Effect Of Solder Volume Research Articles

Effects of solder volume and size on microstructures and mechanical properties of Sn-3.0Ag-0.5Cu solder joints

Effects of solder volume and size on microstructures and mechanical properties of Sn-3.0Ag-0.5Cu solder joints

Effect of Different Solder Volumes on the Laser Soldering Process: Numerical and Experimental Investigation

Abstract Laser soldering is becoming more popular for soldering pin through-hole (PTH) components onto printed circuit boards (PCBs). Solder volume influences soldering joint reliability. However, it is difficult to accurately measure the effect of solder volume during the laser soldering process. The finite volume method (FVM) is used to simulate the molten solder flow in laser soldering to connect the through-hole capacitor onto the PCB in ansysfluent software. The simulation results reveal the effects of different SAC305 solder volumes on joining quality in terms of fillet shape formation, pressure, and velocity. The preferred solder volume is 1.517 mm3 with a filling time of 1.7 s, a temperature of 642 K, a hole diameter of 1.0 mm, a lead diameter of 0.5 mm and a PCB thickness of 1.20 mm, produces a fillet shape similar to a real sample of PTH laser soldering joint from the industry. This ideal volume was chosen with a suitable pressure and velocity to create a nice concave fillet shape and minimize voids during soldering. The pressure and velocity increase when the solder volume increases causing solidified solder to melt. The discrepancy between numerical and experimental values of fillet height is comparable, which inferred that the numerical model was well-validated. The good consistency between both results proves that the finite volume model will effectively predict the optimum solder volume. This opens up new opportunities for the optimization of the laser soldering parameters in the application of electronic manufacturing.

Effects of Solder Volume and Size on Microstructures and Mechanical Properties of Sn-3.0ag-0.5cu Solder Joints

Effects of Solder Volume and Size on Microstructures and Mechanical Properties of Sn-3.0ag-0.5cu Solder Joints

Solder Volume Effect on Electromigration Failure Mechanism of Cu/Ni/Sn-Ag Microbumps

Effects of solder volume on the electromigration (EM) failure mechanism of Cu/Ni/Sn-2.5Ag microbumps were systematically investigated at 150 °C with a current density of $1.5\times 10 ^{5}$ A/cm2. While the electrical resistances of Cu/Ni/Sn-Ag microbump with large solder volume increased quickly, those with small solder volume increased slowly, which depends on the difference in solder volume effect on the intermetallic compound formation mechanisms. For a structure with large solder volume, the Ni barrier layer was extensively consumed due to substantial reaction between Ni barrier and large solder volume. For a structure with small solder volume, the initial Ni barrier structure was preserved due to the limited volume of solder reacting with Ni barrier, which mainly contributes to better EM reliability of Cu/Ni/Sn-Ag microbump.

Effects of Solder Volume and Reflow Conditions on Self-Alignment Accuracy for Fan-Out Package Applications

The effects of solder volume and reaction time between molten solder and a metal pad at the peak temperature of reflow on the self-alignment effect have been investigated in flip chip bonding. A glass die with two different pad designs and a flame retardant-4 (FR-4) organic substrate were used. Sn-3.0Ag-0.5Cu and Sn-3.5Ag solders were formed on Cu-organic solderability preservation (Cu-OSP) and electroless nickel electroless palladium immersion gold (ENEPIG) pads on FR-4 substrates using the stencil printing method. To assess the effect of solder volume, the thickness and opening size of the stencil mask were controlled. Reflow experiments were performed at 250°C with wetting times of 40 s, 55 s, 65 s, and 75 s. After flip chip reflow soldering, the bonding areas were cross-sectioned to inspect the shape of the interconnected solder using scanning electron microscopy. The results revealed that using an insufficient solder volume on the pad was responsible for die shifts larger than 1 μm, while a sufficient solder volume on the pad and a stable solder joint shape could ensure misalignment less than 1 μm. The Sn-3.0Ag-0.5Cu solder showed a lower die shift value than the Sn-3.5Ag solder because the Sn-3.0Ag-0.5Cu solder has stronger surface tension than the Sn-3.5Ag solder. Using a longer wetting time between the solder and the pad at the peak temperature also improved the die shift value because the increased reaction time changed the interconnected solder shape between the die and substrate from concave to convex, moving the die to a more accurate position. Furthermore, the restoring forces on die self-alignment influenced the die shift value. A stronger solder surface tension and a larger volume of solder on the pad produced stronger restoring forces for die self-alignment, thereby improving the die shift value.

Solder Volume Effect on Interfacial Reaction between Sn-Ag-Cu/ENImAg Substrate

The purpose of this study is to investigate the effect of solder volume on interfacial reaction during reflow soldering between Sn-3.0Ag-0.5Cu (SAC305) and Sn-4.0Ag-0.5Cu (SAC405), and electroless nickel/immersion silver (ENImAg) surface finish. Different solder balls with sizes of 300μm, 500μm and 700μm diameters were used. The characteristics of intermetallic compound (IMC) were analysed by using field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM), optical microscope and energy dispersive x-ray (EDX). After the plating process, the result showed that ENImAg surface finish was free from black line nickel. After reflow soldering, a thin layer Ni3P or P-rich layer was formed. The result also revealed that an IMC layer was formed at the interface of (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 as well as Ag3Sn platelet. In term of morphologies, the grains type of IMC layer appeared as chuck, needles, rode, plate, diamond and bar shape. The result also indicated that, the solder volume can influence the IMC thickness, where the smaller size of solder balls produced a thinner IMC layer compared with a larger solder ball during the reflow soldering process. Meanwhile, a total of the IMC thickness for SAC305 was thinner than SAC405 solder ball.

Influence of Difference Solders Volume on Intermetallic Growth of Sn-4.0Ag-0.5Cu/ENEPIG

In recent years, portable electronic packaging products such as smart phones, tablets, notebooks and other gadgets have been developed with reduced size of component packaging, light weight, high speed and with enhanced performance. Thus, flip chip technology with smaller solder sphere sizes that would produce fine solder joint interconnections have become essential in order to fulfill these miniaturization requirements. This study investigates the interfacial reactions and intermetallics formation during reflow soldering and isothermal aging between Sn-4.0Ag-0.5Cu (SAC405) and electroless nickel/immersion palladium/immersion gold (EN(P)EPIG). Solder diameters of 300 μm and 700 μm were used to compare the effect of solder volume on the solder joint microstructure. The solid state isothermal aging was performed at 125°C starting from 250 hours until 2000 hours. The results revealed that only (Cu,Ni)6Sn5 IMC was found at the interface during reflow soldering while both (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 IMC have been observed after aging process. Smaller solder sizes produced thinner IMC than larger solder joints investigated after reflow soldering, whereas the larger solders produced thinner IMC than the smaller solders after isothermal aging. Aging duration of solder joints has been found to be increase the IMC’s thickness and changed the IMC morphologies to spherical-shaped, compacted and larger grain size.

Effect of Solder Volume on Interfacial Reaction between SAC405 Solders and EN(B)EPIG Surface Finish

The electronic packaging industry is now being driven towards smaller, lighter, and thinner electronic products but with higher performance and more functions. Thus, smaller solder ball sizes are needed for fine solder joint interconnections to fulfill these requirements. This study investigates the interfacial reactions during reflow soldering and isothermal aging between Sn-4.0Ag-0.5Cu (SAC405) and electroless nickel (boron)/ immersion palladium/immersion gold (EN(B)EPIG). Reliability of solder joint has also been investigated by performing solid state isothermal aging at 125 °C for up to 2000 hours. The results revealed that after reflow soldering, (Cu, Ni)6Sn5 IMC is formed between solder and substrate while after aging treatment another IMC was found between (Cu, Ni)6Sn5 and substrate known as (Ni, Cu)3Sn4. Aging time of solder joints resulted in an increase in IMC thickness and a change in morphology into more spherical, dense and with larger grain size. By using optical microscope, the average thickness of the intermetallics was measured and it found that the larger solder balls produced thicker IMC than the smaller solder balls during reflow soldering. However, after aging the smaller solders produced thicker IMC than the larger solders.

(Invited) Solder Volume Effect on Interfacial Reaction between Sn-3.0Ag-0.5Cu Solder Balls and Cu Substrates - Experiment and Simulation

With the continuous miniaturization of electronic devices, solder joints are downsizing simultaneously. The downsizing of the solder balls may have a detrimental effect on the reliability of the solder joints. Because smaller solder joint has thicker intermetallic compound (IMC) layer which may degrade the mechanical properties of the solder joints. The solder volume effect on interfacial reaction was demonstrated in the present work. It was shown that, when the smaller solder ball was used, the Cu6Sn5 grains became larger and the interfacial intermetallic compound (IMC) layer became thicker, which were accompanied by less Cu consumption and higher Cu concentration in molten solder. A theoretical model was established to calculate the growth kinetics of the interfacial IMC and the consumption kinetics of the Cu pad during the liquid/solid reaction. The calculated results were compared with the experimental ones, and a good agreement was achieved.

Massive spalling of Cu-Zn and Cu-Al intermetallic compounds at the interface between solders and Cu substrate during liquid state reaction

The interfacial intermetallic compound (IMC) formation between Cu substrate and Sn-3.8Ag-0.7Cu-X (wt.%) solder alloys has been studied, where X consists of 0–5% Zn or 0–2% Al. The study has focused on the effect of solder volume as well as the Zn or Al concentration. With low solder volume, when the Zn and Al concentrations in the solder are also low, the initial Cu-Zn and Al-Cu IMC layers, which form at the solder/substrate interface, are not stable and spall off, displaced by a Cu6Sn5 IMC layer. As the total Zn or Al content in the system increases by increasing solder volume, stable CuZn or Al2Cu IMCs form on the substrate and are not displaced. Increasing concentration of Zn has a similar effect of stabilizing the Cu-Zn IMC layer and also of forming a stable Cu5Zn8 layer, but increasing Al concentration alone does not prevent spalling of Al2Cu. These results are explained using a combination of thermodynamic- and kinetics-based arguments.

Effect of Solder Volume on Interfacial Reaction between Sn-3.0Ag-0.5Cu Solder Balls and the Substrates

Nowadays, with the continuous miniaturization of electronic packages, the solder balls used to join chips and substrates are downsizing. While the decrease in solder size may have a detrimental effect on the reliability of solder joints. In this paper, Sn-3.0Ag-0.5Cu solder balls were reflow soldered on two kinds of pads (Cu and Ni-P) to give a comparative study of the volume effect. Cu/Sn-3.0Ag-0.5Cu and Ni-P/Sn-3.0Ag-0.5Cu joints displayed volume effect of different forms. In the reaction of Cu/Sn-3.0Ag-0.5Cu, scallop-type Cu6Sn5 grains formed at the interface. The grain size and thickness of Cu6Sn5 IMC together with the Cu consumption were influenced by solder volume. In the reaction of Ni-P/Sn-3.0Ag-0.5Cu, different type of interfacial IMCs formed for solder balls with different sizes. Changes of Cu content in solder balls play an important role in both kinds of reactions.

Solder Volume Effect on the Microstructure of Solder Joints Using Au/Pd(P)/Ni(P) Surface Finish

The liquid–solid reaction between Sn3Ag0.5Cu and Au/Pd(P)/Ni(P) tri–layer with three different joint diameters (djoint), 200μm, 150μm, and 60μm, were investigated in this study. The reaction product(s) strongly depended on djoint. In the case of djoint = 200μm, the predominant product after reaction at 245oC for 80s was a continuous (Cu,Ni)6Sn5. When djoint slightly reduced to 150μm, a mixture of (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 grew at the interface. When djoint further reduced to 60μm, the (Cu,Ni)6Sn5 was completely replaced by (Ni,Cu)3Sn4. Moreover, a significant amount of isolated (Pd,Ni)Sn4 domains scattered inside the solder matrix near the interface. The transition of the microstructure was attributed to the decrease of Cu concentration (CCu) and increase of Pd concentration (CPd) as djoint reduced. This finding suggests that the solder volume is an important factor in determining the microstructure of solder joints.

Consumption of Cu pad during multiple reflows of Ni-doped SnAgCu solder

Abstract The effects of solder volume and the number of reflows on the Cu consumption rate were studied. Nickel-doped Sn3Ag0.5Cu0.02Ni solder balls of different diameters (300, 400, 600 and 760 μm in diameter) were reflowed over Cu soldering pads with an opening of 600 μm in diameter. The reflow profile had a peak temperature of 235 ± 2°C and a 90 s duration during which the solder was molten. The nominal ramp rate and cooling rate were both 1.5 K s−1. The first reflow consumed the largest amount of Cu, and the subsequent reflows only consumed marginally more Cu. It was argued that the solder joints became saturated with Cu during the first reflow so that during the subsequent reflows the Cu substrates were consumed at markedly reduced rates. The Cu consumption increased with the diameter of the solder balls. This was because a larger amount of Cu was needed in order to saturate a solder joint with a larger solder volume. The doping of Ni did not change the Cu consumption rate despite the fact that the am...

The effects of solder volume and Cu concentration on the consumption rate of Cu pad during reflow soldering

Abstract The combined effect of solder volume and Cu concentration in solder on the Cu consumption rate is of significant practical importance but has never been satisfactorily addressed in literature so far. In this study, lead-free solder balls of different volumes (400, 500, 760 and 960 μm in diameter) and different Cu concentrations (Sn3Ag x Cu with x = 0, 0.3, 0.5, and 0.7 wt.%) were reflowed over Cu soldering pads in order to resolve this issue. The data obtained afforded the establishment of an empirical equation that could predict the Cu consumption during reflow. Such consumption rate information is crucial for designing the Cu conduction traces with minimum but reliable dimensions. Both the solder volume and the Cu concentration had marked effects on the morphology of the reaction product. Rationalizations for the effects on the consumption rate and the morphology are presented.

Cross-Interaction between Ni and Cu across Sn Layers with Different Thickness

The Ni/solder/Cu material sequence is one of the most common material sequences in the solder joints of electronic packages. In this study, the Ni/Sn/Cu ternary diffusion couples were used to investigate the solder volume effect on the cross-interaction between Ni and Cu. Experimentally, a pure Sn layer with the thickness of 100–400 μm was electroplated over Cu foils. A pure Ni layer (20 μm) was then deposited over the as-deposited Sn surface. The diffusion couples were aged at 160°C for different periods of time. With this technique, the diffusion couples were assembled without experiencing any high temperature process, such as reflow, which would have accelerated the interaction and caused difficulties in analysis. This study revealed that the cross-interaction could occur in as short as 30 min. A detailed atomic flux analysis showed that the Cu flux through the Sn layer was about 25–40 times higher than the Ni flux. Moreover, it was found that (Cu1−xNix)6Sn5 on the Ni side reduced the consumption rate of the Ni layer, and the cross-interaction also reduced the Cu3Sn thickness on the Cu side.

Effects of Solder Volume on Formation and Redeposition of Au-Containing Intermetallics in Ni/Au-SnAgCu-Ni(P) Solder Joints

SnAgCu is one of the most promising candidates for lead-free solders to replace conventional eutectic SnPb solders. The effects of solder volume on interfacial reactions and microstructure evolution in Ni/Au-SnAgCu-Ni(P) solder joints have been investigated under soldering and thermal aging conditions. The results show that solder volume has a strong effect on the formation of Au-containing intermetallic compounds (IMCs) and their redeposition at the interfaces. The size and volume fraction of Au-containing IMCs dispersed in the solder bulk increased with decreasing solder joint dimensions. For the small solder joint with 300-μm solder ball, the (Au,Ni)Sn4 IMCs redeposited to the interfaces after thermal aging at 150°C for 9 days, but this was not observed for the other two solder joints with large solder volume. These results also indicate that the redeposition of (Au,Ni)Sn4 is closely associated with the migration of Cu toward the interfaces.

Effects of limited cu supply on soldering reactions between SnAgCu and Ni

The volume difference between the various types of solder joints in electronic devices can be enormous. For example, the volume difference between a 760-µm ball grid array solder joint and a 75-µm flip-chip solder joint is as high as 1000 times. Such a big difference in volume produces a pronounced solder volume effect. This volume effect on the soldering reactions between the Sn3AgxCu (x=0.4, 0.5, or 0.6 wt.%) solders and Ni was investigated. Three different sizes of solder spheres (300, 500, and 760 µm in diameter) were soldered onto Ni soldering pads. Both the Cu concentration and the solder volume had a strong effect on the type of the reaction products formed. In addition, (Cu,Ni)6Sn5 massively spalled from the interface under certain conditions, including smaller joints and those with lower Cu concentration. We attributed the massive spalling of (Cu,Ni)6Sn5 to the decrease of the available Cu in the solders. The results of this study suggest that Cu-rich SnAgCu solders can be used to prevent this massive spalling.

A study of the effects of solder volume on the interfacial reactions in solder joints using the differential scanning calorimetry technique

The differential scanning calorimetry (DSC) technique was employed to understand the interfacial reactions during soldering by simulating the soldering process as well as analyzing the interfacial reactions. The measurement of peak temperatures and heat involved provides useful information about the interfacial reactions, such as the amount of intermetallic compounds (IMCs) formed and the amount of Cu dissolved. Tin-plated Cu balls with different Sn thicknesses were used to investigate the solder-volume effect. As the Sn-layer thickness decreases, the amount of the IMC formed during reflow increases in general. This suggests IMC formation depends on the Sn volume. In addition, a Ni layer (electroless and electroplated), introduced as a diffusion barrier between Cu and Sn, was found effective in reducing Cu out diffusion. The results from the DSC study were confirmed by conventional metallography, scanning electron microscopy (SEM), and energy dispersive x-ray (EDX) techniques.

Computer simulation of three-dimensional castellated solder joint geometry in surface mount technology

In this paper, the problem of the 3D castellated solder joint geometry of a leadless chip component in surface mount technology is investigated using the minimum potential energy theorem; the method of simulation of 3D solder joint geometry as a function of parameters of the design and manufacturing process through the Surface Evolver program is presented. The effects of solder volume, pad extension and stand-off height on solder joint geometry are analysed. In addition, a primary estimate of optimal solder volume and pad extension is obtained. Experimental verification shows that there is good agreement between experimental results and calculated ones.

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

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