Evolution of a unique flip-chip MCM-L package

Flip-chip (FC) packaging is gaining acceptance in the electronics packaging arena. More sources of bumped die and high density printed wiring boards (PWBs) laminates become available every day. Also, known good die (KGD) issues are being resolved by several companies, and design tools to perform FC packaging designs are becoming more available. This is the infrastructure FC packaging requires to become the packaging method of choice, particularly for >200 I/O applications. FC packages come in a variety of styles: FC plastic ball grid arrays (FC/PBGAs), FC plastic quad flat packs (PC/PQFPs), etc. Presently, the industry's drive is toward single chip packages on low cost laminates; i.e., organic substrates. Work is starting to occur in the area of multichip FC packages, due to the need to increase memory to microprocessor speed communication. In this article, a unique FC/MCM-L package is discussed. Part I will concentrate on the development and reliability testing of a one to four chip leadless FC/MCM-L package. Unlike traditional surface mount (SM) components that are attached to printed wiring boards (PWBs) with leads, the SM pads within the body of the package are used for attachment to a PWB. Collapsible eutectic solder domes are deposited on the SM pads by traditional screen printing. After reflow, these domes are used to connect the FC/MCM-L to the PWB. Challenges encountered during package design, PWB fabrication and first and second level assembly will be discussed. Part II of this article will focus on the extension of this FC/MCM-L package to a BGA second level interconnect. Change of FC attachment method, design enhancements, assembly, and reliability testing results will be presented.