Browse Prior Art Database

SOLDER WAVE HEIGHT MEASUREMENT AND CONTROL SYSTEM

IP.com Disclosure Number: IPCOM000006941D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2002-Feb-11
Document File: 3 page(s) / 122K

Publishing Venue

Motorola

Related People

Hans Stendel: AUTHOR [+2]

Abstract

The height of a solder wave at wave soldering machines is a major variable to guarantee the perfect solder result. Most common, soldering machines are using a manual wave height adjustment system only, where the machine operator checks the wave height and adjusts the system.

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MOTOROLA INC. Technical Developments Volume 19 June 1993

SOLDER WAVE HEIGHT MEASUREMENT AND CONTROL SYSTEM

by Hans Stendel and Rainer Woerthmann

1. BACKGROUND

  The height of a solder wave at wave soldering machines is a major variable to guarantee the perfect solder result. Most common, soldering machines are using a manual wave height adjustment system only, where the machine operator checks the wave height and adjusts the system.

  In practice, there are lots of interferences, that may influence the wave height, f.e. line voltage, mechanical system setup, solder tin level, contamination, tempera- ture, atmosphere etc. So the operators performance and the period of readjustment will result in the solder qual- ity. A closed loop control system is highly recommended to improve the precision ofwave solder height.

  Approaches for closed loop systems have been made with visual or inductive systems. This report describes a fully automated solder wave height measurement and control system, using an oscillating switch as a sensor, developed by MOTOROLA Taunusstein. This system is designed to be used for smooth solder waves as well as for turbulent solder waves.

2. THEORY OF OPERATION

To control the solder wave height, it is essential to measure the actual height with a sensing element.

  Therefore, a new approach has been made to develop a sensor of high performance. We are using a contact plate, that oscillates above the solder wave. When the contact touches the solder wave, it electrically shuts down, otherwise it gets open. Biasing the contact plate, we are getting a pulse-width-modulated output voltage, where the pulse-pause relation is a measure for the wave height. Filtering the PWM signal with a low pass filter, a linear output voltage is achieved. This voltage is.inversely pro- portional to the wave height.

The voltage is compared to a preset value and any difference readjusts the speed of the solder pump motor

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across a PID regulator. With the preset value, we are able to adjust the PWM duty cycle between 10% and 90%, or, the wave height between 10% and 90% ampli- tude of the oscillating contact.

3. SENSOR DESCRIPTION

Figure 1 is a functional sketch of the wave height sensor.

  With a DC-gear motor a cam/lever system is driven. A sensor plate is mounted electrically isolted at the far end of the lever. The lever is adjusted such that the sen- sor plate dives into and leaves the solder wave with every rotation of the gearmotor. To allow the solder...