Effects of Corner/Edge Bond and Side-fill for Automotive MCM Applications

For the high reliability and harsh environment applications such as automotive grade MCM (multi-chip modules) or SiP (System in Package), normally requires under-fill to achieve the needed thermal cycles, mechanical shock and vibration reliability. And, these high reliability applications often incorporate high process cost, spending on module ilux cleaning, baking, plasma treatment even under-fill capillary time consuming. Despite of that, the extra environmental regulation compliance issues of energy saving and wastes disposal also challenge the manufacturer to consider more cost effective and environment friendly manufacturing processes with moderate reliability to meet modern automotive industrial requirements. This study focus on non-cleaning side-fill and corner / edge bond (hereafter be cited within the text as CEB) reinforcement techniques including material selection, verification, and dispensing process design to improve the solder-joint reliability of BGAs or BTC in MCM or SiP to meet the minimum automotive industrial standards (AECQ104 Failure Mechanism Based Stress Test Qualification for Multichip Modules in Automotive Applications). The reliability testing protocol used here, included pre-conditioning(3X multi-reflow) and thermal cycling ($-40^{\circ}C-85^{\circ}C$). Four adhesive materials (commercially available) were studied with test vehicles including wafer glass attachment and BGA packages with plans to expand the study on WLCSP BGAs. For side-fill and CEB processing, establishing side-fill adhesion and edge bond that maximizes adhesion/bond area with proper fillet height without encapsulating the solder balls is key success to prevent the process quality issues as well as to reliability improvements.