Sub-100 μm SnAg Solder Bumping Technology and the Bump Reliability

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
Xiaoqin Lin ◽  
Le Luo
Keyword(s):  
Cu6sn5 Phase ◽  
X Ray ◽  
Solder Bumps ◽  
Average Shear Strength ◽  
Average Shear ◽  
Snag Solder ◽  
Packaging Industry ◽  
Negative Impacts ◽  
Free Solder ◽  
Electroplating Process

Lead-free solder bumping and its related interconnection and reliability are becoming one of the important issues in today’s electronic packaging industry. In this paper, alloy electroplating was used as SnAg solder bumping process. Multiple reflow was preformed on as-plated solder bumps. Scanning electron microscopy and energy dispersive X-ray analysis were used to investigate the intermetallic compound and microvoids of cross-sectioned solder bump. Shear test was used to evaluate the reliabilities of the SnAg bumps. The 13×13 area-array Sn/3.0Ag solder bumps of 70 μm in height and 90 μm in diameter were fabricated with a smooth and shiny surface and with a uniform distribution of Ag. During multireflow, the scalloped Cu6Sn5 phase grows by a ripening process. Volume shrinkage was the main reason for the formation of microvoids during multireflow. The average shear strength of solder bumps on TiW/Cu under bump metallurgy (UBM) increased with reflow times. The electroplating process is suitable for mass production of well-controlled geometry and uniformity of SnAg solder bumps. Microvoids have trivial negative impacts on the solder bonds. The combination of TiW/Cu UBM and SnAg solder is reliable.

Quantitative Evaluation of Voids in Lead Free Solder Joints

2015 ◽  
Vol 772 ◽  
pp. 284-289 ◽  
Author(s):  
Sabuj Mallik ◽  
Jude Njoku ◽  
Gabriel Takyi
Keyword(s):  
Solder Bump ◽  
Solder Joints ◽  
Void Formation ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Paste ◽  
X Ray ◽  
Size And Shape ◽  
Solder Bumps ◽  
Free Solder

Voiding in solder joints poses a serious reliability concern for electronic products. The aim of this research was to quantify the void formation in lead-free solder joints through X-ray inspections. Experiments were designed to investigate how void formation is affected by solder bump size and shape, differences in reflow time and temperature, and differences in solder paste formulation. Four different lead-free solder paste samples were used to produce solder bumps on a number of test boards, using surface mount reflow soldering process. Using an advanced X-ray inspection system void percentages were measured for three different size and shape solder bumps. Results indicate that the voiding in solder joint is strongly influenced by solder bump size and shape, with voids found to have increased when bump size decreased. A longer soaking period during reflow stage has negatively affectedsolder voids. Voiding was also accelerated with smaller solder particles in solder paste.

Analysis of the Interfacial Reaction Between Sn-3.5Ag and Electroplating Interlayers

2005 ◽  
Vol 863 ◽  
Author(s):  
S.M. Yang ◽  
Y.Y. Chang ◽  
Weite Wu
Keyword(s):  
Diffusion Barrier ◽  
Interfacial Microstructure ◽  
X Ray ◽  
Soldering Process ◽  
Free Process ◽  
Snpb Solder ◽  
Microstructure Examination ◽  
Free Solder ◽  
Electroplating Process ◽  
Morphology Characterization

AbstractAt present, Pb-free process is imperative in the electronic packaging industry. Many reports focus on Pb-free solder to improve the solderability, it seems not obtain wettability as good as SnPb solder. In this study, an alloy interlayer with different content was deposited on Cu to balance wettability and diffusion barrier in the interface of joint by electroplating process. There are three types of interlayers including Cu, Ni, and SnNi alloy. The interlayer may react with Sn-3.5Ag solder during reflow process. Sn-Ni alloy plating layer is selected to improve wettability and provide diffusion barrier at the same time in soldering process. For interfacial microstructure examination, morphology characterization can be obtained by using scanning electron microscope (SEM) and energy-dispersive x-ray analysis (EDX). The structure of IMC is identified by x-ray diffraction (XRD).

High-speed SnAG Solder Electroplating Process and Developments on Cost Reduction

2011 ◽  
Vol 2011 (DPC) ◽  
pp. 000717-000753
Author(s):  
Bob Forman
Keyword(s):  
High Speed ◽  
Consumer Electronics ◽  
Wafer Level ◽  
Solder Bumps ◽  
New Process ◽  
Snag Solder ◽  
Single Use ◽  
Current Densities ◽  
Electroplating Process ◽  
Short Time

The use of wafer level packaged ICs with Lead (Pb) free Tin Silver (SnAg) solder bumps is prevalent in consumer electronics. One method of making these bumps is by electroplating. The current process requires the use of a complex and expensive, single use chemistry. These chemistries do provide smooth, void free bumps, but with a very high Cost of Ownership (COO). Up to now these chemistries were expensive to operate, mainly because they are used for a short time and then disposed. This paper will discuss a new process using chemistry that provides improved COO by incorporating higher plating rates with recycling of used chemistry. With this process it is possible to recover nearly 100% of the metals, acids and organic agents previously discharged as waste. The recovered chemistry is then processed and certified to be reused in the originating fab, resulting in virtually zero waste. In addition to closed loop recycling, the process also forms bumps at a higher rate, by plating at higher current densities, with no trade-off in bump performance.

Void Inspection in Lead-Free Solder Bumps on Ball Grid Array (BGA) Packages Using Laser Ultrasound Technique

2011 ◽  
Author(s):  
Jie Gong ◽  
I. Charles Ume
Keyword(s):  
Ball Grid Array ◽  
Lead Free ◽  
Inspection System ◽  
Laser Ultrasound ◽  
Lead Free Solder ◽  
X Ray ◽  
Bga Packages ◽  
Solder Bumps ◽  
Free Solder ◽  
Ultrasound Inspection

Solder joint voids are usually formed by the entrapped gas bubbles during the reflow process, and are common in all surface mount applications. It is a controversial issue on the reliability of the solder joint, however the consensus is that voiding is acceptable at low contents, while excessive voiding affects mechanical properties, and decreases strength, ductility and fatigue life of the interconnections. X-ray is the most widely used technique to evaluate the voids, including the size and occurrence frequency. In this paper, a laser ultrasound and interferometer inspection system is used to inspect the voids in lead-free solder bumps in ball grid array (BGA) packages. This system uses a pulsed Nd:YAG laser to induce ultrasound in the chip packages in the thermoelastic regime; and laser interferometer is used to measure the transient out-of-plane displacement response of the package surface to the laser irradiation. The quality of solder bumps is evaluated by analyzing the transient responses. In this work, voids were intentionally created by adding the volatile flux during the assembly process. By controlling the volume of flux dip, three different levels of voiding were proposed: void-free, relatively low and relatively high. The presence of voids in the solder bumps was first verified using 2-D X-ray techniques. Meanwhile, the built-in image-processing software in X-ray tool measured the void fraction to quantify the level of voiding. Then the laser ultrasound inspection system was used to evaluate the voids in these samples. By comparing the vibration responses from voided samples and void-free samples, it was found that the laser ultrasound inspection system is capable to differentiate samples with relatively high voiding from void-free samples while the relatively low voiding was below the resolution of the inspection system. Lastly, a further comparison between the void-free and voided solder bumps was carried out by the destructive cross-section technique. The comparisons between these three solder bump evaluation methods will be presented in this paper.

Nondestructive Evaluation of Thermal Fatigue Crack Propagation in Sn-Ag-Cu Solder Joints by Synchrotron Radiation X-Ray Micro-Tomography

2009 ◽  
Author(s):  
Hiroyuki Tsuritani ◽  
Toshihiko Sayama ◽  
Yoshiyuki Okamoto ◽  
Takeshi Takayanagi ◽  
Kentaro Uesugi ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Nondestructive Evaluation ◽  
Thermal Cycle ◽  
Solder Joints ◽  
Fatigue Cracks ◽  
Lead Free Solder ◽  
X Ray ◽  
Solder Bumps ◽  
Micro Tomography ◽  
Free Solder

An X-ray micro-tomography system called SP-μCT, which has a spatial resolution of 1 μm, has been developed in SPring-8, the largest synchrotron radiation facility in Japan. In this work, SP-μCT was applied to the nondestructive evaluation of micro-crack propagation appearing as thermal fatigue damage in lead-free solder joints. The observed specimens include two typical micro-joint structures by Sn-3.0wt%Ag-0.5wt%Cu lead-free solder. The first is an FBGA (Fine pitch Ball Grid Array) joint specimen in which an LSI package is connected to a substrate by solder bumps 360 μm in diameter, while the second is a chip joint specimen in which chip type resistors 1.6 mm in length and 0.8 mm. in width are mounted on a substrate. A thermal cycle test was carried out, and the specimens were picked up at fixed cycle numbers. The same solder joints were observed repeatedly using SP-μCT at beamline BL20XU in SPring-8. An X-ray energy of 29.0 keV was selected to obtain CT (Computed Tomography) images with high contrast among some components, and a refraction-contrast imaging technique was also applied to the visualization of fatigue cracks in the solder joints. In the FBGA type specimens, fatigue cracks appeared at the periphery of the interfaces between the solder and the UBM (Under Bump Metallization) on the LSI package. As the thermal cycle proceeds, the cracks propagate gradually to the inner region of the solder bumps in the vicinity of the interface. On the basis of the three-dimensional crack images, the fatigue crack propagation lifetime was accurately estimated by means of the average crack propagation rate. On the other hand, in the chip joint specimens, fatigue cracks appeared and propagated through the thin solder layer between the chip and substrate. In contrast to the FBGA specimen, many small voids roughly 5 to 10 μm in length were formed in the solder layer. The important observed fact is that these voids deform and connect to each other due to the thermal cyclic loading prior to crack propagation. Consequently, the obtained CT images clearly show the process of crack propagation due to the thermal cyclic loading of the same solder joint. In contrast, such information has not been obtained, whatsoever by industrially employed X-ray CT systems.

Intermetallic Effects of Electroplated Lead-Free Solder Bumps Using a Novel Single Chamber Electroplating Process for Large Diameter Wafers

2007 ◽  
Author(s):  
J. Teye Brown ◽  
Ajay M. Popat ◽  
Chad B. O’Neal ◽  
Yixiang Xie
Keyword(s):  
Cross Sections ◽  
Visual Inspection ◽  
Large Diameter ◽  
Lead Free Solder ◽  
Elemental Mapping ◽  
Single Chamber ◽  
Metal Plating ◽  
Solder Bumps ◽  
Free Solder ◽  
Electroplating Process

In this study solder bumps of various alloys and less than 100 microns in diameter were electroplated using a novel single chamber electroplating process in which the plating baths are exchanged between the different metal plating layers. This equipment is new to the manufacturing arena. The reflow profile and process was then optimized for the various alloys such as SnAg, and electroplated layered SnPb, and PbSn 95/5%, with PbSn 95/5% being the control leaded solder for comparison. Various fluxes were also used during the reflow of these bumps. The solder bumps were reflowed on a conduction reflow oven in a nitrogen environment such that the temperature profile could be carefully controlled. The bumps were analyzed by examining the bump diameter and height uniformity, surface quality, and elemental composition and distribution inside the bumps. These analyses were done by visual inspection by optical microscopy, scanning electron microscopy, and electron dispersive spectroscopy (EDS). The wafers were diced near a row of solder bumps, then podded and polished using a metallographic polishing system to the center of solder bumps. These bump cross-sections were then examined by EDS to perform elemental mapping of the alloy constituents.

scholarly journals Effect Of 3% Molybdenum (Mo) Nanoparticles on The Melting, Microstructure and Hardness Properties of As- Reflowed Low Mass Sn-58Bi (SB) Solder Alloy

2020 ◽  
Vol 77 (1) ◽  
pp. 69-87
Author(s):  
Amares Singh ◽  
Rajkumar Durairaj ◽  
How Kuan Seng
Keyword(s):  
Solder Alloy ◽  
Vickers Microhardness ◽  
Dispersion Strengthening ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Lamellar Structures ◽  
Low Mass ◽  
Packaging Industry ◽  
Free Solder

The Sn-58Bi (SB) lead free solder alloy tested in this research with addition of 3% Molybdenum (Mo) nanoparticles equivalent to 0.6g mass to analyse the influences in the thermal, microstructure and microhardness. Elevation of 3.8°C was observed from the Differential Scanning Calorimetry (DSC) for the 3% Mo nanoparticles added SB solder alloy compared to the bare Sn-58Bi (SB) solder alloy that has a melting temperature of 142.25°C. The microstructures of the reinforced SB solder alloy were refined with closer lamellar structures of ?-Sn and Bi phases compared to the unreinforced SB solder. The SEM/EDX and X-ray Diffraction (XRD) results validate the presence of the 3% Mo nanoparticles in the SB solder. Mechanical properties by means of Vickers microhardness of the Mo reinforced solder alloy showed an increment in hardness value by 2% compared to the bare SB solder alloy. The presence of 3% Mo as discrete particles (dispersion strengthening) contributes to the increase on the hardness value. The introduction of 3% Mo in to the SB solder alloy resulted in increase in the hardness due to the refinement of the microstructure and at the same time allows low temperature soldering in the electronic packaging industry.

Tensile fracture behaviors of solid-state-annealed eutectic SnPb and lead-free solder flip chip bumps

2004 ◽  
Vol 19 (6) ◽  
pp. 1826-1834 ◽  
Author(s):  
Jin-Wook Jang ◽  
Ananda P. De Silva ◽  
Jong-Kai Lin ◽  
Darrel R. Frear
Keyword(s):  
Solid State ◽  
Fracture Behavior ◽  
Flip Chip ◽  
Interfacial Fracture ◽  
Bulk Solder ◽  
Tensile Fracture ◽  
Solder Bumps ◽  
Snag Solder ◽  
Free Solder ◽  
Eutectic Snpb

The tensile fracture behavior for solid-state-annealed eutectic SnPb and lead-free solder flip chip bumps was examined. The annealing temperatures were in the range of 125–170 °C for 500 h. Prior to solid state annealing, the eutectic Sn–37Pb (SnPb) and Sn–0.7Cu (SnCu) solders showed fracture through the bulk solder. Brittle interfacial fracture occurred in the Sn–3.5Ag (SnAg) solder. After solid-state annealing, the fracture behavior changed dramatically. For eutectic SnPb solder, the fracture modes gradually changed from cohesive solder failure to interfacial fracture with increasing annealing temperature. The fracture mode of the SnCu solder showed greater change than the SnPb and SnCu solders. After annealing at 125 °C, the SnAg solder had a ductile taffy pull fracture, but an increase in temperature resulted in brittle interfacial fracture again. The SnCu solder maintained the same ductile taffy pull mode up to170 °C annealing, independent of the under bump metallization (UBM) type. Microstructure analysis showed that the interfacial fracture of the SnPb and SnAg solder bumps was ascribed to Pb-rich layer formation and Ag embrittlement at the interface, respectively. The bulk solder fracture of SnAg annealed at 125 °C appeared to be a transient phenomenon due to the abrupt breakdown of the hard lamella structure. The eutectic SnCu solder bumps had no significant change in the interfacial structure, except for interfacial intermetallic growth.

scholarly journals Characterization of Soldering Alloy Type Bi-Ag-Ti and the Study of Ultrasonic Soldering of Silicon and Copper

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 624
Author(s):  
Roman Kolenak ◽  
Igor Kostolny ◽  
Jaromir Drapala ◽  
Paulina Babincova ◽  
Peter Gogola
Keyword(s):  
Eutectic Reaction ◽  
Research Work ◽  
Copper Substrate ◽  
Liquid Bismuth ◽  
Alloy Type ◽  
Average Shear Strength ◽  
Average Shear ◽  
The Matrix ◽  
Solder Microstructure ◽  
Ultrasonic Soldering

The aim of the research work was to characterize the soldering alloy type Bi-Ag-Ti and to study the direct soldering of silicon and copper. Bi11Ag1.5Ti solder has a broad melting interval. Its scope depends mainly on the content of silver and titanium. The solder begins to melt at the temperature of 262.5 ∘C and full melting is completed at 405 ∘C. The solder microstructure consists of a bismuth matrix with local eutectics. The silver crystals and titanium phases as BiTi2 and Bi9Ti8 are segregated in the matrix. The average tensile strength of the solder varies around 42 MPa. The bond with silicon is formed due to interaction of active titanium with the silicon surface at the formation of a reaction layer, composed of a new product, TiSi2. In the boundary of the Cu/solder an interaction between the liquid bismuth solder and the copper substrate occurs, supported by the eutectic reaction. The mutual solubility between the liquid bismuth solder is very limited, on both the Bi and the Cu side. The average shear strength in the case of a combined joint of Si/Cu fabricated with Bi11Ag1.5Ti solder is 43 MPa.

Morphology and Intermetallic Study of (Sn-8Zn-3Bi)-1Ni Solder under Liquid State Aging

2015 ◽  
Vol 1087 ◽  
pp. 162-166
Author(s):  
Nor Aishah Jasli ◽  
Hamidi Abd Hamid ◽  
Ramani Mayappan
Keyword(s):  
Liquid State ◽  
Copper Substrate ◽  
Lead Free ◽  
Lead Free Solder ◽  
Reflow Time ◽  
Intermetallic Formation ◽  
X Ray ◽  
Ni Addition ◽  
Free Solder ◽  
Scanning Electron

This study investigated the effect of Ni addition on intermetallic formation in the Sn-8Zn-3Bi solder under liquid state aging. The intermetallic compounds were formed by reacting the solder alloy with copper substrate. Different reflow time was used at temperature 220°C. Morphology of the phases formed was observed using scanning electron microscope (SEM) and in order to determine elemental compositions of the phases, energy dispersive x-ray (EDX) was used. The formation of the reaction layer led by Cu5Zn8 intermetallic and then followed by Cu6Sn5 and Cu3Sn when reflow time increases. Keywords: lead free solder, intermetallic, Cu5Zn8, Cu6Sn5, liquid state aging.

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