Product Code: ICAL05_M803

Two-Dimensional Transient Modeling of CO2 Laser Drilling of Microvias in High Density Flip Chip Substrates
Authors:
Chong Zhang, Univ. of Central Florida, CREOL; Orlando Florida USA
Islam Salama, Intel-Assembly and Technology Development; Chandler AZ USA
Nathaniel Quick, AppliCote Associates LLC; Orlando FL USA
Aravinda Kar, Univ. of Central Florida, CREOL; Orlando Florida USA
Presented at ICALEO 2005

Thermal modeling is essential to understand the laser-materials interactions and to control CO2 laser drilling of blind microvias (< 50 um) through polymeric dielectric in multilayer electronic substrates. In order to understand the profile of the drilling front irradiated with a Gaussian laser beam, a two-dimensional transient heat conduction model including vaporization parameters is constructed. The absorption length in the dielectric is also considered in this model. Therefore the volumetric heating source criteria are applied in the model and the equations are solved using the Galerkin method. The drilling speed, temperature distribution in the dielectric and the thickness of the residue, termed smear, along the microvia walls and at via bottom/copper pad interface are studied under different laser parameters. In particular; the temperature distribution along the radial direction (governed by various laser drilling parameters) is controlled to minimize the thermal damage and smear residue on the microvia wall/bottom diameter.