SMTA International Conference Proceedings


ALL LASER PROCESS FOR HIGH DENSITY MULTI-LAYER CIRCUIT BOARDS

Author: Ken Inaba
Company: SSK Ltd.
Date Published: 9/22/2002   Conference: SMTA International


Abstract: Three direct laser imaging processes have been combined to build high density multi-layer circuit boards and rigid/flex. A new direct carbon dioxide laser system can generate high quality micro blind holes through copper foil without the chemical etching process of conformal mask. The new laser process has a much higher productivity than the UV-YAG laser and it can make the micro hole drilling process simpler.

The process can provide reliable micro blind holes with a low cost. The laser direct imaging processes have been employed for fine copper trace generation. The process is capable of generating 50micron line and space circuits for both inner layers and outer layers with high accuracy dimensional compensation. The laser process provides an exact alignment between micro via holes and small pads, and it allows 150 micron pads for micro size blind via holes.

A new laser direct imaging process was introduced to make a zero clearance opening on the solder mask for high density SMT assembling. The process minimizes the clearance between the opening of the mask and soldering pads to 25 micron or less. More spaces are left for the lines between the soldering pads. It is a valuable capability for the mounting of high pin count BGA and CSP substrates.

All laser processes are capable of making an exact dimensional compensation for both the whole board shrinkage and partial distortions, therefore, the whole process can increase the manufacturing yield of high density multi-layer boards and rigid/flex by harmonizing the three laser processes.

The new laser process provides the design flexibility extremely higher for both of the layer constructions and the routing. The process allows an application for the inner layers of the build-up process and it generates micro size connections between the inner layers with a low cost.



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