Ball Grid Array Components Research Articles

Fatigue life prediction of BGA solder joint of several alloy compositions under an isothermal harmonic vibration

To ensure durable performance and optimal function of electronic components, it is crucial to guarantee their reliability, robustness and goodness of fit. The solder joints used in the BGA (Ball Grid Array) component play an intrinsic role in the reliability of the system. The vibration present in BGA triggers fatigue in solder joints, which raises a major reliability problem in various sectors such as aerospace, automotive and military industries. This study handles the response to a harmonic vibration at three specific temperatures (−40°C, 25°C, and 125°C) for four types of solder alloys in BGA Soldering. Within this framework, predicting the fatigue life of BGA solder joints with various alloy compositions under the influence of an isothermal harmonic vibration emerges as a crucial challenge in the design as well as reliability of modern electronic devices. The investigated solder compositions are SAC105, SAC305, SAC405, and InnoLot. To simulate and analyze the behavior of solder joints, we used the Ansys APDL finite element analysis (FEA). At both 125°C and −40°C, the Von Mises values proved to exceed those observed at 25°C. Likewise, an S-N curve for InnoLot and the different SACs, under a harmonic vibration at 25°C, was fitted using the Basquin power law relationship. As far as the current research work is concerned, an initial comparison was enacted between InnoLot and SAC alloys under an isothermal harmonic vibration, aiming to ascertain the most reliable alloy. The fatigue life under a harmonic vibration loading at 25°C was estimated. The results revealed that under a harmonic vibration at 25°C, the InnoLot solder displayed the longest lifespan, while the SAC105 solder exhibited the shortest fatigue life.

Effect of filer content on the thermal characteristics of underfill materials for Ball-Grid-Array component package

High-density integration and fast processing speed in the semiconductor industry have increased heat generation in electronic devices. Underfill materials, known for their high thermal conductivity and low coefficient of thermal expansion (CTE), offer a potential solution to dissipate heat and improve device reliability. In this study, we investigate the effect of filler content on the thermal reliability of underfill materials for ball grid array (BGA) component packaging. Mainly, we investigate the thermal conductivity, CTE, and mechanical properties of different filler contents of Al2O3 and Al2O3–BN hybrid underfills to facilitate heat dissipation and improve device reliability. The thermal conductivity of the underfill materials was evaluated by measuring the surface temperatures of underfill molded flip-chip light-emitting diodes (FCLEDs). The mechanical properties and thermo-mechanical reliability of the underfill materials were evaluated via a three-point bending test of the underfill packaged BGA components after the thermal shock test. The results showed that optimizing underfill properties based on specific application environments is crucial for obtaining enhanced thermal reliability and mechanical properties of underfill packaged BGA components.

Laser Rework Process for Efficient Lead-Free Solder Joints Ball Grid Array (BGA) Component Rework

Laser Rework Process for Efficient Lead-Free Solder Joints Ball Grid Array (BGA) Component Rework

Reliable Solder Columns to Replace Solder Balls in Large 2.5D Heterogeneous Packages

Solder balls are well suited for interconnecting normal sized ball grid array (BGA) components to printed circuit boards (PCB). However, solder balls are prone to cracking (failure) caused by excessive stresses inherently found in advanced packaging such as large-sized heterogeneous 2.5D packages where multiple dies are placed side-by-side. The growth trend is to make larger and larger BGA processors exceeding 60x60mm in size for AI and data centers. A plethora of new processor substrate and interposer designs are coming on line such as Chip-on-Wafer-on-Substrates (CoWoS). For that reason, more instances of solder ball delamination and cracking on large-sized BGA packages are probable. Solder columns were produced more than 50 years ago to reduce cracking in large ceramic packages, especially for use in harsh environments found in aerospace and defense applications. However, such legacy solder column technology is limited to Tin-Lead (SnPb) alloys. The challenge is to make Lead Free solder columns that satisfy demand for RoHS compliance, while still providing adequate stress relief (compliancy) for extending the operational life of large sized heterogeneous 2.5D processors for mission critical applications. This paper describes our ongoing work to innovate non-collapsible, compliant Lead-Free Braided Copper Solder Columns to reduce strain caused by the Coefficient of Thermal Expansion (CTE) mismatch between large BGA packages and FR4 PCBs. A braid, consisting of 16 fine copper alloy wires, serves as an exoskeleton sleeve around a solder column to provide mechanical support as well as compliancy. This novel solder column technology supports market trends to scale up the size of chip packaging while maintaining reliability. Our focus was to quickly characterize Lead-Free solder column core materials and braiding alloys by employing “Fail-Fast” destructive accelerated mechanical bend testing in our lab. Since there is an ongoing interest in Tin-Lead alloys, this paper also discusses data on Tin-Lead alloys for comparative purposes.

Fatigue performance and microstructure of lead-free solder joints in BGA assembly at room temperature

One of the crucial factors in evaluating the reliability of an electronic appliance is fatigue failure of the interconnecting solder joints. In most situations, large bulk samples are used to investigate the fatigue characteristics of the solder materials. Only a few studies have examined the solder joints frequently observed in ball grid array (BGA) components. This study implemented a specialized test vehicle in BGA assembly connecting two substrates with nine identical solder joints. Four SAC-based solder alloys were tested using an Instron micromechanical tester in the stress-controlled and strain-controlled methods at room temperature and constant strain rate. At two distinctive stress and strain levels, the fatigue performance of alloys featuring organic solderability preservative (OSP) and electroless nickel-immersion gold (ENIG) surface finishes was investigated. The fatigue results obtained from the stress-controlled and strain-controlled tests were compared. Microstructural analysis was performed using scanning Electron Microscopy (SEM) and energy dispersive spectroscopy (EDS) to identify the precipitates in the bulk solder and the morphologies of IMC layers. The thickness of intermetallic compound (IMC) layers and the failure mode were examined in each case. The results demonstrated that the OSP surface finish significantly outperformed the ENIG surface finish regardless of the testing process and solder alloy. Various failure modes were observed, depending on the solder alloy and IMC layer.

Enhancing ball grid array (BGA) component design and reliability using a novel reliability-based design optimization (RBDO) methodology

In industry and research areas, the importance of reliable and optimally designed BGA components has remarkably grown. To tackle this challenge, we elaborated an innovative approach that optimizes of the BGA’s structure. By adopting the RBDO method, we assess the geometric design variables of the BGA component and determine the optimal variables that promote the structure’s efficiency level. Our approach considers technical and economic feasibility, ensuring an optimal design of the BGA solder joints. This work rests upon coupling Ansys and MATLAB software. The current paper reports our investigation’s results, highlighting our approach’s benefits and potential for practical applications.

Optimal performance and cost-effective design of BGA solder joints using a deterministic design optimization (DDO) under real operating conditions

Users of electronic devices expect efficiency, affordability, and long service life. From this perspective, the optimization of their performance while reducing costs is paramount. The objective of this paper is to find the best compromise between minimizing the volume and thus cost, and preserving the efficiency of the component. This work is based on coupling the finite element model on Ansys with an optimization algorithm on MATLAB. First, fatigue analysis tests were simulated to determine the geometric design variables' sensitivity, having an impact on the service life, then these variables are incorporated into the Deterministic Design Optimisation (DDO) loop. This efficient approach is used to identify the optimal configuration of the BGA (Ball Grid Array) component to increase operational life and efficiency under electro-thermomechanical conditions. The elaborated method constitutes a great impetus for electronic industries and researchers to successfully find the best combination of cost reduction and performance increase, allowing improved design.

Drop and impact reliability investigation of BGA and LGA interconnects

PurposeBecause of growing demand for slim, thin and cheap handheld devices, reduced-volume solder interconnects like land grid array (LGA) are becoming attractive and popular choices over the traditional ball grid array (BGA) packages. This study aims to investigate the mechanical shock and impact reliability of various solder alloys and BGA/LGA interconnect configurations.Design/methodology/approachTherefore, this paper uses drop testing experiments and numerical finite element simulations to evaluate and compare the reliability performance of both LGA and BGA components when exposed to drop and impact loadings. Additionally, three common solder alloys, including 63Sn37Pb, SAC305 and Innolot, are discussed.FindingsThe results of this study showed that electronic packages’ drop and impact reliability is strongly driven by the solder configuration and the alloy type. Particularly, the combination of stiff solder alloy and shorter joint, LGA’s assembled with SAC305, results in highly improved drop reliability. Moreover, the BGA packages’ performance can be considerably enhanced by using ductile and compliant solder alloys, that is, 63Sn37Pb. Finally, this paper discussed the failure mode of the various solder configurations and used simulation results to explain the crack and failure situations.Originality/valueIn literature, there is a lack of published work on the drop and impact reliability evaluation and comparison of LGA and BGA solders. This paper provides quantitative analysis on the reliability of lead-based and lead-free solders when assembled with LGA and BGA interconnects.

Intense Pulsed Light Soldering of Sn–3.0Ag–0.5Cu Ball Grid Array Component on Au/Pd(P)/Ni(P) Surface‐Finished Printed Circuit Board and Its Drop Impact Reliability

Intense pulsed light (IPL) soldering is investigated as an alternative soldering process to conventional reflow soldering. IPL soldering is suitable for achieving a carbon‐neutral society due to its low power consumption. In addition, it has several advantages in electronic device manufacturing, including low thermal damage, short processing time, and applicability to large‐area processes. Herein, an electroless‐nickel/electroless‐palladium/immersion‐gold surface finish and Sn–3.0Ag–0.5Cu solder are used. Three IPL parameters, pulse width, pulse number, and frequency, are considered in the soldering process. The microstructures of the interface and solder matrix are observed using a field‐emission scanning electron microscope equipped with an electron probe microanalyzer. Furthermore, board‐level drop impact tests are conducted to investigate the mechanical reliability of the joints. The results show that the compositions and morphologies of intermetallic compounds (IMCs) vary with the IPL parameters, which significantly affect the reliability. Specifically, the number of drops to failure increases ≈6.7 times under optimum IPL condition compared to reflow soldering. This is because cracks propagate through the solder matrix and discontinuous IMCs. Based on the obtained results, IPL‐based soldering is a promising alternative to reflow soldering.

Assessing the SAC305 Solder Joint Fatigue in Ball Grid Array Assembly Using Strain-Controlled and Stress-Controlled Approaches

Abstract One of the crucial factors in determining the reliability of an electronic device is fatigue failure of the interconnecting solder joints. In most cases, large bulk samples are used to study the fatigue characteristics of the solder materials. Real solder joints often encountered in ball grid array (BGA) components have only been considered in limited investigations. In this study, a specialized sandwich BGA test vehicle with a 3 × 3 solder joint was connected to the two substrates. The alloys were tested at room temperature using an Instron micromechanical tester in both the stress-controlled and strain-controlled methods. The tests were performed at a constant strain rate. Four stresses and four strain levels of the solder alloy Sn-3.0Ag-0.5Cu (SAC305) were examined using organic solderability preservative (OSP) and electroless nickel-immersion silver (ENIG) surface finishes. The work per cycle and plastic strain range was computed based on a systematic recording of the stress–strain (hysteresis) loops of each sample. A novel approach based on inelastic work is developed to calculate the fatigue life of a BGA assembled test vehicle. The results of the stress-controlled and strain-controlled tests indicated that the OSP surface finishes outperformed the ENIG surface finish. Regardless of the testing process and surface finish, the Coffin–Manson and Morrow energy models were acceptable for SAC305.

THERMAL-INDUCED DAMAGE ON SOLDER JOINTS OF HIGH-DENSITY ADJACENT BALL GRID ARRAY COMPONENTS DURING THE REWORK PROCESS

Correlation between adjacent ball grid array (BGA) components' temperature and thermal-induced damage to their solder joints on both the top and bottom printed circuit board assembly (PCBA) sides during the rework process is studied in this work. Total often adjacent BGA components from the rework area on the top (F - K) and bottom (A - E) PCBA side were observed. The dye and pull (D&P) test results, infrared thermography images, and temperature measurements were analyzed for solder joint crack induced by the thermal damage with precise temperature measurement on each adjacent BGA component. Scanning electron microscope (SEM) analysis complemented the post-D&P test solder joint crack observation. The D&P test results shows that 76 % or higher and solder joint separation locations at the copper pad on BGA occurred when the temperature of the adjacent components of the rework location exceeded 195 °C and 210 °C on the centre and corner of the component, respectively.

Effect of heat shield locations on rework-induced thermal management in ball grid array solder joint

This study investigated the effectiveness of heat shield placement locations during the rework process to avoid thermal and mechanical damage to adjacent ball grid array components and their solder joints on double-sided printed circuit board assembly. Three types of heat shield placement locations were used: sample X, individual heat shield placement on adjacent components of the rework location; sample Y, a U-shaped, and sample Z, a square-shaped heat shield placed respectively at the heat source location. The dye and pull test results, infrared thermography, and temperature measurements were analysed to understand the relationship between the location of the heat shield and solder joint damage during rework. Heat shield placement at the heat source location on the reworked component can reduce the peak temperatures on the adjacent rework component locations by up to 8.18%. The peak temperatures of the centre and corner of the BGA component can be maintained below 195 °C and 210 °C, respectively to improve the adjacent rework component locations' solder joint quality by reducing solder joint damage by more than 50% solder cracks. This is useful for thermal management during rework involving high-density ball grid array component placements on double-sided printed circuit board assembly.

Cardinal and Ordinal Directions Approach in Investigating Arrayed Solder Joints Crack Propagation of Ball Grid Array Semiconductor Packages

An accelerated reliability testing via thermal cycling test (TCT) was used to test ball grid array (BGA) components’ reliability. Five variables were observed; control sample J and samples K, L, M, and N were BGA component samples that have been exposed to TCT between 500 and 1250 cycles with the TCT profile in the range of 0 °C–100 °C. The crack orientation of the individual solder joint was analyzed along with the propagation path pattern on the solder array of the BGA component pad by analyzing the dye and pull test results that were then mapped and analyzed using the cardinal and ordinal directions approach. This is to determine the crack propagation path direction in the solder array and track the potential of warpage on the BGA package as the TCT cycles progressed. A cross section was performed on sample M with the 3-D X-ray and scanning electron microscopy (SEM) analysis to observe the solder joints’ fracture lines and surface topographies. The results showed that individual solder joint crack orientation is correlated to the crack propagation location on the BGA package. The solder joint from northwest (NW), northeast (NE), southeast (SE), and southwest (SW) of the BGA package is prone to solder crack compared to the solder joint array in the middle. A solder grain structure coarsening occurred at the crack propagation due to the high cyclic strain from the TCT.

Impact of temperature on the corrosion of lead-free solder alloy during salt spray test

This paper presents the impact of temperature on the corrosion behaviour of lead-free solder alloy during neutral salt spray (NSS) test. The focus is made on the Sn-Ag-Cu (SAC305) solder alloy Ball Grid Array components. Components were aged during 24, 48, 72, and 96 h in a salt spray chamber Ascott at 35 °C with 5% sodium chloride (NaCl) solution at temperatures ranging from 25 °C to 45 °C to investigate the effect of temperature on the corrosion. Two observables corrosion criteria were defined for this analysis. Solder balls deterioration is visible after 72, 48, and 24 h, respectively, at 25 °C, 35 °C, and 45 °C. This shows that the temperature has a significant effect on the corrosion behaviour of lead-free solder balls. An increase in temperature from 25 °C to 35 °C and 45 °C led to an earlier onset of corrosion. Tin (Sn), oxygen (O), and chloride ion (Cl) are found on solder balls. Finally, thermal “Arrhenius Law” is used to estimate an acceleration factor (AF) and an indicative value of the activation energy (Ea) after 96 h of exposure. The kinetic of the corrosion failure mechanisms is being investigated in order to predict lead-free solder balls lifetime.

Thermal fatigue life of ball grid array (BGA) solder joints made from different alloy compositions

As temperature cycling drives fatigue failure of solder joints in electronic modules, characterisation of the thermal fatigue response of different solder alloy formulations in BGA solder joints functioning in mission-critical systems has become crucial. Four different lead-free and one eutectic lead-based solder alloys in BGA solder joints are characterised against their thermal fatigue lives (TFLs) to predict their mean-time-to-failure for preventive maintenance advice. Five finite elements (FE) models of the assemblies of the BGAs with the different solder alloy compositions are created with SolidWorks. The models are subjected to standard IEC 60749–25 temperature cycling in ANSYS mechanical package environment. Plastic strain, shear strain, plastic shear strain, and accumulated creep energy density responses of the solder joints are obtained and inputted into established life prediction models – Coffin Manson, Engelmaier, Solomon and Syed – to determine the lives of the models. SAC405 joints have the highest predicted TFL of circa 13.2 years, while SAC387 joints have the least life of circa 1.4 years. The predicted lives are inversely proportional to the magnitude of the areas of stress–strain hysteresis loops of the BGA solder joints. The prediction models are significantly not consistent in predicted magnitudes of TFLs across the solder joints. With circa 838% variation in the magnitudes of TFL predicted for Sn63Pb37, the damage parameters used in the models played a critical role and justifies that a combination of several failure modes drives solder joints damage. This research provides a technique for determining the preventive maintenance time of BGA components in mission-critical systems. It proposes developing a new life prediction model based on a combination of the damage parameters for improved prediction.

Effect of different temperature distribution on multi-stack BGA package

PurposeThis paper aims to determine the optimum set of temperatures through correlation study to attain the most effective capillary flow of underfill in a multi-stack ball grid array (BGA) chip device.Design/methodology/approachFinite volume method is implemented in the simulation. A three-layer multi-stack BGA is modeled to simulate the underfill flow. The simulated models were well validated with the previous experimental work on underfill process.FindingsThe completion filling time shows high regression R-squared value of up to 0.9918, which indicates a substantial acceleration on the underfill process because of incorporation of thermal delta. An introduction of 11 °C thermal delta to the multi-stacks BGA managed to reduce the filling time by up to 16.4%.Practical implicationsTemperature-induced capillary flow is a relatively new type of driven underfill designed specifically for package on package BGA components. Its simple implementation can further improve the productivity of existing underfill process in the industry that is desirable in reducing the process lead time.Originality/valueThe effect of temperature-induced capillary flow in underfill encapsulation on multi-stacks BGA by means of statistical correlation study is a relatively new topic, which has never been reported in any other research according to the authors’ knowledge.

Impact of crystalline orientation of lead-free solder joints on thermomechanical response and reliability of ball grid array components

The microstructure of lead-free solder joints often consists of only one or a few randomly oriented tin grains as a result of cooling conditions and reactions that take place during the solidification. Due to severe anisotropy of the tin phase and this complex microstructure, the stress state of each joint will be unique, and lead to a dispersion in times to fail. This study aims at evaluating the impact of orientations of tin grains on the stress state of a BGA component. Different combinations of solder joint grain orientations are studied through thermo-mechanical simulations in order to assess the stress state of each joint. A significant effect of neighbouring joints has been observed for the different cases.

Developing a Machine Vision Inspection System for Electronics Failure Analysis

Ball grid array (BGA) package components are widely used in various electronic products, as they shorten the conductive path and greatly reduce the interference during current transmission. The BGA component solder ball has little flexibility for distortion, which may cause stress concentration and solder joint cracking. Red ink dye stain analysis testing can visually analyze the cracking area and the interface of the solder joint. At present, most companies use failure analysis (FA) specialists to observe the components and circuit board end images with a microscope. As component packaging technology becomes more complex and the number of input–output (I/O) signals of the chip increases sharply, FA operations require a long time and may be misjudged due to personnel fatigue and subjective determination. This paper aims to develop a machine vision image recognition system for intelligent decision analysis to judge the severity of solder ball cracking and the cracking interface type. This system uses charge-coupled devices (CCDs) to obtain the image. First, this paper uses affine transformation compensation to perform horizontal correction, which recognizes the actual position coordinates of each solder joint, estimates the solder ball according to the Hough Circle to obtain the center and the radius of the solder ball, and then a 2-D vector map (Gerber) file is used to establish the mask, and the region of interest (ROI) in the image feature is obtained through the iterator of the pixel access program. Second, the color space is converted from red, green, and blue (RGB) to hue, saturation, and value (HSV) to reduce the effects of light variations during image capture. This paper develops the range analysis model (uses the multiple-threshold method to judge whether a particular pixel in an image has the cracking (color) feature, as well as its cracking interface), and uses a morphology filter to filter image noise (filter pixels of overlapping features). The verification results show that the system developed in this paper and FA specialists have a consistency of more than 85% in the judgment of the severity of the cracking, and the false alarm ratio and the escape ratio of the system are about 9% and 16%, respectively. Regarding the judgment result of the solder ball cracking interface type, the consistency reaches 98%, which shows that the automatic failure identification system for solder joints, as developed in this paper, can effectively assist red ink solder joint FA.

Experimental SAC305 Shear Stress–Strain Hysteresis Loop Construction Using Hall's One-Dimensional Model Based on Strain Gages Measurements

Temperature-induced solder joint fatigue is a main reliability concern for aerospace and military industries whose electronic equipment used in the field is required to remain functional under harsh loadings. Due to the RoHS directive, which eventually will prevent lead from being utilized in electronic systems, there is a need for a better understanding of lead-free thermomechanical behavior when subjected to temperature variations. Characterizing solder joints properties remains a challenge as viscoplastic behavior during thermal cycling is complex, and their small dimensions prevent direct measurements from being performed. This paper reports the experimentation based on strain gage measurements, allowing the construction of the shear stress–strain hysteresis loop corresponding to Sn3.0Ag0.5Cu (SAC305) solder joints behavior during thermomechanical loading. This methodology, initially developed in 1984 by Hall for Sn60Pb40 interconnects, allows the measurement of the strain energy density dissipated during temperature cycles. Custom daisy-chained 76 I/O ceramic ball grid array (CBGA76) components were designed and assembled on flame retardant (FR-4) multilayered printed circuit boards (PCB). Four strain gages were specifically placed at the center of the assembly on top and bottom faces of both PCB and CBGA76 component. The assembly was subjected to temperature cycles and the SAC305 solder joints shear stress–strain hysteresis loop was plotted. The correlation between the measured strain energy density and measured lifetime corresponds to one point of the energy based fatigue curve for SAC305 solder joints. The hysteresis loop also provides the necessary data to derive SAC305 solder joints constitutive laws.

Advances on high current load effects on lead-free solder joints of SMD chip-size components and BGAs

Purpose This paper aims to present a novel approach on investigating critical current densities in the solder joints of chip-size surface-mounted components or device (SMD) components and ball grid array (BGA) lead-free solder joints with the focus of via-in-pad geometries. The investigation involves a numerical approach and a physical validation with selected geometry configurations and high current loads to reveal possible failure sources. The work is a continuation of a previous study. Design/methodology/approach Current density was investigated using finite element modeling on BGA joints. Dummy BGA components, 0402 and 0603 zero ohm jumper resistors, were used, both in daisy chain setups on standard FR4 printed circuit boards (PCBs). Respective physical loading experiments were set to find effects of elevated current density at hot zones of the joints. Cross-section analysis, scanning electron microscopy and shear force tests were used to analyze the joints. Findings The findings reveal alterations in the joints, while the current loading is not directly affecting the structure. The modeling reveals the current density map in the selected formations with increased current crowding zones. Overall, the degradation does not reach the level of electromigration (EM)-induced voiding due to the limiting factor of the FR4 substrate. Practical implications The heavy current load affects joint reliability, but there are limitations of EM-induced failures on PCB-based assemblies due to the thermomechanical weakness of the FR4 material. Originality/value The experiments investigate current density from a novel aspect on frequently used BGA surface mounted components with modeling configurations focusing on possible effects of via-in-pad structure.