Ball Grid Array Devices Research Articles

Detrimental angle range between c axis of Sn crystal and electron flow for the electromigration reliability of ball grid array devices

Detrimental angle range between c axis of Sn crystal and electron flow for the electromigration reliability of ball grid array devices

“Rey Resin Dispense Pattern” A Solution to Package Voids Defect on Thinner Package Thickness in Compression Mold

This paper will discuss how package voids Mold defect was addressed on thinner Compression mold packages like BGA (Ball Grid Array) and Sensor Devices. Significant action was the application of “Rey Resin Dispense” pattern in compression mold granule compound dispensing was a key action in reducing package voids defect. Using a DMAIC methodology (Define, Measure, Analyze, Improve and Control), a powerful analytical tool that serves as a guide towards the success of eliminating package voids defect. Using this methodology, all Key Process Input Variables (KPIVs) of compression mold and its molding compound material were identified as X’s or potential causes and test its significance to affect Y-response which is the package voids. Funneling of X’s further trimmed to the most possible contributor to package voids. The remaining possible contributor X’s undergo statistical validation which point to granule compound resin dispensing as the main contributor to induce package voids defect. Several actions were tried but failed to zero-out the defect. With the help of brainstorming and imaginative ideas and data gathered on how to improve granule resin dispense of compression mold positive outcome was realized. From the concept of light ray, to naming it as “Rey Resin Dispense” significantly reduce package voids defect in all thin BGA and Sensor devices. This learning was then applied to all existing thin packages and to new packages in compression molding process.

Flux Shorting Mitigation on Semiconductor BGA Device through Process Design Enhancement

With the new and upcoming technologies in semiconductor industry, packages like the ball grid array (BGA) are getting more challenging to process due to inherent issues that come along. Process improvement through modification in the design of indirect material is one key direction to improve the productivity during assembly manufacturing. In this paper, an enhanced design of dipping plate is presented to solve the issue of flux shorting due to out-of-specs dipping plate at ball attach process. The study used a side by side comparison to prove that the new design is better than that of the out-of-specs indirect material. With the new enhanced design of dipping plate and the optimized flux depth parameter, flux shorting occurrence was successfully mitigated.

Pick and Place Process Defect Mitigation on Semiconductor BGA Device

With the new devices and new technologies in semiconductor industry are getting more challenging to process because of new processes and process bricks. One of the most challenging assembly processes is the pick and place or the die attach process. Issues were encountered during product development phase of a semiconductor ball grid array (BGA) device of radio frequency (RF) applications and one of which is the “thrown” dies during die picking. This paper is focused on addressing the thrown dies issue at pick and place process. Installation of blower ionizer on the machine is an extensive improvement done to eliminate the foreign materials resulting to thrown dies during picking. With this improvement, a reduction of around 80 percent of thrown dies was achieved. For future works, the improvement and learnings could be used for devices with similar requirement.

Critical Insights in the Application of Convection and Pressure Curing in Eliminating DAF Voids

The absent of reliable production controls for Die Attach Film (DAF) voids detection allowed defect escapee for Ball Grid Array (BGA) devices using non-conductive film material leading to gross assembly rejection and customer complaints. This paper presents the evaluation of pressure curing as an alternative to the convection curing in die attach process with additional capability to eliminate the DAF voids on non-conductive films. Through Analysis of Variance (ANOVA) analysis, green peeling test, Scanning Acoustic Microscope (SAM), cross section analysis and reliability test performed between samples arrives to the conclusion that pressure oven has a significant impact in die shear strength improvement and DAF voids elimination with positive response in reliability requirement. The result of the study improves the assembly flow and production control of BGA devices through the transition of convection to pressure curing technology.

Using Fundamental Concepts to Determine How to Monitor Dye Penetrant Use

Dye penetration inspection (DPI) is used to detect surface-exposed cracks in objects. For example, it is used in ball grid array (BGA) microelectronics packaging reliability studies. DPI is a significant time-saver over traditional cross-sectioning when data on every solder joint are required. Wet-dye joints occur when the dye solvents do not evaporate fully after the drying step, leaving behind a dye solution that clings to the solder joints and still flows. As the BGA device is removed from the substrate or motherboard, the wet dye around the solder joint will flow across the newly formed surface, indicating a crack before separation when in fact no crack existed before separation. This behavior only happens with a dye solution that has been reused many times. Using basic concepts and readily available data, it was shown which ingredients of the commercially available dye solution are responsible for the wet-dye joint phenomena. Metrologies that analyze organic concentrations, such as FTIR, are recommended to use for quality control. Furthermore, by monitoring dye solution metrics, the reuse life can be maximized and consequently solution waste—a hazardous substance—can be minimized.

Correlation of Warpage Distribution With the Material Property Scattering for Warpage Range Prediction of PBGA Components

In recent years, due to the increased size of ball grid array (BGA) devices, the assembly of BGAs on printed circuit boards through surface mount technology has encountered unprecedented challenges from thermal warpage. The excessive warpage of BGAs in the reflow process may cause manufacture problems and even the risk of failure. Thus, it is essential to acquire warpage values and corresponding distribution ranges of BGAs before the surface mount technology process. In order to avoid assembly failure, theoretically, it is necessary to guarantee that all BGA devices meet the acceptance requirement of relevant standards. Generally, a large number of samples should be measured to obtain a relatively reliable warpage data distribution in the reflow temperature range, which makes this test quite costly and extremely time consuming. This study proposes another method to estimate the BGA warpage value and its possible corresponding range from the material property point of view. Because the mechanism of BGA warpage is related to the coefficient of thermal expansion (CTE) mismatch between the different materials, the warpage data scattering can be correlated with the scattering of material properties through finite element method (FEM) analysis. With a known mean value and range of material properties, the warpage value and corresponding distribution range can be solved. A sensitivity study is also presented in this paper. The accuracy of the proposed method is evaluated and the corresponding warpage data fluctuation range is estimated. From the comparison of the simulation and experiment results, determining the material properties could lead to a reasonable prediction of warpage in both the qualitative and quantitative sense. The proposed methodology for BGA warpage estimation can be used for academic research and industrial applications.

Comparative Study of the Scaling Effect on Pressure Profiles in Capillary Underfill Process

Optimization of the capillary underfill (CUF) encapsulation process is vital to enhance the package’s reliability. Therefore, the design and sizing of the newly developed ball grid array (BGA) device must be considered so that it is compatible with the CUF process. The scaling effect of BGA on CUF flow and its dynamic properties is thoroughly investigated by means of fluid-structure interaction (FSI) numerical simulation. This paper generally highlighted the differences in CUF flow behaviours, together with the pressure distributions between the actual industrial size BGA and the scaled up models for large BGA setup. While flow front profiles appeared to be similar across BGA of various sizes at relative error less than 10%, the CUF filling time gradually increases as the BGA become larger. The scaling limit is found to be at 20, based on the analysis of dimensionless number. The entrant pressure however decreases when the BGA device being scaled up. These findings will assist in the future BGA designs for various sizes used in the CUF encapsulation process.

Effects of Multiple Reworks on the Accelerated Thermal Cycling and Shock Performance of Lead-Free BGA Assemblies

In this paper, the effect of multiple rework cycles (up to 5×) on reliability of lead-free assemblies is investigated. The test vehicle is designed to capture the reliability impact of rework processes on interconnects of ball grid array (BGA) devices, the solder joints of its adjacent components, and BGA devices of clamshelled devices. The effects on high aspect ratio plated through hole (PTH) vias and microvias are also considered. A variety of BGA packages, such as flip-chip BGA, plastic BGA, and chip array BGA are selected to represent different package technologies and stress levels. The effect of multiple reworks on the behavior of lead-free solder joints during accelerated thermal cycling (ATC) and mechanical shock is extensively explored in this paper. The experimental and analytical findings showed that multiple reworks significantly degraded the ATC performance of the reworked assemblies by up to 50% in terms of characteristic life. It is also found that multiple reworks affect the PTH vias significantly. The combination of increased lead-free rework temperature excursions and high-end printed circuit board (PCB) aspect ratios may incur higher stresses in the PTH copper barrel. Early failures are observed post multiple reworks and the subsequent ATC test due to PTH barrel cracking. However, the effects of multiple reworks are less severe for devices with microvias compared to those with PTH vias. Multiple reworks also cause severe degradation of long-term performance of devices with clamshell designs. With proper control in rework process, multiple reworks have minimum effects on the adjacent BGA solder joints. In addition, failure analysis is performed in order to study the impact of multiple rework on the microstructure of SnAgCu solder joints. It is found that the intermetallic compounds (IMC) layer grows thicker as the number of reworks increases; however, the IMC growth rate and morphology are dependent on the surface finish of the package substrate. The failure mode and failure mechanism after ATC are also compared for different number of rework cycles. The implications of these results for the reliability of lead-free solder joints are discussed in this paper.

Reliability of BGA and CSP on Metal-Backed Printed Circuit Boards in Harsh Environments

Increased use of sensors and controls in automotive applications has resulted in significant emphasis on the deployment of electronics directly mounted on the engine and transmission. Increased shock, vibration, and higher temperatures necessitate the fundamental understanding of damage mechanisms, which will be active in these environments. Electronics typical of office benign environments uses FR-4 printed circuit boards (PCBs). Automotive applications typically use high glass-transition temperature laminates such as FR4-06 glass∕epoxy laminate material (Tg=164.9°C). In application environments, metal backing of printed circuit boards is being targeted for thermal dissipation, mechanical stability, and interconnections reliability. In this study, the effect of metal-backed boards on the interconnect reliability has been evaluated. Previous studies on electronic reliability for automotive environments have addressed the damage mechanics of solder joints in plastic ball-grid arrays on non-metal-backed substrates (Lall et al., 2003, “Model for BGA and CSP in Automotive Underhood Environments,” Electronic Components and Technology Conference, New Orleans, LA, May 27–30, pp. 189–196;Syed, A. R., 1996, “Thermal Fatigue Reliability Enhancement of Plastic Ball Grid Array (PBGA) Packages,” Proceedings of the 1996 Electronic Components and Technology Conference, Orlando, FL, May 28–31, pp. 1211–1216;Evans et al., 1997, “PBGA Reliability for Under-the-Hood Automotive Applications,” Proceedings of InterPACK ’97, Kohala, HI, Jun. 15–19, pp. 215–219;Mawer et al., 1999, “Board-Level Characterization of 1.0 and 1.27mm Pitch PBGA for Automotive Under-Hood Applications,” Proceedings of the 1999 Electronic Components and Technology Conference, San Diego, CA, Jun. 1–4, pp. 118–124) and ceramic ball-grid arrays (BGAs) on non-metal-backed substrates (Darveaux, R., and Banerji, K., 1992, “Constitutive Relations for Tin-Based Solder Joints,” IEEE Trans-CPMT-A, Vol. 15, No. 6, pp. 1013–1024;Darveaux et al., 1995, “Reliability of Plastic Ball Grid Array Assembly,” Ball Grid Array Technology, Lau, J., ed., McGraw-Hill, New York, pp. 379–442;Darveaux, R., 2000, “Effect of Simulation Methodology on Solder Joint Crack Growth Correlation,” Proceedings of 50th ECTC, May, pp. 1048–1058). Delamination of PCBs from metal backing has also been investigated. The test vehicle is a metal-backed FR4-06 laminate. The printed circuit board has an aluminum metal backing, attached with pressure sensitive adhesive (PSA). Component architectures tested include plastic ball-grid array devices, C2BGA devices, QFN, and discrete resistors. Reliability of the component architectures has been evaluated for HASL. Crack propagation and intermetallic thickness data have been acquired as a function of cycle count. Reliability data have been acquired on all these architectures. Material constitutive behavior of PSA has been measured using uniaxial test samples. The measured constitutive behavior has been incorporated into nonlinear finite element simulations. Predictive models have been developed for the dominant failure mechanisms for all the component architectures tested.

The effects of flux materials on the moisture sensitivity and reliability of flip-chip-on-board assemblies

This paper discusses the nonproprietary aspects of the work-in-progress regarding developments in flux materials to improve the moisture-induced stress sensitivity of flip chip plastic ball grid array devices. Studies addressing the moisture characterization and preconditioning, using JEDEC Level 3, of assemblies built with four proprietary fluxes and two alternative underfill materials will be presented. This report includes the evaluation of the weight loss during a simulated die attach reflow profile for each flux type using thermogravimetric analysis. Also, the underfill adhesion strength to the die surface after assembly, after moisture preconditioning and after 48 h of autoclave stressing will be discussed. The integrity of the solder joint corresponding to each flux type and measured using die pull techniques will also be presented. The effects of the experimental variables on underfill to die/substrate adhesion will also be reviewed using C-SAM imaging methods. Proprietary aspects of Motorola's FC-PBGA materials and assembly technology will not be disclosed.