Reliability Of Ball Grid Array Research Articles

Investigation of the Impacts of Solder Alloy Composition and Temperature Profile on Fatigue Life of Ball Grid Array Solder Joints Under Accelerated Thermal Cycling

Abstract This study investigated the thermal fatigue reliability of ball grid array (BGA) solder joints under accelerated thermal cycling, considering the impacts of solder alloy and temperature profile. Applying the Darveaux solder joint reliability assessment, simulations consider lead-based (63Sn37Pb and 62Sn36Pb2Ag) and lead-free (SAC105, SAC305, and SAC405) solder alloys under temperature profiles: 0°C (Tmin) to 100°C (Tmax), −40°C to 85 °C, −40 °C to 125 °C, and −40 °C to 150 °C. Results indicate that SAC305 exhibited the highest equivalent stress, while 63Sn37Pb demonstrated the highest plastic strain and creep strain energy density. SAC105 displayed the lowest stress and strain parameters. Moreover, increasing the thermal cycling temperature range intensifies stress, strain, and damage parameters, with −40 °C to 150 °C showing the highest magnitudes. SAC405 exhibited superior thermal fatigue life compared to other alloys, with its cycles to failure outperforming 63Sn37Pb, SAC105, 63Sn36Pb2Ag, and SAC305 by 16832, 11992, 6218, and 3601 cycles, respectively. Lower temperature ranges enhance thermal fatigue life, with 0 °C to 100 °C recording 8%, 33%, and 53% higher life than −40 °C to 85 °C, −40 °C to 125 °C, and −40 °C to 150 °C, respectively. Notably, higher silver content and lower temperature ranges were associated with increased thermal fatigue life, providing valuable insights for BGA solder joint reliability enhancement.

The Effect of Acrylic Conformal Coating in the Reliability of Solder Joints

During the product life, electronic components are subjected to environmental conditions, such as humidity or temperature fluctuations. Solder joints, which allow the electrical and mechanical connection, are one of the most critical spots to have failures due to environmental conditions. Conformal coating, a thin layer that encapsulates all components and consequently solder joints, is one of the techniques that allows the protection of the component against these detrimental effects. Nevertheless, the application of conformal coating has not been recommended in some components, namely in ball grid arrays (BGAs) and quad-flat-no-leads (QFN), since it can compromise the reliability of their solder joints when exposed to temperature fluctuations. Herein, by using an accelerative test, the reliability of BGA- and QFN-coated solder joints with an acrylic conformal coating was studied. A thermal cycle test of temperature ranging from −40 °C to +125 °C comprising 837 cycles demonstrated no failures (confidence level of 0.99; <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R = 4$ </tex-math></inline-formula> ppm/year; <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta = 3$ </tex-math></inline-formula> ) to occur due to acrylic conformal-coating application. However, the solder joints analysis indicated that conformal coating causes an excess of deformations on solder joints, compromising their reliability. Therefore, this study suggests that this acrylic conformal coating is not suitable for these electronic components.

Comparative Study on Reliability and Advanced Numerical Analysis of BGA Subjected to Product-Level Drop Impact Test for Portable Electronics

In this paper, drop reliability of various PBA (printed board assembly) mounting structures is investigated and compared. Then, we built SAC305 (Sn3.0Ag0.5Cu) interconnects for BGA (ball grid array) package failure model to evaluate the drop impact reliability of handheld devices. In order to simulate actual behavior of the solder joint under the drop impact load of handheld devices, we perform explicit full FEA (finite element analysis) modeling. However, this takes a lot of computing time because of the large aspect ratio of element size between solder joints and other structures such as PCB (printed circuit board) and electronic packages. Therefore, an effective way to represent solder interconnects for FEA is needed which would be relatively simpler yet detailed. Comparable board-level drop tests are conducted after equipping test vehicles with various fixtures considering PBA mounting structures, which make it possible to apply different loading conditions to BGA packages. The results show different drop impact life for solder interconnects depending on the mounting design of the PBA. Particularly, the solder interconnect of the component located at the middle of the PCB exhibits the shortest impact life where the highest tensile stress occurs. Also, the mounting design restraining PBA deflections shows better reliability under the drop impact loading. Sequentially, simulating with a PBA composed of the BGA package and the PCB is considered to assess the feasibility of the solder ball failure modeling when the drop impact load is applied. Especially, for the modeling of the solder balls, detailed solid model and simple beam model are compared regarding computational efficiency and numerical accuracy. We found that the simple beam model significantly shortens computational time from 110 h to less than an hour. Accordingly, the feasibility of the beam model for the solder balls is shown by correlating the stress level and the drop impact life obtained from the experiments.

Experimental and numerical investigations of the vibration reliability of BGA and LGA solder configurations and SAC105 and 63Sn37Pb solder alloys

PurposeThis paper aims to investigate and compare the reliability performance of land grid array (LGA) and ball grid array (BGA) solders, as well as the SAC105 and 63Sn37Pb solder alloys, in vibration loading conditions.Design/methodology/approachReliability tests were conducted using a sine dwell with resonance tracking vibration experiment. Finite element simulations were performed to help in understanding the observed failure trends.FindingsReliability results showed that the tin-lead solders out-perform lead-free solders in vibrations loading. Additionally, the LGA solder type could provide a better vibration reliability performance than BGA solders. Failure analysis results showed that in LGAs, the crack is initiated at the printed circuit board side and at the component side in BGAs. In both types, the crack is propagated throughout in the intermetallic compound layer.Originality/valueIn literature, there is a lack of published data in the comparison between LGA and BGA reliability performance in vibration loadings. This paper provides useful insights in the vibration reliability behavior of the two common solder joint types.

Improving the reliability of ball grid arrays under random vibration by optimization of module design

In this work, three different arrangements of circuit board in an electronic device were designed and the effects of random vibration frequencies on the reliability of ball grid arrays (BGA) in these arrangements were evaluated. The failure criterion in solder balls was the root mean square of peeling stress exerted during the dynamical loadings. According to the finite element method (FEM) results, the uttermost stress concentration was generated at the interface of printed circuit board (PCB) and the solder balls. It was also revealed that the increase of input power spectral density (PSD) decreased the fatigue life of solder joint in all the arrangements. Considering the arrangements of circuit boards, it was found that the maximum domain of peeling stress had a minimum effect on the solder balls when the heat sinks were away from the packages. The microstructural characterization of critical zone in solder balls indicated that with the increase of maximum peeling stress, the crack initiated and propagated along the interface.

Evaluation of ENEPIG and Immersion Silver Surface Finishes Under Drop Loading

The effect of printed circuit board surface finish on the drop loading reliability of ball grid array (BGA) solder interconnects has been examined. The finishes examined include electroless nickel/electroless palladium/immersion gold (ENEPIG) and immersion silver (ImAg). For the ENEPIG finish, the effect of the Pd plating layer thickness was evaluated by testing two different thicknesses: 0.05 μm and 0.15 μm. BGA components were assembled onto the boards using either eutectic Sn-Pb or Sn-3.0Ag-0.5Cu (SAC305) solder. Prior to testing, the assembled boards were aged at 100°C for 24 h or 500 h. The boards were then subjected to multiple 1500-g drop tests. Failure analysis indicated the primary failure site for the BGAs to be the solder balls at the board-side solder interface. Cratering of the board laminate under the solder-attached pads was also observed. In all cases, isothermal aging reduced the number of drops to failure. The components soldered onto the boards with the 0.15-μm-Pd ENEPIG finish with the SAC305 solder had the highest characteristic life, at 234 drops to failure, compared with the other finish–solder combinations.

Failure Analysis of the Solder Joints in Flip-Chip BGA Packages under Free-Drop Test

The failure of plastic ball grid array under intense dynamic loading was studied in the project. This paper presents the drop test reliability results of SnPb flip-chip on a standard JEDEC drop reliability test board. The failure mode and mechanism of planar array package in the drop test was comprehensively analyzed. High acceleration dropping test method was used to research the reliability of BGA (ball grid array) packages during the free-drop impact process. The model RS-DP-03A drop device was used to simulate the falling behavior of BGA chip packages under the real conditions, The drop condition meets the JEDEC22-B111 standards (pulse peak 1500g, pulse duration 0.5 ms) when dropping from the 650mm height . In the testing, according to the real-time changes of dynamic voltage, the relationship between drop times and different phases of package failure was analyzed. With the dye-penetrated method and optical microscopy, it was easy to observe the internal crack and failure locations. The growth mechanism of the cracks in solder joints under the condition of drop-free was analyzed and discussed.

Shear Speed Analysis on Sn-3.9Ag-0.6Cu Solder

Ball Grid Array (BGA) is a type of semiconductor interconnection used in Integrated Circuit (IC) which is being scaled down to micro and nanosize. The reliability of BGA in IC becomes a concern as the size of IC reduces. Hence, this leads to the study of stress on the BGA. This paper discussed the load effects of varying shear speed analysis on the BGA. A Pb-free material, Sn-3.9Ag-0.6Cu solder was applied in the simulation. Shear height value is fixed while the shear speed is varied to investigate the dynamic stress on a BGA package using Ansys software. The results from the graph plotted showed that higher shear speed results to higher shear force.

Effect of glue on reliability of flip chip BGA packages under thermal cycling

Glue is widely used to improve the reliability of ball grid array (BGA) under mechanical shock and vibration. Although it has been demonstrated to have a positive effect on the reliability of BGA under mechanical impact, it can have adverse effects on BGA under thermal cycling. This paper investigates the effect of glue on the reliability of BGA under thermal cycling using both experimental and numerical methods. The digital image correlation (DIC) technique was used to obtain the thermal mechanical behavior of the package. The experimental results explain in detail how the glue negatively affects the reliability of the BGA. Furthermore, a finite element analysis was performed and its results were verified with experimental results. A numerical parametric study was carried out on various mechanical properties, configurations of the glue, and introduction of a stiffener using the validated FEM model. The results show that the reliability of BGA strongly depends on geometries and material properties of the glue. Based on the results, a guideline of glue selection for BGA reliability under thermal cycling is formulated.

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.

Reliability of BGA Solder Joints on the Au/Ni/Cu Bond Pad-Effect of Thicknesses of Au and Ni Layer

A systematic experimental work has been carried out to investigate the effect of thicknesses of the Au and Ni layers in the bond pad metallization on the reliability of ball grid array (BGA) solder joints as well as to understand the mechanism of Au diffusion to the solder interface. BGA solder balls of Sn-37 wt.% Pb have been bonded on BGA solder bond pads of Au/electrolytic Ni/Cu by reflowing at 225 degC for 0.5 min. The thickness of the Ni layer was varied from 0.35 to 2.8 mum, while the thickness of Au layer was varied from 0.1 to 1.3 mum. Solid state aging at 150 degC up to 1000 h has been carried out to simulate the ultimate interfacial reactions during the operational life of electronic devices. Cross-sectional studies of the solder-to-bond pad interfaces have been conducted by scanning electron microscopy equipped with an energy-dispersive X-ray analyzer to investigate the interfacial reaction phenomena. Ball shear tests have been carried out to obtain the mechanical strength of the solder joints and to correlate shear behavior with the interfacial reaction products. After the shear tests, fracture surfaces have also been investigated to understand the fracture modes. It has been found that Au embrittlement in the BGA Sn-Pb solder joints on Au/Ni/Cu BGA bond pads can be reduced by using either a thin Au layer or a thin Ni layer in the trilayer metallization of Au/Ni/Cu. It is easy to understand why Au embrittlement is reduced when a thin Au layer in the BGA bond pad is used; however, contrary to the usual expectation, it has been realized in this paper that a very thin Ni metallization is an effective means to maintain the mechanical integrity of the BGA SnPb solder joint. It is revealed that the out-diffusion of the Cu atoms during the aging period changes the chemistry and morphology of the intermetallic compounds (IMCs) at the solder interface, contributing to a significant reduction in brittleness. During aging at 150 degC, the thin Ni layer facilitates Cu diffusion from the bond pad toward IMCs. As a result, the brittle continuous layers of (Au,Ni)Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> are transformed into a nodular-shaped discontinuous layer of AuSn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and a layer of (Au,Cu,Ni) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6 </sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> , respectively. New interfacial reaction products with the modified morphology change the typical scenario of Au embrittlement at the BGA solder interface and thus improve the interfacial joint strength significantly

Effect of multiple reflow processes on the reliability of ball grid array (BGA) solder joints

This paper studies the mechanical behaviors and microstructures of the ball grid array (BGA) solder joints against OSP-coated Cu pads on FR4 substrates after multiple reflow process. A new Pb-free solder, Sn–3Ag–0.5Cu–8In (SACI), has been compared with the popular Pb-free solder Sn–3Ag–0.5Cu (SAC), and the traditional Sn–37Pb (SP) solder. It is found that SACI solder joints provide higher shearing strength over SAC and SP solder joints during multiple reflow. The shearing force of the three types of solder joints does not have significant change with the increase of the number of reflow cycles. The fracture of all SAC and SP solder joints mainly occurs in the bulk solder, whereas the SACI solder joints show a diverse manner, with various combinations of bulk solder facture, solder/IMC interface dissociation, and pad/resin interface failure. The differences in mechanical behaviors are interpreted in terms of diffusion and interaction, as well as chemical and thermal induced degradation. The microstructure evolutions of the solder joints during multiple reflow soldering are also examined. A continuous change of chemical compositions in the IMC layer/particles has been noticed. Large-shaped Ag–In–Sn phase near the IMC layer has been found within the SACI solder joints on the Cu pads.

Model for BGA and CSP Reliability in Automotive Underhood Applications

Fine-pitch ball grid array (BGA) and underfills have been used in benign office environments and wireless applications for a number of years, however their reliability in automotive underhood environment is not well understood. In this work, the reliability of fine-pitch plastic ball grid array (PBGA) packages has been evaluated in the automotive underhood environment. Experimental studies indicate that the coefficient of thermal expansion (CTE) as measured by thermomechanical analyzer (TMA) typically starts to change at 10-15/spl deg/C lower temperature than the T/sub g/ specified by differential scanning calorimetry (DSC) potentially extending the change in CTE well into the accelerated test envelope in the neighborhood of 125/spl deg/C. High T/sub g/ substrates with glass-transition temperatures much higher than the 125/spl deg/C high temperature limit, are therefore not subject to the effect of high coefficient of thermal expansion close to the high temperature of the accelerated test. Darveaux's damage relationships were derived on ceramic ball grid array (CBGA) assemblies, with predominantly solder mask defined (SMD) pads and 62Sn36Pb2Ag solder. In addition to significant differences in the crack propagation paths for the two pad constructions, SMD pads fail significantly faster than the non solder mask defined (NSMD) pads in thermal fatigue. The thermal mismatch on CBGAs is much larger than PBGA assemblies. Crack propagation in CBGAs is often observed predominantly on the package side as opposed to both package and board side for PBGAs. In the present study, crack propagation data has been acquired on assemblies with 15, 17, and 23mm size plastic BGAs with NSMD pads and 63Sn37Pb on high-T/sub g/ printed circuit boards. The data has been benchmarked against Darveaux's data on CBGA assemblies. Experimental matrix also encompasses the effect of bis-maleimide triazine (BT) substrate thickness on reliability. Damage constants have been developed and compared against existing Darveaux Constants. Prediction error has been quantified for both sets of constants.

Reliability and failure analyses of thermally cycled ball grid array assemblies

The reliability of ball grid arrays (BGAs) was assessed as part of a consortium effort led by the Jet Propulsion Laboratory. Nearly 200 test vehicles, each with four packages, were assembled and tested using an experiment design. The most critical variables incorporated in for the experiment were package types, ceramic and plastic; board materials, FR-4 and polyimide; surface finishes, OSP, HASL, and Ni/Au; solder volumes, low, standard, and high; and environmental conditions. Thermal cycling test results to 3000 cycles for ceramic packages with 625 inputs/outputs (I/Os) and depopulated full array plastic packages with 313 I/Os were presented in a previous paper by the authors (see Proc 30th Int. Symp. Microelectron., Philadelphia, PA, Oct. 1997, p. 396-400). This paper presents the most current thermal cycling test results (>6000 cycles) for plastic OMPAC and SuperBGA packages with 352 I/Os and 560 I/Os. Failure mechanisms detected by electrical continuity interruptions as well as optical and scanning electron microscopy results are also compared for ceramic and plastic package assemblies.

Ball grid array reliability assessment for aerospace applications

Reliability of ball grid arrays (BGAs) was evaluated with special emphasis on space applications. This work was performed as part of a consortium led by the Jet Propulsion Laboratory (JPL) to help build the infrastructure necessary for implementing this technology. Nearly 200 test vehicles, each with four package types, were assembled and tested using an experiment design. The most critical variables incorporated in this experiment were package type, board material, surface finish, solder volume, and environmental condition. The packages used for this experiment were commercially available packages with over 250 I/Os including both plastic and ceramic BGA packages. The test vehicles were subjected to thermal and dynamic environments representative of aerospace applications. Two different thermal cycling conditions were used, the JPL cycle ranged from −30°C to 100°C and the Boeing cycle ranged from −55°C to 125°C. The test vehicles were monitored continuously to detect electrical failure and their failure mechanisms were characterized. They were removed periodically for optical inspection, scanning electron microscopy (SEM) evaluation, and cross-sectioning for crack propagation mapping. Data collected from both facilities were analyzed and fitted to distributions using the Weibull distribution and Coffin–Manson relationships for failure projection. This paper will describe experiment results as well as those analyses.

Effect of PCB finish on the reliability and wettability of ball grid array packages

Organic protective coatings (OPC) and metallic plating chemistries have emerged as alternatives to traditional hot air solder leveling (HASL) to ensure the solderability of printed circuit boards (PCB). This study examined a number of commercially-available printed circuit board finishes to determine their intrinsic solderability and their effect on the solder joint reliability of ball grid array (BGA) packages. The PCB finishes included OPC (Entek Plus CU-106A and MEC-seal), immersion Au over electroless Ni (LeaRonal, MacDermid, Shipley, and Technique), electroless Pd over Ni, electroless Sn over Cu, immersion Bi over Cu, and HASL. Solderability tests were performed by reflowing 20-mil diameter solder spheres on variously aged test coupons and then quantitatively measuring the area and shape of the solder after cooling. The immersion Au finishes generally exhibited excellent wettability as a function of N/sub 2/ reflow aging as compared with the OPCs and HASL. The Pd-Ni, Sn, and one of the Ni-Au finishes exhibited poor wetting when exposed to an 85/spl deg/C/85% RH environment. Solder joint reliability was measured for a 41 I/O ceramic BGA using cyclic thermal shock (nominally -55-125/spl deg/C) and three point bending. All finishes tested behaved similarly in thermal shock. The Au finishes generally performed worse in three-point bending as compared to OPC and HASL. The wetting and reliability results are correlated with the structure and composition of the finishes and the solder joints.