Monitoring of laser micro spot welding for packaging three dimensional molded interconnect devices

Abstract

This paper shows the possibility of monitoring the laser spot welding (LSW) processes based on detecting and analyzing the optical process emission. Hence integration of online quality inspection is realizable, which enables the automation of packaging three dimensional molded interconnect devices (3-D MID).SO16 and lead frames as two components of widely used surface mounted devices (SMDs) were packaged on flexible printed circuits (FPCs) in the experiments. Due to the flexibility of FPC and its deformable shape, the results can be easily transferred to 3-D MID. The reproducibility of the weld quality for SO16 (FeNi) is greater than for lead frames (CuFe2P); this points out the difficulties appearing during copper or copper alloy welding. However, a correlation between the weld quality and the detected emission signals recorded during the weld process has been found for both components.The detected signals of the optical process emission for successful welds depict identical characteristics which are divided into three relevant signal phases. Changes in the signal characteristics, especially in these phases, imply information about the weld quality. While monitoring the welding processes for both components are possible, the detected signals for SO16 are less sensitive to process variations compared to those for lead frames. Based on spectral analysis, the intensity of the detected emission due to SO16 welding is slightly higher than the intensity due to lead frames welding.This paper shows the possibility of monitoring the laser spot welding (LSW) processes based on detecting and analyzing the optical process emission. Hence integration of online quality inspection is realizable, which enables the automation of packaging three dimensional molded interconnect devices (3-D MID).SO16 and lead frames as two components of widely used surface mounted devices (SMDs) were packaged on flexible printed circuits (FPCs) in the experiments. Due to the flexibility of FPC and its deformable shape, the results can be easily transferred to 3-D MID. The reproducibility of the weld quality for SO16 (FeNi) is greater than for lead frames (CuFe2P); this points out the difficulties appearing during copper or copper alloy welding. However, a correlation between the weld quality and the detected emission signals recorded during the weld process has been found for both components.The detected signals of the optical process emission for successful welds depict identical characteristics which are div...