A Review on Effect of Surface Finish and Cooling Rate on Solder Joint Reliability

The increasing environmental concern over the toxicity of lead (Pb) combined with strict regulations, the use of lead-based solders providing an inevitable driving force for the development of lead-free solder alloys. Many studies have been conducted for evaluation of the solder joint reliability with respect to solder alloys and surface finishes. However, as the demand of electronic devices is increasing, there is a need to improve the mechanical properties of the solder joint in order to keep up with the current evolution of electronic device's technology. In this study, the effect of surface finish and cooling rate on solder joint reliability using Nickel-based surface finish was summarizes. Study was focusing on Nickel based surface finish (ENIG and ENEPIG) with different cooling medium, slow (furnace), medium (air) and fast (water). It was found that the type of surface finish and the cooling rate can change the morphology of the solder intermetallic compound (IMC) and directly changes the solder joint mechanical properties. Faster cooling rate was reported to provide finer IMC grains which might be translated into a better solder joint strength. The findings presented here may provide a better understanding for a further study and facilitate improvements in term of solder joint reliability

The effect of rice husks as filler in polymer matrix composites

In this study, rice husks filler polyester composites were produced with rice husks as filler and unsaturated polyester resin as the matrix. Several weight percentages of filler loadings were used; 10 wt%, 15 wt%, 20 wt% and 25 wt% in order to gain insights into the effect of filler content on the mechanical properties and water intake of the composites. The surface fractured of the tensile test specimens were analysed by using Scanning Electron Microscopy. From the findings, the tensile strength of the rice husks filled unsaturated polyester resin composites was found to be decrease as the filler loading increased. However, as it increased to 25 wt%, the strength was slightly increased. As for the young modulus, it showed remarkable increased for 15 wt% of rice husks. Nevertheless, it was decreasing as the rice husks were continually increased up to 25 wt%. Water absorption test was also conducted and the results showed that the composites absorb more water as the weight percentage of rice husks increased, which attributed to the ability of rice husks fillers to absorb water

Effect of electroless nickel-boron (EN-B) surface finish on solderability of SAC305 and solder joint strength

Rapid developments in technology have been a great challenge for the electronics industry to keep up with the industrial requirement to provide cost-effective smart devices while, at the same time, maintaining their quality. The quality of electronic packaging is directly related to the solder joints, which turn out to be the main concern in the electronics industry. In the current study, an attempt was made to study the ability of electroless nickel boron as printed circuit board’s surface finish by study the solderability, investigate the type of intermetallic compound formation and growth after reflow soldering and isothermal aging as well as determine the effect of cooling rate and isothermal aging temperature (125°C and 150°C) on the intermetallic compound formation and solder joint's strength. Electroless nickel boron was deposited on a copper substrate through electroless plating method. Several sodium borohydrade concentration were used, 0.4, 0.6, 0.8, 1.0 and 1.2 g/L. in order to investigate the effect of Boron content on the electroless nickel boron. The morphology of the electroless nickel boron surface finish was analysed by using scanning electron microscopy. The phase structure analysis of the surface finish also analysed using x-ray diffraction and surface roughness measurement was carried out using 3D Roughness Reconstruction software. Then, reflow soldering was conducted using Sn-3.0Ag-0.5Cu solder alloy to form the solder joint prior to cooling process which two different cooling medium was used which is air (for slow cooling rate) and water (for fast cooling rate). The solderability of the surface finishes then evaluated by measuring the contact angle between the Sn-3.0Ag-0.5Cu solder alloy and the electroless nickel boron surface finish. After that, a set of samples were underwent isothermal aging for 250, 500, 1000 and 2000 hours for 125°C and another set for 150°C prior to lap shear test to study the strength of the solder joint. Thickness of the intermetallic compound and surface fractured of the shear test were analysed by using Optical microscope, Scanning Electron Microscopy while Field Emission Scanning Electron Microscope that equipped with energy dispersive x-ray spectroscopy system was used to identify the element on the intermetallic compound. From the results, it was observed that the suitable NaBH4 concentration to be used on printed circuit board to deposit an electroless nickel boron surface layer is 0.6 g/L NaBH4 based on its ability to provide most solderable surface with 42.5° contact angle. After reflow process, it was observed that intermetallic compound consist of of Ni3Sn4 and (Ni, Cu)3Sn4 for both air and water cooling. However, as the joint thermally aged (1000 hours), the intermetallic compound changes to only (Ni, Cu)3Sn4 for both cooling. In term of cooling rate, it was found that slow cooling rate (15.7 ˚C/min) produced higher intermetallic compound thickness for both as reflow and aging compared to fast cooling rate (110.5˚C/min) regardless the aging temperature used. However, 125°C provided thinner intermetallic compound compare to 150°C due to its higher activation energy. Besides, the strength of the solder joint was found to decrease as intermetallic compound thickness increased owing to the cooling rate and 125°C shows stronger joint than 150°C aging temperature. However, the influent is minimal compared to the formation of underfill and spalling behaviour of the intermetallic compound that seems to affect the solder joint strength significantly instead. Nevertheless, electroless nickel boron surface finish shows promising ability to be an alternative in regards to the surface finish on printed circuit board in electronic industry

A Review on Effect of Nickel Doping on Solder Joint Reliability

Currently, the demands for portable electronic gadgets such as Personal Digital Assistant, tablets and smart phone have increased due to its light weight and multifunctionality. But the major drawbacks of these portable devices are prone to accidental drops and may cause internal circuit board damage. When an electronic product drops on the ground, the impact force and deformation which is transferred internally to the print circuit board (PCB) can cause brittle fracture at the solder joint interface or by impact ±8.tigue in the solder materials. Thus, in order to further enhance the mechanical properties of the solder joints, doping an element such as such as rare earth, Bi, Sb, Fe, Co, Cr, :Mn, Ti, In, Ni, and Ge as alloying addition has been selected in previous researchers as one of those solutions. This paper summarizes the effect of Ni doping element on intermetallic compound (IMC) formation, interfacial reaction and solders joint reliability. These reviews should provide an important basis of understanding the development of lead-free solders with addition of alloying elements

Effect of Flux onto Intermetallic Compound Formation and Growth

In this study, the effect of different composition of no-clean flux onto intermetallic compound (IMC) formation and growth was investigated. The solder joint between Sn 3Ag-0.5Cu solder alloy and printed circuit board (PCB) was made through reflow soldering. They were further aged at 125°C and 150°C for up to 1000 hours. Results showed that fluxes significantly affect the IMC thickness and growth. In addition, during aging, the scallop and columnar morphology of IMC changed to a more planar type for both type of flux during isothermal aging. It was observed that the growth behavior of IMC was closely related to initial soldering condition

EFFECT OF RICE HUSKS AS FILLER IN POLYMER MATRIX COMPOSITES

In this study, rice husk-filled polyester composites were produced with rice husks (RH) as the filler and unsaturated polyester resin (UPR) as the matrix. Several percentages of filler loadings were used (10, 15, 20 and 25 wt %) in order to gain insights into the effect of filler content on the mechanical properties and water intake of the composites. The tensile strength of the RH-filled UPR composites was found to decrease as the filler loading increased; however, as it reached 25 wt %, the strength showed a moderate increase. The Young’s modulus showed a remarkable increase for 15 wt % of RH but decreased as the RH percentage increased further to 25 wt %. A water absorption test was conducted and the results showed that the composites absorb more water as the percentage weight of RH increased, which is attributed to the ability of the RH filler to absorb water

Influence of Second Reflow on the Intermetallic Compound Growth with Different Surface Finish

The formation and growth of the intermetallic were frequently discussed since lead-free solder took place replacing the lead solder. However, the effect of multiple reflow process on the intermetallic morphology that was subjected to aging still needs further investigation. Thus, this study aimed to investigate the effect of the second reflow towards the intermetallic compound formation and growth. Two types of surface finishes were used such as Immersion Tin (ImSn) and Electroless Nickel Immersion Gold (ENIG). Both test boards were reflowed once with Sn-3.0Ag-0.5Cu at the temperature of 225 °C and soaking for 8 seconds. Then, they were reflowed again at the same temperature for 25 minutes prior to an isothermal aging process for 250, 500, 1000 and 2000 hours at the temperature of 150 °C. The ProgRes C3 IM7200 Optical Microscope and ImageJ were used for the microstructural study, which includes morphology and thickness. Results indicated that IMC thickness formed between solder and ImSn surface finish increased significantly with 1.28 μm incremental when exposed to the second reflow whereas the IMC thickness of ENIG surface finish was increased for up to 0.15 μm. In addition, ENIG showed higher activation energy as compared to ImSn. © 2016 Trans Tech Publications, Switzerland

Intermetallic Growth and Shear Strength of SAC305/EN-Boron

The paper aimed to study the effect of aging and cooling rate on the reliability of the solder joint using electroless nickel boron (EN-Boron) as a surface finish in the electronic packaging area.EN-Boron was plated on Cu substrate through electroless plating method. This process was followed by reflow soldering of a Sn-3.0Ag-0.5Cu solder alloy on metallized Cu substrate to form a joining. Then, the specimens were cooled using different cooling medium which were air (slow cooling) with 15.7°C/min and water (fast cooling) with 110.5°C/min. After that, the specimens were subjected to isothermal aging at 150°C for 0, 250, and 1000 hours. Finally, they went through a lap shear test following a standard of ASTM D1002. Optical microscope and SEM were used for IMC characterization. The type of IMC formed was confirmed by FESEM-EDX. The results showed that the IMC type changed from the combination of Ni3Sn4 and (Ni, Cu)3Sn4 after reflow soldering into fully (Ni,Cu)3Sn4 when aged for 1000 hours. The formation of (Ni,Cu)3Sn4 and Cu3Sn underneath the IMC layer played a role in reducing the shear strength of joining. Overall, water cooling was reported to provide higher shear strength of solder joint compared to air cooling medium. The shear strength between solder alloy and EN-Boron surface finish is comparable to the surface finish conventionally used

Effect of Cooling and Isothermal Aging on Microstructure Using Electroless Nickel (Boron) Plating

This paper presents a study on relationship of cooling rates towards the intermetallic compound (IMC) morphology. Cooling rate is an important parameter as it has significant effect towards the IMC microstructure formation that indirectly affects solders joint reliability. However, there is still insufficient study regarding the effect of cooling rate on the IMC thickness and microstructure behavior by using Nickel Boron as surface finish material in the electronic packaging industry. In this study, Sn-3Ag-0.5Cu solder was used on Nickel Boron as coating layer. Cooling rates were obtained by cooling specimens in different media which is water and air. The elemental composition was confirmed using Energy-dispersive X-ray spectroscopy and the microstructure of each IMC then analyzed using optical microscope, image analyzer and ImageJ. In this study, faster cooling rate (water) found to provide thicker IMC (6μm) compared to the other medium used. The morphology shape of each IMC also differs between different medium of cooling. IMC that undergoes faster cooling showed continues like layer while the one using air cooling formed scallo

Microstructure Evolution at the Solder Joint During Isothermal Aging

The intermetallic compound formation and growth between Sn-3.0Ag-0.5Cu solder and surface finish, mainly immersion Au-plated Cu and immersion Sn-plated Cu were investigated in this study. This study aimed to examine the effect of different immersion types of surface finish towards the intermetallic compound formation in terms of its thickness and activation energy. In this works, evolution of microstructure at the interfacial region was studied for after reflow and isothermal aging at 150 °C, up to 1000 hours. The thickness of the intermetallic was measured using ImageJ software and activation energy was calculated using measured data. The compositions of intermetallic compound were confirmed using Scanning Electron Microscopy-Energy-dispersive X-ray spectroscopy (SEM-EDX) and its microstructure were observed using optical microscope. The cross sectional microstructure of Sn-3.0Ag-0.5Cu/ImAu joint shows that Au layer disappears completely, suggesting that it was entirely dissolved into the molten solder. The same result obtained from reflowed Sn-3.0Ag-0.5Cu/immersion Sn. The thickness of IMC layer at Sn-3.0Ag-0.5Cu /ImAu interface is similar to that at at Sn-3.0Ag-0.5Cu /ImSn interface, especially for Cu6Sn5 layer. The intermetallic growths of the intermetallic structure during isothermal aging were discussed