OREANDA-NEWS. Hitachi, Ltd. and Hitachi Metals, Ltd. have developed the LTCC (Low Temperature Co-fired Ceramics) package substrate with 2µm line and space re-distribution layer (RDL). Compared with current package substrate LTCC package substrate has achieved more than ten times of data processing capability by connecting LSI dies with memory dies by more than 1,000 fine lines. Furthermore, the capability of high reliability and low cost of this package substrate compared with the organic package substrate with silicon interposer are also shown.

In recent years, much attention has been placed on the Internet of Things (IoT). As the IoT spreads, it is inevitably to perform real-time processing of the massive volume of data from internet connected devices such as sensors, cameras, home appliances, or smart devices in automobiles. To enhance the data processing capability of these devices, increase of data transfer rate and number of signals are required. Conventionally, many advanced technologies have been proposed to the development of improving data processing capability.

One of these technologies is the silicon interposer stacked with organic package substrate on which several thousands of µm width wires are fabricated. However, silicon interposer fabrication includes a costly process of forming through silicon via and thinning wafer. The thinned silicon interposer will be stacked on an organic substrate. Both cost and reliability are the obstacles for adapting silicon interposer.

Therefore, Hitachi and Hitachi Metals focused on the technology of LTCC to develop the LTCC package substrate with fine line layers (Fig.1). This newly developed LTCC package substrate is capable of forming thin film layers directly on a LTCC substrate. This has not only eliminated the use of silicon interposer, but also removed one process step from assembly flow, which achieves a low cost manufacturing. Also, due to the coefficient of thermal expansion of the LTCC substrate is close to LSI dies and memory dies compared with the organic substrate, the warpage of substrate by thermal expansion during soldering process is smaller, which enhances its reliability. Furthermore, the LTCC substrate is capable of forming thicker lines compared with the silicon substrate, which is capable of minimizing the insertion loss.