Ceramic Ball Grid Array Research Articles

Integrated Circuit Ceramic Ball Grid Array Package Antenna

The recent advances in such highly integrated RF transceivers as radio system-on-chip and radio system-in-package have called for the parallel development of compact and efficient antennas. This paper addresses the development of a new type of dielectric chip antenna known as integrated circuit package antenna (ICPA) for highly integrated RF transceivers. A compact ICPA of this type has, for the first time, been designed and fabricated in a ceramic ball grid array (CBGA) package format. The novel ICPA, except economical advantage of mass production and automatic assembly, has potential benefit to the system-level board miniaturization and the system-level manufacturing facilitation. The simulated and measured antenna performance of the ICPA is presented. The effects of the different physical parts of the ICPA on the antenna performance are investigated. Results show that the ICPA achieved impedance bandwidth of 4.1% and radiation efficiency of 72%, and gain of 4.8 dBi at 5.715 GHz.

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.

CBGA solder joint thermal fatigue life estimation by a simple method

A simple analysis method was developed to determine the fatigue life of a ceramic ball grid array (CBGA) solder joint when exposed to thermal environments. The solder joint consists of a 90Pb/10Sn solder ball with eutectic SnPb solder on both top and bottom of the ball. A closed‐form solution, based on the calculation of the equilibrium of the displacements within the electronic package assembly, was first derived in order to calculate the solder joint strains during temperature cycling. In the calculation, an iteration technique was used to obtain a convergent solution for the solder strains, and the elastic material properties were used for all the electronic package assembly components except for the solder materials. A fatigue life prediction model was established.

Temperature Dependent Deformation Analysis of Ceramic Ball Grid Array Package Assembly Under Accelerated Thermal Cycling Condition

A robust scheme of moire´ interferometry for real-time observation is employed to study the temperature dependent thermo-mechanical behavior of a ceramic ball grid array package assembly. The scheme is implemented with a convection-type environmental chamber that provides the rapid temperature control required in accelerated thermal cycling. Thermal deformations are documented at various temperatures. Thermal-history dependent analyses of global and local deformations are presented. A significant nonlinear global behavior is documented due to complete stress relaxation at the maximum temperature. An analysis of solder interconnections reveals that inelastic deformation accumulates at the bottom eutectic solder fillet only at high temperatures.

Finite-Difference Time-Domain Analysis of Integrated Ceramic Ball Grid Array Package Antenna for Highly Integrated Wireless Transceivers

This paper presents a study of the integration of an antenna in a ceramic ball grid array package for highly integrated wireless transceivers. The study has been carried out on an 11/spl times/11.66 mm/sup 2/ small microstrip antenna in a thin 48-ball ceramic ball grid array package with the finite-difference time-domain (FDTD) method in C band. The impedance and radiation characteristics of the antenna are examined. More importantly, the loading effects of the complementary metal-oxide-semiconductor (CMOS) chip and bond wires on the performance of the antenna are investigated. It is found that the loading generally increases the impedance bandwidth but decreases the radiation efficiency of the antenna. To minimize detrimental loading, the shield of the antenna from the CMOS chip is considered. A new design has been realized. The new antenna achieves impedance bandwidth of 4.65%, radiation efficiency of 63%, and gain of 5.6 dBi at 5.52 GHz.

0.18-/spl mu/m CMOS push-pull power amplifier with antenna in IC package

A novel architecture of power amplifier with antenna implemented in a ceramic ball grid array (CBGA) package is presented. The monolithic power amplifier designed in a standard 0.18- μm CMOS technology offers 19.5 dBm maximum output power at 5.2 GHz to the antenna with the PAE of 32%. The antenna integrated in the CBGA package achieves impedance bandwidth of 3.86% and gain of 2 dBi at 5.2 GHz. Results demonstrate the feasibility of using this innovative configuration to the design of single-chip 5 GHz transmitter front-end.

Creep Characterization Of Ceramic BGA

Long term creep of a ceramic ball grid array (CBGA) solder ball under compressive loading was investigated. An experiment was conducted with two levels of loading and four of temperature. Analysis of the data assumed the composite ball structure could be simulated by an interconnection having the same shape, but of a single equivalent material. Curve fitting determined the stress exponent and activation energy of the equivalent material in the Norton creep model; the values were consistent with the range of values of the individual components available in the literature. Nonlinearity of the change in ball height with time was hypothesized to be due to geometric stiffening, a hypothesis which was confirmed by a simplified model. The model may be used to estimate creep behavior of other ball geometries having the same material set. The final result of this work - a closed form equation describing height decrease as a function of compressive force, temperature and time - can be used to simplify complex modeling of an entire package, and as an aid in designing accelerated thermal cycles which appropriately synchronize solder creep and fatigue.

Lead-free ceramic ball grid array: Thermomechanical fatigue reliability

Flip-chip carriers have become the preferred solution for high-performance, application-specific integrated circuit and microprocessor devices. Typically, these are packaged in organic or ceramic ball grid array (BGA) packages, which cover a wide range of package input/output (I/O) capabilities required for high-performance devices, typically, between 300 to more than 1,600 I/O. Recently, there has been a move toward Pb-free solders as replacement alloys for standard, eutectic Sn/Pb and other Pb-based BGAs. The leading solder that has emerged from various Pb-free solder evaluations by industry and academic consortia is the Sn/Ag/Cu (SAC) alloy. One of the primary issues with changing solders is the reliability of the joints when these are subjected to thermomechanical fatigue (TMF). This evaluation has previously been conducted on SAC ceramic ball grid array (CBGA) assemblies in a 1.27-mm pitch.1 However, with the need to shrink the I/O pitch to accommodate higher wiring density, it has become increasingly important to conduct TMF reliability assessments in a 1-mm pitch format. This paper describes such an evaluation conducted using SAC BGA assemblies. The results show that, for a 1-mm pitch, the Pb-free SAC CBGA solution provides superior reliability as compared to the standard Sn/Pb CBGA solutions. This finding is an added incentive for a new CBGA offering employing the new Pb-free, SAC, single-alloy, self-aligning system.

Impact of flip-chip packaging on copper/low-k structures

Copper/low-k structures are the desired choice for advanced integrated circuits (ICs). Nevertheless, the reliability might become a concern due to the considerably lower strength and greater coefficient of thermal expansion (CTE) of the low-k materials. To ensure successful integration of the new chips within advanced packaging products, it is essential to understand the impact of packaging on chips with copper/low k structures. In this study, flip-chip die attach process has been studied. Multilevel, multiscale modeling technique was used to bridge the large gap between the maximum and minimum dimensions. Interface fracture mechanics-based approach has been used to predict interface delamination. Both plastic ball grid array (PBGA) and ceramic ball grid array (CBGA) packages were evaluated. Critical failure locations and interfaces were identified for both packages. The impact of thin film residual stresses has been studied at both wafer level and package level. Both PBGA and CBGA packaging die-attach processes induce significantly higher crack driving force on the low-k interfaces than the wafer process. CBGA die-attach might be more critical than PBGA die-attach due to the higher temperature. During CBGA die-attach process, the crack driving force at the low-k/passivation interface may exceed the measured interfacial strength. Two solutions have been suggested to prevent catastrophic delamination in copper/low-k flip-chip packages, improving adhesion strength of low-k/barrier interface or adding tiles and slots in low-k structures to reduce possible area for crack growth.

Modified micro–macro thermo-mechanical modelling of ceramic ball grid array packages

The ceramic ball grid array (CBGA) packages are typically used for high I/O count area array assemblies. As the package size is large, the distance to neutral point is also high resulting in a large thermal deformation mismatch between the CBGA package and the printed circuit board (PCB). In order to cope with this problem, a special solder joint connection is used. As CBGA assemblies are used for high pin count assemblies, a full 3D thermo-mechanical modelling of an assembly to an FR4 board is not possible anymore. Therefore, a modified micro–macro methodology is proposed where only the critical solder joint is modelled in detail, while the other connections are replaced by equivalent connections. For several CBGA configurations, simulation results are correlated to thermal cycling test results. Finally, a parameter sensitivity study shows that the PCB properties have a significant influence on the solder joint reliability.

ICPA for highly integrated concurrent dual-band wireless receivers

A single-feed dual-band integrated circuit package antenna (ICPA) is reported. The ICPA, intended for use in either single-chip or single-package highly integrated concurrent dual-band wireless receivers, is implemented in the format of a cavity-down ceramic ball grid array package of 15/spl times/15/spl times/1.9 mm/sup 3/. Results show that the ICPA achieved a frequency ratio of 2.2, return loss bandwidth of 1.67% and gain of -8 dBi at 2.4 GHz, and return loss bandwidth of 0.69% and gain of -2 dBi at 5.25 GHz.

Modeling and simulation of core switching noise for ASICs

This paper presents simulation and analysis of core switching noise for a CMOS ASIC test vehicle. The test vehicle consists of a ceramic ball grid array (CBGA) package on a printed circuit board (PCB). The entire test vehicle has been modeled by accounting for all the plane resonances using the cavity resonator method. The models included both the on-chip and off-chip decoupling capacitors. Using both time domain and frequency domain simulations, the role of plane resonances on power supply noise for fast current edge rates has been discussed. The models have been constructed to amplify certain parts of the test vehicle during simulations.

Methodology for predicting solder joint reliability in semiconductor packages

A new experimental method for detecting solder joint strain in package assemblies using digital image correlation metrology has been developed. A new methodology is proposed which utilizes strain data generated by this technique for predicting solder joint fatigue life for any desired package configuration based on a reference configuration. This approach has significant practical appeal since it obviates brute-force temperature cycle testing for the qualification of every new variation of an existing package configuration. In this paper, we describe the principle, experimental set-up and sample preparation techniques for this method. We present typical strain data on solder joints for a ball grid array (BGA) package mounted to a FR4 PC board. We apply the technique to the prediction of temperature cycling reliability of a Ceramic BGA package wherein, the effect of a new substrate material is examined and the predictions are confirmed based on empirical temperature cycle testing data. Finally, we show a co-relation of measured strain data with computations by finite element modeling performed for a specific package configuration.

Effect of thermal cycling on the solder joints' reliability of ceramic ball grid array

Solder joints are known as one of the weakest elements of microelectronics assemblies. The integrity of solder joints in most microelectronics assemblies is of concern in systems where reliability is of great importance since the stresses experienced by the joints during service can lead to premature failure. This is mainly because the solder joints often constraint materials of different coefficient of thermal expansion (CTE) that imposes cyclic strain (fatigue) through the joints when thermal fluctuations are encountered. In addition, the high homologous temperature at which solder operates at constant stress, makes creep predominant in the solder joints. Due to viscoplastic nature of plastic, large creep and plastic deformations accumulate in a solder joint during thermal cycling, which eventually lead to thermal fatigue failures [1, 2]. Therefore, such fatiguecreep interaction effect in microelectronic packages must be considered when evaluating the reliability of solder. The reliability assessment of solder joints under creep-fatigue effect can be carried out by thermal cycling (TC) test. TC imposes cyclic strains over the solder joints of electronic components. Made by surface mount technology (SMT), which may cause the joints to fail by thermo-mechanical fatigue [3]. Pb-Sn solder used in microelectronics is expected to function at relatively high homologous temperatures over a wide range of temperatures. This is especially true for space and avionics applications where the solder joints may be required to endure extreme thermal fluctuations of −62 ◦C and 140 ◦C which correspond to 0.46TM and 0.91TM respectively for eutectic Pb-Sn alloys. The focus of this project is to study the failure characteristics of solder joints in ceramic ball grid array (CBGA) assembly that have been subjected to thermal cycling. Metallographic sections and fracture surfaces of the failed solder joints were investigated using both optical and scanning electron microscopy (SEM). The most likely location to fail first was identified by calculation of the strains imposed upon each solder joint by the following formula:

Integration of microstrip patch antenna on ceramic ball grid array package

A novel concept of integration of an antenna on an integrated circuit package is proposed for the single-chip solutions of wireless transceivers. A prototype antenna integrated on a thin ceramic ball grid array package is reported. Results show that the antenna achieved impedance bandwidth of 4.65% and radiation efficiency of 65% at 5.52 GHz.

Integration of microstrip antenna on cavity-down ceramic ball grid array package

The integration of a microstrip antenna on a thin 17/spl times/17/spl times/2 mm cavity-down ceramic ball grid array package is reported. The antenna, intended for use in either single-chip or single-package wireless transceivers, has achieved an impedance bandwidth of 1.25% and gain of 4.6 dBi at 5.15 GHz.

Integration of dual-mode RF bandpass filter on ceramic ball grid array package

A novel concept of integration of an RF bandpass filter on an integrated circuit package is proposed for the single-chip solutions of wireless transceivers. A prototype dual-mode bandpass filter integrated on a thin ceramic ball grid array package is reported. Results show that the filter achieved 2 dB insertion loss and 6.17% bandwidth at 2.43 GHz.

Effect of cooling rate on the isothermal fatigue behavior of CBGA solder joints in shear

This paper investigates the distribution characteristics of the isothermal fatigue lifetime of ceramic ball grid array (CBGA) solder joints in shear. Placement direction of the board-level assembly on the oven conveyor during reflow critically influences the fatigue lifetime of solder joints in shear: the front or outer solder joints have a longer shear lifetime than the rear or inner ones. The solder joints that moved diagonally during reflow have a longer fatigue lifetime and a tighter distribution. Cracks initiated in the eutectic solder region on the card and package side and tend to propagated in that region, while final failure occurred mainly on the card-said eutectic solder region. This phenomenon can be explained that the front or outer solder bumps have a resistant effect to the gas fluid which passes through the rear or inner solder bumps, and lower these solder joints' cooling rate during solidification. Fast cooling rate can cause a more fine-grained and homogeneous microstructure in eutectic solder alloy, which can delay crack initiation and slow crack growth. When the board-level assembly moves diagonally during reflow, the resistant effect of front solder bumps to the gas fluid reduces markedly. So the fatigue lifetime of solder joints and its distribution characteristic enhance substantially. The theories of fluid dynamics and heat transmission are used to calculate the decrease of gas fluid velocity and the corresponding reduction of mean coefficient of heat transfer (h/sub m/).

CBGA Solder Joint Reliability Evaluation Based on Elastic-Plastic-Creep Analysis

Three-dimensional nonlinear finite element analysis of a ceramic ball grid array (CBGA) package was conducted to determine the solder joint creep and plastic strain deformations in a simulated thermal cycling loading. Two methods of analysis were carried out to model the creep deformations during the dwell and during the temperature ramps in the thermal cycling loading. The equivalent plastic and creep strains are presented for the two analysis method to demonstrate the differences in the strain components. Both creep and plastic strain fatigue life prediction models were used to estimate the thermal cycling life of CBGA solder joints subjected to accelerated thermal cycling tests. The lives predicted using this nonlinear finite element analysis results were satisfactory and conservative compared to the experimental test results. [S1043-7398(00)01103-8]

Accelerated Thermal Cycling and Failure Mechanisms for BGA and CSP Assemblies

This paper reviews the accelerated thermal cycling test methods that are currently used by industry to characterize the interconnect reliability of commercial-off-the-shelf (COTS) ball grid array (BGA) and chip scale package (CSP) assemblies. Acceleration induced failure mechanisms varied from conventional surface mount (SM) failures for CSPs. Examples of unrealistic life projections for other CSPs are also presented. The cumulative cycles-to-failure for ceramic BGA assemblies performed under different conditions, including plots of their two Weibull parameters, are presented. The results are for cycles in the range of −30°C to 100°C, −55°C to 100°C, and −55°C to 125°C. Failure mechanisms, as well as cycles to failure for thermal shock and thermal cycling conditions in the range of −55°C to 125°C, were compared. Projection to other temperature cycling ranges using a modified Coffin-Manson relationship is also presented. [S1043-7398(00)00104-3]