Monitoring and control system for hot air solder leveling process
The goal of this project and report is to develop and implement a control and monitoring system for the hot air solder leveling (HASL) process used in the manufacture of printed wiring boards at the AT&T Microelectronics Printed Wiring Board Headquarters in Richmond, Virginia. The control and monitoring system consists of an AEG Modicon programmable logic controller (PLC) for each of the machines on the line, networked together using Modicon Modbus, and interfaced to an industrial hardened 6386 computer running Microtie man machine interface (MMI) software.
The PLCs perform the functions of machine control and monitoring of process parameters such as temperatures and pressures. The MMI serves as the operator interface and provides process status, alarm annunciation, data logging, trending and SPC charting. The process status function shows the status of each device on the line. The alarm annunciation function gives the operator a text alarm message display that is color coded to indicate the severity of the alarm. Color coded symbols are also used on the displays to point out the particular device that is in an alarm state. The data logging feature collects process data for all of the process parameters for an extended period of time. Data from the data logging routine are used for real-time trending and SPC charting of process data. The SPC chart developed is an individual and moving range chart. A traffic light system consisting of a stacked red, yellow and green lamp is used to indicate the overall status of the HASL Line. Host communication capability will be built into the system for future use when data from several processes may be merged and studied.