality Printed Circuit Board (PCB) rework/repair, selective soldering/desoldering, and assembly systems, Air-Vac (Seymour, CT) has addressed the necessary factor in adhering to the International Electronics Manufacturing Initiative 2013 Technology Roadmap that requires lead-free rework of plated-through-hole (PTH) components on large, high thermal mass assemblies. The company's PCBRM100 was specifically designed to remove, site clean, and replace through hole components from large boards (26" x 26").
The overall design of the new system was based on customer feedback as well as years of experience and market need. The platform was designed and built entirely in house. According to Joe Koutrakos, Engineering Team Leader, "At one point, we sent one of our first PCBRM100 prototype machines to a customer for evaluation and design review. The prototype machine is still running at the customer's facility three years later."
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AllMotion's EZSV17 is a fully intelligent servo controller that operates with brushed or brushless DC motors, and is only 1.6-inches by 1.6-inches in size for compact placement in automated systems. |
The PCBRM100 incorporates the EZSV17 servo motion controller designed and manufactured by AllMotion (Union City, CA). The EZSV17 measures only 1.6-inches by 1.6-inches and requires little to no tuning when used with most motors measuring less than 2-inches in diameter. It was designed to allow the rapid implementation of brushless DC motors or brushed DC motors in automation systems. The motion system for the PCBRM100 also includes several linear encoders operating with rotary motors that are switched back and forth between being belt driven and used in a direct drive operation. Linear motors would have been too expensive for such a large system.
When asked about major features that Air-Vac was able to take advantage of while using the EZSV17 from AllMotion, Joe rattled off five right away. "The biggest factor," he said, "was price." Ultimately, any manufacturer wants the highest capability for the most reasonable price. Another factor included reliability. As Joe explains, "We've used the EZSV17 on other products for years and have had absolutely no issues with the controllers. They perform just as their specifications guarantee."
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During operation, the PCBRM100 uses a camera-assisted alignment and joystick control to precisely position components for removal and site cleaning. |
Other key features of the controllers that Joe mentioned included the 485 communications capability at 115,200 baud, which helped to increase the speed of operations; software flexibility that allows the machine to send a command and get it instantly executed; and the use of a direct drive joystick control, which allowed for easy operator interaction with the machine. Additional features of the controllers include a single 4-wire bus that can link up to 16 stepper/servo motors; a 2-Amp motor driver; operating voltages from 20 to 40 volts, RS232, RS485, or USB based communications; on-board EEPROM for user program storage; and standalone operation.
The PCBRM100 is totally automatic. A carrier is programmed through the EZSV17 controller along X and Y axes through the use of linear encoder feedback for the ultimate in accuracy and repeatability. It moves to a taught position where a down-looking digital camera with zoom lens relays an image to the operator. The camera superimposes the image of the solder stack over the top of the board. At this point, the operator can align the part using an X-Y joystick-based control. The desired rework position can be taught on-the-fly or stored in the program. After alignment is completed, the board moves into the oven where it is heated using focused convective heating to about 150°C. Once board reaches temperature, the board comes out of the oven and returns to the previously taught aligned position where it is then lowered to 15mm above the flowing solder. At this time, an additional nozzle is lowered to 5mm above the part, as well. The part is now heated to 217°C and lowered into the solder for removal.
Once inside the solder flow, either a vacuum is turned on and the upper nozzle removes the loosened component or the operator manually removes the part. After the part is extracted, the board moves to 25mm above the solder flow for solder removal. A solder scavenger nozzle is installed and lowered back to the top of the board for this purpose. Using the joystick control, an operator moves the nozzle over the barrels of the board to remove any solder left in the barrels. This process can also be automated where the machine can perform the removal with no operator interaction. Finally, the board returns to the unload position for removal. The board can now have a new component inserted and the machine can be used once again—this time to solder in the new component.
Due to the use of the best motion technology available, the machine has an accuracy of 0.001-inch. Because the PCBRM100 is an open machine, the speed of operation doesn't have to be fast in most cases. The joystick control does offer the operator a very accurate and easy to use interface to the machine. In addition, the software used with the machine is user-friendly for the operators. Originally, the engineer in charge of first programming the machine performs the majority of the work needed for operation. This includes the setup of part locations, board thicknesses, part thicknesses, and other key data based on the particular board being worked on. Once the initial setup is completed on a particular component, it can easily be copied and pasted to similar parts or boards.
The machine itself is 120-inches long, 52-inches wide, and 77-inches high. Its solder pot capacity is 90 pounds, the top and bottom preheater sizes are 28-inches by 28-inches, with a clearance of three-inches on the top and bottom. The system also has eight thermocouple channels.
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