NON-DESTRUCTIVE TECHNIQUES FOR IDENTIFYING DEFECT IN BGA JOINTS: TDR, 2DX, AND CROSS-SECTION/SEM COMPARISON

摘要

The industry needs Non-Destructive Techniques to identify BGA opens and cracks. Currently X-ray and Time Domain Reflectometry (TDR) are most widely used.In this paper we report the results of our comparison of the following techniques: TDR, Automatic X-ray inspection (AXI), Transmission X-ray (2DX), Cross-section/SEM and Dye & Pry. The first three are Non-Destructive; the Cross-section/SEM and Dye & Pry are destructive techniques.We looked for a correlation among the various techniques in finding opens and cracks in BGA joints. Our experiment included:1. Testing thirty pins on a particular BGA from ten different boards using TDR, AXI, and 2DX.2. Further examining eight of those boards with Cross-section/SEM, and the remaining two boards with Dye &Pry.These studies helped us to gain a good understanding of TDR, AXI, 2DX, Cross-section/SEM and Dye & Pry techniques. With 1,200 experimental data points, we found the following correlation figures: 15.1%, 21.9%, 23.8% for TDR versus SEM, 2DX and Dye & Pry; 51.3%, 51.9% for 2DX versus SEM and Dye & Pry respectively. TDR has the capability to identify BGA opens and larger cracks while 2DX can easily detect opens and much smaller sized BGA cracks.Further, we will discuss the methods for effective identification of cracks in BGA joints using 2DX. The limitation of TDR, AXI, 2DX, Cross-section/SEM, and Dye & Pry techniques will also be addressed.