Development of all-photonics-function embedded package substrate using 2.3D RDL interposer for co-packaged optics

Toward a next generation co-packaged optics, we have worked on a novel packaging substrate working as optoelectronic conversion engine and providing optical redistribution function and detachable optical connector. In this paper, we show design of the test vehicle using 2.3D RDL interposer and provide its thermal and electrical analysis results.

I. Introduction

Co-packaged optics (CPO) has attracted much attention from many applications requiring very high bandwidth for data transfer, such as data center switching, artificial intelligence and disaggregated computing [1]. Recently, first generation CPO was released from Broadcom which supports total bandwidth of 51.2 Tbps for a switch application specific integrated circuit (ASIC) [2], and many research groups have worked on next generation CPO technologies [3]-[5]. In Japan’s Green Innovation Fund Projects, development of optical smart network interface card (NIC) using CPO technology has been worked for next-generation green data centers. Within this project, we have worked on active optical package (AOP) substrate for next generation CPO. AOP substrate is a novel package substrate in which photonic integrated circuits (PICs) are embedded as shown in Fig. 1 [6]. It provides all required photonics functions to realize CPO, such as optoelectronic conversion function, optical redistribution layer (ORDL) function and detachable optical connector. The AOP substrate will be provided and assembled in the same condition as conventional package substrates. We demonstrated key technologies for the AOP substrate, such as PIC die embedding, micro mirror optical coupling, polymer-waveguide ORDL and self-aligned optical connector [7]-[9]. Recently, we are fabricating the first active demonstration sample as the test vehicle. In this paper, we show its overall design and report its thermal and electrical analysis results.