Bump Application Research Articles

Experimental analysis of car drag reduction through contour bump application

Experimental analysis of car drag reduction through contour bump application

THE ASSESSMENT OF NATIONAL ROAD SURFACE CONDITIONS ANALYSIS BASED ON THE INTERNATIONAL ROUGHNESS INDEX (IRI) METHOD USING ROADBUMP APPLICATION

Roads are infrastructure that has a vital role for the community in supporting social and economic activities. Therefore, appropriate handling information is needed for road maintenance and improvement to be on target. One of the methods used is the International Roughness Index (IRI) method with the help of the Road bump application. The purpose of this study is to analyze and recommend handling road surface conditions, as well as to test the validity of the Road bump application with a Laser Profilometer. This research was conducted on the 10 KM section of Trans Kalimantan Road. Comparative data is obtained from secondary data issued by BPJN in 2021 using the Laser Profilometer tool. This study found that the condition of the Trans Kalimantan Road was 80% in the excellent category, 18% in the moderate category, and 2% in the slightly damaged category, and had similarities with the BPJN IRI value of 95%. Road bump also tends to the IRI value to be greater than the BPJN IRI value. Based on the results of this study, the Road bump application can be used as an alternative tool for measuring road surface conditions using the International Roughness Index (IRI) method.

Use of shape memory alloy for active shock control bump application

A shape memory alloy (SMA) with composition of Ni50.1Ti49.9 (at. %) was used for fabrication of a 3-D bump structure intended for use as an active shock control bump (SCB) into a transonic wing. This kind of bump is a variable-geometry structure designed to reduce the drag induced by shock wave ensure wing’s aerodynamic performance over the entire range of operating conditions. To meet this target, the SMA bump requires to exhibit two-way shape memory effect (TWSME) so that it can yield continuous shape change by properly changing the driving temperature. Result from differential scanning calorimetry was first presented to provide material’s phase transformation temperatures. To obtain the TWSME, a thermo-mechanical training procedure was proposed and a set of training devices were designed for training SMA bump. The SMA bump in this paper is trained to have a relatively flat shape in high temperature and can swell up when cooling. After more than 80 times training, the TWSME of the material tends to be stable. Then the thermo-mechanical responses of the SMA bump which is subjected to about 100 times training was tested. The result shows that the trained SMA bump can generate about 1.2 mm maximum recoverable deformation during martensitic transformation, which is about 3% of the ratio of the deformation region. Finally, the influence of external load on the thermo-mechanical response of the trained SMA bump were also studied.

A Study of Low-Cost Sequential Electroplating Bumping Process and its Metallurgical Behavior

Studies were conducted to validate from a metallurgical point of view whether a lower cost sequential plating approach to SnAg and SnAgCu (SAC) solder bumping is a suitable alternative to the conventional alloy plating process. A range of Ag content corresponding to typical bump applications was explored with respect to Ag diffusion and intermetallic compound (IMC) formation. Variables that can affect such IMC formation were further explored as a function of underbump metallization (UBM) structure and cooling rate during bump solidification. By comparing the results to those previously reported on SnAg-based alloys, it is demonstrated that the proposed sequential plating process produces very similar microstructures and Ag3Sn IMC morphologies, due to the rapid diffusion and distribution of Ag through the liquid Sn. Known means to mitigate the less desirable large Ag3Sn platelets, that is by changing the top UBM layer from Cu to Ni or by employing an ultrarapid cooling rate, are shown to be equally effective for sequential plating. These observations, in conjunction with the simplicity and flexibility of plating multiple single metals, propose adoption of the sequential plating process as a cost-effective and robust Pb-free bumping solution for fine pitch flip-chip packaging.

High Reliability and High Throughput Ball Bumping Process Solution – Solder Joint Encapsulant Adhesives

Abstract The miniaturization of microchips is always driving force for revolution and innovation in the electronic industry. When the pitch of bumps is getting smaller and smaller the ball size has to be gradually reduced. However the reliability of smaller ball size is getting weaker and weaker, so some traditional methods such as capillary underfilling, corner bonding and edge bonding process have been being implemented in board level assembly process to enhance drop and thermal cycling performance. These traditional processes have been increasingly considered to be bottleneck for further miniaturization because the completion of these processes demands more space. So the interest of eliminating these processes has been increased. To meet this demand, YINCAE has developed solder joint encapsulant adhesives for ball bumping applications to enhance solder joint strength resulting in improving drop and thermal cycling performance to eliminate underfilling, edge bonding or corner bonding process in the board level assembly process. In this paper we will discuss the ball bumping process, the reliability such as strength of solder joints, drop test performance and thermal cycling performance.

Application of robust color composite fringe in flip-chip solder bump 3-D measurement

This study developed a 3-D measurement system based on flip-chip solder bump, used fringes with different modulation intensities in color channels, in order to produce color composite fringe with robustness, and proposed a multi-channel composite phase unwrapping algorithm, which uses fringe modulation weights of different channels to recombine the phase information for better measurement accuracy and stability. The experimental results showed that the average measurement accuracy is 0.43μm and the standard deviation is 1.38µm. The results thus proved that the proposed 3-D measurement system is effective in measuring a plane with a height of 50μm. In the flip-chip solder bump measuring experiment, different fringe modulation configurations were tested to overcome the problem of reflective coefficient between the flip-chip base board and the solder bump. The proposed system has a good measurement results and robust stability in the solder bump measurement, and can be used for the measurement of 3-D information for micron flip-chip solder bump application.

A Metal Bump Bonding Method Using Ag Nanoparticles as Intermediate Layer

The future development of low-temperature and low-pressure bonding technology is necessary for fine-pitch bump application. We propose a bump structure using Ag nanoparticles as an intermediate layer coated on a fine-pitch Cu pillar bump. The intermediate layer is prepared using an efficient and cost-saving squeegee-coating method followed by a 100°C baking process. This bump structure can be easily flattened before the bonding process, and the low-temperature sinterability of the nanoparticles is retained. The bonding experiment was successfully performed at 250°C and 39.8 MPa and the bonding strength was comparable to that achieved via other bonding technology utilizing metal particles or porous material as bump materials.

Data-Sharing Method for Multi-Smart Devices at Close Range

We proposed a useful data-sharing method among multi-smart devices at close range using inaudible frequencies and Wi-Fi. The existing near data-sharing methods mostly use Bluetooth technology, but these methods have the problem of being unable to be operated using different operating systems. To correct this flaw, the proposed method that uses inaudible frequencies through the inner speaker and microphone of smart device can solve the problems of the existing methods. Using the proposed method, the sending device generates trigger signals composed of inaudible sound. Moreover, smart devices that receive the signals obtain the shared data from the sending device through Wi-Fi. To evaluate the efficacy of the proposed method, we developed a near data-sharing application based on the trigger signals and conducted a performance evaluation experiment. The success rate of the proposed method was 98.8%. Furthermore, we tested the user usability of the Bump application and the proposed method and found that the proposed method is more useful than Bump. Therefore, the proposed method is an effective approach for sharing data practically among multi-smart devices at close range.

New Cu(TiIrNx) Alloy Films for Solder Bump Flip-Chip Application

A new copper alloy that shows fine thermal stability and adhesion to the substrate is developed in this study by cosputtering Cu, Ti, and Ir on a barrierless Si substrate within an Ar/N2 gas atmosphere to form a Cu(TiIrNx) film. To reduce manufacture cost, we can replace both the wetting and diffusion layers underneath flip-chip solder joints in conventional under bump metallurgy with this thermally stable film, which exhibits weak, if any, interactions between the film and the substrate after annealing at 700 °C for 1 h. The alloy film's dissolution rate is lower than that of pure Cu by at least one order of magnitude, with a fine solderability similar to that of pure Cu. The film developed in this study seems to be a good candidate material for barrierless Si metallization and/or flip-chip solder bump application, with a low consumption rate comparable to that of Ni.

Electrical behavior of Au–Ge eutectic solder under aging for solder bump application in high temperature Electronics

As deep earth oil exploration transits into deeper earth, it faces challenges in producing reliable microelectronics devices and sensors that will not degrade at high temperature, especially those related to packaging materials and assembly of the devices. It has been reported that the mechanical performance of a high temperature Au–Ge eutectic solder is able to fulfill the minimum interconnection properties specified by the oil and gas exploration industry. However, the impact of thermal aging to Au–Ge eutectic solder’s electrical property is not clear. In this work, it is observed that the bulk Au–Ge electrical resistivity decreased initially with thermal aging and then saturated. This effect is mainly contributed by the grain growth of Au, which results in a reduction in grain boundaries, as well as coarsening of the Ge phases. On the other hand, study on the microstructure and electrical resistance of Au–Ge solder bump joint after aging shows that the electrical resistance increased. The increase in resistance is contributed mainly by the NiGe and Ni5Ge3 intermetallic compounds growth, which also led to a degradation in the Ni(P) barrier layer.

Super Fine Lead-Free Solder Powder for Fine Pitch Bump Applications

We have successfully developed super fine lead-free and low alpha solder powder, which contains more than two elements by the method of wet chemical reduction. The size (D50) of super fine powder is around 2–3 micrometer to meet finer pitch assembly in the near future. This new method made it available to synthesize various compositions of solder powder like Sn-Ag, Sn-Cu, Sn-Ag-Cu, etc. Also, this method achieves very high yield compared to a gas atomization method. A solder paste for printing method composed of the fine solder powder has a superior printing ability because of the unique powder shape. The powder shows anisotropic shape, and it can make printed figure excellent after printing without bridge and coplanarity issues for finer pitch applications. With our super fine solder paste, we will be ready for <100um pitch of solder bumps which will come in a few years. Furthermore, the super fine powder is applied to the Cu pad pre-coat. The solder paste for pre-coat composed of the super fine powder shows an excellent coverage and solders flatness on the outer pad after reflow.

Nonconductive Films (NCFs) With Multifunctional Epoxies and Silica Fillers for Reliable NCFs Flip Chip on Organic Boards (FCOBs)

Nonconductive films (NCFs) have become one of the promising interconnection adhesives for flip-chip assembly. Because NCFs have many advantages such as low cost, easy handling, and fine-pitch application. However, effects of the material properties of NCFs on the reliability of NCFs flip-chip assemblies have not been fully understood. In this paper, effects of multifunctional epoxy and the addition of silica fillers on thermomechanical properties of cured NCFs and thermal cycling reliability of NCFs flip-chip-on-organic board (FCOB) assemblies were investigated. For the NCF materials, two kinds of thermosetting polymers, di-functional and multifunctional epoxies, and silica fillers of various contents (0 wt%, 10 wt%, and 20 wt%) were used. The curing behavior and thermomechanical properties of NCFs were measured for the NCF materials characterization. According to the results, NCFs using multifunctional epoxy had higher glass transition temperature ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tg</i> ), lower coefficient of thermal expansion (CTE), and higher storage modulus (E <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">'</sup> ) in high-temperature regions than NCFs using di-functional epoxy. As the silica filler content increased, the CTE and the storage modulus of cured NCFs decreased and increased, respectively. Thermal cycling test (-40degC - 150degC, 1000 cycles) was performed to investigate effects of thermomechanical properties of cured NCFs on thermal cycling reliability of NCF FCOB assemblies. According to the results, NCF FCOB assemblies using NCFs with multifunctional epoxy had better thermal cycling reliability than those using NCFs with di-functional epoxy, and 10 wt% and 20 wt% silica added NCFs showed the best thermal cycling reliability in the electroplated Au bump application and the stud Au bump application, respectively. Consequently, thermal cycling reliability of NCFs FCOB assemblies could be enhanced with the increased <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tg</i> and the improved thermomechanical properties of NCFs by using multifunctional epoxy and the addition of silica fillers.

Back-End Copper Metallization for Advanced Packaging

We developed various back-end copper processes for advanced packaging. Deposition conditions for bump applications were optimized to achieve a high deposition rate (3-4um/min) due to thick deposits and simple die patterns. Bath composition, waveform, deposit thickness, and mask parameters (open area and resist thickness) significantly impact surface properties at high-rate deposition. For other through-mask applications such as redistribution lines and embedded passives, we modified process conditions and lowered deposition rate (1- 2um/min) to obtain better within-die thickness uniformity. Pattern complexity, deposition rate, waveform, and bath conductivity drastically impact within-die thickness distribution. For through-silicon-via applications, we investigated the impact of varying deposition conditions on the filling profile. Reducing current crowding at the via mouth and mass transfer limitations at the via bottom is critical in achieving void-free filling. Void-free filling can be achieved only with a proper combination of surface wettability, seed conformality, bath composition, waveform, current density, and flow conditions.