Emerging Flux Challenges for BGA Packages

2016 ◽  
Vol 2016 (DPC) ◽  
pp. 001359-001390
Author(s):  
Maria Durham ◽  
Andy Mackie ◽  
Jason Chou
Keyword(s):  
Solder Joint ◽  
Failure Modes ◽  
Value Added ◽  
Ball Grid Array ◽  
Deposition Process ◽  
Testing Methods ◽  
Bga Packages ◽  
Bga Package ◽  
One Step ◽  
Process Cost

The formation of a Ball Grid Array (BGA) solder joint is critical for a BGA package where typically a flux deposition process is used. Reflowing solder spheres to solderable pads on the bottom of substrates in standard BGA, FCBGA, CSP, and similar packages is considered to be a trivial step: a specialized BGA flux is usually pin-transferred onto the pads, followed by balldrop onto the substrate. However, with the increasing complexity and number of assembly processes taken prior to this final step, the formation of a reliable final joint is far from certain. In order to eliminate variability, many OSATs and ODMs use the so-called “two step” (double fluxing) approach, which is comprised of the non-value-added extra processes of prefluxing, reflowing, cleaning, and drying substrates immediately prior to the final flux-based ball-attach process. This paper details the sequence of processes seen in typical FCBGA assembly, and examines the effects of each set of prior processes on the solderability of the final pad. The introduction of a “one-step” pin-transfer ball-attach flux is shown to be a means of reducing both process cost and time, and also reducing the risk of increased warpage in the finished package. The paper also investigates the solderable surface and metallurgy of the substrate pad. The variety of new and emerging failure modes for the BGA process as well as the different testing methods for the materials will also be discussed.

Thermomechanical Durability of High I/O BGA Packages

2002 ◽  
Vol 124 (3) ◽  
pp. 266-270 ◽  
Author(s):  
P. Davuluri ◽  
S. Shetty ◽  
A. Dasgupta ◽  
S. Young
Keyword(s):  
Solder Joint ◽  
Ball Grid Array ◽  
Element Model ◽  
Hybrid Technique ◽  
Failure Data ◽  
Bga Packages ◽  
Analysis Technique ◽  
Bga Package ◽  
Parametric Studies ◽  
Failure Predictions

Efficient modeling strategies are developed to study thermomechanical durability of high I/O Ball Grid Array (BGA) packages, in order to facilitate virtual qualification and accelerated testing of component designs. A viscoplastic stress analysis technique is developed where the critical solder joint(s) (joint(s) where failure first occurs) are modeled in detail with a multi-domain Rayleigh-Ritz (MDRR) methodology while the load-sharing offered by noncritical joints is modeled with a simplified compact model. This hybrid technique is used to study the behavior of solder interconnects in selected Ball Grid Array (BGA) package under thermal cycling environments. Parametric studies are conducted to determine the optimal scheme for allocating a critical number of solder joints to the MDRR model, and the remaining non-critical joints to the compact models. Damage calculations are made with the Energy Partitioning Solder Durability model and cycles-to-failure predictions are compared with both finite element model predictions as well as experimental failure data provided by CALCE EPSC sponsors. Parametric studies on change in solder joint durability with interconnect volume are also discussed in this paper.

Solderability Challenges in Emerging BGA Packages

2014 ◽  
Vol 2014 (DPC) ◽  
pp. 000913-000929
Author(s):  
Maria Durham ◽  
Yan Liu ◽  
Andy Mackie
Keyword(s):  
Value Added ◽  
Bga Packages ◽  
One Step ◽  
Process Cost

The final step of reflowing solder spheres to solderable pads on the bottom of substrates in FCBGA, CSP, and WLCSP packages is often considered to be a trivial step. However, with the increasing complexity and number of assembly processes taken prior to this final soldering step, the formation of a reliable final joint is far from certain. In order to eliminate this problem, many OSATs and ODMs are adopting the non-value-added process of prefluxing, reflowing, cleaning, and drying substrates immediately prior to the final ball-attach process. This paper details the sequence of processes seen in typical BGA assembly, and examines the effects of each set of prior processes on the solderability of the final pad. It also details investigations of the solderable surface and metallurgy of the substrate pad. The introduction of a “one-step” pin-transfer ball-attach flux is shown to be a means of reducing both process cost and time, and also reducing the risk of significant warpage in the finished package.

Thermomechanical Durability of High I/O BGA Packages

2000 ◽  
Author(s):  
Pavan Davuluri ◽  
Abhijit Dasgupta ◽  
Steven Young
Keyword(s):  
Solder Joint ◽  
Ball Grid Array ◽  
Element Model ◽  
Hybrid Technique ◽  
Failure Data ◽  
Bga Packages ◽  
Analysis Technique ◽  
Bga Package ◽  
Parametric Studies ◽  
Failure Predictions

Abstract Efficient modeling strategies are developed to study thermomechanical durability of high I/O Ball Grid Array (BGA) packages, in order to facilitate virtual qualification and accelerated testing of component designs. A viscoplastic stress analysis technique is developed where the critical solder joint(s) (joint(s) at which failure first occurs) are modeled in detail with a multi-domain Rayleigh-Ritz (MDRR) methodology (Ling and Dasgupta, 1996; Ling and Dasgupta 1997; Ling 1997; and Rassian and Lee, 1998) while the load-sharing offered by non-critical joints is modeled with a simplified compact model. This hybrid technique is used to study the behavior of solder interconnects in selected Ball Grid Array (BGA) package under thermal cycling environments. Parametric studies are conducted to determine the optimal scheme for allocating a critical number of solder joints to the MDRR model, and the remaining non-critical joints to the compact models. Damage calculations are made with the Energy Partitioning Solder Durability model (Dasgupta et al., 1992) and cycles-to-failure predictions are compared with both finite element model predictions as well as experimental failure data provided by CALCE EPSC sponsors. Parametric studies on change in solder joint durability with interconnect volume are also discussed in this paper.

Development of Reliability and Moldability on Fine Pitch Ball Grid Array by Optimizing Materials

2000 ◽  
Vol 123 (1) ◽  
pp. 88-94 ◽  
Author(s):  
Takashi Aihara ◽  
Shingo Ito ◽  
Hideaki Sasajima ◽  
Ken Oota
Keyword(s):  
Ball Grid Array ◽  
The Other ◽  
Molding Compounds ◽  
Other Hand ◽  
Die Attach ◽  
Bga Packages ◽  
Fine Pitch ◽  
The World ◽  
Bga Package ◽  
Materials Used

The market for BGA packages is expanding all over the world, owing to the ease of its mounting onto the PC boards. On the other hand, BGA packages possess certain shortcomings compared to QFPs. Anti-solder crack performance on Fine Pitch BGA (=FPBGA) and warpage on Mold Array Package-BGA(=MAP-BGA) are significant disadvantages. To improve the performance of BGA packages, we studied various combinations of materials used for BGA package including molding compounds, die attach pastes, and substrates.

Evaluation of Surface Finish on Build Up Substrate

2003 ◽  
Author(s):  
L. Y. Hung ◽  
Y. P. Wang ◽  
C. S. Hsiao
Keyword(s):  
Solder Joint ◽  
Surface Finish ◽  
Joint Strength ◽  
Failure Modes ◽  
Electroless Nickel ◽  
Deposition Process ◽  
Sodium Hypophosphite ◽  
Ball Shear ◽  
Phosphorous Content ◽  
Electroless Ni

In recent years, the most explosive technologies in electronic systems have demanded ever-higher functionality, ever-faster circuit speeds, and always increasing interconnection density. Electrolytic and electroless nickel/gold (Ni/Au) deposition process are used commonly to provide flat, solderable pad surface finish on area array (BGA or CSP) packages and printed wiring boards (PWB). The electroless nickel/immersion gold (ENIG) process is widely used which do not requires plating lines for electrolytic plating, better meets the fine pitch wiring requirements. However, ENIG deposition process may cause or contribute to catastrophic, brittle, interfacial solder joint fractures. ENIG plating has previously shown lower reliability at solder joints. This is because Phosphorous segregation at the interface Sn-Ni intermetallic and Ni layer caused poor adhesion at that interface, especially high phosphorous content (10∼15%) of the electroless Ni. There have been many studies verified that Ni3P formation is a major factor, which causes weaker joint strength and flat fracture surface. Owing to sodium hypophosphite (NaH2PO2) was used to provide electron and return Ni ion to deposit on Cu pad for ENIG plating, it is not dodge that phosphorous element exist at the Ni layer. Hence, ph value, temperature and loading factor (plating area/ plating tank volume) in the plating path are controlled to reduce phosphorous content (less than 10%) to avoid Ni3P formation. Furthermore, ENIG has a potential risk of black pad, because Porous Au plating layer caused the oxidation of Ni layer underneath the Au plating to occur solder joint failure and low shear forces after assembly. In order to overcome foregoing problem, a flip chip ball grid array (FCBGA) test vehicle is used to compare three kinds surface finish electroless Ni/Au, direct gold and solder on Cu pad in this study 63Sn/37Pb solder bump is reflowed onto these substrates. High temperature storage test (HTS) is used to evaluate thickness and structure of IMC to affect solder joint attachment reliability. Ball shear test is used to measurement joint strength at various HTS time. Optical microscopy (OM) and scanning electron mcroscopy (SEM) are used to observe failure modes after ball shear.

Thermal analysis and optimization for a ball grid array package

2005 ◽  
Vol 219 (4) ◽  
pp. 381-393 ◽  
Author(s):  
C-I Ho ◽  
T-C Hung ◽  
C-I Hung
Keyword(s):  
Thermal Resistance ◽  
Heat Dissipation ◽  
Ball Grid Array ◽  
Optimization Method ◽  
Heat Transfer Analysis ◽  
Bga Packages ◽  
Solder Balls ◽  
Bga Package ◽  
Computational Fluid Dynamics Cfd ◽  
Artificial Neural Network Ann

In this study, a computational fluid dynamics (CFD) approach is employed for heat transfer analysis of a ball grid array (BGA) package that is widely used in the modern electronics industry. Owing to the complicated geometric configuration of the BGA package, the submodel approach is used to investigate in detail the temperature distributions of thermal vias and solder balls. The effective thermal resistance of a BGA package has been successfully obtained from numerical simulations. An artificial neural network (ANN) is trained to establish the relationship between the geometry input and the thermal resistance output. The well-trained network is then coupled with the complex optimization method to search for the optimum design of the BGA package to achieve the lowest thermal resistance. The results of this study provide the electronic packaging industry with a reliable and rapid method for heat dissipation design of BGA packages.

Plastic Strain Based Criterion for Reliability Assessment of CSP Packages Subjected to Dynamic Shock Loads

2005 ◽  
Author(s):  
Liping Zhu ◽  
Rick Williams
Keyword(s):  
Plastic Strain ◽  
Solder Joint ◽  
Failure Modes ◽  
Mechanical Load ◽  
Failure Criteria ◽  
Dynamic Responses ◽  
Finite Element Software ◽  
Bga Package ◽  
Shock Event ◽  
Reliability Performance

Drop impact induced crack in ball grid array (BGA) solder joint is one of the most dominant failure modes found in BGA package under mechanical load. The failure in BGA due to its excess stress resulting from over bended deformation in a PCB board during shock event is not only a function of solder material but a board and package structure as well. Due to extremely difficult and infeasible in directly measuring responses in BGA solder joint during drop shock event, computer modeling approach has been increasingly played an important role in evaluating product reliability performance during product development. Modeling technique with a comprehensive failure criterion and metric including high strain rate effect is necessary to be developed to quantitatively evaluate and benchmark BGA package reliability performance for different board designs. In this paper, dynamic responses in CSP/BGA in different boards and product phone have been characterized by using nonlinear dynamic finite element software, LS-Dyna. Different failure criteria, such as plastic strain and stress based are investigated and compared. It is shown that a good correlation between validation test and numerical result can be achieved by using proposed plastic strain based criterion only and thus it can be used in cross comparisons between different board designs.

Effects of Ceramic Ball-Grid-Array Package’s Manufacturing Variations on Solder Joint Reliability

1994 ◽  
Vol 116 (4) ◽  
pp. 242-248 ◽  
Author(s):  
Teh-Hua Ju ◽  
Wei Lin ◽  
Y. C. Lee ◽  
Jay J. Liu
Keyword(s):  
Fatigue Life ◽  
Solder Joint ◽  
Solder Joints ◽  
Ball Grid Array ◽  
Printed Wiring Board ◽  
Ceramic Ball ◽  
Solder Volume ◽  
Bga Package ◽  
Reliability Of Solder Joints ◽  
Wiring Board

The effects of manufacturing variations on the reliability of solder joints between a ceramic ball grid array (BGA) package and a printed wiring board (PWB) are investigated. Two cases are studied, namely, with and without spacers between the BGA package and the PWB to maintain the solder joint height. Manufacturing variations considered include changes in solder volume, joint height, and pad size. To evaluate the effect of manufacturing variations on reliability, every possible solder joint profile is first derived. The maximum strain is calculated next. Finally, the fatigue life is predicted. The calculations show that these manufacturing variations change the joint profile, and subsequently affect the fatigue life. Since the package is heavy, the use of spacers is necessary to control the solder joint height for reliable connections, and to maintain a large gap for cleaning. The solder joints formed with the use of spacers, may have convex, cylindrical or concave profiles. The concave solder joints are preferred, since they have long fatigue lives and are less sensitive to the manufacturing variations. For the convex solder joints, their fatigue lives are strongly affected by the joint height variation caused by package warpage and by the combined effects of solder volume and pad size.

Waldpolitischer Jahresrückblick 2010 | Annual review of swiss forest policy 2010

2011 ◽  
Vol 162 (5) ◽  
pp. 137-145 ◽  
Author(s):  
Willi Zimmermann
Keyword(s):  
Spatial Planning ◽  
Forest Conservation ◽  
Forest Policy ◽  
Value Added ◽  
Political Agenda ◽  
Annual Review ◽  
Forest Law ◽  
One Step ◽  
Climate Convention ◽  
Article 5

In 2010, there were no major forest policy issues that attracted media attention. The year 2010 was rather marked by the preparation of decisions “offstage” and by recurring administrative implementation activities. The partial revision of the forest law, which has been launched, can be regarded as special, because it is not a routine affair: the Committee for the Environment, Spatial Planning and Energy of the Council of States decided to revise particularly article 7 (compensation for deforestation) and article 10 (assessing forest status) of the forest law, and thus loosen the strict regime for forest conservation. Concerning the sectoral policies related to forest, the parliament took the law on spatial planning (RPG) one step further towards its revision. With the proposed revision of the spatial planning law's article 5 (value-added charge) a forest policy relevant article is now up for discussion. Different forest relevant topics on the international political agenda were discussed during the two international conferences on biodiversity and climate convention just as during the treatment of the alpine and the landscape convention. Next year the discussions will presumably be about the future forest conservation policy.

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