A novel mechanical shock test method to evaluate lead-free BGA solder joint reliability

Author(s):  
D. Reiff ◽  
E. Bradley
Author(s):  
Kayleen L. E. Helms ◽  
Ketan R. Shah ◽  
Dan Gerbus ◽  
Vasu S. Vasudevan ◽  
Jagadeesh Radhakrishnan ◽  
...  

Increasing power and I/O demands in HDI (high density interconnect) components coupled with the industry-wide conversion to lead-free products has introduced additional risk for solder joint reliability (SJR) of BGA (ball grid array) Flip-Chip electronic packages. One particular concern is SJR under mechanical shock (dynamic bend) loading. While leaded alloys provided good performance in shock for many years due to the unparalleled ability of lead’s slip systems to absorb the energy in shock events, lead-free alloys cannot provide the same benefit. To mitigate this risk, better approaches for understanding damage propagation are needed to enable better design to limit and reduce the SJR risk during shipping and end-user handling. To this end, a characterization study is undertaken to monitor damage progression at the second-level interconnect in BGA’s on flip-chip electronic packages during mechanical shock loading. The study uses a board-level, strain-monitoring approach plus the dye and peel failure analysis technique to track the initiation and propagation of solder joint cracks under loading. The approach being used differs from conventional reliability testing in that both design and load variables are used to quantify damage growth and strain response to bridge the understanding of design feature impact to traditional reliability testing. The scope of the study includes investigating the impact of such factors as package placement, board layout, and enabling load on the monitored board strain and the damage propagation observed. From this study, directions and design guidelines for improving solder joint reliability of future BGA’s on flip-chip electronic packages under mechanical shock loading conditions are proposed.


2006 ◽  
Vol 504 (1-2) ◽  
pp. 426-430 ◽  
Author(s):  
Dae-Gon Kim ◽  
Jong-Woong Kim ◽  
Seung-Boo Jung

Author(s):  
Felix Bruno ◽  
Purushothaman Damodaran ◽  
Krishnaswami Srihari ◽  
Guhan Subbarayan

The electronics manufacturing industry is gradually migrating towards to a lead-free environment. During this transition, there will be a period where lead-free materials will need to coexist with those containing lead on the same assembly. The use of tin-lead solder with lead-free parts and lead-free solder with components containing lead can hardly be avoided. If it can be shown that lead-free Ball Grid Arrays (BGAs) can be successfully assembled with tin-lead solder while concurrently obtaining more than adequate solder joint reliability, then the Original Equipment Manufacturers (OEMs) will accept lead-free components regardless of the attachment process or material used. Consequently, the Electronics Manufacturing Service (EMS) providers need not carry both the leaded and the unleaded version of a component. Solder voids are the holes and recesses that occur in the joints. Some say the presence of voids is expected to affect the mechanical properties of a joint and reduce strength, ductility, creep, and fatigue life. Some believe that it may slow down crack propagation by forcing a re-initiation of the crack. Consequently, it has the ability to stop a crack. The primary objective of this research effort is to develop a robust process for mixed alloy assemblies such that the occurrence of voids is minimized. Since there is no recipe currently available for mixed alloy assemblies, this research will study and 'optimize' each assembly process step. The difference between the melting points of lead-free (217°C) and tin-lead (183°C) solder alloys is the most important constraint in a mixed alloy assembly. The effect of voids on solder joint reliability in tin-lead assembly is well documented. However, its effect on lead-free and mixed alloy assemblies has not received due attention. The secondary objective of this endeavor is to determine the percentage of voids observed in mixed alloy assemblies and compare the results to both tin-lead and lead-free assemblies. The effect of surface finish, solder volume, reflow profile parameters, and component pitch on the formation of voids is studied across different assemblies. A designed experiments approach is followed to develop a robust process window for mixed alloy assemblies. Reliability studies are also conducted to understand the effect of voids on solder joint failures when subjected to accelerated testing conditions.


2012 ◽  
Vol 626 ◽  
pp. 791-796 ◽  
Author(s):  
Mohd Arif Anuar Mohd Salleh ◽  
Muhammad Hafiz Hazizi ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
N.Z. Noriman ◽  
Ramani Mayapan ◽  
...  

Researches and studies on composite solder have been done by many researchers in an effort to develop viable lead-free solders which can replace the conventional lead-based solders as lead is considered as toxic. Solder materials developed by composite approach showed improvement in their properties and importantly it improved their service performance when compared with solder materials developed by other methods. This paper reviews the solder properties of various types of composite lead-free solder that were fabricated via powder metallurgy route. The fabrication processes of the composite solder material by using powder metallurgy route which involved mixing the powder homogeneously, compaction of the mixed powder and sintering the green body were discussed in detail. The types of reinforcements used in order to enhance its properties and the roles of the reinforcement used were also discussed in detail. Properties of a desirable composite solder and the effects of the reinforcement addition to the composite solder microstructure, changes in its wettability and improvement of its mechanical properties were later discussed in this paper. In conclusion, by reviewing various research advances in composite solder material, a solder material with high solder joint reliability at elevated temperature have yet to be found. Thus, a novel composite solder material with higher solder joint reliability at room and elevated temperature was proposed.


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