Module packaging for high-speed serial and parallel transmission

Abstract

This paper discusses module packaging aspects with regard to high-speed data transmission for both single channel serial and multi channel parallel transmission. The increasing demand for bandwidth and data throughput of opto-electronic modules leads to continuously changing design rules for these modules. These rules are now completely different compared to those of the time of 100 Mbit/s transmission with light emitting diodes. More specifically, one of the key parameters or figure of merit in today's system design is the data throughput per board edge of the printed circuit boards of the corresponding electronic systems, e.g. switches, routers, clustered computers etc. This has a twofold effect on the module design and the module packaging: firstly, the transmission speed of the module has to be continuously increased, and secondly, the size of the module has to be shrunk. The first requirement leads directly to challenges with electromagnetic interference due to the bandwidth increase, the second to challenges in connector technology, precision of fabrication techniques, and, most severe, to challenges in heat dissipation as now at least the same number of watts of power has to be dissipated in a smaller volume. Both requirements together, of course, multiply the requirements on module packaging. In this paper comparisons of pin through hole, lead frame and ball grid array packages are given. Examples like a 2.5 Gbit/s Small Form Factor serial transceiver, a 2.5 Gbit/s OC48 transceiver with parallel electrical connections, first results of a 10 Gbit/s transceiver with opto-electronic components in a TO package, and 12/spl times/2.5 GBd parallel optical transmitter and receiver (Paroli) are presented. Requirements given by standard assembly techniques like pick-and-place ability and reflow solderability are discussed.