Force Control in a Placement Head for Surface-Mount Devices

Abstract

For recent surface mount devices, chip components have been becoming ever smaller and thinner, requiring the utmost care in their handling. The impact force occurring at the time of mounting with present surface mount devices placement systems can damage delicate components, reducing their service life. A contact operation which suppresses this impact force and a pressure operation which mounts components using a force corresponding to the component are necessary.
In this paper, we examined a technique in which the structure of the control system is simple and which applies satisfactory pressure even for high-rigidity subjects. The technique is applied to a surface mount devices placement system. This is accomplished using a speed control mode which adjusts the contact speed to suppress the impact force and a force control mode for pressure with no overshoot. In the force control mode, a satisfactory response for reference was accomplished for even high-rigidity subjects by utilizing a reference filter. In the speed control mode, motion is stopped momentarily immediately after contact to prevent the vibrations which occur due to the condition of switching to the force control mode; it was shown that there is a proportional relationship between the contact speed and the impact force which occurs during the stop operation. Further, contact and pressure operations at the optimum contact speed according to this proportional relationship were verified, showing the validity of this technique.