MODEL ANALYZING FOR REUSING GOLD WIRE CAPILLARY IN THE GOLD WIRE BONDING PROCESS

Manufacturing process improvement is necessary for manufacturers to gain business advantages. Re-using or increasing the useful lives of machine parts is considered to be a process of performance improvement. To re-use parts, the manufacturers must know the effects of the factors related to workpieces' qualities to prevent defects. This research study aims at presenting the results of analysing the effects of the factors and mathematical models for bond shear strength when reusing gold wire bonding capillary in the gold wire bonding process of integrated circuit (IC) products using design experiment. The operation factors in the reference experiment, including bond force, bond time, USG current, EFO current and EFO gap, are investigated. The Fractional Factorial Design was used to determine five factors that affect the bond shear strength. The analysis of the results show that the bond force is a significant factor where increasing bond force factors leads to increasing bond shear strength. In the end, a Regression model of bond shear strength is obtained to show the result between the bond shear strength and effect of factors. ABSTRAK: Proses pembaharuan pengilangan adalah penting untuk para pengilang bagi memperoleh keuntungan bisnes. Guna-semula atau menambah jangka hayat pada bahagian-bahagian tertentu pada mesin adalah dianggar sebahagian proses penambahbaikan prestasi mesin. Bagi mengguna semula bahagian-bahagian ini, pengilang mesti mengetahui akibat sesuatu faktor berkaitan kualiti bahan bagi mengelak kecacatan. Kajian ini bertujuan menyampaikan dapatan kajian melalui kesan faktor dan model matematik pada kekuatan ricihan ikatan apabila mengguna semula wayar emas melalui proses kapilari ikatan wayar emas pada produk litar bersepadu melalui rekaan eksperimen. Faktor operasi melalui rujukan eksperimen dari daya ikatan, masa ikatan, arus USG, arus EFO dan jarak EFO dikaji. Rekaan Faktorial Pecahan digunakan bagi mendapatkan lima faktor yang mempengaruhi kekuatan ricihan ikatan. Dapatan kajian menunjukkan daya ikatan merupakan faktor penting di mana, pertambahan faktor daya ikatan menguatkan ricihan ikatan. Akhirnya, model Regression kekuatan ricihan ikatan diperoleh bagi menjelaskan dapatan kajian antara kekuatan ricihan ikatan dan kesan faktor.

Predicting the effect of weathering and corrosion on the bond properties of bamboo- and steel-reinforced cement-stabilized rammed earth blocks

In this article, the effect of weathering and corrosion on the bond properties of bamboo- and steel-reinforced cement-stabilized rammed earth blocks was investigated. The treated, untreated bamboo and steel reinforcement types were considered under regular and weathered categories. Reinforcement of 8 mm, 10 mm and 12 mm diameters were used along with 10% of cement as stabilizer. A total of 90 reinforced cement-stabilized rammed earth blocks were prepared and tested for bond strength. The investigation shows that the bond force and bond strength of all the blocks reduced due to weathering and corrosion of reinforcement. In case of blocks with bamboo reinforcement only, a minor reduction in bond properties (bond force and bond strength) was identified, but in case of blocks with steel reinforcement, a major reduction in bond properties was identified. All the blocks failed by either lateral splitting, pullout or pullout along with lateral splitting. However, the pullout failure was observed only in the blocks with weathered or corroded reinforcement, making it clear that the mode of failure was influenced by the type and physical condition of the reinforcement. Based on the results obtained, it was not advisable to use of corroded steel (CS) bars as reinforcement in rammed earth. However, considering the bond properties, treated bamboo can be a potential and economical alternative to CS. A series of statistical analysis was performed using the test data to predict the bond properties correlating perimeter, diameter, type and condition of reinforcement. The regression equations generated from statistical analysis represent a strong correlation between the actual and predicted values and can be used for predicting the bond properties of rammed earth accurately.

Atomic Forces

This chapter discusses the physics and properties of four types of atomic forces occurring in STM and AFM: the van der Waals force, the hard core repulsion, the ionic bond, and the covalent bond. The general mathematical form of the van der Waals force between a tip and a flat sample is derived. The focus of this chapter is the covalent-bond force, which is a key in the understanding of STM and AFM. The concept of covalent bond is illustrated by the hydrogen molecular ion, the prototypical molecule used by Pauling to illustrate Heisenberg’s concept of resonance. The Herring-Landau perturbation theory of the covalent bond, an analytical incarnation of the concept of resonance, is presented in great detail. It is then applied to molecules built from many-electron atoms, to show that the perturbation theory can be applied to practical systems to produce simple analytic results for measurable physical quantities with decent accuracy.

Atomic Forces and Tunneling

This chapter presents a unified theory of tunneling phenomenon and covalent bond force, as a result of the similarity between the Bardeen theory of tunneling and the Herring-Landau theory of the covalent bond. Three general theoretical treatments are presented, which show that tunneling conductance is proportional to the square of the covalent bond interaction energy, or equivalently, the square of covalent bond force. The constant of proportionality is related to the electronic properties of the materials. For the case of a metal tip and a metal sample, an explicit equation contains only measurable physical quantities is derived. Several experimental verifications are presented. The equivalence of covalent bond energy and tunneling conductance provides a theoretical explanation of the threshold resistance observed in atom-manipulation experiments, and points to a method of predicting the threshold resistance for atom manipulation. Theory of imaging wavefunctions with AFM is discussed.

A Novel Method for Characterization of Ultralow Viscosity NCF Layers Using TCB for 3D Assembly

For die-to-wafer (D2W) stacking of high-density interconnects and fine-pitch microbumps, underfill serves to fill the spaces in-between microbumps for protection and reliability. Among the different types of underfill, nonconductive film (NCF) has the advantages of fillet and volume control. However, one of the challenges is the solder joint wetting. An NCF must have good embedded-flux activation to mitigate Cu UBM pad oxidation due to the repeated TCB cycles that accelerate oxidation on neighboring dice. The flux in the NCF also helps in wetting the solder bumps. To realize efficient solder wetting, one must also understand the NCF deformation quality, which is a function of its viscosity. This parameter has direct impact on the deformation of solder bumps. High-viscosity NCF would be difficult to deform, thus preventing solder contact to pad during TCB reflow temperature. High bond force is required and could lead to reduced alignment accuracy. For a low viscous NCF, it requires low bond force. Solder joint wetting is a challenge with excessive squeezeout due to fast and instantaneous deformation. We seek to demonstrate in this article a creative methodology for NCF material characterization, considering the factors of NCF viscosity, deformation, and solder squeezeout. We use TCB tool position-tracking data to define the deformation curve of the NCF as a function of temperature and time at very fast profile of TCB. We use the NCF viscosity curve as reference in relation to the actual deformation, and predict dynamic deformation in three different configurations. Deformation test configurations were performed on chips with and without microbumps bonded with a rigid flat glass surface and with a bottom Cu UBM pad. The experiments were performed with different heating ramp rates at target above Sn reflow of ~250°C interface temperature. As validation, we applied the optimized TCB process (force, temperature, and ramp rate) on a test vehicle with 20 and 40 μm pitch daisy chains and obtained very good connectivity with good joint and IMC formation.

Assessment of Existing Bond Models for Externally Bonded SRP Composites

This manuscript assessed the applicability of the existing ultimate bond formulas originally developed for externally bonded carbon fiber-based composites in the analysis of steel-reinforced polymers (SRPs). In the first part, the methods of predicting the bond capacity are reviewed, the differences are indicated, and the factors determining the bond are discussed; then, using the bond test results of over 400 samples available in the literature, the bond prediction methods are assessed by graphical comparison. The evaluation mainly concerned concrete elements and epoxy adhesives; however, to a lesser extent, a similar analysis was performed for the masonry substrate and grout matrices. The results showed the relatively good applicability of the majority of bond prediction models for the analysis of SRP composites. In most cases, the ultimate bond force was slightly underestimated, which was beneficial in the design of this type of strengthening. Larger discrepancies concerned weaker grout matrices.

Influence of selective etching on the enamel and dentin leakage of three low shrinkage composites in class V restoration

This study determined if prior selective enamel etching affected leakage of enamel/dentin margins in Class V low-shrinkage resin-based composite restorations. Round cavities, centered on the cemento/enamel junction, 2 mm in diameter and 2 mm in depth were prepared on the buccal, palatal or lingual surfaces of premolar teeth to have a total of 60 cavities. One side of the tooth received selective enamel etching and both sides were restored using one of 3 restorative materials (n = 10): Aelite LS posterior/All-bond SE, Estelite Sigma Quick/Bond Force, or Filtek P90/P90 System Adhesive. The teeth were fatigued for 5000 thermal cycles, and the marginal sealing was challenged with 50% ammoniacal silver nitrate. The interface was analyzed and the leakage score was calculated. Two-way ANOVA revealed that Filtek P90 (25.5±17.4) had lower leakage than Estelite Sigma Quick (63.1±34.5) and Aelite LS Posterior (64.2±41.8) with self-etching. With selective etching, the three materials showed reduced leakage in enamel. A significant difference (P <0.05) was found between leakage in enamel and dentin for the Aelite LS Posterior selective etch group and for Estelite Sigma Quick. Selective etching reduced enamel leakage for all materials in one-step self-etch materials. Two-step self-etch adhesives bond better to enamel and dentin than one-step resin-based adhesives.

Die Attach Film Bleed out Resolution through Process Optimization on DFN Packages

The development of new technology with thinner and smaller packages has become the movement and focus on semiconductor assembly industry. This paper presents an improvement done in dual-flat no-leads (DFN) package to resolve the quantity of rejection due to die attach film (DAF) bleed out on the die paddle of the leadframe. This reject manifestation was seen after die attach process. Parameter optimization particularly for the bonding with the combination of bond force and bond time parameter was done to eliminate this type of issue after die attach process. With this die attach process optimization and improvement done, DAF bleed out occurrence was eliminated with 100% reduction improvement.

A novel method for characterization of Ultra Low Viscosity NCF layers using TCB for 3D Assembly

For die to wafer bonding of high-density interconnects and fine pitch microbumps developing and characterizing suitable underfill materials are required. In general, underfill serve to fill the spaces in-between microbumps for protection and reliability. Among the different types of underfill, Non-Conductive Film (NCF) has the advantages of fillet and volume control, and a built-in flux to aid wetting. However, challenges arise for thin dies and microbumps with fine pitches on film lamination, voiding, transparency, filler percentage, dicing compatibility and most importantly, deformation behavior and possibility to improve solder joint wetting. In a Die-to-Wafer D2W stacking with a Sn solder bump interconnect to Cu UBM, concern is high on the Cu pad oxidation due to the repeated TCB cycles that accelerate oxidation on neighboring dies. Process mitigation is needed to help reducing the oxidation. But even so, an NCF must have good embedded flux activation. Another main factor for an NCF to have efficient TCB process with good solder joint wetting, is the NCF deformation quality in which is a function of its viscosity. This parameter has direct impact on the deformation of solder bumps. High viscosity NCF would be difficult to deform, thus preventing solder contact to pad during TCB reflow temperature. High bond force is required and could lead to reduced alignment accuracy. Filler entrapment is also a subsequent concern for high filler loading, high viscosity NCF. For a low viscous NCF, careful attention in process characterization is needed in TCB with low bond force. Solder joint wetting is a problem with excessive squeeze-out due to fast and instantaneous deformation. With low viscosity, not only the bond force applied should be low, but the deformation behavior should also be understood to enable an effective NCF. We seek to demonstrate in this paper a creative methodology for Non-Conductive Film (NCF) material characterization, considering the factors of NCF viscosity, deformation, and solder squeeze-out. Characterizing NCF viscosity at fast TCB profiles is challenging considering deformation behavior of both the NCF itself and the solder bumps that shaped the solder squeeze-out and wetting. Furthermore, in this paper we use TCB tool position tracking to define the deformation curve of NCF film as a function of temperature and time at very fast profile of TCB. We use material viscosity curve as reference in relation to the actual deformation, and predict dynamic deformation based on Reynold’s equation within TCB profile duration. The experiments were performed with different heating ramp rates at target above Sn reflow of ~250C interface temperature. The deformation analysis is not limited to thin film sandwiched between parallel plates. Deformation test was performed on chips with and without microbumps and with rigid flat glass surface and its combinations. Deformation of underfill is recorded in the readout of TCB tool. As validation, we applied the optimized TCB process (force, temperature, and ramp rate) on a test vehicle with 20 and 40um pitch daisy chains and obtained close to 95% electrical yield with good joint and IMC formation. The cross-section SEM images show good wetting, revealing good activation of built-in flux when the optimized TCB profile was used.