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Session 1793

A Flexible Automated Solder-Paste Dispensing System Jon R. Plummer, Barry M. Lunt Brigham Young University

Abstract This paper describes a flexible automated solder-paste dispensing system which does away with the need for a dispensing screen, thus avoiding its cost and changeover time. The system described is composed of a 4-axis robot, a solder-paste dispensing tool and controller, a conveyor system, and a processing computer. The processing computer inputs the Gerber file describing the PCB and creates the program to drive the robot with the solder-paste dispensing tool. The PCB is then brought under the robot and the dispensing takes place.

This system has been developed and demonstrated in Brigham Young University’s Electronics Assembly and Automation Laboratory. Due to the absence of a solder-paste screen, this solder- paste dispensing system is capable of lots as small as 1, yet provides the quality of a screen- printing system. The disadvantage is a lower throughput.

Introduction In the process of assembly of electronic printed circuit boards, the solder paste is usually deposited on the printed circuit board (PCB) by means of an automated screen-printing machine. These machines feature good reliability, high throughput, and high quality, but their major weakness is that there must be a screen built for each PCB manufactured. These screens, typically manufactured by very precise etching or laser milling machines, can be quite expensive. Additionally, for each different PCB, the screen-printing machine must be manually set up with the corresponding screen. There are additional disadvantages to the screen-printing method, as discussed in the next section. In general, the present method of screen-printing the solder paste is viable only for large volumes of a given PCB design.

When producing prototypes or small lots of PCBs, it is valuable to have a flexible manufacturing system that can change between PCB shapes, sizes, and layouts with ease. Setup time and changeovers can be costly, wasting valuable time and preventing the PCB from being tested and ultimately sent on to mass production.

In such flexible manufacturing environments, the solder paste dispensing step of manufacturing a PCB is done using a dispensing syringe because the cost of making a dedicated stencil as is typically done in mass production can range from an additional $250 to $500 depending on the requirements of the stencil.1 Often times the design of the PCB will change before mass production thus making the production of a stencil even more costly if changes occur multiple times.

Currently the setup time of the equipment for syringe type solder paste dispensing between PCBs is tedious and time consuming taking away from the flexibility of the system. The current Proceedings of the 2004 American Society for Engineering Education Annual Conference & Exposition Copyright © 2004, American Society for Engineering Education

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Plummer, J., & Lunt, B. (2004, June), A Flexible Automated Solder Paste Dispensing System Paper presented at 2004 Annual Conference, Salt Lake City, Utah. 10.18260/1-2--14120