Embedding and Reliability of Discrete Capacitors Into Build Up Layers of Printed Circuit Boards
Authors: Thomas Löher, Joao Marques, Martin Haubenreisser, Andreas Ostmann, and Norbert Bauer Company: Technische Universitaet Berlin, Fraunhofer IZM, and Murata Elektronik GmbH Date Published: 10/14/2012
Abstract: Electronic component manufacturers are responding to the emerging trend towards embedding technologies into printed circuit boards. One requirement for the embedded components to be met is the proper connector metallization. A typical conventional surface mount component has to be compliant with a lead free soldering process, therefore the contact metal is a combination of copper a diffusion barrier of Ni and Sn as outer metal. The total thickness is around 5 µm. By contrast the embedded component is connected through an electro-plated micro via (typically laser drilled). In this process 5 to 10 µm copper is the preferred metallization of the component contact. The latter is being offered now for a range of components in typical size range of 0402, 0201 with a thickness of 150 and 220 µm (330 µm thickness is used for high cap components). Smaller components are on the roadmaps of suppliers and planned to be on market within the next three years. A series of embedding and reliability tests using thin capacitors were conducted in a co-operation between Fraunhofer IZM and MuRata. Different aspects of the embedding technology were investigated: (a) For printed ciruit board (PCB) fabrication with embedded components a high throughput pick and place process of the components is mandatory in order to be commercially viable, robustness of components with respect to this process was therefore investigated. Given the component thickness the choice of the pick tool and machine parameters are essential for a defect free assembly. (b) Materials and processing of the build up-layer was the second focus of the study. Lamination and µ-via contact formation as typical PCB processes were used and robustness of components agains laser drilling and exposure to chemicals was investigated. (c) The fabricated test coupons where subjected to thermal cycling and storage in humidity for 5000 cycles and 5000 hours storage in the first set of reliability test. Bending, twisting and combinations thereof are be topics of ongoing research in the field. Results of handling, processing and reliability will be presented and compared with typical data for conventional SMD assemblies.