ASSEMBLY DEVELOPMENT OF DIRECT CHIP ATTACH WITH EUTECTIC Pb-Sn SOLDER BUMPS ON ORGANIC SUBSTRATES
Author: Abhay Maheshwari Company: Texas Instruments Date Published: 9/10/1996
Surface Mount International
Abstract: Direct Chip attach (DCA) on Printed Wiring Boards (PW13) is gaining increased popularity these days, especially for applications requiring high I/O in relatively small area. As the I/O count increases and the area available decreases, DCA becomes a very efficient way of miniaturizing PWB assemblies. The process development and implementation of DCA assemblies pose a challenge to the industry, since very little information is available about the intricacy of the process. This paper gives an overview of direct chip attach on organic printed wiring boards. The paper is based on the work performed in developing area array packages using DCA technology. It describes wafer bumping, PWB structures, assembly processes, and underfilling. Various areas of concern (both assembly and reliability) are addressed and briefly discussed. The article also talks about process variables associated with DCA technology and how careful evaluation of these variables can lead to zero defect assembly. This paper is intended to help the process development as well as the manufacturing engineer understand the steps involved in implementing DCA.