Impact of isothermal aging on fine pitch BGA packages with Sn-Ag-Cu solder interconnects

2010 ◽  
Vol 2010 (1) ◽  
pp. 000298-000305
Author(s):  
Tae-Kyu Lee ◽  
Weidong Xie ◽  
Thomas R. Bieler ◽  
Kuo-Chuan Liu ◽  
Jie Xue
Keyword(s):  
Thermal Cycling ◽  
Microstructure Evolution ◽  
Isothermal Aging ◽  
Substrate Surface ◽  
Solder Interconnects ◽  
Surface Finishes ◽  
Bga Packages ◽  
Fine Pitch ◽  
Solder Balls

The interaction between isothermal aging and long-term reliability of fine pitch ball grid array (BGA) packages with Sn-3.0Ag-0.5Cu (wt%) solder ball interconnects are investigated. In this study, 0.4mm fine pitch packages with 0.3mm diameter Sn-Ag-Cu solder balls are used. Two different die sizes and two different package substrate surface finishes are selected to compare the internal strain impact and alloy effect, especially the Ni effect during thermal cycling. To see the thermal impact on the thermal performance and long-term reliability, the samples are isothermally aged and thermal cycled from 0 to 100°C with a 10minute dwell time. Based on weibull plots for each aging condition, the lifetime of the package reduced approximately 44% with 150°C aging precondition. The microstructure evolution is observed during thermal aging and thermal cycling with different phase microstructure transformations between electrolytic Ni/Au and OSP surface finishes, focusing on the microstructure evolution near the package side interface. Different mechanisms after aging at various conditions are observed, and their impacts on the fatigue life of solder joints are discussed.

Mechanical Robustness of Solder Connections to Thick Film Gold

2011 ◽  
Vol 2011 (1) ◽  
pp. 000327-000336
Author(s):  
Thomas F. Marinis ◽  
Joseph W. Soucy
Keyword(s):  
Thick Film ◽  
High Reliability ◽  
Accelerated Aging ◽  
Element Analysis ◽  
Bga Packages ◽  
Fine Pitch ◽  
Solder Balls ◽  
Lift Off ◽  
Extended Area ◽  
Gold Metallization

Thick film gold metallization is required for many high reliability circuits, especially those subjected to operation in high temperature or high humidity environments. Traditionally, wire bonded bare die are used on these circuits, but there is a trend to replace them with BGA packaged devices. State-of-the-art, chip scale packages increase circuit volume by less than 20 percent, while their use greatly simplifies testing and repair, as compared to wire bonded die. The use of small, high density I/O pad arrays for attachment of BGA packages, necessitates very careful control of the solder reflow process to avoid excessive leaching of the gold into the solder. Also, unlike passive chip components and leaded devices, the solder filet associated with a solder ball attachment does not distribute mechanical loads over an extended area. Consequently, the stresses imposed on fine pitch, BGA pads are much higher than those imposed by other components. During aging, the gold metallization is converted to gold-tin intermetallic as inter-diffusion proceeds. This further reduces the mechanical integrity of the solder connection. This manifests itself in the observation that when BGA solder balls are subjected to accelerated aging followed by shear testing, the entire solder pad lifts off of the substrate, rather than failing in the solder joint. What we have done is construct a diffusion based model to estimate the conversion of a thick film gold metallization pad to intermetallic and coupled this result with a finite element analysis to examine the effect of pad size and solder composition on the propensity of a pad to lift off the substrate, when subjected to mechanical or thermal induced loading. We are designing experiments to compare the predictions of our model to experimental results obtained from shearing solder balls, of different compositions and sizes, attached to substrates metalized with several different solderable, thick film gold materials.

scholarly journals Backplate-reinforced structures for enhancing solder joint reliability of server CPU assembly under thermal cycling

2021 ◽  
Vol 37 ◽  
pp. 693-703
Author(s):  
M C Liao ◽  
P S Huang ◽  
T C Huang ◽  
M Y Tsai
Keyword(s):  
Solder Joint ◽  
Thermal Cycling ◽  
Thermal Loading ◽  
Processing Unit ◽  
Solder Joint Reliability ◽  
Central Processing ◽  
Joint Reliability ◽  
Fine Pitch ◽  
Solder Balls ◽  
Von Mises

ABSTRACT To meet the requirement of the high I/O and fine-pitch interconnects, the conventional insertion-mount socket for central processing unit (CPU) has been changed to surface-mount one with ball grid array. The solder ball joint reliability of the socket used in the CPU assembly becomes very important. In this study, the socket's solder joint reliability of the backplate-reinforced CPU assembly and its related mechanics under mechanical and thermal loadings are investigated experimentally using strain gauge and shadow moiré, and numerically by a finite element method (FEM). The validated FEM results have suggested that maximum stress of solder balls increases almost linearly with decreasing the backplate thickness under mechanical loading during the CPU assembly, but is insensitive to the backplate thickness under thermal loading during the thermal cycling. It is also found that the residual (bending) strain on the PCB proportional to the maximum von Mises stresses of solder joints (or balls) can be used as a key parameter to correlate with the solder joint failures or cracks during the thermal cycling. Overall, experimental and FEM results in this study reveal that solder joint reliability in the CPU assembly during thermal cycling can be improved by adopting the thicker reinforced backplate.

Impact of Isothermal Aging on the Long-Term Reliability of Fine-Pitch Ball Grid Array Packages With Different Sn-Ag-Cu Solder Joints

2012 ◽  
Vol 2 (8) ◽  
pp. 1317-1328 ◽  
Author(s):  
Jiawei Zhang ◽  
Sivasubramanian Thirugnanasambandam ◽  
John L. Evans ◽  
Michael J. Bozack ◽  
Richard Sesek
Keyword(s):  
Isothermal Aging ◽  
Solder Joints ◽  
Ball Grid Array ◽  
Fine Pitch ◽  
Ball Grid Array Packages

Fatigue Testing of Copper Nanoparticle Based Joints and Bonds

2021 ◽  
Author(s):  
Rajesh Sivasubramony ◽  
Maan Z. Kokash ◽  
Sanoop Thekkut ◽  
Ninand Shahane ◽  
Patrick Thompson ◽  
...  
Keyword(s):  
Thermal Cycling ◽  
Flip Chip ◽  
Fatigue Testing ◽  
Maximum Temperature ◽  
Nano Particle ◽  
Test Results ◽  
Fine Pitch ◽  
Effects Of Aging ◽  
Sintered Ag

Abstract Fused or sintered Cu nanoparticle structures are potential alternatives to solder for ultra-fine pitch flip chip assembly and to sintered Ag for heat sink attach in high temperature microelectronics. Meaningful testing and interpretation of test results in terms of what to expect under realistic use conditions do, however, require a mechanistic picture of degradation and damage mechanisms. As far as fatigue goes, such a picture is starting to emerge. The porosity of sintered nano-particle structures significantly affects their behavior in cycling. The very different sensitivities to parameters, compared to solder, means new protocols will be required for the assessment of reliability. The present study focused on fatigue in both isothermal and thermal cycling. During the latter, all damage occurs at the low temperature extreme, so life is particularly sensitive to the minimum temperature and any dwell there. Variations in the maximum temperature up to 125 °C did not affect, but a maximum temperature of 200 °C led to much faster damage. Depending on particle size and sintering conditions deformation and damage properties may also degrade rapidly over time. Our picture allows for recommendations as to more relevant test protocols for vibration, thermal cycling, and combinations of these, including effects of aging, as well as for generalization of test results and comparisons in terms of anticipated behavior under realistic long-term use conditions. Also, the fatigue life seems to vary with the ultimate strength, meaning that simple strength testing becomes a convenient reference in materials and process optimization.

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