A Packaging Solution to Enable Moisture Sensitivity Level 1 Zero Delamination for Leaded Surface Mount Device Package

Abstract

Surface mount technology (SMT) is widely used and being the major component assembly technology, it offers more reliable assembly with less package weight, less printing circuit board (PCB) area and much faster assembly speed, when compared to conventional through-hole (TH) technology. The surface mount device (SMD) packages structure, materials, processes, and assembly process are quite different from through-hole packages, as well as quality requirements. The SMD package are mounted on board by soldering process, it can be sensitive to moisture when exposing to environment, the moisture content of the SMD packages must be well controlled in order to prevent the delamination occurring during board solder reflow process. To understanding the moisture sensitivity performance of SMD packages, moisture sensitivity level (MSL) classification is introduced to identify the SMD packages performance from MSL 1 to MSL 6 at a reflow temperature of 260°C. Package achieved the most robust level MSL 1 can be interpreted as not sensitive to moisture, the floor life is unlimited under typical room temperature and humidity, also do not need dry packing as special control. As the continuous tightening of automotive requirements, package delamination level after MSL 1 become more and more concerned as a semiconductor packaging focusing point, zero delamination after MSL 1 is being pushed to be a solid requirement by semiconductor customers. The delamination between epoxy molding compound (EMC) and leadframe (LF), as well as die attach adhesive (DA) and LF are well known and understood, and with quite mature solutions e.g. enhancing the interfacial adhesion etc. In this study, a unique MSL 1 delamination symptom in the area around DA fillet is reviewed and discussed, root cause is identified by surface analysis techniques, and links to the die attach effect. The potential optimization in terms of packaging materials and process is proposed and validated by assembled packages, which subject to MSL 1 conditions and 3 times reflow at 260°C. Material characterization on the optimized packaging material is conducted to understand and verify the material impact, delamination levels are checked by C-Mode Scanning Acoustic Microscope (C-SAM) to assess the package interfaces after MSL 1 and reflow. Result shows zero delamination after MSL 1 can be achieved by the proposed optimization, a packaging solution can be concluded to enable MSL 1 zero delamination for leaded SMD package.