A new configurable sintered interconnect QFN package for high performance, high lead count and low cost applications

Abstract

With the spurt in growth of consumer driven smart phones market and significant resources invested in Internet of Things (IOT) where both form factor and cost play a major role, there is a need for packaging solution that addresses the low cost and thinness of devices. EoPlex, Inc. has developed a low cost, high performance alternative based on its 3D printing technology called Configurable Sintered Interconnect (CSI) that fills this gap. The CSI Platform is based on printing and converting the ink via a curing step, providing a significant cost advantage over the traditional etched type QFN lead frames. With the thickness of packages as low as 250 um, CSI offers the thinnest package form factor available today in the QFN type leadless family of packages. The sintering process removes the need for etching and harsh chemicals which make CSI green and environmentally friendly. Since this process does not use etching, the need for plating and subsequently the presence of tie bars and plating bars is eliminated. As a result, there is a significant reduction in cross-talk noise and antenna like structures due to floating plating tails, at high frequency. Also, since there are no plating bars or tails, more bond pads can be accommodated as compared to a standard QFN for a given size. The number of rows of bond pads is limited only by the ability to route on the PC board and the wire bond length allowed by manufacturing rules. This technology allows for more than 3 rows of bond pads in high volume production. As a result, a size reduction of up to 33% when compared to conventional QFN type packages. The wire bond length in most cases reduces by up to 2mm, compared to a similar lead count traditional QFN type package. This translates into improvement in return loss of over 1GHZ. The wire bond inductance is also reduced proportionately providing lower impedance. Ability to print isolated metal bars and rings gives the advantage of having multiple low impedance power domains in a single layer lead frame type package. Signal Integrity of CSI packages is comparable or better than 4 layer wire bonded BGA packages. Another advantage of this technology is the ease of design for custom applications. Because of the printing process, bond pads can be placed anywhere. Hence, each design can be customized for the silicon, similar to a Ball Grid Array (BGA) routing. This paper will highlight the ease of design with the CSI platform that enable electrical performance improvements and signal integrity analysis of a SERDES type application as compared to the etched type lead frame version.