Laser direct imaging and improved process capability

A detailed multi‐site study has been undertaken to determine the variation in the positional accuracy of circuit features in the manufacture of large panel High‐Density Interconnect (HDI) printed circuit boards. The imaging stages were particularly referenced when it was shown that photo‐tool variation between 7 sites on 19 different photo‐plotters from 3 manufactures differed by substantially more than the typical HDI design rule. After photo‐plotter optimisation the residual errors between them were commonly of 2 types. It was concluded that the errors introduced in the standard photo‐tooling process were such that it was not possible to produce guaranteed yields on large HDI panels. It has been shown that the use of LDI can reduce costs and speed up the photo‐tooling production process. 3 different LDI machines were evaluated to study the concept of large panel high volume production. One was chosen for a long‐term study which concluded that HDI panels up to 30×24″ could be produced with the accuracy required for HDI designs. The output was approximately 9,000 scans per week but the productivity of circuit boards per panel was substantially improved with the larger panel size. It is feasible to double the throughput with the development of improved handling systems.