Masters Abstracts (1994)

MONTOCCHIO, NARISA
(April 1994), Procurement Engineer, Hewlett Packard GPS, Bangkok, Thailand

Email: narisa_montocchio@hp.com

Accuracy Evaluation Methodology for Three Dimensional Laser Based Solder Inspection

The solder paste stencil printing process is widely used in the PCB assembly process. However, the variability associated with this technique is becoming increasingly unacceptable due to the evolution of SMT and also due to the need to meet and exceed quality and reliability goals. The use of on-line real-time inspection would assist in evaluating and controlling the variability associated with the stencil printing process. Laser based inspection methods could be used to inspect solder paste and provide information to proactively control the deposition process.

This research investigated the accuracy and repeatability of a three dimensional laser based solder paste inspection system. This inspection system (the SVS 7530) can measure the height, area and volume of the solder paste deposited on the board. The influence of factors such as the system's resolution, the micro-structure of the surfaces being inspected, and the orientation of the solder pads with respect to the inspection system's axis was studied. A comprehensive set of experiments was designed to ensure the statistical validity of the results.

Two experiments were conducted in this research. The first part of experiment one used plated solder pads as gage blocks, and the SVS 7530, the CMM, and the Cyberoptics were used to measure the area of the plated solder pads and their height, and consequently their volume. Results obtained from each of the measurement systems were then compared to one another with the CMM as the base. The second part of experiment one studied the orientation of the different pads during inspection. The second experiment studied the surface structure of the solder paste to see if the surface structure posed problems for the laser based inspection system (SVS 7530).