Simulation of Embedded Components in PCB Environment and Verification of Board Reliability
Embedded components technology has launched its implementation in volume products demanding for highest miniaturization level. Small modules with embedded dies and passive components on the top side are mounted in hand held devices. Smart phones are the enablers for this new technology using the capabilities of embedded components. These modules have already shown a high level of reliability which has been a pre-requisite to get acceptance for volume products. Embedded dies are relative small with dimensions of about two by two millimeter and therefore all critical topics like the CTE mismatch of components and PCB materials,process die attachment are on a non-critical level. The roadmaps for the application development show a drastic increase of the complexity of the modules and in parallel increasing I/O numbers and die dimensions. Applications in the development pipeline show already die dimensions of seven by seven millimeter.
Based on this development roadmap a simulation project was started with the Material Center Leoben and Thales Global Services to evaluate the stress situation of embedded components and to build a thermo mechanical simulation model. The verification of this model was started by characterization of silicon dies and embedding of standardized components into PCB to get detailed stress parameters for these components. The next step of simulation deals with the simulation of embedding processes. Die assembly is the first process followed by the lamination process to form the embedded core. For the assembly process a DOE has been done to correlate the results with the simulation model.
All along the European funded FP7 HERMES*project huge efforts have been deployed in order to characterize the reliability of active and passive embedded chips,as well as packages assembled on the outer layers of the PCB . To achieve a high level of reliability of future complex modules using HERMES technology,work has been done to address different aspects like process optimization including different build-ups,best choice of base material,different size of active dice and design rules,knowledge of failure mode.
HERMES was successful closed in February 2012 and the final results of the HERMES embedding technology are shown in this paper. A dedicated test vehicle using a 4 (level of stacked µvia) +core +4 simulating a functional demonstrator have been manufactured and stressed under accelerated thermal cycling in the range -40°C/+125°C and under continuous monitoring.
This test vehicle includes embedded chips of different sizes,passive chips and BGA/QFN package assemblies on the external faces of the PCB. The design permits to isolate component (in daisy chain) and interconnections to facilitate the reliability and failure analysis. A detailed construction analysis of the manufactured boards has been done before to start the reliability test in order to have a reference.